INTRODUCTION — Anesthesia providers may be involved in the management of burn patients throughout the perioperative period, including preoperative airway management and resuscitation, intraoperative anesthetic care, postoperative intensive care, management of postoperative pain, and subsequent scar revisions. This topic reviews these aspects of the anesthetic management of burn patients. Other issues encountered during management of burn patients are reviewed separately. (See "Overview of the management of the severely burned patient" and "Emergency care of moderate and severe thermal burns in adults" and "Treatment of minor thermal burns".)
PREANESTHETIC ASSESSMENT
Note estimated burn extent and severity — Major burns (eg, full-thickness burns involving >10 percent total body surface area [TBSA] or partial-thickness burn of >25 percent TBSA (figure 1)) cause an intense physiologic and inflammatory response that affects many aspects of anesthetic care (eg, airway management, fluid management, drug dosing, temperature regulation). High-voltage burns, chemical burns, and associated smoke inhalation injury are also defined as major burns. (See "Overview of the management of the severely burned patient" and "Assessment and classification of burn injury".)
Assess the airway
●Acute burn injury – Assess the airway for signs of possible difficulty with laryngoscopy due to oropharyngeal tissue injury or edema and/or signs of probable inhalation injury. Signs include burns around the mouth, deep facial or neck burns, singed hair in the nares, blistering or edema of the oropharynx, persistent cough or wheezing, carbonaceous sputum, or abnormalities in arterial blood gases (ie, hypoxia or hypercapnia). Stridor, hoarseness, muffled speech, or dysphagia indicate impending airway obstruction and an urgent need for endotracheal intubation. Notably, ongoing fluid resuscitation may exacerbate laryngeal swelling. Once massive edema of the airway has developed, emergency intubation may be extremely difficult. (See "Emergency care of moderate and severe thermal burns in adults", section on 'Airway management'.)
●Subsequent procedures – Even after initial resuscitation for a burn injury, mouth opening and neck mobility may be restricted due to pain, edema, burn eschars, or contractures. Tense edema in the submandibular space can limit displacement of the tongue, making laryngoscopy difficult. A tongue depressor or laryngoscope blade may be used to evaluate the degree of mouth-opening and appearance of the oropharyngeal tissue.
Assess cardiovascular status — (See "Overview of complications of severe burn injury", section on 'Cardiac failure'.)
●Low cardiac output "ebb," phase (resuscitative phase) – In the first 48 hours after a major burn, cardiac output (CO) is reduced up to 60 percent from baseline due to hypovolemia from permeability-induced plasma loss, reduced myocardial response to catecholamines, increased systemic vascular resistance due to elevated vasopressin levels, depressed myocardial contractility, and possible myocardial ischemia due to decreased coronary blood flow [1-4]. The large volumes that these patients require can sometimes result in over-resuscitation, leading to pulmonary edema and right heart failure [5]. (See 'Assess intravascular volume status' below.)
●High cardiac output "flow," phase (recovery phase) – During the recovery phase 72 to 96 hours postburn, hyperdynamic and hypermetabolic responses result in increased CO, tachycardia, increased myocardial oxygen consumption, and decreased systemic vascular resistance [2]. Elevation of catecholamines in major burns produces hyperdynamic circulation, augments energy expenditure, and promotes protein catabolism in skeletal muscle. Nonselective beta blocker therapy is sometimes used to block catecholamine receptors, treat cardiac dysfunction, and modulate the hyperdynamic response during this phase [6,7].
Assess intravascular volume status — During the resuscitative or "ebb phase," in the first 48 hours after burn injury, a systemic inflammatory response causes increased capillary permeability which in turn causes loss of plasma fluid, electrolytes, and proteins due to increased capillary permeability [2,8,9]. Effective preoperative fluid resuscitation is guided by formulas (eg, the American Burn Association [ABA] formula) targeted to achieve ABA-recommended urine output of 0.5 to 1.0 mL/kg per hour as the resuscitative endpoint [10,11]. Therapeutic perioperative plasma exchange to remove inflammatory mediators has been used in selected patients who have signs of failed resuscitation despite appropriate fluid administration [12]. (See "Emergency care of moderate and severe thermal burns in adults", section on 'Fluid resuscitation'.)
Excessive preoperative or intraoperative intravenous (IV) fluid administration (eg, "fluid creep") can increase extravascular lung water causing pulmonary edema, as well as abdominal compartment syndrome and compromised circulation of extremities if burns are circumferential [12-14].
Assess for pulmonary abnormalities
●Early pulmonary manifestations – Burn patients with concomitant smoke inhalation have a higher likelihood of pulmonary complications [15-17]. Singeing of facial or nasal hair, evidence of oropharyngeal carbonaceous deposits, or carboxyhemoglobin (COHb) levels >10 percent predict smoke inhalation injury, with confirmation by bronchoscopy [2,17,18]. The inflammatory response produced by chemicals in the smoke can induce bronchospasm that may require aggressive bronchodilator treatment [19]. Systemic and respiratory effects of chemicals in smoke (carbon monoxide, cyanide) also result in ciliary dysfunction, thickening of secretions with hypoventilation, loss of hypoxic pulmonary vasoconstriction, pulmonary hypertension, atelectasis, and ventilation-perfusion mismatch with increased pulmonary shunting, as discussed in detail elsewhere [17,20]. (See "Emergency care of moderate and severe thermal burns in adults" and "Inhalation injury from heat, smoke, or chemical irritants".)
Aggressive preoperative crystalloid resuscitation during the recovery (flow) phase reduces plasma oncotic pressure and aggravate pulmonary edema which further impairs gas exchange (see 'Assess intravascular volume status' above). Pulmonary failure may occur either immediately after burn injury, or a few days later, due to progression of the inhalation injury and/or development of acute respiratory distress syndrome (ARDS) [2,21]. (See "Overview of complications of severe burn injury", section on 'Pulmonary failure'.)
●Late pulmonary sequelae – A restrictive lung defect with impaired ventilation can result from severe chest wall edema due to circumferential burns to the thorax or from scar restriction [2]. Patients may develop hypoventilation and respiratory failure due to loss of chest wall elasticity and decrease in effective lung volumes. Intubation and mechanical ventilation and/or chest wall escharotomies may be necessary, depending on the degree of compromise [22].
Perioperative nutritional considerations — Nutritional supplementation (enteral, parenteral) is continued throughout the perioperative period in selected severe burn patients, often with enteral tube feedings, because aggressive nutritional support is necessary due to elevated catabolism. Notably, hypermetabolic responses to a burn injury can persist for three years following a severe burn. (See "Hypermetabolic response to moderate-to-severe burn injury and management".)
At our institution, we continue enteral nutrition if the patient is intubated and there is no plan to manipulate the airway (ie, tube exchange, tracheostomy placement). This management differs from management of most surgical patients who fast before and during surgery (see "Preoperative fasting in adults"). The goal is to improve long-term outcomes by reducing caloric deficit, need for exogenous albumin supplementation, and incidence of wound infections [2,23,24].
Surgical considerations — Patients with deep burn wounds typically undergo multiple procedures requiring anesthetic management, both in the operating room and at the hospital bedside (eg, escharotomies of circumferential burns upon admission). An understanding of the surgical plan for the current procedure and subsequent planned procedures is necessary.
Early burn wound excision and skin grafting for wound coverage are crucial aspects of the treatment of thermally injured patients. The burn wound is excised either at a dermal level (eg, tangential excision, for partial-thickness burns) or deep to the subcutaneous tissue (eg, fascial excision, for full-thickness burns), depending on the depth of the burn. Then, the excised areas are covered, ideally with split-skin autografts. When there is insufficient donor skin, other coverage is used (eg, allografts, xenografts, synthetic skin products, and cultured epithelial autografts) [25,26]. Blood loss during burn excision operations can be extensive [2]. (See 'Transfusion decisions' below and "Emergency care of moderate and severe thermal burns in adults" and "Overview of surgical procedures used in the management of burn injuries".)
Subsequent burn dressing changes usually occur at the bedside as part of the spectrum of care for burn injuries. Depending on wound complexity, patient age, and anticipated procedural pain intensity, moderate to deep sedation, regional anesthesia, or occasionally general anesthesia may be necessary for procedures performed outside of the operating room setting [27]. Later, scar revision procedures may be performed at variable timepoints weeks or even years after the original burn injury. (See 'Later scar revision procedures' below.)
In contrast to treatment of patients with deep burn wounds, superficial and small burns (<5 percent TBSA) that do not involve joints or vital organs can generally be treated on an outpatient basis. (See "Treatment of minor thermal burns".)
INTRAOPERATIVE MONITORING
Standard monitoring considerations — Burn patients often present challenges in the use of standard American Society of Anesthesiologists (ASA) monitors [28]:
●Electrocardiogram – Burns on the torso and upper extremities prevent adhesive electrocardiogram lead placement. In these cases, needle electrodes or surgical stapling of the electrodes may be necessary.
●Pulse oximetry – Sites for pulse oximeter probe application may be limited in patients with extensive burns to the face, neck, extremities, and/or planned skin graft harvests in unburned extremities. Thus, probes for multiple sites should be immediately available. Also, carboxy-hemoglobinemia in patients with smoke inhalation and carbon monoxide poisoning may falsely elevate pulse oximetry values. In these cases, a co-oximeter may be necessary to obtain an accurate measurement of oxyhemoglobin. (See "Pulse oximetry", section on 'Carboxyhemoglobin' and "Carbon monoxide poisoning", section on 'Diagnosis'.)
●Blood pressure (BP) cuff – Placement of a noninvasive BP cuff may not be possible in patients with significant edema or generalized burns to the extremities. In these cases, an intra-arterial catheter may be necessary. When no other options are available, the catheter may be placed into burned or newly grafted skin and secured with sutures. An intra-arterial catheter provides moment-to-moment measurement of BP and also enables assessment of respiratory variations in the intra-arterial waveform as a dynamic hemodynamic variable to guide fluid therapy (figure 2 and table 1) [29]. (See 'Dynamic hemodynamic parameters' below.)
●Other standard monitors – Standard monitors also include temperature probes (eg, esophageal, bladder). The bladder catheter is used to monitor and maintain urine output between 30 and 50 mL/hour, or 0.5 to 1.0 mL/kg per hour. (See "Intraoperative fluid management", section on 'Traditional static parameters'.)
Dynamic hemodynamic parameters — We typically monitor dynamic hemodynamic parameters in patients with severe burn injuries. This may include qualitative visual assessment of intra-arterial waveform (figure 2) [30] or use of a commercially available device that provides automated calculations of respiratory variations in systolic BP, pulse pressure (PP), or stroke volume (SV) derived from the intra-arterial pressure waveform, to maintain optimal intravascular volume and guide vasoactive therapy to maintain optimal hemodynamics and fluid administration (table 1) [2,11,29]. Alternative monitors include an esophageal Doppler device to estimate SV [31]. (See "Intraoperative fluid management", section on 'Dynamic parameters to assess volume responsiveness' and "Intraoperative fluid management", section on 'Goal-directed fluid therapy'.)
Transesophageal echocardiography (TEE) is used in selected patients to assess left ventricular cavity size to provide valuable information regarding ventricular filling (ie, hypovolemia or fluid overload) (movie 1 and image 1 and image 2 and table 2), and both left and right ventricular function [32]. However, no randomized controlled trials exist to assess the utility of echocardiography to determine endpoints of resuscitation in the management of burn injured patients. (See "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Volume status' and "Intraoperative transesophageal echocardiography for noncardiac surgery", section on 'Ventricular function'.)
Emergency use of intraoperative or perioperative TEE is indicated to determine the cause of any unexplained persistent or life-threatening hemodynamic instability ("rescue echo") when equipment and expertise are available [33]. (See "Intraoperative rescue transesophageal echocardiography (TEE)".)
Laboratory values
●Arterial blood gases (ABGs) and lactate – We intermittently monitor ABGs (eg, every hour during a major excision). We include lactate since elevated lactate levels are an important indicator of reduced global tissue perfusion. Other centers use base deficit measurements as an alternative to lactate levels. Although increasing serum lactate levels (or lactic acidosis with a large base deficit) on sequential ABGs indicates persistent poor perfusion, these laboratory values do not provide information regarding contemporaneous clinical intravascular volume status since they are measured intermittently and do not immediately reflect acute changes. (See "Etiology, clinical manifestations, and diagnosis of volume depletion in adults", section on 'Clinical manifestations'.)
●Blood glucose – We monitor blood glucose levels throughout the perioperative period because of peripheral insulin resistance, elevated protein and lipid catabolism, increased energy expenditure, and stimulated synthesis of acute phase proteins in burn patients.
AIRWAY MANAGEMENT
●Bag-mask ventilation – Bag-mask ventilation of patients with burns to the face may be challenging due to burn dressings that prevent a good seal around the mask. We employ two-person bag-mask ventilation technique for these patients. Removal of the burn dressing may be necessary, but extreme care is taken to prevent further damage to the burned area.
●Fiberoptic flexible scope intubation – When upper airway patency is a concern, we employ fiberoptic flexible scope intubation to identify specific abnormalities and maximize chances for successful intubation (algorithm 1 and algorithm 2) [34,35] (see "Management of the difficult airway for general anesthesia in adults"). If the patient can cooperate, we use awake fiberoptic tracheal intubation. If the patient cannot cooperate, we attempt to preserve spontaneous ventilation (with or without bag-mask assistance) to ensure adequate gas exchange during induction of anesthesia and fiberoptic laryngoscopy attempts. Preserving spontaneous ventilation may also facilitate advancement of the fiberoptic scope into the trachea. (See "Flexible scope intubation for anesthesia", section on 'Awake intubation'.)
After intubation and induction of anesthesia, we test ability to ventilate before administering any neuromuscular blocking agent (NMBA). (See 'Induction' below.)
●Securing the endotracheal tube (ETT) – Securing the ETT for patients with burns to the face is challenging. Techniques to achieve adequate fixation of the tube include placement of cloth tape around the tube that can then be secured with trach ties, a technique which also works for patients with thick beards. Other methods include placement of interdental/maxillary wires [36], or surgical sutures around the teeth to secure the ETT at a desired depth [37]. Circum-mandibular, nasomaxillary, or transseptal sutures can also be used to secure the ETT in patients with facial burns, achieving reliable tube fixation with minimal obstruction of the surgical field [38].
Performing a tracheostomy is controversial in severely burned patients. The decision, including timing, is made on an individualized basis. (See "Overview of complications of severe burn injury", section on 'Pulmonary failure'.)
ANESTHETIC MANAGEMENT
Altered pharmacokinetics and pharmacodynamics — Doses of anesthetic agents required to induce and maintain appropriate anesthetic depth depend on the pathophysiologic state of the patient. Notably, altered pharmacokinetics and pharmacodynamics affect commonly used anesthetics, analgesics, and muscle relaxants [2,39-41]. Causes include changes in plasma protein concentrations, alterations in specific drug receptors, and cardiovascular factors. In particular, reduced plasma albumin levels increase the volume of distribution and the available free fraction of any medication that binds to albumin (eg, benzodiazepines). Albumin levels are decreased because of plasma protein loss through endovascular "leaking," as well as protein dilution resulting from crystalloid resuscitation (see 'Assess intravascular volume status' above). Severely burned patients with burn shock have decreased cerebral, hepatic, and renal blood flow, which further affects pharmacokinetics and pharmacodynamics [42].
Induction — We administer a reduced dose of an intravenous (IV) anesthetic induction agent (eg, ketamine, etomidate, propofol), usually combined with a small dose of opioid, to induce anesthesia during the acute resuscitative (ebb) phase immediately after burn injury. Similar to induction for other patients undergoing trauma surgery who may have intravascular volume depletion, ketamine or etomidate is typically preferred. Furthermore, all anesthetic induction agents should be administered cautiously (ie, slow administration in reduced doses) because intravascular volume depletion and other factors such as burn severity or concurrent sepsis may contribute to development of hypotension during the resuscitative phase [2,43,44]. (See "Anesthesia for adult trauma patients", section on 'Induction'.)
In contrast to the resuscitative (ebb) phase, higher doses of anesthetic agents may be necessary during the recovery (flow) phase. (See 'Assess cardiovascular status' above.)
●Ketamine – Induction with ketamine usually results in significant increases in mean arterial pressure, heart rate, and plasma epinephrine levels due to centrally mediated sympathetic nervous system stimulation [45]. However, this stimulatory effect depends upon the presence of adequate sympathetic reserve. In patients who have maximally activated their sympathetic response (eg, burn patients with hypovolemic shock), administration may result in hypotension due to a mild direct myocardial depressant effect [2]. Advantageous effects of ketamine include analgesic and bronchodilatory properties. Furthermore, if intubation proves to be difficult, a theoretical advantage of ketamine is maintenance of airway reflexes, respiratory drive, and spontaneous respiration. Potential adverse effects include nausea and vomiting, hallucinations, and emergence delirium. (See "General anesthesia: Intravenous induction agents", section on 'Ketamine'.)
●Etomidate – Induction with etomidate results in few hemodynamic changes in patients with cardiovascular compromise compared with propofol; thus, the dose is not typically decreased [43-46]. However, as noted above with ketamine, in patients who have maximally activated their sympathetic response (eg, burn patients with hypovolemic shock), administration of etomidate may result in hypotension due to a mild direct myocardial depressant effect. A disadvantage is the association of etomidate with transient acute adrenal insufficiency [47-50], and possibly increased risk of mortality in both critically ill patients [49] and those not critically ill [51]. However, this finding is not consistent [52], and there are no studies examining safety of etomidate compared with other induction agents in burn patients. (See "General anesthesia: Intravenous induction agents", section on 'Etomidate'.)
●Propofol – The induction dose of propofol is reduced during the acute resuscitative (ebb) phase, similar to other traumatically injured patients, to avoid further cardiovascular depression and reduction in systemic vascular resistance [43,45,53]. (See "General anesthesia: Intravenous induction agents", section on 'Propofol'.)
However, during the hyperdynamic recovery (flow) phase three to four days later, larger bolus doses or increased infusion rates of propofol may be necessary to attain and maintain therapeutic plasma propofol concentrations in patients with burn injuries (compared with those who are not burned) [54,55]. Hepatic clearance continues to account for the majority of total propofol clearance during this hyperdynamic flow state despite a burn-induced hepatic ischemic-reperfusion injury [54]. Both hepatic and renal clearance increase because reduction in albumin plasma levels increases the free propofol fraction. These pharmacokinetic changes result in plasma propofol concentrations that are lower for a given dosing regimen, accounting for increased dosing requirements during the flow phase [55]. Although higher doses of propofol may be necessary during the recovery phase, caution is still necessary during administration of induction doses because interaction with other prescribed medications (eg, opioids, beta blockers) may produce hypotension.
Use of succinylcholine — During the first 48 hours following a major burn (see 'Note estimated burn extent and severity' above), succinylcholine (SCh) may be used, but must be avoided for at least one year after that first 48 hours due to risk of acute severe hyperkalemia and life-threatening arrhythmias [2,56]. Since serum potassium may be initially elevated after a major burn due to cellular injury, any further increase may trigger cardiac arrhythmias. Risk of hyperkalemia is further increased in burn patients with infection, sepsis, or immobilization [56].
Severe hyperkalemia after SCh administration occurs because of upregulation of immature extrajunctional nicotinic acetylcholine receptor (nAChR) subunits caused by inflammation and local denervation of muscle [56,57]. Upregulation of nAChR receptors has been demonstrated to occur as soon as 24 hours after injury in the alpha-7 and gamma gene subunit, although there are no reports of hyperkalemia before 72 hours after a burn in humans [57]. In animal models, upregulation of nAChR receptors occurs approximately 72 hours after the injury even with burns of 5 percent of total body surface area (TBSA) [58]. Thus, a conservative approach is to avoid administration of SCh after 48 hours after any burn injury.
Choice of maintenance technique — To maintain anesthesia for burn surgery, we typically select an inhalation-based or a "balanced," technique employing an inhalation anesthetic, an opioid such as fentanyl or hydromorphone, and a neuromuscular blocking agent (NMBA) due to lower costs compared with use of total IV anesthesia (TIVA) techniques. We titrate inhalation agents cautiously while monitoring the patient's hemodynamic responses. We typically administer small doses of a benzodiazepine and/or ketamine as adjuvants to decrease risk of intraoperative awareness, and we administer an NMBA as needed. (See "Maintenance of general anesthesia: Overview".)
We reserve use of TIVA for patients who require special ventilator parameters (eg, high-frequency ventilation). When we do select a TIVA technique, we prefer continuous infusions of ketamine, propofol, and an opioid (eg, fentanyl or remifentanil), in combination with an NMBA. A retrospective study in burn patients undergoing debridement and grafting compared an inhalation-based anesthesia technique to a ketamine-based TIVA technique that included propofol and an opioid; overall outcomes and use of vasopressors were similar [59].
Use of NMBAs — Close monitoring of degree of neuromuscular blockade is critically important after administration of NMBAs. Approximately one week after burns involving >30 percent of TBSA, resistance to all nondepolarizing NMBAs develops that is proportional to burn size, with peak resistance occurring five to six weeks after injury [60]. Also, recovery time from neuromuscular blockade is shortened. Thus, it is often necessary to increase doses and frequency of NMBA administration to partially overcome this increased resistance and more rapid recovery [41,61-64].
Resistance to all nondepolarizing NMBAs occurs, in part, due to upregulation of nAChR subunits, as described above [56,57]. An additional factor is an increase in acute phase alpha 1-glycoprotein levels, with increased binding of NMBAs to the protein [61]. Also, enhanced renal elimination of NMBA may occur in the later hyperdynamic (flow) stage of the burn injury because of normalization of acute glycoprotein levels and increased glomerular filtration [41,62].
In the case of the nondepolarizing NMBAs atracurium and cisatracurium, which are metabolized in the plasma through organ-independent Hofmann elimination, resistance occurs primarily due to upregulation of nAChRs rather than altered protein binding [63]. (See "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Cisatracurium' and "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Atracurium'.)
Despite ACh receptor upregulation and these pharmacokinetic effects on NMBA activity, we do not modify dosing or timing of anticholinesterase agents (eg, neostigmine) or sugammadex administered to reverse neuromuscular blockade. (See "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Reversal of neuromuscular block'.)
Use of intraoperative opioids — Opioids such as fentanyl or hydromorphone are an essential component of a balanced anesthetic technique, particularly since significant postoperative pain is anticipated.
Opioid doses are reduced during the acute resuscitative (ebb) phase because metabolic clearance may be impaired by liver dysfunction [65]. In the subsequent recovery (flow) phase, opioid requirements may increase due to their substantially expanded volumes of distribution (ie, dilutional expansion) [2,40]. Furthermore, the degree of preoperative opioid use affects intraoperative opioid dosing, particularly for patients with large burns who have required prolonged opioid therapy and/or long-acting opioids. Near the end of the surgical procedure, opioids may be titrated to achieve an adequate spontaneous respiratory rate to individualize dosing.
Use of local and regional anesthesia — Local and regional anesthetic techniques provide supplemental intraoperative anesthesia, improve postoperative analgesia, and decrease opioid requirements [2]. (See 'Challenges in pain management' below.)
●Local anesthesia – The volume of local anesthesia that can be infiltrated without reaching toxic doses is limited. Subcutaneous tumescent infiltration of local anesthetics for cutaneous surgery may provide adequate surgical anesthesia, with less blood loss from the graft donor sites [66-68]. Donor sites are typically more painful than the grafted burn wound itself because they are fresh injuries. In one feasibility study (n = 8 patients), postoperative pain was decreased by continuous infusion of subcutaneous bupivacaine into the donor sites [69].
●Regional anesthesia – Regional anesthetic techniques are particularly useful for intraoperative excision of small and/or localized burns [70]. However, efficacy of regional techniques as the sole anesthetic for surgical procedures in burn patients is usually limited due to the location and size of burn injuries, use of multiple distant donor sites for skin harvesting, and associated painful traumatic injuries.
FLUID AND TRANSFUSION MANAGEMENT — Intravascular volume and hemodynamics are maintained to optimize end-organ perfusion and prevent burn shock [2]. The American Burn Association (ABA) recommends maintaining urine output ≥0.5 mL/kg per hour for adults and ≥1 mL/kg per hour for children, although the best endpoints for adequacy of resuscitation after major burn injury are not conclusively determined. (See "Overview of the management of the severely burned patient", section on 'Intensive care management' and "Moderate and severe thermal burns in children: Emergency management", section on 'Monitoring fluid status'.)
Fluid administration
●Selection of fluid – We typically administer crystalloid solutions rather than colloid solutions during the initial phase of burn resuscitation [10,71]. However, some institutions administer hypertonic or colloid solutions (eg, purified albumin, fresh frozen plasma [FFP]), particularly if patients have inadequate urine output or evidence of poor perfusion (eg, elevated lactate values) [11,72] (see 'Laboratory values' above). Although vasoactive agents such as norepinephrine are administered in some centers to reduce initial volume administration and improve cardiac output in the early phases of resuscitation [11], vasoconstrictors are avoided or minimized during the perioperative period because they may induce ischemia at the burn graft site that may negatively impact graft success. (See "Emergency care of moderate and severe thermal burns in adults", section on 'Fluid resuscitation' and "Intraoperative fluid management", section on 'Choosing fluid: Crystalloid, colloid, or blood'.)
●Volume of fluid – In general, intraoperative volume losses are added to formula-guided resuscitative fluid volume (eg, ABA formula) to estimate optimal fluid administration during surgical procedures for burn management (eg, debridement or escharotomies). (See "Emergency care of moderate and severe thermal burns in adults", section on 'Estimating initial fluid requirements'.)
However, intraoperative fluid administration, as well as transfusion decisions (see 'Transfusion decisions' below), are adjusted according to the magnitude of burn excisions, volume of blood loss (large excisions incur more blood loss and require more volume replacement), burn depth (partial-thickness excisions involve more blood loss than full-thickness excisions), specific hemostatic techniques used (eg, topical vasoconstrictors), and surgical administration of tumescent fluid. (See "Emergency care of moderate and severe thermal burns in adults", section on 'Fluid resuscitation'.)
Optimal fluid replacement avoids under- or over-resuscitation, both of which may lead to further complications in the postoperative period (see 'Assess intravascular volume status' above). Guiding factors include estimated severity of ongoing blood loss, hemoglobin measurements, development of hypoxemia, adequacy of urine output, and clinical assessment of perfusion. Laboratory values (eg, base deficit and serum lactate) provide additional information regarding adequacy of intravascular fluid volume, although this information is not contemporaneous and do not immediately reflect acute changes. (See 'Dynamic hemodynamic parameters' above and 'Laboratory values' above.).
Transfusion decisions
●Restrictive transfusion strategy – We employ a restrictive transfusion strategy in hemodynamically stable patients without massive blood loss, with transfusion of a unit of packed red blood cells (RBCs) at a hemoglobin transfusion threshold of <7 to 8 g/dL (hematocrit <21 to 24 percent), similar to other surgical procedures [73-77] (see "Intraoperative transfusion of blood products in adults"). However, decisions to transfuse are individualized, and we typically use a higher hemoglobin threshold of <9 g/dL (approximately equivalent to a hematocrit ≤27 percent) in patients who have significant ongoing bleeding, a known acute coronary syndrome, or signs of myocardial or other organ ischemia. Intraoperative blood losses during burn debridement or escharotomies can be large. It is estimated that 2.6 percent of an adult patient's total blood volume is lost (or 3.4 percent in children) for each 1 percent of burn wound excised or autograft harvested [78,79]. (See "Emergency care of moderate and severe thermal burns in adults", section on 'Blood transfusion'.)
In one randomized multicenter trial in 345 patients with ≥20 percent TBSA burns, a restrictive hemoglobin transfusion strategy with the threshold set at 7 to 8 g/dL resulted in fewer transfused units of RBCs compared with a liberal strategy with the threshold set at 10 to 11 g/dL [74]. Mean transfused units/patient were 20.3 ± 32.7 in the restrictive transfusion group versus 31.8 ± 44.3 in the liberal transfusion group (p <0.001). Secondary outcomes that included blood stream infection, organ dysfunction, and mortality did not differ between the restrictive and liberal transfusion groups [74]. Potential benefits of a restrictive RBC transfusion threshold in other surgical and critically ill patient populations (eg, reduced risk for infectious complications and mortality) are discussed separately. (See "Intraoperative transfusion of blood products in adults", section on 'Red blood cells'.)
●Other techniques to minimize transfusion – Several techniques are used to minimize intraoperative bleeding and need for transfusion during surgical procedures in burned patients, including application of topical thrombin, use of compressive devices (tourniquets), topical or subcutaneous injection of vasoconstrictors (eg, epinephrine, vasopressin analogs, phenylephrine), and use of staged procedures [80]. A combination of these techniques may be used to decrease blood loss and transfusion requirements [81]. Despite these efforts, burn excisions are often accompanied by significant blood loss.
Topical epinephrine is the most commonly used technique to limit blood loss in both burn excision and donor skin harvest sites. The anesthesiologist should monitor for potential systemic effects of absorbed epinephrine (eg, increased blood pressure, heart rate, or serum glucose) after topical application or subcutaneous injection [82,83]. Compared with other patients needing skin grafts, topical epinephrine use during skin grafting in burn patients resulted in increased serum epinephrine and lactate levels, a higher lactate-pyruvate ratio, and higher heart rates in one study [82]. However, other studies reported no difference in catecholamine levels or hemodynamic parameters when epinephrine solutions were used in burn patients versus patients undergoing other surgical procedures [84,85]. Subcutaneous infiltration of skin donor sites with phenylephrine 5 mcg/mL effectively reduces blood loss without systemic effects [86]. However, use of topical or subcutaneous vasoconstrictors, including phenylephrine or epinephrine, can mask hypovolemia during excision of large areas of burned tissue.
Administration of tranexamic acid (TXA), a lysine analog that inhibits fibrinolysis, may improve hemostasis in burn surgery as in other types of trauma surgery. However, risk of thromboembolism is a concern, particularly in burn patients [87,88]. Small studies of TXA administered as a single dose before surgical incision for surgical procedures in burn patients noted reduced blood loss, while side effects such as thromboembolism were not noted [89,90]. (See "Perioperative blood management: Strategies to minimize transfusions", section on 'Antifibrinolytic agents' and "Anesthesia for adult trauma patients", section on 'Specific blood products and other therapies'.)
We do not administer activated recombinant factor VII (rFVIIa) to reduce transfusion due to increased risk of thromboembolic complications in burn patients [87,88]. Although the use of rFVIIa was associated with a 60 percent reduction in the number of blood products transfused in one small study of 18 patients with burn injuries [91], increased risk of thrombosis has been noted in various settings [92].
●Massive blood transfusion and coagulopathy – Severely burned patients may experience an intraoperative trauma-induced coagulopathy due to fluid shifts, hemodilution, and hypothermia, particularly if there are other concurrent traumatic injuries [93,94]. (See 'Fluid administration' above.)
Occasional patients experience massive intraoperative blood loss (ie, >50 percent of blood volume) during excision and grafting procedures for large or severe burns. When this occurs, we limit crystalloid administration (see 'Fluid administration' above), and we employ a resuscitation protocol using a 1:1 ratio of RBCs to packed FFP with administration of platelets and cryoprecipitate as necessary. This approach is similar to protocols for massive transfusion in other settings [95]. (See "Massive blood transfusion", section on 'Approach to volume and blood replacement'.)
TEMPERATURE MANAGEMENT — We prevent intraoperative hypothermia by using convective warming devices (ie, forced air warmers), administering warmed intravenous fluids, maintaining a warm ambient room temperature ≥25°C, and minimizing exposed body surface area. As explained in a separate topic, hypothermia is associated with increased risk of coagulopathy, infection including sepsis, and mortality. (See "Perioperative temperature management".)
Burn patients have a particularly high risk for perioperative hypothermia because of accelerated evaporative, convective, and radiative heat loss through injured skin, exacerbated by prolonged exposure of a large surface area to ambient temperature during the length of the surgical procedure [2,96]. Even if there are no burned skin areas, cold room temperatures can significantly lower core temperature, particularly during the first hour after induction of anesthesia. Exposure time includes skin preparation and the surgical procedures including excision at donor and graft sites. Hypothermia is exacerbated by administration of cold intravenous (IV) fluids. For all of these reasons, patients with major burns can lose up to 1°C every 15 minutes if exposed to ambient temperature.
POSTOPERATIVE MANAGEMENT
Use of mechanical ventilation — Postoperative mechanical ventilation is typically necessary for patients with:
●Inhalation burn injury, particularly if acute respiratory distress syndrome (ARDS) develops. The role of extracorporeal membrane oxygenation for severe respiratory failure in patients with burns and smoke inhalation is unclear and requires further study [97,98].
●Increased risk of ongoing bleeding or frequent return to the operating room for additional surgery are generally not extubated [2].
●Risk for graft disruption due to movement (eg, delicate sheet grafting to the face and neck). Postoperative mechanical ventilation in a deeply sedated patient minimizes this risk.
Challenges in pain management — Continuous pain management and intermittent sedation for bedside procedures are treatment priorities in the postoperative period [2]. Opioid tolerance, characterized by increasingly poor analgesic response to standard doses of analgesics, is a factor that makes pain management challenging during all phases of burn care [99]. Thus, we use multimodal opioid-sparing techniques including nonopioid analgesics and local or regional anesthetic techniques whenever possible. These pharmacologic and nonpharmacologic pain management techniques have been reviewed by the American Burn Association (ABA) Committee on Delivery of Burn Care [100]. Key recommendations include the need for regular pain assessment using appropriate tools, individualizing opioid therapy, using non-opioid analgesics (eg, acetaminophen, ketamine) whenever possible, incorporating regional analgesia techniques, and emphasizing use of concomitant non-pharmacologic techniques. (See "Management of burn wound pain and itching" and "Pain control in the critically ill adult patient", section on 'Multimodal analgesia'.)
●Pharmacologic agents – Specific pharmacologic agents used to manage postoperative pain in burn patients include:
•Opioids - Opioids remain a mainstay of therapy in burn patients. However, acute tolerance, a phenomenon whereby administration of opioids has a diminishing effect over a short period of time, may develop in burn patients after only two weeks of uninterrupted opioid use, particularly in patients with preexisting opioid abuse. Use of long-acting opioids may be helpful in some burn patients [101,102]. Methadone has an additional analgesic advantage due to N-methyl-D-aspartate (NMDA) receptor blockade, thereby reducing release of glutamate (see "Perioperative uses of intravenous opioids: Specific agents", section on 'Methadone'). Notably, it is possible for burn-injured patients to develop opioid-induced hyperalgesia (OIH), a condition distinct from acute tolerance that is characterized by nociceptive sensitization, with greater sensitivity to painful stimuli. These phenomena may increase postoperative pain and opioid dose requirements. Details regarding use of opioids in patients with burn injuries and other critical illnesses are available in other topics:
-(See "Management of burn wound pain and itching", section on 'Opioid analgesics'.)
-(See "Pain control in the critically ill adult patient", section on 'Opioid analgesics'.)
•Ketamine – Ketamine has potent analgesic efficacy mediated by NMDA receptor blockade, which can produce analgesic relief in patients with opioid tolerance and/or OIH [99,103-105]. For these reasons, ketamine is often administered to burn patients outside of the operating room during dressing changes, hydrotherapy, and other procedures [100].
Other beneficial effects of ketamine include bronchodilation, and maintenance of hemodynamic stability and airway reflexes [2,106,107]. Also, ketamine-based total intravenous anesthesia (TIVA) has been used to manage critically ill burn patients who require specialized perioperative mechanical ventilation precluding use of an anesthesia machine and inhalation anesthetic agents [59]. (See "Management of burn wound pain and itching", section on 'Nonopioid analgesics' and "Pain control in the critically ill adult patient", section on 'Ketamine'.)
•Dexmedetomidine – Dexmedetomidine provides sedation, anxiolysis, and analgesia, with less respiratory depression than other sedatives, and is often used as a pain management adjunct, particularly as a first-line sedative in the intubated burn patient [100,108]. (See "Pain control in the critically ill adult patient", section on 'Dexmedetomidine'.)
•Acetaminophen – Acetaminophen is routinely used in many burn centers as part of a multimodal pain regimen. (See "Pain control in the critically ill adult patient", section on 'Acetaminophen'.)
Although administration of other systemic analgesic agents (eg, gabapentinoids, lidocaine) has been described, data demonstrating their efficacy are limited in patients with burn injuries; thus, use of these agents is uncommon.
●Nonpharmacologic agents – Nonpharmacologic techniques are used to manage postoperative pain when feasible, including infiltration of local anesthetics and regional anesthetic techniques, which may reduce opioid requirements, improve pain relief and patient satisfaction, and promote rehabilitation [2]. (See 'Use of local and regional anesthesia' above.).
Other issues — Other critical therapeutic interventions, including nutritional support, temperature management, beta blocker administration, and deep venous thrombosis prophylaxis are initiated or continued in the early postoperative period. (See "Overview of complications of severe burn injury".)
LATER SCAR REVISION PROCEDURES — Scar revision procedures may be performed weeks or years after the initial burn injury. Lung injury is generally resolved at the time of these later procedures. However, airway management may be difficult due to fibrous tissue deposition and scarring. For example, skin contractures of the neck and mouth can distort upper airway anatomy, causing severely constricted mouth opening and/or limited neck movement (particularly neck extension). Some patients develop tracheal stenosis as a consequence of prolonged tracheal intubation and/or tracheostomy placement. Management of a potentially difficult airway management is described in detail in a practice guideline developed by the American Society of Anesthesiologists (ASA), and in a separate topic [109]. (See "Management of the difficult airway for general anesthesia in adults".)
Notably, chest wall contractures can result from spontaneously healed or grafted circumferential truncal burns, creating a restriction due to decreased chest wall compliance. (See "Anesthesia for patients with interstitial lung disease or other restrictive disorders".)
Other considerations include the need for a multimodal analgesic approach after painful procedures to treat burn scars, including vigilant pain assessment and compassionate attention to anxiety and other psychosocial contributors to pain [27]. Opioid tolerance (or even hyperalgesia) acquired during the initial management of a major burn create challenges for pain management during subsequent procedures. Strategies include early consultation with pain specialists and use of lidocaine infusion and/or N-methyl-D-aspartate (NMDA)-modulating analgesic agents.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Care of the patient with burn injury".)
SUMMARY AND RECOMMENDATIONS
●Preanesthetic assessment – The preanesthetic assessment includes understanding the proposed procedure (eg, positioning, limitations for vascular access limitations, potential blood loss), presence of inhalation injury and associated respiratory dysfunction, potential for difficult airway, current cardiovascular and intravascular volume status, and whether nutritional supplementation (enteral, parenteral) should be continued throughout the perioperative period. (See 'Preanesthetic assessment' above.)
●Monitoring considerations – Strategies to address limitations in available sites for standard monitors (eg, electrocardiogram pads, blood pressure cuff, pulse oximetry probe) may be necessary. We typically monitor dynamic hemodynamic parameters to maintain optimal intravascular volume and guide vasoactive therapy, using qualitative visual assessment of intra-arterial waveform (figure 2) or commercially available devices (table 1). We intermittently monitor arterial blood gases including lactate since elevated levels indicate reduced global tissue perfusion. (See 'Intraoperative monitoring' above.)
●Airway management (See 'Airway management' above.)
•Bag-mask ventilation – A two-person bag-mask ventilation technique may be necessary to achieve adequate ventilation in patients with facial burns.
•Fiberoptic flexible scope intubation – When upper airway patency is a concern, we suggest fiberoptic flexible scope intubation to identify specific abnormalities and maximize chances for successful intubation (algorithm 1).
•Securing the endotracheal tube (ETT) – Techniques to achieve adequate fixation of the ETT include placement of cloth tape around the tube secured with trach ties, interdental wires, surgical sutures around the teeth, or circum-mandibular, nasomaxillary, or transseptal sutures.
●Anesthetic management – Altered pharmacokinetics and pharmacodynamics affect anesthetics, analgesics, and muscle relaxants due to reduced plasma albumin levels (with increased volume of distribution and available free fraction of medications that bind to albumin), alterations in specific drug receptors, and cardiovascular factors. (See 'Altered pharmacokinetics and pharmacodynamics' above.)
•Induction – We typically administer ketamine or etomidate to induce anesthesia during the acute resuscitative (ebb) phase, together with a small opioid dose. Induction anesthetics are administered cautiously (ie, slow administration in reduced doses) to avoid hypotension. (See 'Induction' above.)
•Succinylcholine – During the first 48 hours following a major burn, succinylcholine (SCh) may be used. However, SCh is avoided after that first 48 hours, and for at least one year thereafter, due to risk of acute severe hyperkalemia and life-threatening arrhythmias. (See 'Use of succinylcholine' above.)
•Maintenance – We typically select an inhalation-based or a "balanced," technique to maintain anesthesia for burn surgery (employing an inhalation anesthetic, opioid, and a neuromuscular blocking agent [NMBA]) because costs are lower compared with using total intravenous anesthesia (TIVA) techniques. (See 'Choice of maintenance technique' above.)
•Use of nondepolarizing NMBAs – Close monitoring of degree of neuromuscular blockade is critically important after administration of NMBAs. Approximately one week after burns involving >30 percent total body surface area (TBSA), resistance to all NMBAs develops and peaks at five to six weeks after injury. Also, recovery time from neuromuscular blockade is shortened. Thus, it is often necessary to increase doses and frequency of NMBA administration to partially overcome increased resistance and more rapid recovery. (See 'Use of NMBAs' above.)
•Use of opioids – Opioid doses are reduced during the acute resuscitative (ebb) phase because metabolic clearance may be impaired by liver dysfunction. In the subsequent recovery (flow) phase, opioid requirements may increase due to increased volume of distribution resulting in protein dilution and decreased protein binding. (See 'Use of intraoperative opioids' above.)
•Local and regional anesthesia - Local and regional anesthetic techniques provide supplemental intraoperative analgesia and may improve postoperative analgesia to decrease opioid requirements. (See 'Use of local and regional anesthesia' above.)
●Fluid and transfusion management
•Crystalloid administration - We typically administer crystalloid solutions during the resuscitative phase, although some institutions administer hypertonic or colloid solutions (eg, purified albumin, fresh frozen plasma [FFP]), particularly if patients have inadequate urine output or evidence of poor perfusion. (See 'Fluid administration' above.)
Intraoperative volume losses are added to formula-guided (eg, Parkland formula) resuscitative fluid volume, with adjustments according to magnitude of burn excisions, volume of blood loss, burn depth, and use of surgical hemostatic techniques or administration of tumescent fluid. (See "Emergency care of moderate and severe thermal burns in adults", section on 'Estimating initial fluid requirements'.).
•Transfusion decisions – We employ a restrictive transfusion strategy in hemodynamically stable patients without massive blood loss, with transfusion of a unit of packed red blood cells (RBCs) at a hemoglobin transfusion threshold of <7 to 8 g/dL (hematocrit <21 to 24 percent). (See 'Transfusion decisions' above.)
●Temperature management – We prevent intraoperative hypothermia by using convective warming devices (ie, forced air warmers), administering warmed intravenous (IV) fluids, maintaining a warm ambient room temperature ≥25°C, and minimizing exposed body surface area. (See 'Temperature management' above.)
●Postoperative management
•Mechanical ventilation – Postoperative mechanical ventilation is typically necessary for patients with inhalational burn injury, increased risk of ongoing bleeding or frequent return to the operating room for additional surgery, or risk for graft disruption due to movement. (See 'Use of mechanical ventilation' above.)
•Pain management – Opioid tolerance makes pain management challenging. Thus, we use multimodal opioid-sparing techniques including nonopioid analgesics (eg, ketamine, dexmedetomidine) and local or regional anesthetic techniques when feasible. (See 'Challenges in pain management' above.)
●Later scar revision procedures – Scar revision procedures may be performed weeks or years after the initial burn injury when airway and ventilation management may be difficult due to skin contractures of the neck and mouth that distort upper airway anatomy (eg, severely constricted mouth opening, limited neck movement), tracheal stenosis, or chest wall contractures that cause a restrictive lung defect. (See 'Later scar revision procedures' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Sam Sharar, MD, who contributed to earlier versions of this topic review.
