61. Which of the following statement(s) is/are true concerning the Advanced Trauma Life Support (ATLS) classification system of hemorrhagic shock?
a. Class I shock is equivalent to voluntary blood donation
b. In Class II shock there will be evidence of change in vital signs with tachycardia, tachypnea and a significant decrease in systolic blood pressure
c. Class III hemorrhage can usually be managed by simple administration of crystalloid solution
d. Class IV hemorrhage involves loss of over 40% of blood volume loss and can be classified as life-threatening
Answer: a, d
The classification of hemorrhagic shock as defined by the ATLS classification system of the American College of Surgeons is useful in comprehending the manifestations and physiologic changes associated with shock. Mild hemorrhage, up to 15% of total blood volume, is exemplified by voluntary blood donation. In the supine position, there are no measurable changes in heart or respiratory rates, blood pressure or pulse pressure. Class II hemorrhage involves loss of 15% to 30% of volume loss. Clinical signs include tachycardia and tachypnea. The systolic blood pressure may be only slightly decreased, especially in the supine position, but the pulse pressure is narrowed. Patients with Class II hemorrhage can generally be resuscitated with crystalloid solutions but some may require blood transfusions. With Class III hemorrhage, 30% to 40% of total body volume is lost. Patients with Class III hemorrhage present with obviously inadequate perfusion; marked tachycardia and tachypnea, cool, clammy extremities with significant delayed capillary refill; hypotension; and significant changes in mental status. Class III hemorrhage represents the smallest volume of blood loss that consistently produces a decrease in systolic blood pressure. The resuscitation of these patients requires blood transfusion in addition to crystalloid administration. Class IV hemorrhage involves loss of greater than 40% of blood volume. This represents life-threatening hemorrhage. These patients require immediate transfusion for resuscitation and frequently require immediate surgical intervention.
62. Which of the following statement(s) is/are true concerning traumatic pericardial tamponade?
a. The condition only develops in cases of penetrating trauma
b. Beck’s triad, consisting of muffled heart sounds, decreased pulse pressure, and jugular venous distention can be seen in most patients
c. Two-dimensional echocardiography has replaced diagnostic pericardiocentesis in most hemodynamically stable patients
d. The majority of patients with a small injury to a single chamber of the heart arriving with vital signs at the hospital will die of their injuries
Answer: c
Injuries to the heart resulting in cardiac tamponade can occur from either blunt or penetrating trauma, though penetrating injuries are much more common. Pericardial tamponade occurring after blunt trauma usually results from rupture of a chamber of the heart, with many associated with death at the scene. Penetrating trauma is the usual cause of pericardial tamponade and the outcome is directly related to the character of the weapon. Reported survival rates for small injuries to a single chamber are between 60 and 87%, although patients who arrive moribund do poorly regardless of care. The diagnosis of pericardial tamponade should be considered in any patient with penetrating chest trauma, particularly to the central portion of the chest. The classic Beck’s triad, consisting of muffled heart sounds, decreased pulse pressure, and jugular venous distention, occurs in only the minority of patients. The diagnosis of pericardial tamponade can be somewhat difficult but should be suspected in patients with trauma who remain hypotensive and have no evidence of external blood loss or hemorrhage into the thorax, abdomen, or pelvis. Unfortunately, CVP measurements are neither sensitive or specific for the diagnosis of pericardial tamponade, and are dependent upon the patient’s volume status and the level of agitation. Two-dimensional echocardiography is very sensitive to the presence of pericardial fluid and wall motion abnormalities. If available in a timely fashion, cardiac echo is a very good diagnostic test to rule out cardiac tamponade in a stable patient. Under most circumstances, there is no role for diagnostic pericardiocentesis.
63. The intravenous fluid that a 60 kg., 30-year-old woman with an 80% burn should be given in the first 24 hours following burn injury is:
A. 19.2 liters of 5% glucose in lactated Ringer's.
B. 14.4 liters of lactated Ringer's.
C. 9.6 liters of hypertonic salt solution (sodium concentration 200 mEq. per liter).
D. 7.2 liters of 5% albumin solution.
E. 5.5 liters of the pentafraction component of hydroxyethyl starch.
Answer: B
DISCUSSION: The consensus range for estimating fluid needs of burn patients in the first 24 hours is 2 to 4 ml. of a physiologic crystalloid solution per kilogram body weight per percent of body surface burned. In this patient that would be 9.6 to 19.2 liters of lactated Ringer's solution. The early elevation of circulating levels of catecholamines and glucocorticoids following burn injury induces glycogenolysis, which results in elevated circulating blood glucose levels. Glucose should not be administered in the resuscitation fluids, since the resulting exaggeration of hyperglycemia could induce osmotic diuresis. In the first 24 hours colloid-containing solution is not commonly used, but if it is used even the Evans formula recommends only 1 ml. per kg. body weight per percent of body surface burned. Moreover, patients in one study who received colloid-containing fluids continued to gain weight during the first 3 postinjury days, retained more sodium, and had less urine output than patients who received only crystalloid fluids in the first 24 hours. Hypertonic salt solution is also not commonly used for burn patient resuscitation because of the recently described and surprisingly frequent occurrence of acute renal failure and increased mortality associated with its use. If hypertonic salt is used, the amount infused should be less than 9 liters, to avoid excessive elevation of the serum sodium concentration (i.e., above 160 mEq. per liter). The recommended limit of hydroxyethyl starch infusion is currently 1500 ml. per day. Although a 10% pentastarch form of hydroxyethyl starch has been used to expand the plasma volume of burn patients at the end of the first 24 hours, even as little as 500 ml. of that solution has been reported to prolong both prothrombin and plasma thromboplastin time.
64. Indications for escharotomy of a circumferentially burned right lower limb include all of the following except:
A. Progressively severe deep tissue pain.
B. Coolness of the unburned skin of the toes of the right foot.
C. A pressure of 40 mm. Hg in the anterior compartment of the distal right leg.
D. Edema of the unburned skin of the right foot.
E. Absence of pulsatile flow in the posterior tibial artery.
Answer: BD
DISCUSSION: The blood flow to distal and underlying unburned tissue in a limb can be compromised by vascular compression due to edema formation beneath the unyielding eschar of a full-thickness circumferential burn. The most reliably noninvasive means of monitoring adequacy of the circulation in a circumferentially burned limb is serial examination using the ultrasonic flowmeter. The absence or progressive diminution of pulsatile flow in the posterior tibial artery in the lower limb or the palmar arch arteries in the upper limb indicates a need for escharotomy. Delayed capillary refilling, cyanosis of the digits, and progressively severe paresthesias, particularly deep tissue pain, are all clinical signs that may indicate vascular compromise and should be monitored if an ultrasonic flowmeter is not available. Persistent deep tissue pain and progressively severe paresthesias are the most reliable of the nonspecific clinical signs. A muscle compartment pressure that exceeds 30 mm. Hg, which is greater than normal capillary pressure, has also been used as an indication for escharotomy in burn patients. Edema and coolness to the touch of distal unburned tissue commonly accompany thermal injury and are not useful in assessing the need for escharotomy.
65. Which of the following is/are true about inhalation injury in burn patients?
A. A chest x-ray obtained within 24 hours of injury is an accurate means of diagnosis.
B. Its presence characteristically necessitates administration of resuscitation fluids in excess of estimated volume.
C. When moderate or severe, it exerts a comorbid effect that is related to both extent of burn and the age of the patient.
D. It increases the prevalence of bronchopneumonia.
E. Prophylactic high-frequency ventilation reduces the occurrence of pneumonia and the mortality in burn patients with inhalation injury.
Answer: BCDE
DISCUSSION: Extensive inflammatory changes are evoked in the airway following the inhalation of smoke and other irritating products of incomplete combustion. Clinical signs are nonspecific and may be delayed. Chest x-rays are also unreliable in detecting even severe inhalation injury. Chest x-rays taken within 24 hours of injury were found to be falsely negative in 92% of 106 patients with inhalation injury. Fiberoptic bronchoscopic examination is the most reliable single means of diagnosing inhalation injury of the large airways, but in patients who inhaled finely particulate smoke the large airways may show little if any inflammatory change. The distance smoke particles travel before deposition in the airways is inversely related to particle size. When the smoke particle mass median diameter is less than 0.5 mm., deposition occurs in the terminal bronchioles and alveoli. In such patients, inhalation injury is best identified by prolonged retention of xenon 133 as assessed by a ventilation perfusion lung scan.
Historically, fluid restriction was recommended for patients with inhalation injury, but in recent years it has become obvious that such patients typically require more resuscitation fluid than the volume estimated by commonly used formulas. Edema of the small airways and occlusion due to endobronchial sloughing and inspissation predispose burn patients to develop pneumonia. In one study, 46% of burn patients with inhalation injury developed pneumonia and 69% of the pneumonias occurred in the first postburn week. The comorbid effect of moderate to severe inhalation injury is related to both age and burn size and increases mortality by a maximum of 20% above that predicted on the basis of age and burn size in patients whose burn injury alone would be associated with a 75% likelihood of death. In patients with only mild inhalation injury there is little if any increase in mortality above that predicted on the basis of age and burn size alone. Prophylactic use of high-frequency percussive ventilation minimizes airway collapse and atelectatic changes, as a consequence of which the incidence of pneumonia is reduced and survival is significantly increased.
66. Adequacy of fluid resuscitation in burn patients is indicated by which of the following?
A. Urine output of 45 ml. per hr. in a 70-kg. 30-year-old man with flame burns involving 55% of the total body surface.
B. Hourly urine output of 7 ml. in a 7-kg. 15-month-old child with burns involving 40% of the total body surface.
C. A pulmonary capillary wedge pressure of 17 to 20 mm. Hg.
D. Hourly output of 40 ml. of port wine–colored urine in an 80-kg. male who has severe high-voltage electric injury of the right arm and left leg.
E. A urinary sodium concentration of 4 mEq. per liter.
Answer: ABC
DISCUSSION: The goal of burn patient resuscitation is the maintenance of vital organ function at the least immediate or delayed physiologic cost. Fluid resuscitation of burn patients does not need to be a test of maximum renal function. Adequacy of volume replacement and of renal blood flow are indicated by an hourly urine output of 30 to 50 ml. in adults and 1 ml. per kg. per hr. in children weighing less than 30 kg. In patients with extensive muscle damage caused by high-voltage electric injury, heavy loads of hemochromagens give the urine the appearance of port wine. Such patients are prone to develop acute renal failure unless brisk urine output is maintained until the pigment concentration is reduced to insignificant levels. Fluid should be infused into such patients at the rate needed to achieve an hourly urine output of 75 to 100 ml., but if the patient does not respond to increased fluid input with an increase in urine volume and clearing of the heme pigments, a diuretic should be given. A pulmonary capillary wedge pressure of 17 to 20 mm. Hg is indicative of an adequate circulating blood volume, but a urinary sodium concentration of less than 20 mEq. per liter is consistent with an intravascular volume deficit.
67. Common electrolyte changes during and after resuscitation in a patient with a burn of 65% of the total body surface include:
A. A serum sodium concentration of 128 mEq. per liter following 48 hours of resuscitation fluid therapy.
B. A serum sodium concentration of 152 mEq. per liter on the fifth postburn day in a 75-kg. male with a 75% burn who has received only calculated maintenance fluids each day following successful resuscitation.
C. A serum potassium concentration of 5.7 mEq. per liter as a consequence of the destruction of red cells and other tissues in a patient with high-voltage electrical injury.
D. Hypokalemia due to the kaliuretic effect of 0.5% silver nitrate soaks.
E. Hypocalcemia with a low ionized calcium level on the third postburn day as a consequence of dilution and hypoalbuminemia.
Answer: ABC
DISCUSSION: At the end of the first 48 hours of resuscitation, when lactated Ringer's solution is used in the first 24 hours and colloid-containing fluid and electrolyte-free fluid in the second 24 hours, modest hyponatremia (serum sodium concentration of 128 to 130 mEq. per liter) is commonly observed but requires no treatment. The total body salt load is actually increased, and appropriate fluid management permits the increased evaporative water loss to correct that imbalance. The most common postresuscitation fluid and electrolyte disturbance is hypernatremia associated with dehydration due to inadequate replacement of insensible water loss. The hourly insensible water loss, which far exceeds maintenance fluid requirements in uninjured patients, can be calculated thus:
Insensible water loss (in ml./hr.)=(25 + % of body surface burned) × total body surface area (sq. m.)
The release of potassium from red cells and other tissues injured by the burn or by electrical current can cause usually modest hyperkalemia. If acidosis occurs, the hyperkalemia may be exaggerated to symptomatic levels that require treatment. Hypokalemia can be induced following resuscitation by the kaliuretic effect of sulfamylon burn cream, but the hypokalemia associated with 0.5% silver nitrate soak treatment is due to transeschar leaching of potassium. Hypocalcemia is frequently associated with hypoalbuminemia as a consequence of hemodilution by the resuscitation fluid and the cytokine-induced reprogramming of hepatic protein synthesis. In such cases ionized calcium levels are commonly normal.
68. The clinical and histologic signs of invasive burn wound infection include which of the following?
A. Focal dark red or dark brown discoloration of the eschar.
B. Delayed separation of the eschar.
C. Conversion of an area of partial-thickness burn to full-thickness necrosis.
D. The presence of micro-organisms in the unburned subcutaneous tissue in a burn wound biopsy specimen.
E. Perineural and perivascular microbial migration through the eschar with proliferation of micro-organisms in the subeschar space.
Answer: ACD
DISCUSSION: It is essential to examine the entire burn wound at the time of the daily cleansing to identify invasive burn wound infection at the earliest possible time. The appearance of focal areas of dark red or dark brown discoloration are the most common changes indicative of burn wound infection, but similar changes may be caused by hemorrhage due to local trauma or maceration. Accelerated separation of the eschar is often produced by burn wound infections, but delayed separation of the eschar is indicative of effective control of the microbial population in the burn wound. Conversion of an area of partial-thickness burn to full-thickness necrosis is the most reliable clinical sign of invasive burn wound infection. Identification of such a change mandates histologic examination of a burn wound biopsy, which is the only reliable means of differentiating the colonization of nonviable tissue from the invasion of viable tissue. Identification of micro-organisms in the unburned viable tissue of a burn wound biopsy confirms the diagnosis of invasive burn wound infection. Microbial migration along the skin appendages, terminal nerve radicles, and thrombosed capillaries in the eschar and heavy growth of micro-organisms in the subeschar space are manifestations of the colonization of nonviable tissue and represent the mechanisms by which eschar separation occurs.
69. The treatment of invasive burn wound infection may include which of the following?
A. Subeschar infusion of half the daily dose of a broad-spectrum penicillin suspended in 1 liter of normal saline.
B. Use of 0.5% silver nitrate soaks for topical therapy.
C. Specific systemic antibiotic therapy.
D. Excision and immediate autografting.
E. Amputation when the infection has extended to involve underlying muscle.
Answer: ACE
DISCUSSION: The Pseudomonas organisms that most commonly cause invasive bacterial burn wound infection are typically sensitive to high concentrations of broad-spectrum penicillins. When the diagnosis of invasive Pseudomonas burn wound infection has been made, one half of the daily dose of a broad-spectrum penicillin, typically piperacillin, suspended in 1 liter of normal saline, should be infused into the subeschar tissues beneath the infected wound. A number 20 spinal needle should be used for the infusion, to minimize the number of injection sites. Following a second subeschar infusion of the broad-spectrum penicillin just prior to operation, the infected tissue should be excised. The excised wounds should not be autografted but covered with a biologic dressing or a dressing soaked with an antimicrobial solution such as 5% mafenide acetate. The patient is returned to the operating room in 24 to 48 hours to examine the excised wound and assess the adequacy of the débridement. The frequency of perilymphatic and perivascular proliferation of invading Pseudomonas organisms is associated with a risk of metastatic spread to remote organs or tissues. Consequently, systemic antimicrobial therapy should be instituted based on the sensitivity patterns of the resident microbial flora and adjusted as necessary on the basis of the patient's culture and sensitivity results. Amputation is frequently necessary to control invasive burn wound infection when a phycomycotic infection on a limb has traversed the investing fascia and involves significant amounts of the subfascial tissue.
70. The treatment of patients with high-voltage electric injury differs from that of patients with conventional thermal injury with respect to the need for:
A. Fasciotomy.
B. Hemodialysis.
C. Amputation.
D. Pulse oximetry.
E. Prehospital cardiopulmonary resuscitation.
Answer: ABCE
DISCUSSION: Both lightning injury and contact with electric current can induce cardiopulmonary arrest due to either asystole or fibrillation. Cardiopulmonary resuscitation must be initiated at the site of injury if cardiac arrest is present. Cardiac arrhythmias may also occur following resuscitation, necessitating electrocardiographic (ECG) monitoring for at least 48 hours following injury in patients with a history of loss of consciousness or an abnormal ECG. Tissue damage and tissue destruction beneath the investing fascia can result in the formation of edema that increases muscle compartment pressure to a level that necessitates fasciotomy (> 30 mm. Hg). The current flow in a limb in contact with high-voltage current can be so great as to damage even the periosseous muscles and make amputation necessary. Liberation of hemochromogens as a consequence of deep tissue injury is associated with an increased incidence of acute renal failure necessitating hemodialysis. Electric injury does not influence the need for monitoring by pulse oximetry, and in fact the destruction of deep tissue in a limb may preclude application of the pulse oximeter to that extremity.
71. Therapeutic interventions needed for specific chemical agents include which of the following?
A. Prolonged saline irrigation of eyes injured by concentrated sodium hydroxide using a scleral lens with an irrigating sidearm.
B. Administration of an emetic agent as immediate treatment following lye ingestion.
C. Intra-arterial infusion of calcium gluconate for relief of refractory deep tissue pain due to hydrofluoric acid injury.
D. Use of propylene glycol to remove residual phenol following water lavage.
E. Application of 5% copper sulfate solution soaks to areas of embedded particles of white phosphorus.
Answer: ACD
DISCUSSION: An eye injured by a strong chemical agent must be irrigated immediately at the site of the accident to minimize corneal damage. Prolonged irrigation for 12 to 72 hours is recommended for eyes injured by a strong alkali solution. Irrigation is difficult because of blepharospasm unless a modified scleral contact lens with an irrigating sidearm is used. Emetics should be avoided in the early treatment of patients following chemical ingestion since additional injury of the esophagus, oropharynx, and upper airway may be caused as the chemical is regurgitated. The intra-arterial infusion of calcium gluconate has been reported to limit tissue damage and relieve pain, but local excision of the involved tissue may be necessary for definitive control of pain and removal of the injured tissue.
Even though phenol is only slightly soluble in water, initial water lavage of burns caused by phenol should be carried out. Following that initial lavage, the involved area should be washed with a lipophilic solvent such as polyethylene glycol, propylene glycol, or glycerol to remove the residual phenol. A dilute 0.5% to 1% solution of copper sulfate can be used as a wash to facilitate identification and impede the ignition of embedded phosphorus particles. If excessive amounts of copper sulfate are absorbed through the injured tissues, intravascular hemolysis can occur and may cause renal failure. Consequently, one should avoid the use of more concentrated solutions of copper sulfate and should never apply the copper sulfate solution as a soak. The important principle of treatment is to prevent ignition of the particles by preventing their exposure to air, and that can be done most safely by applying an occlusive dressing soaked with saline or water.
72. Characteristics of the hypermetabolic response to burn injury include:
A. Elevation of core temperature, skin temperature, and core-to-skin heat transfer.
B. Ambient temperature dependency of metabolic rate.
C. A marked increase of blood flow to the burn wound.
D. A curvilinear relationship to the extent of burn.
E. Oxidation of stored lipid as the major source of metabolic energy.
Answer: ACE
DISCUSSION: At thermal neutral and higher temperatures, the core temperature, skin temperature, and core-to-skin heat transfer in burn patients remain elevated, but metabolic rate can be diminished in patients with burns of more than 50% of the body surface by maintaining the ambient temperature above 30؛ C. Blocking evaporative water loss by application of an impermeable membrane is not attended by a consistent diminution in metabolic rate, indicating that the burn patient is not externally cold but is internally warm. The hypermetabolism in burn patients is temperature sensitive but not temperature dependent. Even though earlier measurements described a curvilinear relationship between metabolic rate and extent of burn, recent measurements have shown that metabolic rate increases in linear fashion and rises to levels of twice normal in patients with burns of 75% and more of the total body surface. Lipid stores are the major source of metabolic fuel that is oxidized for energy, and not lean body mass, which undergoes proteolysis to provide the amino acids necessary for protein synthesis and wound healing as well as gluconeogenic processes that provide fuel for tissues requiring glucose. Blood flow to a burned limb is markedly increased as compared with flow in an unburned limb of the same patient, and the flow increase is directed to the wound per se, not the underlying muscles.
73. A 32-year-old mountain climber who struck his head in a fall lay in the snow overnight before he could be rescued and brought to the hospital. Upon admission he is semicomatose and not shivering, with a pulse rate of 48 beats per minute and a blood pressure of 80/50 mm. Hg. His rectal temperature as measured by a standard thermometer is reported as 34؛ C. All the digits on both feet appear to be frozen. Treatment for this patient should include:
A. Administration of inotropic and chronotropic vasoactive agents.
B. Intra-arterial infusion of vasodilating agents.
C. Infusion of lactated Ringer's solution warmed to 40؛ C.
D. Immersion in a circulating water bath heated to 40؛ C.
E. Excision of damaged tissue within 48 hours after thawing.
Answer: CD
DISCUSSION: A standard clinical thermometer will not measure body temperatures below 34؛ C. This patient's clinical condition—depressed mental status, bradycardia, and hypotension—indicates that the patient is likely suffering from severe hypothermia and, so, requires prompt active rewarming by immersion in a water bath at 40؛ C. or the use of partial cardiopulmonary bypass, if available, and the administration of resuscitation fluid warmed to 40؛ C. Vasoactive agents do not treat the basic pathology in hypothermic patients and are typically ineffective. Vasodilating agents will be of little if any value in the treatment of the frozen tissue in the feet since histologic studies have indicated that the vasculature in freeze-injured tissue is dilated, not constricted. Since assessment of tissue viability immediately after thawing is difficult and often erroneous, one should await clear demarcation of dead tissue before undertaking surgical excision of damaged tissue.
74. Valid points in the management of burns on special areas include:
a. The large majority of genital burns are best managed by immediate excision and autografting
b. All digits with deep dermal and full-thickness burns should be immobilized with six weeks of axial Kirschner wire fixation
c. Deep thermal burns of the central face are best managed with immediate excision and autografting
d. Burns of the external ear are commonly complicated by acute suppurative chondritis if topical mafenide acetate is not applied
Answer: d
Because of the thickness and deep appendages of the skin of the central face, relatively deep burns of these areas frequently heal. This is fortunate, because it is difficult to achieve a favorable result with primary excision and grafting of the central face. Management of the burned hand is dictated by the depth of injury. Superficial burns are managed with elevation, topical antimicrobials, and full passive range of motion for each joint twice daily. Deep, partial and full-thickness injuries are best managed by excision and sheet grafting as soon as practical. Hands are immobilized in a functional position for seven days after surgery before passive and active therapy is resumed. Fourth degree hand burns, which involve the underlying extensor mechanism, joint capsules or bone are significantly more difficult management problems and are managed by staged sheet autografting and often benefit from temporary axial Kirschner wire fixation of open and unstable interphalangeal or metacarpophalangeal joints. Burns of the external ear are treated with twice daily cleansing and application of mafenide acetate. Deep burns of the external ear are commonly complicated by acute suppurative chondritis if topical mafenide acetate is not applied. In general, the practice for deep genital burns is to manage these limited surface area injuries with topical therapy for a period of two to three weeks unless the wounds are remarkably deep. Unhealed injuries are debrided and grafted with sheet autograft at this time, with generally excellent cosmetic and functional results.
75. The hypermetabolic response seen in patients with large burns, who are successfully resuscitated, is thought to be driven by which of the following factors?
a. Deficient gastrointestinal barrier function
b. Bacterial contamination of the burn wound
c. Evaporative heat loss
d. Changes in hypothalamic function
Answer: a, b, c, d
The physiologic challenge of a burn in excess of 20% of the body surface frequently results in an initial decrease in cardiac output and metabolic rate. Subsequently, effected by a complex cascade of mediators, a hypermetabolic response is seen with a near doubling of cardiac output and resting energy expenditure over the next 24 to 48 hours in those who are successfully resuscitated. The magnitude of this response peaks in those with injuries of 60% or more of the body surface at as high as twice the normal basal metabolic rate. The etiology of the hypermetabolic response is not entirely understood but is assumed to involve a combination of factors including a change in hypothalamic function with coincident increases in glucagon, cortisol and catecholamine secretion, deficient gastrointestinal barrier function with translocation of bacteria and their byproducts, bacterial contamination of the burn wound with systemic release of similar products from this source, and some element of enhanced heat loss via transeschar evaporation of fluid. An important element of successful management of patients who have sustained large injuries is support of this response through the provision of adequate quantity and quality of substrate.
76. Which of the following statement(s) is/are true concerning inhalation injury?
a. The physiology of these injuries include upper airway obstruction secondary to progressive edema, reactive bronchospasm from aerosolized irritants, and microatelectasis from loss of surfactant and alveolar edema
b. Endotracheal intubation is indicated immediately in all patients with suspected inhalation injury
c. Distal airway injuries are usually caused by heat injury
d. Peak inspiratory pressures of > 40 cm of water are indicated to maintain functional residual capacity
Answer: a
The pathophysiology of inhalation injury is complex and varies with the aerosolized toxins particular to the circumstances of individual injuries. However, these injuries routinely demonstrate the following: 1) upper airway obstruction secondary to progressive edema; 2) reactive bronchospasm from aerosolized irritants; 3) small airway occlusion initially from edema and subsequently from sloughed endotracheal debris and loss of ciliary clearance mechanisms; 4) microatelectasis from the loss of surfactant and alveolar edema; and 5) interstitial and alveolar edema secondary to loss of capillary integrity. The physiologic consequences of these aberrations are upper and lower airway obstruction, increased airway resistance, decreased compliance, and an increase in the dead space to tidal volume ratio and intrapulmonary shunting.
Upper airway obstruction is best managed with prompt endotracheal intubation which is maintained for 48 to 72 hours and elevation the head. In equivocal cases, bronchoscopy is performed and patients with significant airway edema are intubated using the bronchoscope as a stylet. Although severe steam inhalation can result in direct heat injury to the distal tracheobronchial tree, more distal airway injuries are usually caused by aerosolized toxins rather than thermal injury, as the upper airway is a highly effective heat sink. Although moderate inflating pressures will help expand recruitable segments, peak inspiratory pressures in excess of 40 cm H2O should be avoided because they are associated with both overt barotrauma as well as more subtle overpressure injuries to the pulmonary microvasculature and alveoli which themselves exacerbate respiratory failure. High inflating pressures are also ineffective in recruiting additional lung, because the compliance decrements are not homogeneous and high pressures simply over distended more compliant segments.
77. Which of the following statement(s) is/are true concerning the initial fluid resuscitation of a burn patient?
a. Rigid adherence to the Modified Brooke formula is advised
b. In general, children require less fluid than that predicted by standard formulae
c. Patients with inhalation injuries require less fluid than predicted by standard formulae
d. Dextrose should not be given as the primary resuscitative fluid for any age group
e. Most resuscitative formulae withhold colloid solutions until 24 hours post-injury
Answer: e
The large number of fluid resuscitation formulae in common use is attributed to the fact that no formula accurately predicts fluid requirements in every patient. No formula can replace a physician at the bedside repeatedly evaluating the patient’s physiology through the resuscitative period. A reasonable consensus formula is the Modified Brooke formula, however, regardless of the formula chosen to initiate resuscitation, subsequent fluid administration is best guided by regular assessment of the resuscitation end points, rather than prediction of any formula. Vasoactive mediators released from the injured tissue result in diffuse capillary leaks seen shortly after major burn injury with resulting extravasation of both crystalloid and colloid for the first 18 to 24 hours after burn. The pathophysiology explains the enormous volume requirements seen in such patients and is the reason that most resuscitative formulae withhold colloid until 24 hours post-injury. Children have been found to commonly require fluid in excess of that predicted by several formulae. These requirements are generated if one uses a urine output of 1–2 cc/kg/hour as a resuscitation end point. These needs are real in infants and very young children whose renal concentrating abilities are not completely mature. However, in toddlers and older children whose concentrating abilities are more mature, targeting urine flow of 0.5–1 cc/kg/hour results in overall fluid requirements closer to that of an adult and less overall edema. Patients with inhalation injury have demonstrated to have overall volume requirements greater than that predicted by standard formulae, possibly secondary to release of vasoactive mediators from injured burned parenchyma. During the first 24 hours, Ringer’s lactate is the primary resuscitative fluid. Because children less than 10 kg can develop hypoglycemia if glucose is not administered, Ringer’s lactate or half normal saline with 5% dextrose at a maintenance rate is given along with the reduced amount of Ringer’s lactate. Dextrose containing fluids should not be given as a primary resuscitative fluid in adults, as hyperglycemia and osmotic diuresis will result.
78. Which of the following statement(s) is/are true concerning techniques of burn excision, and temporary and definitive wound closure?
a. Techniques to conserve blood include subeschar injection of dilute epinephrine solution, exsanguination of the extremity and inflation of a pneumatic tourniquet
b. Fresh or cryopreserved human allograft is usually rejected within 2 to 4 weeks
c. A common use for human allograft is as a physiologic cover for selected clean superficial wounds as they epithelialize
d. A donor site can only serve as a single source for autograft
Answer: a, b
A common argument against the policy of early burn wound excision is the prodigious blood loss which has been associated with these procedures. However, modern blood conserving practices as well as earlier excision of wounds have diminished this concern. Tangential excision of the torso, neck and head are done after subeschar injection of dilute epinephrine solutions. Tangential excisions of the extremities are done after exsanguination and inflation of a pneumatic tourniquet. Once necrotic eschar is excised to a bed of viable tissue, immediate biologic closure is mandatory. Ideally, immediate autografting is performed. When donor sites are insufficient for this purpose, a temporary biologic cover must be chosen while awaiting healing of donor sites for further use. Such covers should prevent desiccation and provide a vapor and bacterial barrier over the excised wound. Fresh or cryopreserved human allograft is most appropriate for this use. Once placed on a viable wound bed, it will vascularize and provide physiologic wound closure until rejected 2 to 4 weeks later at which time or before, it is replaced with reharvested autograft. A second common use for biologic dressings is a physiologic cover for selected clean superficial wounds as they epithelialize, which minimizes the pain associated with open partial thickness burns. Allograft, screened for malignant and infectious diseases, a precarious resource, is however, not commonly used as a biologic dressing in these circumstances. For this purpose, reconstituted porcine xenograft should be used.
79. Which of the following statement(s) is/are true concerning topical antimicrobials in common use in the United States today?
a. Of the common topical antimicrobials, only mafenide acetate is painful upon application
b. The use of 0.5% silver nitrate is associated with trans-eschar leeching of sodium and potassium from the wound
c. Silver sulfadiazine has the best eschar penetration
d. Silver sulfadiazine, mafenide acetate, and 0.5% silver nitrate all have a broad spectrum activity, however, only silver nitrate has anti-fungal activity
Answer: a, b, d
80. The anthropometric changes observed as a patient progresses from infancy to adulthood include which of the following statement(s)?
a. The major anthropometric changes involve the head and torso
b. A decrease in the relative size of the head from 18% to 9% of the body’s surface area occurs
c. The total surface area of the legs increases from 14 to 18%
d. The upper extremities increase to 12% of the body surface area
Answer: b, c
An accurate assessment of burn size can be made early and is important to the initial management as resuscitative fluid administration is primarily determined by overall burn size. Burn size in children is best estimated with an age-specific chart, because the child’s body proportions change with growth. The major anthropometric change involves the head and legs. The infant’s head represents 18% of the total body surface and legs 14%. In older adolescents and adults, the head represents 9% of the body surface and the legs 18%. Each upper extremity in the adult is usually considered to represent 9% of the total body surface area.
a. Class I shock is equivalent to voluntary blood donation
b. In Class II shock there will be evidence of change in vital signs with tachycardia, tachypnea and a significant decrease in systolic blood pressure
c. Class III hemorrhage can usually be managed by simple administration of crystalloid solution
d. Class IV hemorrhage involves loss of over 40% of blood volume loss and can be classified as life-threatening
Answer: a, d
The classification of hemorrhagic shock as defined by the ATLS classification system of the American College of Surgeons is useful in comprehending the manifestations and physiologic changes associated with shock. Mild hemorrhage, up to 15% of total blood volume, is exemplified by voluntary blood donation. In the supine position, there are no measurable changes in heart or respiratory rates, blood pressure or pulse pressure. Class II hemorrhage involves loss of 15% to 30% of volume loss. Clinical signs include tachycardia and tachypnea. The systolic blood pressure may be only slightly decreased, especially in the supine position, but the pulse pressure is narrowed. Patients with Class II hemorrhage can generally be resuscitated with crystalloid solutions but some may require blood transfusions. With Class III hemorrhage, 30% to 40% of total body volume is lost. Patients with Class III hemorrhage present with obviously inadequate perfusion; marked tachycardia and tachypnea, cool, clammy extremities with significant delayed capillary refill; hypotension; and significant changes in mental status. Class III hemorrhage represents the smallest volume of blood loss that consistently produces a decrease in systolic blood pressure. The resuscitation of these patients requires blood transfusion in addition to crystalloid administration. Class IV hemorrhage involves loss of greater than 40% of blood volume. This represents life-threatening hemorrhage. These patients require immediate transfusion for resuscitation and frequently require immediate surgical intervention.
62. Which of the following statement(s) is/are true concerning traumatic pericardial tamponade?
a. The condition only develops in cases of penetrating trauma
b. Beck’s triad, consisting of muffled heart sounds, decreased pulse pressure, and jugular venous distention can be seen in most patients
c. Two-dimensional echocardiography has replaced diagnostic pericardiocentesis in most hemodynamically stable patients
d. The majority of patients with a small injury to a single chamber of the heart arriving with vital signs at the hospital will die of their injuries
Answer: c
Injuries to the heart resulting in cardiac tamponade can occur from either blunt or penetrating trauma, though penetrating injuries are much more common. Pericardial tamponade occurring after blunt trauma usually results from rupture of a chamber of the heart, with many associated with death at the scene. Penetrating trauma is the usual cause of pericardial tamponade and the outcome is directly related to the character of the weapon. Reported survival rates for small injuries to a single chamber are between 60 and 87%, although patients who arrive moribund do poorly regardless of care. The diagnosis of pericardial tamponade should be considered in any patient with penetrating chest trauma, particularly to the central portion of the chest. The classic Beck’s triad, consisting of muffled heart sounds, decreased pulse pressure, and jugular venous distention, occurs in only the minority of patients. The diagnosis of pericardial tamponade can be somewhat difficult but should be suspected in patients with trauma who remain hypotensive and have no evidence of external blood loss or hemorrhage into the thorax, abdomen, or pelvis. Unfortunately, CVP measurements are neither sensitive or specific for the diagnosis of pericardial tamponade, and are dependent upon the patient’s volume status and the level of agitation. Two-dimensional echocardiography is very sensitive to the presence of pericardial fluid and wall motion abnormalities. If available in a timely fashion, cardiac echo is a very good diagnostic test to rule out cardiac tamponade in a stable patient. Under most circumstances, there is no role for diagnostic pericardiocentesis.
63. The intravenous fluid that a 60 kg., 30-year-old woman with an 80% burn should be given in the first 24 hours following burn injury is:
A. 19.2 liters of 5% glucose in lactated Ringer's.
B. 14.4 liters of lactated Ringer's.
C. 9.6 liters of hypertonic salt solution (sodium concentration 200 mEq. per liter).
D. 7.2 liters of 5% albumin solution.
E. 5.5 liters of the pentafraction component of hydroxyethyl starch.
Answer: B
DISCUSSION: The consensus range for estimating fluid needs of burn patients in the first 24 hours is 2 to 4 ml. of a physiologic crystalloid solution per kilogram body weight per percent of body surface burned. In this patient that would be 9.6 to 19.2 liters of lactated Ringer's solution. The early elevation of circulating levels of catecholamines and glucocorticoids following burn injury induces glycogenolysis, which results in elevated circulating blood glucose levels. Glucose should not be administered in the resuscitation fluids, since the resulting exaggeration of hyperglycemia could induce osmotic diuresis. In the first 24 hours colloid-containing solution is not commonly used, but if it is used even the Evans formula recommends only 1 ml. per kg. body weight per percent of body surface burned. Moreover, patients in one study who received colloid-containing fluids continued to gain weight during the first 3 postinjury days, retained more sodium, and had less urine output than patients who received only crystalloid fluids in the first 24 hours. Hypertonic salt solution is also not commonly used for burn patient resuscitation because of the recently described and surprisingly frequent occurrence of acute renal failure and increased mortality associated with its use. If hypertonic salt is used, the amount infused should be less than 9 liters, to avoid excessive elevation of the serum sodium concentration (i.e., above 160 mEq. per liter). The recommended limit of hydroxyethyl starch infusion is currently 1500 ml. per day. Although a 10% pentastarch form of hydroxyethyl starch has been used to expand the plasma volume of burn patients at the end of the first 24 hours, even as little as 500 ml. of that solution has been reported to prolong both prothrombin and plasma thromboplastin time.
64. Indications for escharotomy of a circumferentially burned right lower limb include all of the following except:
A. Progressively severe deep tissue pain.
B. Coolness of the unburned skin of the toes of the right foot.
C. A pressure of 40 mm. Hg in the anterior compartment of the distal right leg.
D. Edema of the unburned skin of the right foot.
E. Absence of pulsatile flow in the posterior tibial artery.
Answer: BD
DISCUSSION: The blood flow to distal and underlying unburned tissue in a limb can be compromised by vascular compression due to edema formation beneath the unyielding eschar of a full-thickness circumferential burn. The most reliably noninvasive means of monitoring adequacy of the circulation in a circumferentially burned limb is serial examination using the ultrasonic flowmeter. The absence or progressive diminution of pulsatile flow in the posterior tibial artery in the lower limb or the palmar arch arteries in the upper limb indicates a need for escharotomy. Delayed capillary refilling, cyanosis of the digits, and progressively severe paresthesias, particularly deep tissue pain, are all clinical signs that may indicate vascular compromise and should be monitored if an ultrasonic flowmeter is not available. Persistent deep tissue pain and progressively severe paresthesias are the most reliable of the nonspecific clinical signs. A muscle compartment pressure that exceeds 30 mm. Hg, which is greater than normal capillary pressure, has also been used as an indication for escharotomy in burn patients. Edema and coolness to the touch of distal unburned tissue commonly accompany thermal injury and are not useful in assessing the need for escharotomy.
65. Which of the following is/are true about inhalation injury in burn patients?
A. A chest x-ray obtained within 24 hours of injury is an accurate means of diagnosis.
B. Its presence characteristically necessitates administration of resuscitation fluids in excess of estimated volume.
C. When moderate or severe, it exerts a comorbid effect that is related to both extent of burn and the age of the patient.
D. It increases the prevalence of bronchopneumonia.
E. Prophylactic high-frequency ventilation reduces the occurrence of pneumonia and the mortality in burn patients with inhalation injury.
Answer: BCDE
DISCUSSION: Extensive inflammatory changes are evoked in the airway following the inhalation of smoke and other irritating products of incomplete combustion. Clinical signs are nonspecific and may be delayed. Chest x-rays are also unreliable in detecting even severe inhalation injury. Chest x-rays taken within 24 hours of injury were found to be falsely negative in 92% of 106 patients with inhalation injury. Fiberoptic bronchoscopic examination is the most reliable single means of diagnosing inhalation injury of the large airways, but in patients who inhaled finely particulate smoke the large airways may show little if any inflammatory change. The distance smoke particles travel before deposition in the airways is inversely related to particle size. When the smoke particle mass median diameter is less than 0.5 mm., deposition occurs in the terminal bronchioles and alveoli. In such patients, inhalation injury is best identified by prolonged retention of xenon 133 as assessed by a ventilation perfusion lung scan.
Historically, fluid restriction was recommended for patients with inhalation injury, but in recent years it has become obvious that such patients typically require more resuscitation fluid than the volume estimated by commonly used formulas. Edema of the small airways and occlusion due to endobronchial sloughing and inspissation predispose burn patients to develop pneumonia. In one study, 46% of burn patients with inhalation injury developed pneumonia and 69% of the pneumonias occurred in the first postburn week. The comorbid effect of moderate to severe inhalation injury is related to both age and burn size and increases mortality by a maximum of 20% above that predicted on the basis of age and burn size in patients whose burn injury alone would be associated with a 75% likelihood of death. In patients with only mild inhalation injury there is little if any increase in mortality above that predicted on the basis of age and burn size alone. Prophylactic use of high-frequency percussive ventilation minimizes airway collapse and atelectatic changes, as a consequence of which the incidence of pneumonia is reduced and survival is significantly increased.
66. Adequacy of fluid resuscitation in burn patients is indicated by which of the following?
A. Urine output of 45 ml. per hr. in a 70-kg. 30-year-old man with flame burns involving 55% of the total body surface.
B. Hourly urine output of 7 ml. in a 7-kg. 15-month-old child with burns involving 40% of the total body surface.
C. A pulmonary capillary wedge pressure of 17 to 20 mm. Hg.
D. Hourly output of 40 ml. of port wine–colored urine in an 80-kg. male who has severe high-voltage electric injury of the right arm and left leg.
E. A urinary sodium concentration of 4 mEq. per liter.
Answer: ABC
DISCUSSION: The goal of burn patient resuscitation is the maintenance of vital organ function at the least immediate or delayed physiologic cost. Fluid resuscitation of burn patients does not need to be a test of maximum renal function. Adequacy of volume replacement and of renal blood flow are indicated by an hourly urine output of 30 to 50 ml. in adults and 1 ml. per kg. per hr. in children weighing less than 30 kg. In patients with extensive muscle damage caused by high-voltage electric injury, heavy loads of hemochromagens give the urine the appearance of port wine. Such patients are prone to develop acute renal failure unless brisk urine output is maintained until the pigment concentration is reduced to insignificant levels. Fluid should be infused into such patients at the rate needed to achieve an hourly urine output of 75 to 100 ml., but if the patient does not respond to increased fluid input with an increase in urine volume and clearing of the heme pigments, a diuretic should be given. A pulmonary capillary wedge pressure of 17 to 20 mm. Hg is indicative of an adequate circulating blood volume, but a urinary sodium concentration of less than 20 mEq. per liter is consistent with an intravascular volume deficit.
67. Common electrolyte changes during and after resuscitation in a patient with a burn of 65% of the total body surface include:
A. A serum sodium concentration of 128 mEq. per liter following 48 hours of resuscitation fluid therapy.
B. A serum sodium concentration of 152 mEq. per liter on the fifth postburn day in a 75-kg. male with a 75% burn who has received only calculated maintenance fluids each day following successful resuscitation.
C. A serum potassium concentration of 5.7 mEq. per liter as a consequence of the destruction of red cells and other tissues in a patient with high-voltage electrical injury.
D. Hypokalemia due to the kaliuretic effect of 0.5% silver nitrate soaks.
E. Hypocalcemia with a low ionized calcium level on the third postburn day as a consequence of dilution and hypoalbuminemia.
Answer: ABC
DISCUSSION: At the end of the first 48 hours of resuscitation, when lactated Ringer's solution is used in the first 24 hours and colloid-containing fluid and electrolyte-free fluid in the second 24 hours, modest hyponatremia (serum sodium concentration of 128 to 130 mEq. per liter) is commonly observed but requires no treatment. The total body salt load is actually increased, and appropriate fluid management permits the increased evaporative water loss to correct that imbalance. The most common postresuscitation fluid and electrolyte disturbance is hypernatremia associated with dehydration due to inadequate replacement of insensible water loss. The hourly insensible water loss, which far exceeds maintenance fluid requirements in uninjured patients, can be calculated thus:
Insensible water loss (in ml./hr.)=(25 + % of body surface burned) × total body surface area (sq. m.)
The release of potassium from red cells and other tissues injured by the burn or by electrical current can cause usually modest hyperkalemia. If acidosis occurs, the hyperkalemia may be exaggerated to symptomatic levels that require treatment. Hypokalemia can be induced following resuscitation by the kaliuretic effect of sulfamylon burn cream, but the hypokalemia associated with 0.5% silver nitrate soak treatment is due to transeschar leaching of potassium. Hypocalcemia is frequently associated with hypoalbuminemia as a consequence of hemodilution by the resuscitation fluid and the cytokine-induced reprogramming of hepatic protein synthesis. In such cases ionized calcium levels are commonly normal.
68. The clinical and histologic signs of invasive burn wound infection include which of the following?
A. Focal dark red or dark brown discoloration of the eschar.
B. Delayed separation of the eschar.
C. Conversion of an area of partial-thickness burn to full-thickness necrosis.
D. The presence of micro-organisms in the unburned subcutaneous tissue in a burn wound biopsy specimen.
E. Perineural and perivascular microbial migration through the eschar with proliferation of micro-organisms in the subeschar space.
Answer: ACD
DISCUSSION: It is essential to examine the entire burn wound at the time of the daily cleansing to identify invasive burn wound infection at the earliest possible time. The appearance of focal areas of dark red or dark brown discoloration are the most common changes indicative of burn wound infection, but similar changes may be caused by hemorrhage due to local trauma or maceration. Accelerated separation of the eschar is often produced by burn wound infections, but delayed separation of the eschar is indicative of effective control of the microbial population in the burn wound. Conversion of an area of partial-thickness burn to full-thickness necrosis is the most reliable clinical sign of invasive burn wound infection. Identification of such a change mandates histologic examination of a burn wound biopsy, which is the only reliable means of differentiating the colonization of nonviable tissue from the invasion of viable tissue. Identification of micro-organisms in the unburned viable tissue of a burn wound biopsy confirms the diagnosis of invasive burn wound infection. Microbial migration along the skin appendages, terminal nerve radicles, and thrombosed capillaries in the eschar and heavy growth of micro-organisms in the subeschar space are manifestations of the colonization of nonviable tissue and represent the mechanisms by which eschar separation occurs.
69. The treatment of invasive burn wound infection may include which of the following?
A. Subeschar infusion of half the daily dose of a broad-spectrum penicillin suspended in 1 liter of normal saline.
B. Use of 0.5% silver nitrate soaks for topical therapy.
C. Specific systemic antibiotic therapy.
D. Excision and immediate autografting.
E. Amputation when the infection has extended to involve underlying muscle.
Answer: ACE
DISCUSSION: The Pseudomonas organisms that most commonly cause invasive bacterial burn wound infection are typically sensitive to high concentrations of broad-spectrum penicillins. When the diagnosis of invasive Pseudomonas burn wound infection has been made, one half of the daily dose of a broad-spectrum penicillin, typically piperacillin, suspended in 1 liter of normal saline, should be infused into the subeschar tissues beneath the infected wound. A number 20 spinal needle should be used for the infusion, to minimize the number of injection sites. Following a second subeschar infusion of the broad-spectrum penicillin just prior to operation, the infected tissue should be excised. The excised wounds should not be autografted but covered with a biologic dressing or a dressing soaked with an antimicrobial solution such as 5% mafenide acetate. The patient is returned to the operating room in 24 to 48 hours to examine the excised wound and assess the adequacy of the débridement. The frequency of perilymphatic and perivascular proliferation of invading Pseudomonas organisms is associated with a risk of metastatic spread to remote organs or tissues. Consequently, systemic antimicrobial therapy should be instituted based on the sensitivity patterns of the resident microbial flora and adjusted as necessary on the basis of the patient's culture and sensitivity results. Amputation is frequently necessary to control invasive burn wound infection when a phycomycotic infection on a limb has traversed the investing fascia and involves significant amounts of the subfascial tissue.
70. The treatment of patients with high-voltage electric injury differs from that of patients with conventional thermal injury with respect to the need for:
A. Fasciotomy.
B. Hemodialysis.
C. Amputation.
D. Pulse oximetry.
E. Prehospital cardiopulmonary resuscitation.
Answer: ABCE
DISCUSSION: Both lightning injury and contact with electric current can induce cardiopulmonary arrest due to either asystole or fibrillation. Cardiopulmonary resuscitation must be initiated at the site of injury if cardiac arrest is present. Cardiac arrhythmias may also occur following resuscitation, necessitating electrocardiographic (ECG) monitoring for at least 48 hours following injury in patients with a history of loss of consciousness or an abnormal ECG. Tissue damage and tissue destruction beneath the investing fascia can result in the formation of edema that increases muscle compartment pressure to a level that necessitates fasciotomy (> 30 mm. Hg). The current flow in a limb in contact with high-voltage current can be so great as to damage even the periosseous muscles and make amputation necessary. Liberation of hemochromogens as a consequence of deep tissue injury is associated with an increased incidence of acute renal failure necessitating hemodialysis. Electric injury does not influence the need for monitoring by pulse oximetry, and in fact the destruction of deep tissue in a limb may preclude application of the pulse oximeter to that extremity.
71. Therapeutic interventions needed for specific chemical agents include which of the following?
A. Prolonged saline irrigation of eyes injured by concentrated sodium hydroxide using a scleral lens with an irrigating sidearm.
B. Administration of an emetic agent as immediate treatment following lye ingestion.
C. Intra-arterial infusion of calcium gluconate for relief of refractory deep tissue pain due to hydrofluoric acid injury.
D. Use of propylene glycol to remove residual phenol following water lavage.
E. Application of 5% copper sulfate solution soaks to areas of embedded particles of white phosphorus.
Answer: ACD
DISCUSSION: An eye injured by a strong chemical agent must be irrigated immediately at the site of the accident to minimize corneal damage. Prolonged irrigation for 12 to 72 hours is recommended for eyes injured by a strong alkali solution. Irrigation is difficult because of blepharospasm unless a modified scleral contact lens with an irrigating sidearm is used. Emetics should be avoided in the early treatment of patients following chemical ingestion since additional injury of the esophagus, oropharynx, and upper airway may be caused as the chemical is regurgitated. The intra-arterial infusion of calcium gluconate has been reported to limit tissue damage and relieve pain, but local excision of the involved tissue may be necessary for definitive control of pain and removal of the injured tissue.
Even though phenol is only slightly soluble in water, initial water lavage of burns caused by phenol should be carried out. Following that initial lavage, the involved area should be washed with a lipophilic solvent such as polyethylene glycol, propylene glycol, or glycerol to remove the residual phenol. A dilute 0.5% to 1% solution of copper sulfate can be used as a wash to facilitate identification and impede the ignition of embedded phosphorus particles. If excessive amounts of copper sulfate are absorbed through the injured tissues, intravascular hemolysis can occur and may cause renal failure. Consequently, one should avoid the use of more concentrated solutions of copper sulfate and should never apply the copper sulfate solution as a soak. The important principle of treatment is to prevent ignition of the particles by preventing their exposure to air, and that can be done most safely by applying an occlusive dressing soaked with saline or water.
72. Characteristics of the hypermetabolic response to burn injury include:
A. Elevation of core temperature, skin temperature, and core-to-skin heat transfer.
B. Ambient temperature dependency of metabolic rate.
C. A marked increase of blood flow to the burn wound.
D. A curvilinear relationship to the extent of burn.
E. Oxidation of stored lipid as the major source of metabolic energy.
Answer: ACE
DISCUSSION: At thermal neutral and higher temperatures, the core temperature, skin temperature, and core-to-skin heat transfer in burn patients remain elevated, but metabolic rate can be diminished in patients with burns of more than 50% of the body surface by maintaining the ambient temperature above 30؛ C. Blocking evaporative water loss by application of an impermeable membrane is not attended by a consistent diminution in metabolic rate, indicating that the burn patient is not externally cold but is internally warm. The hypermetabolism in burn patients is temperature sensitive but not temperature dependent. Even though earlier measurements described a curvilinear relationship between metabolic rate and extent of burn, recent measurements have shown that metabolic rate increases in linear fashion and rises to levels of twice normal in patients with burns of 75% and more of the total body surface. Lipid stores are the major source of metabolic fuel that is oxidized for energy, and not lean body mass, which undergoes proteolysis to provide the amino acids necessary for protein synthesis and wound healing as well as gluconeogenic processes that provide fuel for tissues requiring glucose. Blood flow to a burned limb is markedly increased as compared with flow in an unburned limb of the same patient, and the flow increase is directed to the wound per se, not the underlying muscles.
73. A 32-year-old mountain climber who struck his head in a fall lay in the snow overnight before he could be rescued and brought to the hospital. Upon admission he is semicomatose and not shivering, with a pulse rate of 48 beats per minute and a blood pressure of 80/50 mm. Hg. His rectal temperature as measured by a standard thermometer is reported as 34؛ C. All the digits on both feet appear to be frozen. Treatment for this patient should include:
A. Administration of inotropic and chronotropic vasoactive agents.
B. Intra-arterial infusion of vasodilating agents.
C. Infusion of lactated Ringer's solution warmed to 40؛ C.
D. Immersion in a circulating water bath heated to 40؛ C.
E. Excision of damaged tissue within 48 hours after thawing.
Answer: CD
DISCUSSION: A standard clinical thermometer will not measure body temperatures below 34؛ C. This patient's clinical condition—depressed mental status, bradycardia, and hypotension—indicates that the patient is likely suffering from severe hypothermia and, so, requires prompt active rewarming by immersion in a water bath at 40؛ C. or the use of partial cardiopulmonary bypass, if available, and the administration of resuscitation fluid warmed to 40؛ C. Vasoactive agents do not treat the basic pathology in hypothermic patients and are typically ineffective. Vasodilating agents will be of little if any value in the treatment of the frozen tissue in the feet since histologic studies have indicated that the vasculature in freeze-injured tissue is dilated, not constricted. Since assessment of tissue viability immediately after thawing is difficult and often erroneous, one should await clear demarcation of dead tissue before undertaking surgical excision of damaged tissue.
74. Valid points in the management of burns on special areas include:
a. The large majority of genital burns are best managed by immediate excision and autografting
b. All digits with deep dermal and full-thickness burns should be immobilized with six weeks of axial Kirschner wire fixation
c. Deep thermal burns of the central face are best managed with immediate excision and autografting
d. Burns of the external ear are commonly complicated by acute suppurative chondritis if topical mafenide acetate is not applied
Answer: d
Because of the thickness and deep appendages of the skin of the central face, relatively deep burns of these areas frequently heal. This is fortunate, because it is difficult to achieve a favorable result with primary excision and grafting of the central face. Management of the burned hand is dictated by the depth of injury. Superficial burns are managed with elevation, topical antimicrobials, and full passive range of motion for each joint twice daily. Deep, partial and full-thickness injuries are best managed by excision and sheet grafting as soon as practical. Hands are immobilized in a functional position for seven days after surgery before passive and active therapy is resumed. Fourth degree hand burns, which involve the underlying extensor mechanism, joint capsules or bone are significantly more difficult management problems and are managed by staged sheet autografting and often benefit from temporary axial Kirschner wire fixation of open and unstable interphalangeal or metacarpophalangeal joints. Burns of the external ear are treated with twice daily cleansing and application of mafenide acetate. Deep burns of the external ear are commonly complicated by acute suppurative chondritis if topical mafenide acetate is not applied. In general, the practice for deep genital burns is to manage these limited surface area injuries with topical therapy for a period of two to three weeks unless the wounds are remarkably deep. Unhealed injuries are debrided and grafted with sheet autograft at this time, with generally excellent cosmetic and functional results.
75. The hypermetabolic response seen in patients with large burns, who are successfully resuscitated, is thought to be driven by which of the following factors?
a. Deficient gastrointestinal barrier function
b. Bacterial contamination of the burn wound
c. Evaporative heat loss
d. Changes in hypothalamic function
Answer: a, b, c, d
The physiologic challenge of a burn in excess of 20% of the body surface frequently results in an initial decrease in cardiac output and metabolic rate. Subsequently, effected by a complex cascade of mediators, a hypermetabolic response is seen with a near doubling of cardiac output and resting energy expenditure over the next 24 to 48 hours in those who are successfully resuscitated. The magnitude of this response peaks in those with injuries of 60% or more of the body surface at as high as twice the normal basal metabolic rate. The etiology of the hypermetabolic response is not entirely understood but is assumed to involve a combination of factors including a change in hypothalamic function with coincident increases in glucagon, cortisol and catecholamine secretion, deficient gastrointestinal barrier function with translocation of bacteria and their byproducts, bacterial contamination of the burn wound with systemic release of similar products from this source, and some element of enhanced heat loss via transeschar evaporation of fluid. An important element of successful management of patients who have sustained large injuries is support of this response through the provision of adequate quantity and quality of substrate.
76. Which of the following statement(s) is/are true concerning inhalation injury?
a. The physiology of these injuries include upper airway obstruction secondary to progressive edema, reactive bronchospasm from aerosolized irritants, and microatelectasis from loss of surfactant and alveolar edema
b. Endotracheal intubation is indicated immediately in all patients with suspected inhalation injury
c. Distal airway injuries are usually caused by heat injury
d. Peak inspiratory pressures of > 40 cm of water are indicated to maintain functional residual capacity
Answer: a
The pathophysiology of inhalation injury is complex and varies with the aerosolized toxins particular to the circumstances of individual injuries. However, these injuries routinely demonstrate the following: 1) upper airway obstruction secondary to progressive edema; 2) reactive bronchospasm from aerosolized irritants; 3) small airway occlusion initially from edema and subsequently from sloughed endotracheal debris and loss of ciliary clearance mechanisms; 4) microatelectasis from the loss of surfactant and alveolar edema; and 5) interstitial and alveolar edema secondary to loss of capillary integrity. The physiologic consequences of these aberrations are upper and lower airway obstruction, increased airway resistance, decreased compliance, and an increase in the dead space to tidal volume ratio and intrapulmonary shunting.
Upper airway obstruction is best managed with prompt endotracheal intubation which is maintained for 48 to 72 hours and elevation the head. In equivocal cases, bronchoscopy is performed and patients with significant airway edema are intubated using the bronchoscope as a stylet. Although severe steam inhalation can result in direct heat injury to the distal tracheobronchial tree, more distal airway injuries are usually caused by aerosolized toxins rather than thermal injury, as the upper airway is a highly effective heat sink. Although moderate inflating pressures will help expand recruitable segments, peak inspiratory pressures in excess of 40 cm H2O should be avoided because they are associated with both overt barotrauma as well as more subtle overpressure injuries to the pulmonary microvasculature and alveoli which themselves exacerbate respiratory failure. High inflating pressures are also ineffective in recruiting additional lung, because the compliance decrements are not homogeneous and high pressures simply over distended more compliant segments.
77. Which of the following statement(s) is/are true concerning the initial fluid resuscitation of a burn patient?
a. Rigid adherence to the Modified Brooke formula is advised
b. In general, children require less fluid than that predicted by standard formulae
c. Patients with inhalation injuries require less fluid than predicted by standard formulae
d. Dextrose should not be given as the primary resuscitative fluid for any age group
e. Most resuscitative formulae withhold colloid solutions until 24 hours post-injury
Answer: e
The large number of fluid resuscitation formulae in common use is attributed to the fact that no formula accurately predicts fluid requirements in every patient. No formula can replace a physician at the bedside repeatedly evaluating the patient’s physiology through the resuscitative period. A reasonable consensus formula is the Modified Brooke formula, however, regardless of the formula chosen to initiate resuscitation, subsequent fluid administration is best guided by regular assessment of the resuscitation end points, rather than prediction of any formula. Vasoactive mediators released from the injured tissue result in diffuse capillary leaks seen shortly after major burn injury with resulting extravasation of both crystalloid and colloid for the first 18 to 24 hours after burn. The pathophysiology explains the enormous volume requirements seen in such patients and is the reason that most resuscitative formulae withhold colloid until 24 hours post-injury. Children have been found to commonly require fluid in excess of that predicted by several formulae. These requirements are generated if one uses a urine output of 1–2 cc/kg/hour as a resuscitation end point. These needs are real in infants and very young children whose renal concentrating abilities are not completely mature. However, in toddlers and older children whose concentrating abilities are more mature, targeting urine flow of 0.5–1 cc/kg/hour results in overall fluid requirements closer to that of an adult and less overall edema. Patients with inhalation injury have demonstrated to have overall volume requirements greater than that predicted by standard formulae, possibly secondary to release of vasoactive mediators from injured burned parenchyma. During the first 24 hours, Ringer’s lactate is the primary resuscitative fluid. Because children less than 10 kg can develop hypoglycemia if glucose is not administered, Ringer’s lactate or half normal saline with 5% dextrose at a maintenance rate is given along with the reduced amount of Ringer’s lactate. Dextrose containing fluids should not be given as a primary resuscitative fluid in adults, as hyperglycemia and osmotic diuresis will result.
78. Which of the following statement(s) is/are true concerning techniques of burn excision, and temporary and definitive wound closure?
a. Techniques to conserve blood include subeschar injection of dilute epinephrine solution, exsanguination of the extremity and inflation of a pneumatic tourniquet
b. Fresh or cryopreserved human allograft is usually rejected within 2 to 4 weeks
c. A common use for human allograft is as a physiologic cover for selected clean superficial wounds as they epithelialize
d. A donor site can only serve as a single source for autograft
Answer: a, b
A common argument against the policy of early burn wound excision is the prodigious blood loss which has been associated with these procedures. However, modern blood conserving practices as well as earlier excision of wounds have diminished this concern. Tangential excision of the torso, neck and head are done after subeschar injection of dilute epinephrine solutions. Tangential excisions of the extremities are done after exsanguination and inflation of a pneumatic tourniquet. Once necrotic eschar is excised to a bed of viable tissue, immediate biologic closure is mandatory. Ideally, immediate autografting is performed. When donor sites are insufficient for this purpose, a temporary biologic cover must be chosen while awaiting healing of donor sites for further use. Such covers should prevent desiccation and provide a vapor and bacterial barrier over the excised wound. Fresh or cryopreserved human allograft is most appropriate for this use. Once placed on a viable wound bed, it will vascularize and provide physiologic wound closure until rejected 2 to 4 weeks later at which time or before, it is replaced with reharvested autograft. A second common use for biologic dressings is a physiologic cover for selected clean superficial wounds as they epithelialize, which minimizes the pain associated with open partial thickness burns. Allograft, screened for malignant and infectious diseases, a precarious resource, is however, not commonly used as a biologic dressing in these circumstances. For this purpose, reconstituted porcine xenograft should be used.
79. Which of the following statement(s) is/are true concerning topical antimicrobials in common use in the United States today?
a. Of the common topical antimicrobials, only mafenide acetate is painful upon application
b. The use of 0.5% silver nitrate is associated with trans-eschar leeching of sodium and potassium from the wound
c. Silver sulfadiazine has the best eschar penetration
d. Silver sulfadiazine, mafenide acetate, and 0.5% silver nitrate all have a broad spectrum activity, however, only silver nitrate has anti-fungal activity
Answer: a, b, d
80. The anthropometric changes observed as a patient progresses from infancy to adulthood include which of the following statement(s)?
a. The major anthropometric changes involve the head and torso
b. A decrease in the relative size of the head from 18% to 9% of the body’s surface area occurs
c. The total surface area of the legs increases from 14 to 18%
d. The upper extremities increase to 12% of the body surface area
Answer: b, c
An accurate assessment of burn size can be made early and is important to the initial management as resuscitative fluid administration is primarily determined by overall burn size. Burn size in children is best estimated with an age-specific chart, because the child’s body proportions change with growth. The major anthropometric change involves the head and legs. The infant’s head represents 18% of the total body surface and legs 14%. In older adolescents and adults, the head represents 9% of the body surface and the legs 18%. Each upper extremity in the adult is usually considered to represent 9% of the total body surface area.
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