Advances in prehospital burn resuscitation for the combat injured.
Wartime often leads to advances in medical care as unique problems that surface in an austere environment necessitate urgent solutions. Current combat operations in Iraq and Afghanistan have been no different in their impact on burn care, specifically with regard to fluid resuscitation. The influx of severely burned combat casualties globally evacuated to our burn center at the US Army Institute of Surgical Research in Fort Sam Houston, Texas [hereinafter referred to as the Burn Center], began in early 2003 and has continued through 2010. As the flow of those casualties continued, we discovered processes in need of improvement and addressed them in a timely and robust manner. Such initiatives included reevaluation of the initial fluid resuscitation of burn casualties, as well as continued resuscitation during en route care.
A SIMPLIFIED APPROACH TO FLUID RESUSCITATION IN BURNS
Arguably one of the more challenging aspects of the initial management of severe burn casualties is the fluid resuscitation necessary to prevent or mitigate burn shock and multiple organ failure. Longstanding recommendations provided by the American Burn Association (ABA) include initiating fluid resuscitation of the burn patient utilizing lactated Ringers solution, at an infusion rate of 2 to 4 cc/kg/ percentage total body surface area (TBSA) burn administered over the first 24 hours following the burn injury (postburn); providing one-half of estimated fluid over the first 8 hours, and the remainder over the next 16 hours. (1) This ABA resuscitation guideline is intended to give the provider a prediction of how much fluid should be given over an entire 24-hour period. Although, predicting the total amount of volume that the patient should receive in a 24-hour period via formula is helpful in assessing the precision of the resuscitation post hoc, it should not be used to strictly dictate what the patient receives hour to hour. Once initiated, the ultimate goal of fluid resuscitation is to maintain end-organ perfusion by gradually restoring fluid balance while simultaneously replacing insensible losses and avoiding the consequences of both under- and over-resuscitation. Optimal care of the burn casualty during the early phase of resuscitation requires an attentive medic titrating fluid therapy based on a compilation of various endpoints centered on a goal of maintaining a urine output of 30-50 ml/hr. Urine output of between 30-50 ml/hr is generally accepted as a corollary of renal perfusion indicative of adequate initial resuscitation in casualties with isolated burn injuries. Thus, the practical purpose of any formula is to identify an appropriate starting point for the resuscitation, the initial infusion rate. A prediction of how the first 24 hours should go, the centerpiece of the current resuscitation guidelines, may place the focus of the resuscitation away from the "art" of resuscitation.
Prehospital Burn Resuscitation
Despite general instructions that the predicted fluid requirements are designed to serve only as guidelines, and that actual resuscitation should be based on patient response, many nonburn providers either err on the side of adhering strictly to the formulae regardless of patient response, or not utilizing them at all. A post hoc analysis of prehospital fluid resuscitation practices was performed using data collected from an institutional review board-approved prospective observational trial assessing resuscitation practices in the Burn Center. We reviewed the records of 39 civilian burn patients admitted to the Burn Center with severe thermal injury greater than 20% TBSA. At the time of admission to the Burn Center, we carefully recorded the time of burn, total prehospital fluids given, weight in kilograms, and estimated percentage TBSA burn. We used this data to estimate initial rate of fluid begun for each patient in the first hour postburn. We then determined the formula, in cc/kg/percentage TBSA, that would have been used to derive that initial rate. Essentially, we wanted to evaluate which, if any, formula the pre-Burn Center providers were using, in cc/kg/ percentage TBSA, to calculate the patient's initial fluid resuscitation rate. The results (Table 1) were plotted (Figure 1) and compared to current ABA guidelines. We discovered that only 21% of all patients (8/39) were being initiated on a fluid rate what would have been derived using the 2-4 cc/kg/percentage TBSA formula recommended by the ABA. Thus, we concluded that prehospital providers situated in a large city in the United States were not using a formula to determine the initial fluid rate. If US prehospital providers are not using a formula, it is highly unlikely that providers deployed to austere environments, often tending to multiple casualties simultaneously, are using a formula.
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The most likely reason for this lack of adherence among prehospital providers is the fact that the formulae are too complex, requiring multiple steps. For example, the calculated rate for a patient weighing 70 kg who has suffered a 50% TBSA burn requires 4 separate variables (time, weight, surface area, and volume) with a minimum of 4 computations that must be performed. Such calculation results in an initial fluid rate of 437 ml/hr when using the Modified Brooke formula (2 cc/kg/percentage TBSA). (1) The likelihood of a combat provider at the level I or level II echelon of care performing this calculation under duress or in the face of multiple casualties is exceedingly low.
The Rule of 10
Surely, a more simple method could be found to derive this initial fluid rate. Enter the "Rule of 10" (see inset below). Recently conceived and validated in silico [computer simulation] at the US Army Institute of Surgical Research (ISR), (2) the Rule of 10 is a simplified formula that calculates the initial fluid resuscitation rate by multiplying the estimated burn size by 10. In the example given above, multiplying the surface area of burn (50%) by 10 results in an initial fluid rate of 500 ml/hr, a number falling within the acceptable range of 437 ml/hr (2 ml/kg/TBSA) and 875 ml/hr (4 ml/kg/TBSA) derived from the ABA consensus recommendation. Subsequent and serial adjustments in fluid infusion rate are then based upon response to resuscitation. As demonstrated by our in silico validation, this simplified equation provides an acceptable starting point for the vast majority of patients weighing more than 40 kg. To accommodate burn patients weighing over 80 kg, an increase of 100 ml/hr is added for each 10 kg over 80 kg.
The Rule of 10 allows the combat prehospital providers at levels I and II echelons of care to easily implement the fluid resuscitation, and then to shift the focus towards the patient's response to the resuscitation in order to dictate the amount of fluid administered over the first 24 hours. Traditional resuscitation formulas can still be used as benchmarks to assess the adequacy of the resuscitation. This formula has recently been adopted by the Committee on Tactical Combat Casualty Care *, and has been included in a new chapter for treatment of burn casualties in the military version of the prehospital trauma life support manual published by the National Association of Emergency Medical Technicians. (3)
EN ROUTE CARE
Identification of the problem
For US Warriors burned in the Iraq and Afghanistan theaters, the initial burn resuscitation--the first 24 to 48 hours postburn--is routinely performed by providers possessing variable levels of experience in burn care. In addition, multiple handoffs occur while the patient is being transported. It is common for 4 or more teams of providers to manage a military casualty with severe burns prior to the patient's arrival at the Burn Center for definitive care. Given that variations in practice exist among different sets of providers, variability in the way care is delivered during the resuscitation is unavoidable. In addition, the teams rotate out of theater every 4 to 6 months, which results in the loss of the knowledge and experience gained during their deployment. Together, these issues provide an underpinning that makes it difficult to standardize care in this environment. The multitude of challenges faced by deployed providers with regard to immediate burn care has previously been described. (4)
As a result of these challenges and in an effort to standardize care, in November 2005, we developed the burn resuscitation clinical practice guidelines (Table 2), as well as a burn resuscitation flow sheet (Figure 2). Serendipitously, the Joint Theater Trauma System had been established in early 2005, and it became the vehicle that allowed us to immediately disseminate the guidelines and burn care flow sheet. Within weeks of identifying the insufficiency of documentation and lack of standardization of en route care, a solution was developed and disseminated widely throughout the combat theater. This accomplishment is an example of how the system enabled us to establish guidelines very quickly and educate providers across the evacuation chain. The flow sheet has been a valuable documentation tool to record the first 72 hours of resuscitation as patients move through the various echelons of care. At each level of evacuation, the flow sheet ensures the appropriate repeated assessment of the resuscitation, which is vital in all difficult resuscitations. The flow sheet also provides our staff with the data necessary to evaluate the patient's initial resuscitation course when patients arrive at the Burn Center. (6) This resuscitation tool has been important in providing continuity in documentation as well as system-wide standardization of care.
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Improvement of outcomes as a result of this intervention has also been previously described by Ennis et al. (7) A 50% decrease in the composite endpoint of abdominal compartment syndrome and mortality was revealed when the outcomes of those evacuated after the release of the guidelines were compared to those of casualties who were evacuated before the guidelines were in place. This finding by our group illustrates how our current military trauma landscape allows us to adapt as a system, identify problems, and alter the way care is delivered in an effort to improve outcomes. (7)
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Nonetheless, the burn flow sheet, a valuable and necessary tool, is not perfect. It helps document what was done, but does not assist the provider in the determination of how a resuscitation should be performed. Much variability still exists with regard to how burn resuscitation is conducted from patient to patient. In order to provide better guidance to nonburn providers and to further standardize care, we have developed a computer-based decision support algorithm to assist the deployed care provider. (8) As shown in Figure 3, urine output levels are automatically captured by the system hourly, which generates a recommendation for fluid rates based on the trend of the last few hourly urine outputs. Application of this decision support system (DSS) in our intensive care unit at the Burn Center was evaluated. Compared to 40 control patients who were resuscitated without the DSS, resuscitation using the DSS in 26 consecutive patients resulted in significantly lower fluid requirements during the initial 48 hours following the burn injury (27 [+ or -] 14 vs 15 [+ or -] 6 liters, P<.05). Furthermore, compared to control patients, the DSS was able to maintain patients between the urine output targets of 30 to 50 ml /hr over a higher percentage of the time (22% vs 37%, P <.05). (9)
One of the ISR's primary objectives related to resuscitation is to facilitate the fielding of a user-friendly tool designed for prehospital and hospital-based providers who do not routinely care for burn casualties. The tool may ultimately be delivered in the form of a handheld device (Figure 4) or be incorporated into an intravenous fluid pump. Regardless of the technology used, the key objective is to incorporate a functional and tested version of a burn resuscitation DSS to assist providers in the resuscitation of burn casualties based on real-time physiologic parameters; to be available during all phases of care or evacuation. Ultimately, it is hoped that these efforts will result in improved resuscitation practice, more efficient transmission of clinical data, less morbidity associated with resuscitation, and overall improved outcomes.
Other areas of interest include the choice of resuscitation fluid used in the forward environment. Special operations forces and other highly mobile combat teams are often limited in the amount of medical supplies immediately available to them. The use of colloids and plasma substitutes continues to spark much discussion among prehospital providers. Current research in this area may result in further ways to minimize complications associated with over- and under-resuscitation of the burn casualty, as well as other battlefield casualties.
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The US Army Institute of Surgical Research
Rule of 10
Estimate burn size (using the Rule of Nines) to the nearest 10% TBSA.
Multiply that by 10 to calculate the Initial Fluid Rate for patients weighing 40 to 80 kg.
Increase fluid rate by 100 cc/hr for every 10 kg of body weight above 80 kg.
(1.) Pham TN, Cancio LC, Gibran NS. American Burn Association practice guidelines burn shock resuscitation. J Burn Care Res. 2008;29:257-266.
(2.) Chung KK, Salinas J, Renz EM, et al. Simple derivation of the initial fluid rate for the resuscitation of severely burned adult combat casualties: in silico validation of the rule of 10. J Trauma. 2010;69(suppl 1):S49-S54.
(3.) National Association of Emergency Medical Technicians. PHTLS: Prehosptial Trauma Life Support, Military Edition. 7th ed. St Louis, Missouri: Mosby; 2010.
(4.) Chung KK, Blackbourne LH, Wolf SE, et al. Evolution of burn resuscitation in operation Iraqi freedom. J Burn Care Res. 2006;27:606-611.
(5.) Burris DG, Dougherty PJ, Elliot DC, et al, eds. Emergency War Surgery. 3rd rev. Washington, DC: Borden Institute, Office of the Surgeon General, US Dept of the Army; 2004:28.6.
(6.) Chung K, Wolf S, Cancio L, et al. Resuscitation of severely burned military casualties: fluid begets more fluid. J Trauma. 2009;67: 231-237.
(7.) Ennis JL, Chung KK, Renz EM, et al. Joint Theater Trauma System implementation of burn resuscitation guidelines improves outcomes in severely burned military casualties. J Trauma. 2008;64(suppl 2):S146 S152.
(8.) Salinas J, Drew G, Gallagher J, et al. Closed-loop and decision-assist resuscitation of burn patients. J Trauma. 2008;64(suppl 4):S321-S332.
(9.) Salinas J, Kramer GC, Mann EA, et al. Computer decision support system improves fluid management during resuscitation of burn patients. J Burn Care Res. 2009;30(suppl 2):S46.
MAJ(P) Kevin K. Chung, MC, USA
Jose Salinas, PhD
COL Evan M. Renz, MC, USA
* A committee of the Defense Health Board, US Department of Defense.
MAJ(P) Chung is Medical Director, Burn Intensive Care Unit, US Army Institute of Surgical Research, Fort Sam Houston, Texas.
Dr Salinas is Manager, Combat Critical Care Engineering Research Task Area, US Army Institute of Surgical Research, Fort Sam Houston, Texas.
COL Renz is Director, US Army Institute of Surgical Research Burn Center, Fort Sam Houston, Texas.
Table 1. The calculated initial fluid resuscitation rates for 39 patients. Values are plotted in Figure 1. cc/kg/ Subject percentage TBSA number 0.00 CL-30 1.05 CL-38 1.18 CL-40 1.24 CL-05 1.43 CL-19 1.73 CL-24 2.30 CL-21 2.58 CL-02 2.59 CL-15 2.60 CL-27 2.71 CL-33 2.77 CL-35 3.27 CL-29 3.91 CL-18 4.17 CL-08 4.44 CL-26 4.57 CL-25 4.76 CL-04 4.88 CL-22 5.02 CL-13 cc/kg/ Subject percentage TBSA number 5.19 CL-16 5.59 CL-06 5.70 CL-09 5.79 CL-11 5.89 CL-14 6.35 CL-39 6.41 CL-20 6.85 CL-10 7.51 CL-23 7.67 CL-12 7.77 CL-34 8.30 CL-28 8.64 CL-36 8.90 CL-31 8.94 CL-07 11.82 CL-17 12.23 CL-01 12.59 CL-03 20.13 CL-37 Table 2. The Army Institute of Surgical Research burn resuscitation clinical practice guidelines. At 12 to 18 hours postburn, calculate the PROJECTED 24-hour resuscitation if fluid rates are kept constant. If the projected 24hour resuscitation requirement exceeds 6 cc/kg/percentage TBSA, the following steps are recommended: Initiate 5% albumin early as described in the Emergency War Surgery Handbook. (5) Check bladder pressures every 4 hours. If urine output (UOP)<30 cc/hr, strongly consider the placement of a pulmonary artery (PA) catheter to guide resuscitation with specific pulmonary capillary wedge pressure (PCWP) and mixed venous saturation (Sv[O.sub.2]) goals (goal PCWP 10 to 12, Sv[O.sub.2] 65% to 70%). If a PA catheter placement is not practical, consider monitoring the central venous pressure (CVP) from a subclavian or internal jugular vein along with central venous (Scv[O.sub.2]) saturations (goal CVP 8 to 10, Scv[O.sub.2] 60% to 65%). If CVP or PCWP is not at goal, increase the fluid rate. If CVP or PCWP is at goal, consider vasopressin 0.04 unit/ minute to augment the mean arterial pressure (and thus UOP) or dobutamine 5 mg/kg/min (titrate until Sv[O.sub.2] or Scv[O.sub.2] at goal). The maximum dose of dobutamine is 20 mg/kg/min. If both CVP or PCWP and Sv[O.sub.2] or Scv[O.sub.2] are at GOAL, stop increasing fluids (even if UOP<30 cc/hr). The patient should be considered hemodynamically optimized, and the oliguria is likely a result of established renal insult. Some degree of renal failure should be tolerated and expected. Continued increases in fluid administration despite optimal hemodynamic parameters will only result in "resuscitation morbidity" that is oftentimes more detrimental than renal failure. If the patient becomes hypotensive along with oliguria (UOP<30 cc/hr), then follow the hypotension guidelines. Every attempt should be made to minimize fluid administration while maintaining organ perfusion. If UOP>50 cc/hr, decrease the fluid rate by 20%. After 24 hours, lactated Ringer infusion should be titrated down to maintenance levels and albumin continued until the 48-hour mark.
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|Author:||Chung, Kevin K.; Salinas, Jose; Renz, Evan M.|
|Publication:||U.S. Army Medical Department Journal|
|Date:||Apr 1, 2011|
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