The history of modern burn resuscitation can be traced back to observations made after large urban fires at the Rialto Theatre (New Haven, Conn) in 1921 and the Coconut Grove nightclub (Boston, Mass) in 1942. At the time, physicians noted that some patients with large burns survived the event but died from shock in the observation periods. Underhill and Moore identified the concept of thermal injury–induced intravascular fluid deficits in the 1930s and 1940s, and Evans soon followed with the earliest fluid resuscitation formulas in 1952. [1, 2] Up to that point, burns covering as little as 10-20% of total body surface area (TBSA) were associated with high rates of mortality. Through the 1970s, even a 30% TBSA burn was associated with nearly 100% mortality in older patients. See the image below.
See Thermal Injuries: A Matter of Degree, a Critical Images slideshow, to help identify and treat various types and degrees of burn injuries.
Over the next 50 years, advances in resuscitation further expanded these observations and led to numerous strategies to treat burn shock.  The prognostic burn index (PBI), a crude estimate of mortality involving adding age + TBSA has steadily improved to the point that a PBI score of 90-100 (predicting near certain mortality) now demonstrates mortality rates of 50-70% in adult burns. Nearly 13,000 annual hospital admissions are attributable to burns, and almost a dozen deaths per day result from residential fires. Children younger than 5 years and adults older than 65 years have a mortality from burns that is 6 times the national average. [4, 5]
The underlying process involved is both a local and systemic inflammatory reaction, the end result of which is an almost immediate shift of intravascular fluid into the surrounding interstitial space.  This occurs as a consequence of changes in vascular permeability as the normal capillary barrier is disrupted by a host of mediators, including histamine, serotonin, prostaglandins, platelet products, complement components, and members of the kinin family. This process occurs in burned tissues and, to lesser extent, in unburned tissues. The margination of neutrophils, macrophages, and lymphocytes into these areas is associated with the release of a rich milieu of these mediators, which affect both local and systemic capillary permeability.
Rapid transcapillary equilibration of the components of the intravascular compartment occurs with an iso-isomotic concentration state reached in the interstitium, with a similar proportion of proteins and plasma fluid. At the peak of edema formation, essentially all whole blood elements up to the size of RBCs (350,000 mol wt) are able to transmigrate through the vessel wall in burned tissue. However, some degree of sparing of capillary barrier function occurs in unburned tissues. As a result of this capillary leak, replacing the intravascular deficits incurred drives the continued accumulation of edema fluid as the resuscitative fluid equilibrates, with nearly one half of infused crystalloid volume lost to the interstitium.
As the burn size approaches 15-20% total body surface area (TBSA), shock sets in if the patient does not undergo appropriate fluid resuscitation. The peak of this third-spacing occurs at some point 6-12 hours postburn as the capillary barrier begins to regain its integrity, hence the reduction in fluid requirements observed in resuscitation formulas around this point. At this point, the theoretic benefits of adjuvant colloid therapy during the resuscitation allow the careful downward titration of fluid administration to reduce the obligatory edema.
Other factors in burn edema include the heat-induced denaturing of collagen fibers in the interstitium, causing a physical expansion of the potential third space with a transient -20 to -30 mm Hg negative-pressure gradient favoring extravasation of fluid. In adults with burns approaching 25-30% TBSA, damage to cell membranes also occurs (observed in all forms of hypovolemic shock), which is associated with a decrease in transmembrane potential and the accumulation of intracellular sodium and water, with resultant swelling at the cellular level. Resuscitation is associated with a restoration of the transmembrane potential toward normal, but unlike hemorrhagic shock, this deficit is corrected only partially with burn shock and contributes to the multifactorial edema. Failure to aggressively treat the volume deficit properly leads to progressively decreasing membrane potential with eventual cell death.
The classic description of the burn wound and surrounding tissues is a system of several circumferential zones radiating from primarily burned tissues, as follows:
- Zone of coagulation - A nonviable area of tissue at the epicenter of the burn
- Zone of ischemia or stasis - Surrounding tissues (both deep and peripheral) to the coagulated areas, which are not devitalized initially but, due to microvascular insult, can progress irreversibly to necrosis over several days if not resuscitated properly
- Zone of hyperemia - Peripheral tissues that undergo vasodilatory changes due to neighboring inflammatory mediator release but are not injured thermally and remain viable
The tissues in ischemic areas can potentially be salvaged by proper resuscitation in the initial stages and by proper burn wound excision and antimicrobial therapy in the convalescent period. Underresuscitation can convert this area into deep dermal or full-thickness burns in areas not initially injured to that extent. Reevaluation of these threatened areas over the first several days is used to determine when the first burn excision should be performed (ie, when the depth of burn has become apparent and decisions about which areas are deep dermal or of full thickness are clear).
A new area of interest with immediate resuscitation is the use of subatmospheric pressure dressings (eg, the VAC by KCI) on affected areas. Animal models and early clinical work suggest that this treatment may limit the conversion of zones of hyperemia to zones of ischemia by removing edematous fluid and allowing salvage of areas that would otherwise need excision and grafting. Most useful in the authors' experience in this regard has been the use of circumferential upper extremity VAC dressings.
Initial Evaluation and Treatment
Many patients with smaller burns can be successfully treated as outpatients or in most community hospitals. Identifying burn patients appropriate for immediate or subacute transfer is an important step in reducing morbidity and mortality. The American Burn Association (ABA) has established recommended criteria for transfer to burn centers. These criteria recognize the factors that are associated poorer outcomes, such as advanced age, electrical burns, and smoke inhalation. The following list is excerpted and adapted from Guidelines for the Operation of Burns Centers (p 79-86), Resources for Optimal Care of the Injured Patient 2006, Committee on Trauma, American College of Surgeons. 
Partial-thickness burns greater than 10% of total body surface area in patients who are younger than 10 years or older than 50 years
Partial-thickness burns over more than 20% of total body surface area in other age groups
Burns that involve the face, hands, feet, genitalia, perineum, or major joints
Third-degree burns in any age group
Burns in patients with preexisting medical disorders that could complicate management, prolong recovery, or affect mortality rate
Any patients with burns and concomitant trauma (such as fractures) in which the burn injury poses the greatest risk of morbidity or death
Burn injury in children at hospitals without qualified personnel or equipment for the care of children
Burn injury in patients who will require special social, emotional or long-term rehabilitative intervention
Organizing the evaluation of a burn patient in a manner similar to that of a trauma patient, beginning with the ABCDE assessment (ie, airway, breathing, circulation, disability, exposure) of the primary advanced trauma life support survey. Pay special and immediate attention to the presence of an ongoing thermal insult by way of either smoldering clothing or surface contact with a chemical irritant.
Airway management of burns is an extremely important consideration that can lead to devastating complications if not properly conducted. Very critical in the triage period is the consideration of whether inhalation components of the injury are present. Communication with the transporting EMTs or witnesses can quickly establish whether a closed space was involved, which should immediately trigger suspicion for airway injuries. When the event occurs in open areas or large and well-ventilated indoor areas, the possibility of significant inhalation components diminishes substantially.
Edema formation during resuscitation does not spare the airway. Administer supplemental oxygen with real-time oxygen saturation monitoring (keep saturations >90%) to all burn patients with any significant injury. Almost all patients with large burns require prompt intubation and ventilator support. Small- to- medium-sized burns can be disarming in that a patient can initially have a stable airway but may develop stridor over the next several hours as the edema increases, requiring a difficult and urgent intubation under less-than-ideal circumstances. In addition, large amounts of narcotics are administered, which also depresses the respiratory drive.
Singed facial hairs and carbonaceous sputum are signs that an inhalation injury component is present and further complicate both pulmonary function and fluid management. A history of a fire in a closed space or patients found unconscious at the scene are also often associated with significant inhalation injuries. In nonintubated patients with possible inhalation damage, nasopharyngoscopy is an important adjunct for assessing the extent of inhalation injury and for surveying laryngeal edema, which can help identify patients with impending respiratory failure. Include routine arterial blood gas determinations, chest radiographs, and carboxyhemoglobin levels (maintain at < 7%) as part of the secondary assessment.
New areas of interest in the early treatment of airway burns has focused on acute mechanical clearance of mucus and fibrin clot in the bronchial tree and inhaled bronchodilators to blunt narrowing of the airway in response to irritating elements in smoke. Aerosolized treatments of heparin, TPA, acetylcysteine, and terbutaline/steroid combinations have all been recently reported to have some promise in this area.
The authors cannot emphasize enough how important prompt establishment of large-bore intravenous (IV) access and rapid initiation of fluid resuscitation are in the outcome of patients with significant thermal injuries.  No factor other than airway protection is as critical in the early period after a burn. Ideally, place IV lines away from burned tissues because of the difficulty in isolating veins and problems securing the IV line to burned skin (rather than because of a fear of infectious complications; the native skin flora has essentially been transiently heat-sterilized by the injury in those areas). Other considerations with IV lines in burned areas are the potential for dislodgement from the vein secondary to the developing burn edema and a potential for a tourniquet effect if the IV line is secured improperly with circumferential dressings.
Most younger patients with small- to medium-sized burns do not require central lines and the concomitant morbidity and risks associated with their placement. However, if their use is deemed necessary, place them early, before edema makes assessment of landmarks in the head and neck difficult. If this approach is chosen in a patient with significant head and neck edema, consider using one of the commercial ultrasound probes for vascular access, if available, to assist in the placement of jugular vein central lines. Central lines, like peripheral lines, can become dislodged secondary to massive edema. This is especially true for the shorter, large-bore cordis catheters, which can be retracted into the extravascular space when in a subclavicular placement in a larger patient. Cordis catheters can also become kinked for the same reason, depending on their angle of approach to the vein.
Femoral vein central access is a route usually avoided due to evidence of increased infections, but this vein is sometimes the only accessible large vein in nonburned tissues and must be used. The safety and utility of this approach with burns have been documented, and this approach presents an acceptable option as long as meticulous local care of the site and all precautions to prevent central line infections are observed.
In burn patients who require IV resuscitation, place a Foley catheter early so that urine output can be monitored as a guide for volume status. At this time, also consider placing a nasogastric tube to decompress the stomach and consider beginning early enteral feedings as part of the resuscitation recommended by the American Burn Society. Assess peripheral pulses immediately, and evaluate all extremities and the chest wall for potential compartment syndromes. Initially, assume weak pulses to be from underresuscitation, but maintain a low threshold to perform escharotomies or fasciotomies, especially in patients who are transferred from outside facilities some hours after the event occurred.
Careful observation of involved extremities is demanded in the resuscitative phases. Edema formation can transform a well-perfused limb into an ischemic disaster with myoglobin-related renal failure if unaddressed. Gravity-dependent drainage by elevating the limbs above the heart level and frequent pulse checks using a Doppler device are therefore necessary in the first 24-48 hours.
Patients with circumferential burns have the highest risk of developing a compartment syndrome and demand the closest observation. If pulses are lost in an extremity, several issues must be addressed. First, consider whether the lost pulses are a reflection of underresuscitation in a patient who needs more volume. Second, consider whether the patient has associated trauma with a potential vascular injury. Lastly, consider if a compartment syndrome has developed.
Compartment pressures can be measured with several hand-held commercial devices, or an arterial-line apparatus can be used. Sustained compartment pressures in the range of approximately 30 mm Hg are considered high and are suggestive of a compartment syndrome. Compartment pressures documented in the 40s necessitate an escharotomy or fasciotomy for urgent release. Ensure that an electrocautery unit is immediately available for an escharotomy at the bedside; sedate the patient from the length of the eschar into a small margin of normal tissues. An exquisitely painful escharotomy may reflect that the lost pulse was not related to a compartment syndrome and a reassessment of volume status is needed.
Estimation of Burn Size and Depth
The first step in assessing a burn and planning resuscitation involves a careful examination of all body surfaces. A standard Lund-Browder chart is readily available in most emergency departments for a quick assessment of TBSA burns.  See the image below.
If the Lund-Browder chart is not available, the "rule of nines" is fairly accurate in adult patients.  Note that a patient's palm is approximately 1% TBSA and can be used for estimating patchy areas.  See the image below.
The following details the rule of nines:
Head/neck - 9% TBSA
Each arm - 9% TBSA
Anterior thorax - 18% TBSA
Posterior thorax - 18% TBSA
Each leg - 18% TBSA
Perineum - 1% TBSA
With pediatric patients, the head is a proportionally larger contributor to body surface area (BSA), while the upper legs contribute less. This difference is reflected in the slight differences noted in the pediatric Lund-Browder diagram. A useful tool for estimating BSA of spotty burns is the close approximation of just less than 1% BSA to the patient's palm size. Only second-degree burns or greater should be included in the TBSA determination for burn fluid calculations.
Burn depth has come to be classified into several fairly standardized categories. These include superficial (first-degree) burns, partial-thickness (second-degree) burns, full-thickness (third-degree) burns, and devastating full-thickness (fourth-degree) burns. 
Superficial (first-degree) burns are limited to epidermal layers and are equivalent to a superficial sunburn without blister formation.
Partial-thickness (second-degree) burns are also called dermal burns and can be superficial partial-thickness burns or deep partial-thickness burns.
Superficial partial-thickness burns involve the superficial papillary dermal elements and are pink and moist with exquisite pain upon examination. Blister formation appears with the level of the burn. This type of burn is expected to heal well within several weeks, without skin grafting. See the image below.
Deep partial-thickness burns involve the deeper reticular dermis. They can have a variable appearance ranging from pink to white with a dry surface. Sensation may be present but is usually somewhat diminished, and capillary refill is sluggish or absent. Burns of this depth routinely require excision and grafting for satisfactory healing. See the image below.
Full-thickness (third-degree) burns extend into the subcutaneous tissues and have a firm, leathery texture and complete anesthesia upon examination. Clotted vessels can be observed through the eschar. See the image below.
Fourth-degree burns are devastating full-thickness burns that extend into muscle and bone.
Estimating burn depth at the extremes of severity is relatively easy. Differentiating the subtleties between dermal-level burns is difficult, even for experienced surgeons. However, this distinction is more important for planning excision and grafting of the burn than for resuscitation.  Some burns that initially appear to be limited to epidermal layers (ie, first-degree burns), and thus are not included in resuscitation calculations, may develop the blistered characteristics of dermal level burns over several hours. Evaluation of burn depth with laser Doppler in the first few days of treatment has been an effective adjunct in some centers for assessing moderate to severe burns.
When evaluating burn depth, considering the burn in the context of which factors individually determine burn depth is important. These factors are the temperature, mechanism (eg, electrical, chemical), duration of contact, blood flow to the skin, and anatomic location. The keratinized epidermal depth can vary dramatically by body area from less than 1 mm in the thinnest areas (eyelids, genitals) to 5 mm (palms and plantar surfaces), offering varying degrees of thermal protection. In addition, the dermal elements of young children and geriatric patients are somewhat thinner than those of healthy adults, which explains the observation that burns in persons of these age groups are usually more severe than similar insults in other patients.
Outside reports of burn size and depth are notoriously unreliable, especially from referring physicians with little experience with burns. Estimates state that reports of burn size are estimated correctly only one third of the time and that burn sizes are frequently significantly overestimated (averaging 75% larger than burn unit size estimates).This was supported by a study by Swords et al, which indicated that in children with burn injuries, emergency department physicians may often overestimate the TBSA burned, leading to overresuscitation. The investigators found that in almost 50% of children sent to a burn center, TBSA burned was overestimated by at least 5% by the referring institution. The data also indicated that a statistically significant relationship existed between this 5% or greater overestimation and overresuscitation by at least 10 mL/kg. 
Practitioners should still assume that the burn is somewhat worse than described and be prepared to fully reevaluate the burn upon the patient's arrival because burn size has significant influence on all aspects of the initial management.
Table 1. Differences in TBSA With Age (Open Table in a new window)
|Infant||Age 1 Y||Age 5 Y||Age 10 Y||Age 15 Y||Adult|
Resuscitative Fluid Management
Formulas and solutions
Historically, fluid management for burns has been as much an art as it has been a science; a fine line must be negotiated between an adequate resuscitation and one that is associated with the deleterious effects of fluid overload. Policies and practices have been highly individualized and can vary dramatically from institution to institution. However, the predominant teaching of the last quarter century has a pedigree derived from the influential publications involving regression analysis studies of resuscitative volumes in adult burn patients by Charles Baxter, MD, at Parkland Hospital at Southwestern University Medical Center (Dallas, Tex) in the 1960s. 
From these studies came the venerable Parkland formula, which advocated the guideline for total volume of the first 24 hours of resuscitation (with Ringer lactate [RL] solution) at approximately 4 mL/kg body weight per percentage burn TBSA.  With this formula, half the volume is given in the first 8 hours postburn, with the remaining volume delivered over 16 hours. Multiple formulas exist with variations in both the volumes per weight suggested and the type or types of crystalloid or crystalloid-colloid combinations administered. To date, no single recommendation has been distinguished as the most successful approach. [9, 13]
The time-dependent variables for all of these formulas begin from the moment of injury, not from the time the patient is seen in the emergency department. A scenario that is not uncommon is a burn patient being transferred from an outlying hospital several hours after a burn and arriving in a severely underresuscitated or overresuscitated state. Calculations for the rate of fluid resuscitation should take this into account and reflect the decreased or increased starting IV fluid rate.
RL solution is a relatively isotonic crystalloid solution that is the key component of almost all resuscitative strategies, at least for the first 24-48 hours.  It is preferable to isotonic sodium chloride solution (ie, normal saline [NS]) for large-volume resuscitations because its lower sodium concentration (130 mEq/L vs 154 mEq/L) and higher pH concentration (6.5 vs 5.0) are closer to physiologic levels. Another potential benefit of RL solution is the buffering effect of metabolized lactate on the associated metabolic acidosis. Plasmalyte is another crystalloid solution, the composition of which is even more closely physiologic than RL solution, and Plasmalyte is used in some centers as the initial crystalloid solution for large burns. However, the significant cost difference per unit, with an uncertain benefit, has limited its widespread use at many burn units.
Regardless of the resuscitation formula or strategy used, the first 24-48 hours require frequent adjustments.  Calculated volumes from all of the formulas should be viewed as educated guesses of the appropriate fluid load. Blind adherence to a derived number can lead to significant overresuscitation or underresuscitation if not interpreted within the clinical context. Overresuscitation can be a major source of morbidity for burn patients and can result in increased pulmonary complications and escharotomies of the chest or extremities. [12, 15] In addition, not all burns require use of the Parkland formula for resuscitation. Promptly addressed adult burns of less than 15-20% TBSA without inhalation injury are usually not enough to initiate the systemic inflammatory response, and these patients can be rehydrated successfully primarily via the oral route with modest IV fluid supplementation.
An idea being advanced in some of the tertiary burn centers is to begin burn excision and wound closure during the resuscitation phase. The rationale for this strategy is to remove the devitalized tissue quickly to blunt the systemic inflammatory cascade.
Routine vital signs, such as blood pressure and heart rate, can be very difficult to interpret in patients with large burns. Catecholamine release during the hours after the burn can support blood pressures despite the extensive intravascular depletion that exists. The formation of edema in the extremities can limit the usefulness of noninvasive blood pressure measurements. Evaluation of arterial line pressures likewise is subject to error from peripheral vasospasm from the high-catecholamine state. Tachycardia, normally a clue to hypovolemia, can be secondary to pain and is also almost universally present from the adrenergic state. Following a trend in the gradual normalization of vital signs is thus much more useful than any single reading.
A great deal of interest exists in using antioxidants as adjuncts to resuscitation to try to minimize oxidant-mediated contributions to the inflammatory cascade. In particular, megadose vitamin C infusion during resuscitation has been studied at some length. Some animal models have demonstrated that infusion of vitamin C within 6 hours postburn can lower calculated resuscitation values by up to one half. Whether this phenomenon can be reproduced successfully in human subjects has not been clearly demonstrated.
Proponents have reached no consensus regarding the proper total dose. Some have adopted the strategy of placing up to 10 g in a liter of RL solution, infusing it at 100 mL/h (1 g/h vitamin C), and counting the volume as part of the resuscitation volume. Recently published data using an infusion of 66 mg/kg/h during the first 24 hours demonstrate a 45% decrease in the required fluid resuscitation in a small group of patients.
The safety of high-dose vitamin C has been established in humans, at least for the short-term, but this strategy is probably less safe in patients who are pregnant, those with renal failure, and those with a history of oxalate kidney stones.
End points for resuscitation
The end points for resuscitation are debatable,  but hourly urine output is a well-established parameter for guiding fluid management. The rate of fluid administration should be titrated to a urine output of 0.5 mL/kg/h or approximately 30-50 mL/h in most adults and older children (>50 kg). In small children, the goal should be approximately 1 mL/kg/h (see Pediatric Resuscitation Issues). Failure to meet these goals should be addressed with gentle upward corrections in the rate of fluid administration by approximately 25%.
An important point is that periodically increasing the fluid rate is much more favorable than giving frequent boluses of fluid for low urine output. This results in transient elevations in hydrostatic pressure gradients that further increase the shift of fluids to the interstitium and worsen the edema. However, do not hesitate to administer a bolus to patients as appropriate early in the resuscitation for hypotensive shock. The urge to maintain urine output at rates greater than 30-50 mL/h should be avoided. Fluid overload in the critical hours of early burn management leads to unnecessary edema and pulmonary dysfunction. It can necessitate morbid escharotomies and extend the time required for ventilator support.
Several complicating factors exist with monitoring urine output as a guide for volume status and end organ perfusion. The presence of glycosuria can result in an osmotic diuresis and can lead to artificially elevated urine output values. Performing a urinalysis at some point during the first 8 hours can be prudent, especially for patients with larger burns, to screen for this potentially serious overestimation of the intravascular volume. In addition, older patients with long-standing diuretic use may be dependent on diuretics and may not be able to maintain a desired urine output despite what appears to be an adequate resuscitation volume. Swan-Ganz catheter placement is an important adjunct in the decision-making process in this group of patients regarding fluid replacement and possible diuretic use.
Other physiologic parameters that reflect the adequacy of resuscitation include an improving base deficit and the maintenance of the cardiac index in those in whom invasive monitors are placed. Because of several factors, such as pulmonary vasoconstriction, the same interpretive problems are true for central venous pressure or pulmonary capillary wedge pressure measurements. Swan-Ganz catheters should not be used routinely but may have some role in geriatric patients and those with poor underlying cardiac function.
Again, the overall clinical response and general trends in these numbers are much more useful for adjusting fluid administration or chemotherapy to support cardiac function than values from isolated measurements. Catheter-based resuscitation tends to deliver higher-based volumes then the traditional methods but has not demonstrated an improvement in morbidity or mortality. Research indicates that increased crystalloid cannot restore cardiac preload to baseline during the period of burn shock. 
Certain patient populations frequently require resuscitation volumes that are higher than those calculated. Patients with inhalation injuries are perhaps the most studied subset, with required volumes sometimes as much as 30-40% higher (close to 5.7 mL/kg per percentage) than predicted by the Parkland formula for adequate resuscitation.  Delays in initiating resuscitation promptly have also been shown to increase fluid requirements by as much as 30%, presumably by permitting the occurrence of an increased inflammatory cascade. Patients on home diuretic therapy frequently have preexisting free-water deficits in addition to burn shock. The presence of an escharotomy or fasciotomy can substantially increase free water loss from the wound, and this must be replaced. Patients with electrical burns, often associated with large and underappreciated tissue insult, likewise require large-volume fluid resuscitations.
Do not forget that burn patients are trauma patients and frequently arrive with a poor history of the events surrounding the accident. An unexpected high volume requirement should therefore prompt a very close examination for missed associated injuries. A strategy that has been used with some success for refractory burn shock has been investigated by researchers at the University of Cincinnati and involves plasma exchange.  Appropriate candidates for this innovative technique include those with more than twice the calculated fluid requirements despite hypertonic saline infusion.
Table 2. Resuscitation Formulas (Open Table in a new window)
|Formula||Fluid in First 24 Hours||Crystalloid in Second 24-Hours||Colloid in Second 24-Hours|
|Parkland||RL at 4 mL/kg per percentage burn||20-60% estimated plasma volume||Titrated to urinary output of 30 mL/h|
|Evans ||NS at 1 mL/kg per percentage burn, 2000 mL D5W*, and colloid at 1 mL/kg per percentage burn||50% of first 24-hour volume plus 2000 mL D5W||50% of first 24-hour volume|
|Slater ||RL at 2 L/24 h plus fresh frozen plasma at 75 mL/kg/24 h|
|Brooke ||RL at 1.5 mL/kg per percentage burn, colloid at 0.5 mL/kg per percentage burn, and 2000 mL D5W||50% of first 24-hour volume plus 2000 mL D5W||50% of first 24-hour volume|
|Modified Brooke||RL at 2 mL/kg per percentage burn|
|RL solution with 50 mEq sodium bicarbonate per liter at 4 mL/kg per percentage burn||Half NS titrated to urine output||1 U fresh frozen plasma for each liter of half NS used plus D5W as needed for hypoglycemia|
Demling [22, 23]
|250 mEq/L saline titrated to urine output at 30 mL/h, dextran 40 in NS at 2 mL/kg/h for 8 hours, RL titrated to urine output at 30 mL/h, and fresh frozen plasma 0.5 mL/h for 18 hours beginning 8 hours postburn||One-third NS titrated to urine output|
|*D5W is dextrose 5% in water solution|
Colloid and Hypertonic Saline
Due to the high morbidity associated with high-volume resuscitations, an interest exists in using various colloid solutions to both decrease edema and volume requirements and blunt the myocardial depression phenomena observed with large burns. An important consideration for adding colloid in the first 24 hours is the loss of capillary integrity during early burn shock. This process occurs early and is present for 8-24 hours depending on which authority is referenced. A strategy for testing whether the capillary leak has begun to resolve involves substituting an equal volume of albumin solution for RL solution. An increase in urine output suggests that at least some of the leak has resolved and that the further introduction of colloid can help decrease the fluid load.
Albumin is the plasma protein that most contributes to intravascular oncotic pressure.  When administered intravenously as a 5% solution from pooled plasma product, approximately half the volume remains intravascularly, as opposed to 20-30% of crystalloid solutions. Alternatively, some centers prefer using fresh frozen plasma over using albumin because of the theoretic advantage of replacing the whole range of plasma proteins that are lost rather than just the albumin fraction. Guidelines for this infusion have been reported as 0.5-1 mL/kg per percentage burn during the first 24 hours, beginning 8-10 hours postburn as an adjuvant to RL solution resuscitation.
Dextran is a solution of polymerized, high molecular weight glucose chains with almost twice the oncotic pressure of albumin. An increase in microcirculatory flow is also produced by reducing erythrocyte aggregation. Proponents of dextran point to the reduction of edema in nonburned tissues as justification for its use. The edema-reducing properties are maintained for as long as the infusion is continued, but upon withdrawal and subsequent metabolism of the glucose, rapid loss of fluid occurs back into the interstitium if the capillary leak is still present. Demling and others have used dextran 40 successfully in the early postburn period (first 8 h) at 2 mL/kg/h along with RL solution before switching to some albumin or fresh frozen plasma plus RL solution combination for the second 18-hour phase. 
Hypertonic saline solutions, ranging in concentration from 180-300 mEq sodium per liter, have many theoretic benefits. These benefits are achieved by the reduction in volume requirements by mobilizing intracellular fluid into the vascular space by the increased osmotic gradient. The intracellular depletion of water that results is a debated concern, but it appears to be well tolerated. Close monitoring of serum sodium levels is mandatory, and serum sodium levels should not be allowed to increase to greater than 160 mEq/dL.
As a compromise strategy to limit the risk of hypernatremia and sodium retention, some institutions use RL solution with 50 mEq amps of sodium bicarbonate per bag, for a fluid approaching 180 mEq sodium per liter during the initial 8 hours of the resuscitation, rather than using the more concentrated saline solutions. Then, after the first 8 hours, the fluid is changed to RL solution to complete the resuscitation. Hypertonic saline management must be titrated closely to both urine output and serum sodium checks and probably should not be used routinely outside of tertiary burn centers.
The safety and benefits of hypertonic saline resuscitation extend to both the pediatric and geriatric populations, but using solutions at the lower end of tonicity is probably safer. The greatest benefit may ultimately be for those patients with the most limited cardiopulmonary reserves, those with inhalation injury, and those with larger burns approaching 40% or more.
Exactly when or whether to add colloid to resuscitation fluids is a confusing issue. As mentioned previously, most of the mainstream burn formulas add colloid during the resuscitation, at least in the second 24-hour period. However, what must be recognized is that despite a general consensus that colloid use is both beneficial and appropriate, especially in burns greater than 40% TBSA, demonstrating improved outcomes in morbidity or mortality has been difficult. In fact, some studies have demonstrated harmful effects secondary to increased pulmonary edema and some evidence of renal dysfunction as manifested by a decreased glomerular filtration rate. For smaller burns (ie, 20-40% without inhalation injury), expectant management with RL solution titrated to urine output is a safe and well-tested strategy.
The patients who benefit the most from lower-volume resuscitations aided by colloid are those with larger burns (>40%), those with preexisting heart disease, geriatric patients, and those with burns with associated inhalation injuries
At 24-30 hours after the insult, the patient should be resuscitated adequately, with near complete resolution of the transcapillary leak with fluid requirements. At this point, some authorities recommend a change in fluid management from RL solution to a combination fluid infusion involving albumin and D5W. The rational for this is the massive protein losses that have occurred from the burn wound during the first 24 hours. Replacing this deficit with a steady infusion of 5% or 25% albumin solution can serve to maintain a serum albumin concentration greater than 2, which can help reduce tissue edema and improve gut function. Associated insensible losses of free water from the injured skin barrier can be met by replacing the deficit with an electrolyte-free fluid such as D5W solution, which also serves to restore the extracellular space to an isotonic state, especially if hypertonic solutions were used during the resuscitation.
The formula for the estimate for 5% albumin infusion is as follows:
0.5 mL/kg per percentage burn = mL albumin for 24 hours
The formula for the free water estimate is as follows:
(25 + percentage burn) X BSA (m2) = mL/h of free water required
The US Army Institute of Surgical Research uses a similar approach but stratifies the albumin calculations by the estimated TBSA of the burn. For burns of 30-50%, they use 0.3 mL/kg per percentage burn; for burns of 50-70%, 0.4 mL/kg per percentage burn is used; and for burns of 70% and greater, they use 0.5 mL/kg per percentage burn.
A potential pitfall is iatrogenic hypernatremia as a result of titrating a sodium-rich albumin solution. Serum sodium levels should be checked at least once a day. The relative rate of albumin is titrated to adequate urine output with close monitoring of the serum sodium level. As the serum sodium level rises to unacceptable levels, simply increasing the D5W solution infusion rate corrects it toward normal or vice versa.
The most important thing to recognize with all the discussion regarding fluid management is that many different techniques have proven successful. Replacing the volume deficit to support tissue perfusion and correct the metabolic acidosis can be achieved with multiple fluid types and has been the rationale for treatment for nearly 70 years. Changes to this basic tenet have only come at the periphery. Real progress in the understanding of the very complex associated pathophysiology of burn shock is reflected in the use of newer products to supplement crystalloid resuscitation. Further advances will obviously come from optimizing the timing of the colloid and hypertonic administration and from research into blunting the underlying mediators of burn shock.
Pediatric Resuscitation Issues
Since the recognition of the phenomenon of burn shock, significant progress has been made in the survival rates of pediatric and juvenile patients. Currently, patients with all but the largest TBSA injuries can be expected to survive when treated promptly [26, 27, 28] .
Several very important conceptual differences exist in pediatric burn resuscitation. Intravenous fluid resuscitations are usually required for patients with smaller burns (in the range of 10-20%). Venous access in small children may be a difficult issue, and a saphenous vein cutdown or an interosseous line is an acceptable alternative in the short term. Children have proportionally larger BSAs than adults; TBSA burns must be estimated using pediatric modifications to Lund-Browder tables, which demonstrate the relatively larger head and small thigh. This results in higher weight-based calculations for resection volume (nearly 6 mL/kg per percentage burn) and has led some to advocate a BSA-based resuscitation in addition to the infusion of a maintenance requirement as described by the Galveston Shriners Hospital pediatric formula. Other centers, such as the Shriners Burn Institute in Cincinnati, Ohio, simply use the Parkland formula with the addition of a maintenance rate.
Recommended end points are also higher in children, with urine output closer to 1 mL/kg/h being a more appropriate goal. Children approaching 50 kg are probably better served by adult resuscitation parameters (30-50 mL/h urine output) and calculations. Another concern with this population is the modest hepatic glycogen reserves, which can be exhausted quickly and sometimes require the change from RL solution to dextrose 5% in RL solution to prevent life-threatening hypoglycemia. For this reason, AccuChecks every 4-6 hours should be routine during the hypermetabolic state, especially for patients with larger burns.
Pediatric resuscitation protocols are based on the following formula (H is height [cm], W is weight [kg]):
BSA = [87 (H + W) - 2600] / 10,000
Pediatric resuscitation protocols are as follows:
Shriners Burn Institute (Cincinnati) - 4 mL/kg per percentage burn plus 1500 mL/m 2 BSA
- First 8 hours - RL solution with 50 mEq sodium bicarbonate per liter
- Second 8 hours - RL solution
- Third 8 hours - RL solution plus 12.5 g of 25% albumin solution per liter
Galveston Shriners Hospital - 5000 mL/m 2 TBSA burn plus 2000 mL/m 2 BSA, using RL solution plus 12.5 g 25% albumin per liter plus D5W solution as needed for hypoglycemia
The most important thing to remember regarding fluid management is that many different techniques have proven successful. Replacing the volume deficit to support tissue perfusion and correct the metabolic acidosis can be achieved with multiple fluid types and has been the rationale for treatment for nearly 70 years. Changes to this basic tenet have only come at the periphery. Real progress in the understanding of the very complex associated pathophysiology of burn shock is reflected in the use of newer products to supplement crystalloid resuscitation. According to retrospective analysis, most important predictors of mortality are the size of burn, age of patient, and worst base deficit in the first 24 hours. Further advances will obviously come from optimizing the timing of colloid and hypertonic fluid administration and from research into blunting the underlying mediators of burn shock.