How Should Patients with Burns Be Managed in the Intensive Care Unit?




More than 500,000 burn injuries occur annually in the United States. Although most are minor, approximately 40,000 to 60,000 burn patients require admission to a hospital or major burn center for appropriate treatment every year. The devastating consequences of burns have resulted in the allocation of significant clinical and research resources. This has led to improved care. Indeed, reports reveal a 50% decline in burn-related deaths and hospital admissions in the United States during the past 20 years. This reflects effective prevention strategies decreasing the number and severity of burns. Advances in therapy strategies, based on implementation of critical care bundles, improved understanding of resuscitation, enhanced wound coverage, better support of the hypermetabolic response to injury, more appropriate infection control, and improved treatment of inhalation injury, improved the clinical outcome of this unique patient population. It is important to recognize that successful management of burn patients requires a diversified and multidisciplinary approach. This chapter gives an overview of the evidenced-based management of severely burned patients in the intensive care unit (ICU).


Initial Assessment and Emergency Treatment


All burned patients should initially be managed as trauma patients, following the guidelines of the American College of Surgeons Committee on Trauma and the Advanced Trauma Live Support Center. The algorithms for trauma evaluation should be diligently applied to the burn patient. In particular, any wheezing, stridor, hoarseness, or tachypnea may be a sign of airway compromise. Tracheal tugging, carbonaceous sputum, soot around the patient’s airway passages, and singed facial or nasal hair may suggest an airway burn or smoke inhalation. As in any trauma patient, progression to the next step in the primary survey is delayed until a proper airway is established and maintained.


Cardiac performance may be difficult to evaluate in the burn victim. In particular, burned extremities may impede the ability to obtain a blood pressure reading. In these situations, arterial lines, particularly femoral lines, are useful to monitor continuous blood pressure readings. Use of a pulmonary artery catheter (PAC) may be beneficial in the assessment of cardiovascular performance in certain situations (e.g., inadequate noninvasive monitoring, difficult-to-define end points of resuscitation), but the general practicability, risk-to-benefit ratio, and lack of mortality reduction when the PAC is used have been widely criticized. Currently, there are no studies in burn patients that provide evidence-based recommendations. For disadvantages of the PAC to be overcome, less-invasive techniques have been developed. None of these, though, is specific to burn patients. Several descriptive studies using PiCCO technology, in which cardiac performance is approximated with an arterial thermodilution catheter, have been conducted in burn patients. Prospective trials are underway.




Fluid Resuscitation


Severe burns cause significant hemodynamic changes. These must be managed carefully to optimize intravascular volume, maintain end-organ tissue perfusion, and maximize oxygen delivery to the tissues. Massive fluid shifts after severe burn injury result in the sequestration of fluid in burned and unburned tissue. The result of this generalized edema may be burn shock, a leading cause of mortality in severely burned patients. Therefore early and accurate fluid resuscitation of patients with major burns is critical for survival. Calculations of fluid requirements are based on the amount of body surface involved in second- or third-degree burns (not first-degree burns). The “rule of nines” ( Fig. 76-1 , A ) has been used to estimate the area of burned body surface, but this rule has limitations in children, in whom the head is proportionally larger than the body. A more accurate assessment can be made of burn injury, especially in children, by using the Lund and Browder chart, which takes into account changes associated with growth ( Fig. 76-1 , B ). Various resuscitation formulas have been used. These differ in the amount of crystalloid and colloid to be given and in fluid tonicity ( Table 76-1 ). The modified Brooke and Parkland (Baxter) formulas are the most commonly used early resuscitation formulas, but no formula will accurately predict the volume requirements of an individual patient. In children, maintenance requirements must be added to the resuscitation formula. The Galveston and Cincinnati Shriners Burns Hospitals have devised formulas ( Table 76-2 ). Intravascular volume status must be reevaluated frequently during the acute phase. Fluid balance during burn shock resuscitation is typically measured by hourly urine output through an indwelling urethral catheter. It has been recommended to maintain a urine output of approximately 0.5 mL/kg per hour in adults and 0.5 to 1.0 mL/kg per hour in patients weighing less than 30 kg. No clinical studies, though, have identified the optimal hourly urine output to maintain vital organ perfusion during burn shock resuscitation. Because large volumes of fluid and electrolytes are administered initially and throughout the course of resuscitation, it is important to obtain baseline laboratory measurements. Crystalloid, in particular lactated Ringer’s solution, is the most popular resuscitation fluid currently used for burn patients. Colloid and crystalloid solutions have been used. No outcome differences between the two have been identified despite extensive study. Proponents of the use of crystalloid solutions alone report that other solutions, specifically colloids, are not better and are more expensive. Nonetheless, most burn surgeons agree that patients with low serum albumin during burn shock may benefit from albumin supplementation to maintain oncotic pressure.




Figure 76-1


A , Estimation of burn size with the “rule of nines.” B , Estimation of burn size with the Lund and Browder method. BSA, body surface area.


Table 76-1

Formulas for Estimating Adult Burn Patient Resuscitation Fluid Needs






























Colloid Formula Electrolyte Colloid
Evans Normal saline, 1.0 mL/kg/%burn 1.0 cc/kg/%burn
Brooke Lactated Ringer’s solution, 1.5 mL/kg/% burn 0.5 mL/kg
Slater Lactated Ringer’s solution, 2 L/24 hr Fresh-frozen plasma, 75 mL/kg/24 hr
Crystalloid formulas
Parkland
Modified
Lactated Ringer’s solution
Lactated Ringer’s solution
4 mL/kg/%burn
2 mL/kg/%burn
Hypertonic saline solutions
Monafo
Warden
Volume to maintain urine output at 30 mL/hr; fluid contains 250 mEq Na/L.
Lactated Ringer’s solution +50 mEq NaHCO 3 (180 mEq Na/L) for 8 hr to maintain urine output at 30-50 mL/hr. Lactated Ringer’s solution to maintain urine output at 30-50 mL/hr beginning 8 hr postburn.
Dextran formula (Demling) Dextran 40 in saline, 2 mL/kg/hr for 8 hr.
Lactated Ringer’s solution, volume to maintain urine output at 30 mL/hr.
Fresh-frozen plasma, 0.5 mL/kg/hr for 18 hr beginning 8 hr postburn.

Na, sodium; NaHCO 3 , sodium bicarbonate.

From Warden GD. Burn shock resuscitation. World J Surg . 1992; 16:16–23.


Table 76.2

Formulas for Estimating Pediatric Resuscitation Needs













Cincinnati Shriners Burns Hospital 4 mL × kg × % total BSA burn + 1500 mL × m 2 BSA 1st 8 hr
2nd 8 hr
3rd 8 hr
Lactated Ringer’s solution + 50 mg NaHCO 3
Lactated Ringer’s solution
Lactated Ringer’s solution + 12.5 g albumin
Galveston Shriners Burns Hospital 5000 mL/m 2 BSA burn + 2000 mL/m 2 BSA Lactated Ringer’s solution + 12.5 g albumin

BSA, body surface area; NaHCO 3 , sodium bicarbonate.




Inhalation Injury


Inhalation injury constitutes one of the most critical problems accompanying thermal insult, with mortality paralleling that for acute respiratory distress syndrome in patients requiring ventilator support for more than 1 week. Early diagnosis of bronchopulmonary injury is initiated by a history of closed-space exposure; facial burns; or carbonaceous debris in the mouth, pharynx, or sputum. There are few evidence-based data regarding inhalation injury, though. Therefore the standard diagnostic method is bronchoscopy. Endorf and Gamelli established a grading system for inhalation injury (0, 1, 2, 3, and 4) derived from findings at initial bronchoscopy and based on Abbreviated Injury Score criteria. Bronchoscopic criteria that are consistent with inhalation injury included airway edema, inflammation, mucosal necrosis, presence of soot and charring in the airway, tissue sloughing, or carbonaceous material in the airway. At this time, though, there are neither uniform diagnosis criteria nor standardized treatment guidelines. Management of inhalation injury consists of ventilatory support, aggressive pulmonary toilet, bronchoscopic removal of casts, and nebulization therapy. According to the American Burn Association guidelines, prophylactic antibiotics are not indicated.




Infection/Sepsis


Severely burned patients are susceptible to various infectious complications. Because burns induce a systemic inflammatory response, specific guidelines for the diagnosis and treatments of wound infection and sepsis in burns have been formulated ( Table 76-3 ).



Table 76-3

Definition of Burn Sepsis






























American Burn Association Consensus Definition on Burn Sepsis



  • At least 3 of the following parameters:




    • T >38.5° C or <36.5° C





  • Progressive tachycardia >90 beats/min in adults or >2 SD above age-specific norms in children




  • Progressive tachypnea >30 beats/min in adults or >2 SD above age-specific norms in children




  • WBC >12,000 or <4000 in adults or >2 SD above age-specific norms in children




  • Refractory hypotension: SBP <90 mm Hg, MAP <70, or an SBP decrease >40 mm Hg in adults or < 2 SD below normal for age in children




  • Thrombocytopenia: Platelet count <100,000/μL in adults, < 2 SD below norms in children




  • Hyperglycemia: Plasma glucose >110 mg/dL or 7.7 mM/L in the absence of diabetes




  • Enteral feeding intolerance (residual >150 mL/hr in children or 2 times feeding rate in adults; diarrhea >2500 mL/day for adults or >400 mL/day in children)

and
Pathologic tissue source identified: >105 bacteria on quantitative wound tissue biopsy or microbial invasion on biopsy
Bacteremia or fungemia
Documented infection as defined by Centers for Disease Control.

MAP, mean arterial pressure; SBP, systolic blood pressure; SD, standard deviation; T, temperature; WBC, white blood cell count.

From Greenhalgh DG, Saffle JR, Holmes JH et al. American Burn Association consensus conference to define sepsis and infection in burns. J Burn Care Res. 2007; 28:776–790.




Burn Wound Excision


Methods for handling burn wounds have changed in recent decades. Increasingly, aggressive early tangential excision of the burn tissue and early wound closure primarily by skin grafts have led to significant improvement of mortality rates and substantially lower costs in this particular patient population. Early wound closure also has been associated with decreased severity of hypertrophic scarring, joint contractures and stiffness, and quicker rehabilitation. Techniques of burn wound excision have evolved substantially over the past decade. Published estimates of bleeding associated with these operations range between 3.5% and 5% of the blood volume for every 1% of the body surface excised. Burn wound excision should occur in the operating room soon after the patient is admitted; however, sometimes excision may be necessary in the ICU.




Metabolic Response and Nutritional Support


The metabolic consequences of severe burn injury are profound, and their modulation constitutes an ongoing challenge for successful treatment. Metabolic rates of burn victims exceed those of most other critically ill patients and cause marked wasting of lean body mass within days of injury. Failure to meet the subsequent energy and protein requirements may result in impaired wound healing, organ dysfunction, increased susceptibility to infection, and death. Thus adequate nutrition is imperative. Because of the significant increase in postburn energy expenditure, high-calorie nutritional support was thought to decrease muscle metabolism, but a randomized, double-blind, prospective study found that aggressive high-calorie feeding with a combination of enteral and parenteral nutrition was associated with increased mortality. Therefore most authors recommend adequate calorie intake through early enteral feeding and avoidance of overfeeding. Different formulas have been developed to address the specific energy requirements of burned adult and pediatric patients ( Tables 76-4 and 76-5 ). The caloric requirements in adult burn patients most often are calculated using the Curreri formula. This calls for 25 kcal/kg per day plus 40 kcal/%BSAB (percentage of total body surface area burned) per day. Recommendations suggest administration of 1 to 2 g/kg per day of protein. Because of glucose intolerance and futile cycling in critical illness, most ICUs provide a significant amount of caloric requirements as fat. Burn patients exhibit lipid intolerance, though, that may result in hyperlipidemia and fatty liver infiltration that is associated with a higher incidence of infection and higher postoperative mortality rates. Thus the extent to which exogenous lipid can be used as an energy source is limited. Studies in a large cohort of severely burned children demonstrated that patients receiving a low-fat, high-carbohydrate diet had a significantly lower incidence of fatty liver on autopsy. Relative to historic controls, these patients had a significantly lower incidence of sepsis, prolonged survival, and significantly shorter stays in the ICU (grade C data). On the basis of these findings, I recommend that nutritional regimens for treatment of burn patients include a significantly reduced proportion of fat as the source of total caloric intake.



Table 76-4

Formulas for Estimating Caloric Requirements in Adult Burn Patients




























Formula Age/Sex Equation
Harris-Benedict Men BEE (kcal/day) = 66.5 + (13.75 × W) + (5.03 × H) − (6.76 × A)
Women BEE (kcal/day) = 655 + (9.56 × W) + (1.85 × H) − (4.68 × A)
Comment: Multiply BEE by stress factor of 1.2−2.0 (1.2−1.5 sufficient for most burns) to estimate caloric requirement.
Curreri Age: 16-59 yr Calories (kcal/day) = (25 × W) + (40 × %BSAB)
Age: >60 yr Calories = (20 × W) + (65 × %BSAB)
Comment: Specific for burns, may significantly overestimate energy requirements, maximum 50% BSAB.

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Jul 6, 2019 | Posted by in CRITICAL CARE | Comments Off on How Should Patients with Burns Be Managed in the Intensive Care Unit?
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