Burn Fluid Management

Article Author:
Abby Regan
Article Editor:
David Hotwagner
Updated:
11/11/2018 2:06:16 PM
PubMed Link:
Burn Fluid Management

Introduction

In the United States, approximately 500,000 people seek care for burn injuries each year. For civilians, these injuries are typically sustained in house fires, motor vehicle crashes, and work-related accidents. In combat, burn injuries represent 5% to 10% of combat casualties.[1]

The severity of burns is determined by the intensity of the thermal energy sustained, duration of exposure, and the area of the body affected. These parameters determine whether a patient will require treatment at a dedicated burn center.

Many burn injuries are sustained in motor vehicle crashes, which can often become multi-trauma events. It is imperative that the initial provider not become so engrossed in the apparent injury that they do not consider more life-threatening injuries that might be less overtly evident. Airway assessment, control of hemorrhage, and the advanced trauma life support (ATLS) guidelines must be followed.[2] Additionally, the American Burn Association (ABA) guidelines mirror those of the ATLS.[3]

Anatomy

Arguably the greatest issue surrounding patients sustaining burn injuries is fluid loss. Therefore, volume replacement is crucial. Burns management can be divided into 3 phases: early resuscitative, wound management, and rehabilitative/reconstructive. This article will primarily discuss the early resuscitative phase after initial stabilization has been performed. Although guidelines have been present since the early 1960s, fluid management protocols remain controversial for patients in the first 24 hours.

In the early resuscitative phase, the major concern is hypovolemia due to capillary permeability. Thermal injury prompts release of inflammatory markers not only at the site of injury but also systemically. These inflammatory markers increase the capillary permeability throughout the body and cause a massive fluid shift out of the intravascular compartment. The inflammatory response seen from thermal burns far surpasses that of trauma and sepsis patients.[4] Among these inflammatory markers, histamine is likely responsible for the early phase of burn injury, creating the capillary permeability.[5] Cardiac output is decreased, and systemic vascular resistance is increased, worsening the state of shock. Burn shock is a combination of distributive, cardiogenic, and hypovolemic shock.[6] Therefore, it is imperative to replace the fluid in the intravascular compartment in order to preserve tissue perfusion of vital organs.

Indications

Burns over 15% body surface area (BSA) in adults and 10% BSA in children require formal fluid resuscitation, calculated with the Lund and Browder chart for children and the Wallace rule of 9s for adults.

Goals for fluid resuscitation are generally accepted as urine output greater than 0.5ml/kg per hour, base deficit less than 2, systolic blood pressure greater than 90 mm Hg, and clinically with peripheral pulses palpable and no altered mental status. Although studies have shown each of these variables to be adequate predictors of fluid resuscitation, many physicians rely solely on urine output (UOP). In 1991, Dries and Waxman found that vital signs and urine output did not appreciably change after volume repletion, whereas measurements from pulmonary artery catheterization (PAC) were quite significant.[7] This lead to the suggestion that cardiac output was the most sensitive measure to guide fluid therapy. However, doing so requires placement of the pulmonary artery catheter, and as such, many burn units are reluctant to use this method for guidance.  Other proposed methods for goal-directed therapy include transpulmonary thermodilution and arterial pressure wave analysis, but these have not been extensively studied as yet.

An exception to the previously stated UOP goal occurs in patients with rhabdomyolysis and/or acute renal failure, which has mortality reported as high as 70% in severe burns. These patients require fluids at a rate that produces UOP of 1 ml/kg hour.[8] However, it should be noted that "more is not better," and the risk of fluid creep can be as life-threatening as the burn injury itself.  Neither mannitol nor sodium bicarbonate has been shown to be more effective in acute renal failure than fluid loading alone.[9][10]

Technique

The original Parkland formula incorporates both crystalloids and colloids. Crystalloids have a smaller volume expansion effect than colloids because of the increased capillary permeability during early burn injury. However, colloids will pass into the extravascular space and create a shift in oncotic pressure that expands into the third space.[11] 

A study conducted by Perel et al. concluded that randomized controlled trials provide no evidence that resuscitation with colloids reduces the risk of death compared with crystalloids in burn resuscitation. Given that there is no associated improvement in survival and crystalloids are more expensive than colloids, they are used less in clinical practice. At this time, crystalloids are the consensus of fluids for burn management.[12]

The Evans formula was developed in 1952, and it was the first burn formula created to account for body weight and the burn surface area. In the first 24 hours, it entails 1 ml/kg/% BSA of crystalloids plus 1 ml/kg/% BSA colloids plus 2000 ml glucose in water.  In the next 24 hours, crystalloids at 0.5 ml/kg/% BSA, colloids at 0.5 ml/kg/% BSA and the same amount of glucose in water as in the first 24 hours.      

The Brooke formula, initially described in 1953, used 1.5 ml/kg/% BSA of lactated Ringer’s solution plus 0.5 ml/kg/% BSA of colloid and 2 L of 5% dextrose in water. This formula was later modified to 2 ml/kg/% BSA of lactated Ringer’s solution with colloid not given in the first 24 hours postburn.

The Parkland formula (also called the Baxter formula), developed in 1968 by Dr. Charles Baxter, is perhaps the most widely recognized fluid replacement formula for burn injuries. It stipulates that 2 to 4 ml of Ringer’s Lactate per kilogram of weight per percentage of body surface area burned, with the first half given over the first 8 hours and the remainder given over the next 16 hours. Discrepancies still exist in patients where the body surface area calculation is not reliable, for example, pediatrics and patients who suffer from obesity. The Parkland formula was unique at its time of conception in that it recommended higher volumes of fluid than its predecessors. 

Burn injuries are a leading cause of unintentional death in children; although, the majority of these are considered minor. Due to their small circulating blood volumes, prompt resuscitation for pediatric burn victims is paramount. Adult resuscitation guidelines need to be altered for children because the distribution of their body surface area differs significantly. The Lund and Browder chart considers these differences by providing a pediatric-specific calculation.

Ringer's lactate is recommended for initial resuscitation in all age groups, but infant patients will require dextrose as well due to their limited glycogen stores. Because of this, pediatric burn resuscitation formulas are always 2-figure calculations: the estimated fluid resuscitation (EFR) and added maintenance fluids (MF) with or without dextrose depending on the child’s age. The cutoff for using the adult formula is generally agreed to be between 30 to 50 kg.[13]

At this time, the 2 major pediatric formulas are the Cincinnati formula and the Galveston formula. To date, there has not been a clinical comparison study between these.

Urine output is regarded as the resuscitation goal in pediatric burn management. For children under 30 kg, 1 ml/kg per hour is recommended; for children over 30 kg, 0.5 ml/kg per hour is the goal. As with adults, using UOP as the sole measure of efficacy is controversial and often misleading. Sheridan et al. have suggested that in infants, the goals be determined by sensorium, physical exam, pulse, and systolic blood pressure in addition to UOP.[14] The same additional parameters for therapy endpoints exist in the pediatric population, specifically, lactate, invasive transpulmonary thermodilution, and central venous pressures. These represent areas in need of further investigation for both children and adults.

Complications

Patients often arrive at burn centers having received overzealous hydration en route. First responders and inexperienced physicians often overestimate burn size and run the intravenous fluids wide open, with patients getting their first 8-hour Parkland requirements in only 1 to 2 hours.[15] 

Alternatively, the phenomenon referred to as “fluid creep” presents a challenge to burn patients regarding over-resuscitation. Giving too much volume can be detrimental, potentially creating pulmonary and cerebral edema or compartment syndrome of the extremities or abdomen. Several parameters contribute to fluid overloading, which has become a global issue. These parameters include the modified Parkland formula that has excluded colloid use, the impact of goal-directed resuscitation, and the overzealous, on-the-scene crystalloid resuscitation, combined with subsequent inefficient titration of fluid administration and lack of timely reduction of infusion rates.[4] Several factors have been identified that predispose burn patients to increased fluid requirements, including inhalation injury, delay in resuscitation, polytrauma, or high-voltage electrical injury.[16]

For this reason, infusion rates should be re-calculated hourly, and rates should not be increased by more than 20% to 25% at one time.

Physicians and nurses seem to have mastered the concept of increasing fluid rates when urine output (UOP) is less than 30 ml per hour but are less likely to decrease the infusion rate when UOP rises above the suggested maximum of 1 ml/kg per hour. One study demonstrated that infusion rates were only appropriately decreased 35% of the time.[17] Additionally, it has been suggested that using UOP as the sole indicator of adequate resuscitation is less accurate than other parameters such as base deficit and lactic acid. Differing opinions and conflicting evidence contribute to large inter-physician variability in the treatment of burn patients.

Circumferential burns of the extremities can undergo tourniquet effect due to the forming eschar, and these patients will need urgent escharotomy before fluid resuscitation. However, these events are rare except in cases of electrical burns, burns with underlying fracture, and burns with vascular injury.[18]

Clinical Significance

After many years of researching burn patient pathophysiology and outcomes, it is evident that prompt fluid resuscitation is essential for survival in these patients.[19] Now that efficient fluid replacement protocols have been enacted, fewer patients die in the first 48 hours.  [20] It has been shown that suboptimal resuscitation increases burn depth and creates a longer period of shock, which increases the mortality.[21]

Enhancing Healthcare Team Outcomes

Burn victims represent the necessity of communication between EMS, nursing staff, and physicians. Balancing fluid resuscitation in these patients is the most important and critical aspect of their care. There exists a finite window of appropriate resuscitation, in which too much or too little fluid can have catastrophic consequences.

Communication is a multi-dimensional, multi-factorial tool that is critical to all aspects of health care. Generally, an intensivist and/or plastic surgeon is leading burn victim cases. However, in addition to nursing and ancillary staff, other specialists will be involved in the care of the patient. A cross-sectional, descriptive, analytic study identified communication barriers that exist for these patients, including the hectic environment of the intensive care unity (ICU), and poor communication of symptoms by the patient due to a medical condition.[22] Therefore, providing a safe and calm environment for patients to communicate their needs is imperative to achieve clear communication.