Transcript of "Chapter 3 burn resuscitation and early management"
CHAPTER-3 Burns, Resuscitation and Early Management HISTORYThe history of modern burn resuscitation can be traced back to observations madeafter large urban fires at the Rialto Theatre (New Haven, Conn) in 1921 and theCoconut Grove nightclub (Boston, Mass) in 1942. At the time, physicians notedthat some patients with large burns survived the event but died from shock in theobservation periods. Underhill and Moore identified the concept of thermalinjury–induced intravascular fluid deficits in the 1930s and 1940s, and Evanssoon followed with the earliest fluid resuscitation formulas in 1952 (Yowler,2000). Over the next 50 years, advances in resuscitation further expanded theseobservations and led to numerous strategies to treat burn shock. PATHOPHYSIOLOGYThe underlying process involved is both a local and systemic inflammatoryreaction, the end result of which is an almost immediate shift of intravascularfluid into the surrounding interstitial space. This occurs as a consequence ofchanges in vascular permeability as the normal capillary barrier is disrupted by ahost of mediators, including histamine, serotonin, prostaglandins, plateletproducts, complement components, and members of the kinin family. Thisprocess occurs in burned tissues and, to lesser extent, in unburned tissues. Themargination of neutrophils, macrophages, and lymphocytes into these areas isassociated with the release of a rich milieu of these mediators, which affect bothlocal and systemic capillary permeability.Rapid transcapillary equilibration of the components of the intravascularcompartment occurs with an iso-isomotic concentration state reached in theinterstitium, with a similar proportion of proteins and plasma fluid. At the peak ofedema 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 burnedtissue. However, some degree of sparing of capillary barrier function occurs inunburned tissues. As a result of this capillary leak, replacing the intravasculardeficits incurred drives the continued accumulation of edema fluid as theresuscitative fluid equilibrates, with nearly one half of infused crystalloid volumelost to the interstitium.
As the burn size approaches 15-20% total body surface area (TBSA), shock setsin if the patient does not undergo appropriate fluid resuscitation. The peak of thisthird-spacing occurs at some point 6-12 hours postburn as the capillary barrierbegins to regain its integrity, hence the reduction in fluid requirements observedin resuscitation formulas around this point. At this point, the theoretic benefits ofadjuvant colloid therapy during the resuscitation allow the careful downwardtitration of fluid administration to reduce the obligatory edema.Other factors in burn edema include the heat-induced denaturing of collagenfibers in the interstitium, causing a physical expansion of the potential third spacewith a transient -20 to -30 mm Hg negative-pressure gradient favoringextravasation of fluid. In adults with burns approaching 25-30% TBSA, damageto cell membranes also occurs (observed in all forms of hypovolemic shock),associated with a decrease in transmembrane potential and the accumulation ofintracellular sodium and water, with resultant swelling at the cellular level.Resuscitation is associated with a restoration of the transmembrane potentialtoward normal, but unlike hemorrhagic shock, this deficit is corrected onlypartially with burn shock and contributes to the multifactorial edema. Failure toaggressively treat the volume deficit properly leads to progressively decreasingmembrane potential with eventual cell death.The classic description of the burn wound and surrounding tissues is a system ofseveral circumferential zones radiating from primarily burned tissues, as follows: 1. Zone of coagulation - A nonviable area of tissue at the epicenter of the burn 2. 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 3. Zone of hyperemia - Peripheral tissues that undergo vasodilatory changes due to neighboring inflammatory mediator release but are not injured thermally and remain viableThe tissues in Ischaemic areas can potentially be salvaged by proper resuscitationin the initial stages and by proper burn wound excision and antimicrobial therapyin the convalescent period. Under-resuscitation can convert this area into deepdermal or full-thickness burns in areas not initially injured to that extent.Reevaluation of these threatened areas over the first several days is used todetermine 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 orof full thickness are clear).INITIAL EVALUATION AND TREATMENTOrganize the evaluation of a burn patient in a manner similar to that of a traumapatient, beginning with the ABCDE assessment (ie, airway, breathing,circulation, disability, exposure) of the primary advanced trauma life supportsurvey. Pay special immediate attention to the presence of an ongoing thermalinsult by way of either smoldering clothing or surface contact by a chemicalirritant.Airway managementAirway management of burns is an extremely important consideration that canlead to devastating complications if not properly conducted. Edema formationpresent during resuscitation does not spare the airway. Administer supplementaloxygen with real-time oxygen saturation monitoring (keep saturations >90%) toall burn patients with any significant injury. Patients with large burns almostuniformly require prompt intubation and ventilator support. Small- to- medium-sized burns can be disarming in that a patient can initially have a stable airwaybut may develop stridor over the next several hours as the edema increases,requiring a difficult and urgent intubation under less-than-ideal circumstances. Inaddition, large amounts of narcotics are administered, which also depress therespiratory drive.Singed facial hairs and carbonaceous sputum are signs that an inhalation injurycomponent is present and further complicate both pulmonary function and fluidmanagement. A history of a fire in a closed space or patients found unconsciousat the scene are also often associated with significant inhalation injuries. Innonintubated patients with possible inhalation damage, nasopharyngoscopy is animportant adjunct for assessing the extent of inhalation injury and for surveyinglaryngeal edema, which can help identify patients with impending respiratoryfailure. Include routine arterial blood gas determinations, chest radiographs, andcarboxyhemoglobin levels (maintain at <7%) as part of the secondaryassessment.Intravenous accessThe authors cannot emphasize enough how important prompt establishment oflarge-bore intravenous (IV) access and rapid initiation of fluid resuscitation are inthe outcome of patients with significant thermal injuries. No factor other thanairway protection is as critical in the early period after a burn. Ideally, place IVlines 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 ofinfectious complications; the native skin flora has essentially been transientlyheat-sterilized by the injury in those areas). Other considerations with IV lines inburned areas are the potential for dislodgement from the vein secondary to thedeveloping burn edema and a potential for a tourniquet effect if the IV line issecured improperly with circumferential dressings.Most younger patients with small- to medium-sized burns do not require centrallines and the concomitant morbidity and risks associated with their placement.However, if their use is deemed necessary, place them early, before edema makesassessment of landmarks in the head and neck difficult. If this approach is chosenin a patient with significant head and neck edema, consider using one of thecommercial ultrasound probes for vascular access, if available, to assist in theplacement of jugular vein central lines. Central lines, like peripheral lines, canbecome dislodged secondary to massive edema. This is especially true for theshorter, large-bore cordis catheters, which can be retracted into the extravascularspace when in a subclavicular placement in a larger patient. Cordis catheters canalso become kinked for the same reason, depending on their angle of approach tothe vein.Femoral vein central access is a route usually avoided due to evidence ofincreased infections, but this vein is sometimes the only accessible large vein innonburned tissues and must be used. The safety and utility of this approach withburns have been documented, and this approach presents an acceptable option aslong as meticulous local care of the site and all precautions to prevent central lineinfections are observed.Additional evaluationIn burn patients who require IV resuscitation, place a Foley catheter early so thaturine output can be monitored as a guide for volume status. At this time, alsoconsider placing a nasogastric tube to decompress the stomach and considerbeginning early enteral feedings. Assess peripheral pulses immediately, andevaluate all extremities and the chest wall for potential compartment syndromes.Initially, assume weak pulses to be from under-resuscitation, but maintain a lowthreshold to perform escharotomies or fasciotomies, especially in patients whoare transferred from outside facilities some hours after the event occurred.Careful observation of involved extremities is demanded in the resuscitativephases. Edema formation can transform a well-perfused limb into an ischemic
disaster with myoglobin-related renal failure if unaddressed. Gravity-dependentdrainage by elevating the limbs above the heart level and frequent pulse checksusing a Doppler device are therefore necessary in the first 24-48 hours.Patients with circumferential burns have the highest risk of developing acompartment syndrome and demand the closest observation. If pulses are lost inan extremity, several issues must be addressed. First, consider whether the lostpulses are a reflection of under-resuscitation in a patient who needs more volume.Second, consider whether the patient has associated trauma with a potentialvascular injury. Lastly, consider if a compartment syndrome has developed.Compartment pressures can be measured with several hand-held commercialdevices, or an arterial-line apparatus can be used. Sustained compartmentpressures in the range of approximately 30 mm Hg are considered high and aresuggestive of a compartment syndrome. Compartment pressures documented inthe 40s necessitate an escharotomy or fasciotomy for urgent release. Ensure thatan 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 normaltissues. An exquisitely painful escharotomy may reflect that the lost pulse wasnot related to a compartment syndrome and a reassessment of volume status isneeded.ESTIMATION OF BURN SIZE AND DEPTHThe first step in assessing a burn and planning resuscitation involves a carefulexamination of all body surfaces. A standard Lund-Browder chart is readilyavailable in most emergency departments for a quick assessment of TBSA burns.If this is not available, the "rule of nines" is fairly accurate in adult patients.See the rule of nines as follows. Note that a patients palm is approximately 1%TBSA and can be used for estimating patchy areas. • 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 bodysurface area (BSA), while the upper legs contribute less. This difference isreflected in the slight differences noted in the pediatric Lund-Browder diagram.A useful tool for estimating BSA of spotty burns is the close approximation ofjust less than 1% BSA to the patients palm size. Only second-degree burns orgreater 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 equivalentto a superficial sunburn without blister formation.Partial-thickness (second-degree) burns are also called dermal burns and can besuperficial partial-thickness burns or deep partial-thickness burns. Superficialpartial-thickness burns involve the superficial papillary dermal elements and arepink and moist with exquisite pain upon examination. Blister formation appearswith the level of the burn. This type of burn is expected to heal well withinseveral weeks, without skin grafting. Deep partial-thickness burns involve thedeeper reticular dermis. They can have a variable appearance ranging from pinkto white with a dry surface. Sensation may be present but is usually somewhatdiminished, and capillary refill is sluggish or absent. Burns of this depth routinelyrequire excision and grafting for satisfactory healing.Full-thickness (third-degree) burns extend into the subcutaneous tissues and havea firm, leathery texture and complete anesthesia upon examination. Clottedvessels can be observed through the eschar.Fourth-degree burns are devastating full-thickness burns that extend into muscleand bone.Estimating burn depth at the extremes of severity is relatively easy.Differentiating the subtleties between dermal-level burns is difficult, even forexperienced surgeons. However, this distinction is more important for planningexcision and grafting of the burn than for resuscitation. Some burns that initiallyappear to be limited to epidermal layers (ie, first-degree burns), and thus are notincluded in resuscitation calculations, may develop the blistered characteristics ofdermal level burns over several hours.
When evaluating burn depth, considering the burn in the context of which factorsindividually determine burn depth is important. These factors are the temperature,mechanism (e.g., electrical, chemical), duration of contact, blood flow to the skin,and anatomic location. The keratinized epidermal depth can vary dramatically bybody 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. Inaddition, the dermal elements of young children and geriatric patients aresomewhat thinner than those of healthy adults, which explains the observationthat burns in persons of these age groups are usually more severe than similarinsults in other patients.Outside reports of burn size and depth are notoriously unreliable, especially fromreferring physicians with little experience with burns. Estimates state that reportsof burn size are estimated correctly only one third of the time. With this in mind,always assume that the burn is somewhat worse than described and be preparedto fully reevaluate the burn upon the patients arrival because burn size hassignificant influence on all aspects of the initial management.Table 1. Differences in TBSA With Age Age 1 Age 5 Age 10 Age 15 Infant Adult Year Years Years YearsHead 19 17 13 11 9 7Neck 2 2 2 2 2 2Anterior 13 13 13 13 13 13trunkPosterior 13 13 13 13 13 13trunkButtock 2.5 2.5 2.5 2.5 2.5 2.5Perineum 1 1 1 1 1 1Thigh 5.5 6.5 8 8.5 9 9.5Leg 5 5 5.5 6 6.5 7Foot 3.5 3.5 3.5 3.5 3.5 3.5
Upper 2.5 2.5 2.5 2.5 2.5 2.5armLower 3 3 3 3 3 3armHand 2.5 2.5 2.5 2.5 2.5 2.5 RESUSCITATIVE FLUID MANAGEMENTFormulas and solutionsHistorically, fluid management for burns has been as much an art as it has been ascience; a fine line must be negotiated between an adequate resuscitation and onethat is associated with the deleterious effects of fluid overload. Policies andpractices have been highly individualized and can vary dramatically frominstitution to institution.From these studies came the venerable Parkland formula, which advocated theguideline for total volume of the first 24 hours of resuscitation (with Ringerlactate [RL] solution) at approximately 4 mL/kg body weight per percentage burnTBSA. 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 withvariations in both the volumes per weight suggested and the type or types ofcrystalloid or crystalloid-colloid combinations administered. To date, no singlerecommendation has been distinguished as the most successful approach.The time-dependent variables for all of these formulas begin from the moment ofinjury, not from the time the patient is seen in the emergency department. Ascenario that is not uncommon is a burn patient being transferred from anoutlying hospital several hours after a burn and arriving in a severely under-resuscitated or over-resuscitated state. Calculations for the rate of fluidresuscitation should take this into account and reflect the decreased or increasedstarting IV fluid rate.RL solution is a relatively isotonic crystalloid solution that is the key componentof almost all resuscitative strategies, at least for the first 24-48 hours. It ispreferable to isotonic sodium chloride solution (i.e., normal saline [NS]) forlarge-volume resuscitations because its lower sodium concentration (130 mEq/Lvs. 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 ofmetabolized lactate on the associated metabolic acidosis. Plasmalyte is anothercrystalloid solution, the composition of which is even more closely physiologicthan RL solution, and Plasmalyte is used in some centers as the initial crystalloidsolution for large burns. However, the significant cost difference per unit, with anuncertain benefit, has limited its widespread use at many burn units.Regardless of the resuscitation formula or strategy used, the first 24-48 hoursrequire frequent adjustments. Calculated volumes from all of the formulas shouldbe viewed as educated guesses of the appropriate fluid load. Blind adherence to aderived number can lead to significant over-resuscitation or under-resuscitation ifnot interpreted within the clinical context. Over-resuscitation can be a majorsource of morbidity for burn patients and can result in increased pulmonarycomplications and escharotomies of the chest or extremities. In addition, not allburns require use of the Parkland formula for resuscitation. Promptly addressedadult burns of less than 15-20% TBSA without inhalation injury are usually notenough to initiate the systemic inflammatory response, and these patients can berehydrated successfully primarily via the oral route with modest IV fluidsupplementation.Vital signsRoutine vital signs, such as blood pressure and heart rate, can be very difficult tointerpret in patients with large burns. Catecholamine release during the hoursafter the burn can support blood pressures despite the extensive intravasculardepletion that exists. The formation of edema in the extremities can limit theusefulness of noninvasive blood pressure measurements. Evaluation of arterialline pressures likewise is subject to error from peripheral vasospasm from thehigh-catecholamine state. Tachycardia, normally a clue to hypovolemia, can besecondary 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 moreuseful than any single reading.Vitamin CA great deal of interest exists in using antioxidants as adjuncts to resuscitation totry to minimize oxidant-mediated contributions to the inflammatory cascade. Inparticular, megadose vitamin C infusion during resuscitation has been studied atsome length. Some animal models have demonstrated that infusion of vitamin Cwithin 6 hours postburn can lower calculated resuscitation values by up to onehalf. Whether this phenomenon can be reproduced successfully in humansubjects has not been clearly demonstrated.
Proponents have reached no consensus regarding the proper total dose. Somehave adopted the strategy of placing up to 10 g in a liter of RL solution, infusingit at 100 mL/h (1 g/h vitamin C), and counting the volume as part of theresuscitation volume. Recently published data using an infusion of 66 mg/kg/hduring the first 24 hours demonstrate a 45% decrease in the required fluidresuscitation in a small group of patients.The safety of high-dose vitamin C has been established in humans, at least for theshort-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 resuscitationThe end points for resuscitation are debatable, but hourly urine output is a well-established parameter for guiding fluid management. The rate of fluidadministration should be titrated to a urine output of 0.5 mL/kg/h orapproximately 30-50 mL/h in most adults and older children (>50 kg). In smallchildren, the goal should be approximately 1 mL/kg/h. Failure to meet these goalsshould be addressed with gentle upward corrections in the rate of fluidadministration by approximately 25%.An important point is that periodically increasing the fluid rate is much morefavorable than giving frequent boluses of fluid for low urine output. This resultsin transient elevations in hydrostatic pressure gradients that further increase theshift of fluids to the interstitium and worsen the edema. However, do not hesitateto administer a bolus to patients as appropriate early in the resuscitation forhypotensive shock. The urge to maintain urine output at rates greater than 30-50mL/h should be avoided. Fluid overload in the critical hours of early burnmanagement leads to unnecessary edema and pulmonary dysfunction. It cannecessitate morbid escharotomies and extend the time required for ventilatorsupport.Several complicating factors exist with monitoring urine output as a guide forvolume status and end organ perfusion. The presence of glycosuria can result inan 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 seriousoverestimation 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 adequateresuscitation volume. Swan-Ganz catheter placement is an important adjunct inthe decision-making process in this group of patients regarding fluid replacementand possible diuretic use.Other physiologic parameters that reflect the adequacy of resuscitation include animproving base deficit and the maintenance of the cardiac index in those inwhom invasive monitors are placed. Because of several factors, such aspulmonary vasoconstriction, the same interpretive problems are true for centralvenous pressure or pulmonary capillary wedge pressure measurements. Swan-Ganz catheters should not be used routinely but may have some role in geriatricpatients and those with poor underlying cardiac function. Again, the overallclinical response and general trends in these numbers are much more useful foradjusting fluid administration or chemotherapy to support cardiac function thanvalues from isolated measurements.Certain patient populations frequently require resuscitation volumes that arehigher than those calculated. Patients with inhalation injuries are perhaps themost 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 foradequate resuscitation. Delays in initiating resuscitation promptly have also beenshown to increase fluid requirements by as much as 30%, presumably bypermitting the occurrence of an increased inflammatory cascade. Patients onhome diuretic therapy frequently have preexisting free-water deficits in additionto burn shock. The presence of an escharotomy or fasciotomy can substantiallyincrease free water loss from the wound, and this must be replaced. Patients withelectrical burns, often associated with large and under-appreciated tissue insult,likewise require large-volume fluid resuscitations.Do not forget that burn patients are trauma patients and frequently arrive with apoor history of the events surrounding the accident. An unexpected high volumerequirement should therefore prompt a very close examination for missedassociated injuries. A strategy that has been used with some success forrefractory burn shock has been investigated by researchers at the University ofCincinnati and involves plasma exchange. Appropriate candidates for thisinnovative technique include those with more than twice the calculated fluidrequirements despite hypertonic saline infusion.Table 2. Resuscitation Formulas
Formula Fluid in First 24 Crystalloid in Colloid in Second 24- Hours Second 24-Hours HoursParkland RL at 4 mL/kg per 20-60% estimated Titrated to urinary percentage burn plasma volume output of 30 mL/hEvans NS at 1 mL/kg per 50% of first 24- 50% of first 24-hour(Yowler, percentage burn, hour volume plus volume2000) 2000 mL D5W*, and 2000 mL D5W colloid at 1 mL/kg per percentage burnSlater RL at 2 L/24 h plus(Yowler, fresh frozen plasma2000) at 75 mL/kg/24 hBrooke RL at 1.5 mL/kg per 50% of first 24- 50% of first 24-hour(Yowler, percentage burn, hour volume plus volume2000) colloid at 0.5 mL/kg 2000 mL D5W per percentage burn, and 2000 mL D5WModified RL at 2 mL/kg perBrooke percentage burnMetroHealt RL solution with 50 Half NS titrated 1 U fresh frozen plasmah mEq sodium to urine output for each liter of half NS(Cleveland) bicarbonate per liter used plus D5W as at 4 mL/kg per needed for percentage burn hypoglycemiaMonafo 250 mEq/L saline One-third NShypertonic titrated to urine titrated to urineDemling output at 30 mL/h, output 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*D5W is dextrose 5% in water solution COLLOID AND HYPERTONIC SALINEDue to the high morbidity associated with high-volume resuscitations, an interestexists in using various colloid solutions to both decrease edema and volumerequirements and blunt the myocardial depression phenomena observed withlarge burns. An important consideration for adding colloid in the first 24 hours isthe loss of capillary integrity during early burn shock. This process occurs earlyand is present for 8-24 hours depending on which authority is referenced. Astrategy for testing whether the capillary leak has begun to resolve involvessubstituting an equal volume of albumin solution for RL solution. An increase inurine output suggests that at least some of the leak has resolved and that thefurther introduction of colloid can help decrease the fluid load.Albumin is the plasma protein that most contributes to intravascular oncoticpressure. When administered intravenously as a 5% solution from pooled plasmaproduct, approximately half the volume remains intravascularly, as opposed to20-30% of crystalloid solutions. Alternatively, some centers prefer using freshfrozen plasma over using albumin because of the theoretic advantage of replacingthe whole range of plasma proteins that are lost rather than just the albuminfraction. Guidelines for this infusion have been reported as 0.5-1 mL/kg perpercentage burn during the first 24 hours, beginning 8-10 hours postburn as anadjuvant to RL solution resuscitation.Dextran is a solution of polymerized, high molecular weight glucose chains withalmost twice the oncotic pressure of albumin. An increase in microcirculatoryflow is also produced by reducing erythrocyte aggregation. Proponents of dextranpoint 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 iscontinued, but upon withdrawal and subsequent metabolism of the glucose, rapidloss 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 postburnperiod (first 8 h) at 2 mL/kg/h along with RL solution before switching to somealbumin or fresh frozen plasma plus RL solution combination for the second 18-hour phase.
Hypertonic saline solutions, ranging in concentration from 180-300 mEq sodiumper liter, have many theoretic benefits. These benefits are achieved by thereduction in volume requirements by mobilizing intracellular fluid into thevascular space by the increased osmotic gradient. The intracellular depletion ofwater that results is a debated concern, but it appears to be well tolerated. Closemonitoring of serum sodium levels is mandatory, and serum sodium levels shouldnot be allowed to increase to greater than 160 mEq/dL.As a compromise strategy to limit the risk of hypernatremia and sodiumretention, some institutions use RL solution with 50 mEq amps of sodiumbicarbonate per bag, for a fluid approaching 180 mEq sodium per liter during theinitial 8 hours of the resuscitation, rather than using the more concentrated salinesolutions. Then, after the first 8 hours, the fluid is changed to RL solution tocomplete the resuscitation. Hypertonic saline management must be titratedclosely to both urine output and serum sodium checks and probably should not beused routinely outside of tertiary burn centers.The safety and benefits of hypertonic saline resuscitation extend to both thepediatric and geriatric populations, but using solutions at the lower end oftonicity is probably safer. The greatest benefit may ultimately be for thosepatients with the most limited cardiopulmonary reserves, those with inhalationinjury, and those with larger burns approaching 40% or more.Exactly when or whether to add colloid to resuscitation fluids is a confusingissue. As mentioned previously, most of the mainstream burn formulas addcolloid 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 isboth beneficial and appropriate, especially in burns greater than 40% TBSA,demonstrating improved outcomes in morbidity or mortality has been difficult. Infact, some studies have demonstrated harmful effects secondary to increasedpulmonary edema and some evidence of renal dysfunction as manifested by adecreased glomerular filtration rate. For smaller burns (ie, 20-40% withoutinhalation injury), expectant management with RL solution titrated to urineoutput is a safe and well-tested strategy.The patients who benefit the most from lower-volume resuscitations aided bycolloid 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, withnear complete resolution of the transcapillary leak with fluid requirements. At
this point, some authorities recommend a change in fluid management from RLsolution to a combination fluid infusion involving albumin and D5W. Therational for this is the massive protein losses that have occurred from the burnwound during the first 24 hours. Replacing this deficit with a steady infusion of5% or 25% albumin solution can serve to maintain a serum albuminconcentration greater than 2, which can help reduce tissue edema and improvegut function. Associated insensible losses of free water from the injured skinbarrier can be met by replacing the deficit with an electrolyte-free fluid such asD5W solution, which also serves to restore the extracellular space to an isotonicstate, 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 hoursThe formula for the free water estimate is as follows: (25 + percentage burn) X BSA (m2) = mL/h of free water requiredThe US Army Institute of Surgical Research uses a similar approach but stratifiesthe albumin calculations by the estimated TBSA of the burn. For burns of30-50%, they use 0.3 mL/kg per percentage burn; for burns of 50-70%, 0.4mL/kg per percentage burn is used; and for burns of 70% and greater, they use0.5 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 aday. The relative rate of albumin is titrated to adequate urine output with closemonitoring of the serum sodium level. As the serum sodium level rises tounacceptable levels, simply increasing the D5W solution infusion rate corrects ittoward normal or vice versa.The most important thing to recognize with all the discussion regarding fluidmanagement is that any number of different techniques have proven successful.Replacing the volume deficit to support tissue perfusion and correct themetabolic acidosis can be achieved with multiple fluid types and has been therationale for treatment for nearly 70 years. Changes to this basic tenet have onlycome at the periphery. Real progress in the understanding of the very complexassociated pathophysiology of burn shock is reflected in the use of newerproducts to supplement crystalloid resuscitation. Further advances will obviously
come from optimizing the timing of the colloid and hypertonic administrationand from research into blunting the underlying mediators of burn shock. PEDIATRIC RESUSCITATION ISSUESSeveral important differences exist in pediatric burn resuscitation. IV fluidresuscitations are usually required for patients with smaller burns (in the range of10-20%). Venous access in small children may be a difficult issue, and asaphenous vein cutdown or an interosseous line is an acceptable alternative in theshort-term. Children have proportionally larger BSAs than adults; TBSA burnsmust be estimated using pediatric modifications to Lund-Browder tables, whichdemonstrate the relatively larger head and small thigh. This results in higherweight-based calculations for resection volume (nearly 6 mL/kg per percentageburn) and has led some to advocate a BSA-based resuscitation in addition to theinfusion of a maintenance requirement as described by the Galveston ShrinersHospital (Galveston, Tex) pediatric formula. Other centers, such as the ShrinersBurn Institute in Cincinnati, Ohio, simply use the Parkland formula with theaddition of a maintenance rate.Recommended end points are also higher in children, with urine output closer to1 mL/kg/h being a more appropriate goal. Children approaching 50 kg areprobably better served by adult resuscitation parameters (30-50 mL/h urineoutput) and calculations. Another concern with this population is the modesthepatic glycogen reserves, which can be exhausted quickly and sometimesrequire the change from RL solution to dextrose 5% in RL solution to preventlife-threatening hypoglycemia. For this reason, AccuChecks every 4-6 hoursshould be routine during the hypermetabolic state, especially for patients withlarger burns.Pediatric resuscitation protocols are based on the following formula (H is height[cm], W is weight [kg]): BSA = [87 (H + W) - 2600] / 10,000Pediatric resuscitation protocols are as follows: • Shriners Burn Institute (Cincinnati) - 4 mL/kg per percentage burn plus 1500 mL/m2 BSA
o First 8 hours - RL solution with 50 mEq sodium bicarbonate per liter o Second 8 hours - RL solution o Third 8 hours - RL solution plus 12.5 g of 25% albumin solution per liter • Galveston Shriners Hospital - 5000 mL/m2 TBSA burn plus 2000 mL/m2 BSA, using RL solution plus 12.5 g 25% albumin per liter plus D5W solution as needed for hypoglycemia CONCLUSIONThe most important thing to remember regarding fluid management is that anynumber of different techniques have proven successful. Replacing the volumedeficit to support tissue perfusion and correct the metabolic acidosis can beachieved with multiple fluid types and has been the rationale for treatment fornearly 70 years. Changes to this basic tenet have only come at the periphery. Realprogress in the understanding of the very complex associated pathophysiology ofburn shock is reflected in the use of newer products to supplement crystalloidresuscitation. Further advances will obviously come from optimizing the timingof colloid and hypertonic fluid administration and from research into blunting theunderlying mediators of burn shock. THE END