Anesthesia for burn surgery

Overview

Anesthesia for burn surgery presents unique challenges that distinguish it from general surgical anesthesia. Burn patients undergo repeated operative procedures for wound excision and grafting, often over weeks to months, creating cumulative exposure to anesthetic agents in the setting of profoundly altered physiology. Key considerations include difficult airway management (edema, scarring, limited mobility), dramatically altered pharmacokinetics, massive intraoperative blood loss, thermoregulatory failure, and the need to balance surgical access with physiologic stability. Bittner et al. provide the most comprehensive modern review of perioperative burn anesthesia ^[7].

Pharmacokinetic Alterations

Burn injury produces predictable, phase-dependent changes in drug disposition that affect virtually every class of anesthetic agent ^[6]. In the acute phase (first 48 hours), reduced cardiac output, capillary leak, and decreased hepatic blood flow decrease drug clearance. Beyond 48 hours, the hypermetabolic response increases cardiac output by 50-100%, augments hepatic blood flow, increases renal clearance (glomerular hyperfiltration), and expands total body water. Plasma albumin falls, increasing the free fraction of protein-bound drugs. The net effect is increased volume of distribution and accelerated elimination of most agents, requiring higher and more frequent dosing ^[6][7].

These changes are proportional to burn size and persist for months. The clinical implication is straightforward: standard dosing for unburned patients will underdose burn patients, sometimes dramatically.

Neuromuscular Blockade

Succinylcholine is contraindicated from approximately 24-48 hours after burn injury through at least 1-2 years post-burn due to the risk of life-threatening hyperkalemia ^[4][5]. Burn injury triggers proliferation of immature (fetal-type) acetylcholine receptors across the entire muscle membrane, not just the neuromuscular junction. Depolarization by succinylcholine opens all of these receptors simultaneously, causing massive potassium efflux sufficient to produce ventricular fibrillation and cardiac arrest ^[4]. The risk begins as early as 24 hours post-injury, peaks at 7-10 days, and persists until receptor populations normalize, which may take more than a year after wound closure. Gronert and Theye described the pathophysiology of this potassium release in denervation-like states, establishing the mechanistic framework ^[5]. Martyn and Richtsfeld later defined the molecular basis: upregulation of the alpha-7 nicotinic acetylcholine receptor subtype and fetal-type receptors containing the gamma subunit across extrajunctional membranes ^[4].

Nondepolarizing agents are the appropriate alternative. However, burn patients typically require 2-3 times the normal dose of nondepolarizing agents due to the same receptor upregulation, increased volume of distribution, and enhanced hepatic clearance ^[7]. Rocuronium and cisatracurium are the most commonly used agents. Dose requirements should be guided by train-of-four monitoring, not by standard weight-based protocols.

Volatile and Intravenous Anesthetics

Burn patients require increased concentrations of volatile anesthetic agents to achieve equivalent depth of anesthesia ^[7]. The mechanisms are multifactorial: increased cardiac output accelerates uptake and redistribution, the hypermetabolic state increases minimum alveolar concentration (MAC), and chronic opioid exposure from prolonged ICU stays produces cross-tolerance. In the ICU setting, volatile agents delivered via miniature vaporizer systems offer an alternative sedation strategy to intravenous agents, with advantages including reduced delirium rates and faster awakening ^[3].

Intravenous anesthetic requirements are similarly increased. Propofol clearance rises substantially in the hypermetabolic phase. Opioid requirements escalate due to both pharmacokinetic changes (expanded Vd, increased clearance) and pharmacodynamic tolerance from prolonged exposure during ICU care ^[7].

Airway Management

Burn patients present some of the most challenging airways in all of surgery. The challenges are phase-dependent and cumulative ^[8].

Acute Phase

In the first 24-72 hours, the primary threats are progressive facial and neck edema from resuscitation, oropharyngeal or supraglottic edema from inhalation injury, and loss of external landmarks from facial burns. Edema peaks around 12-24 hours into resuscitation and can convert a straightforward airway to an impossible one over hours. Video laryngoscopy should be considered first-line for intubation in acute burn patients, as it provides improved glottic visualization when edema distorts normal anatomy ^[9]. Direct laryngoscopy remains acceptable when the airway appears favorable, but a video laryngoscope should be immediately available.

Securing the endotracheal tube to burned facial skin is a practical challenge. Cloth ties, wire, or circumferential methods may be needed when tape will not adhere. Tube position must be confirmed and rechecked frequently, as facial edema can displace a properly positioned tube.

Contracture Phase

Patients returning for reconstruction months to years after injury present a different problem: cervical and mentosternal contracture that restricts or eliminates neck extension. Prakash and Mullick reviewed airway management strategies for burn contracture patients, establishing fiberoptic bronchoscopy as the technique of choice for anticipated difficult airways in this population ^[8]. Awake fiberoptic intubation allows maintenance of spontaneous ventilation while navigating a fixed, distorted airway. Gupta and Sahni compared video laryngoscopy to direct laryngoscopy in contracture-neck patients and found video laryngoscopy produced better glottic views and higher first-attempt success rates, supporting its role as an adjunct or alternative when fiberoptic equipment is unavailable ^[9].

Laryngotracheal Complications

Repeated intubations across multiple operative procedures, combined with mucosal injury from inhalation, place burn patients at elevated risk for laryngotracheal stenosis. Zhen et al. conducted a scoping review of long-term laryngotracheal complications after inhalation injury and identified subglottic and tracheal stenosis, granulation tissue, and vocal cord injury as recognized sequelae ^[10]. The incidence is difficult to quantify because many cases are diagnosed late or attributed to inhalation injury alone rather than cumulative intubation trauma. Awareness of this risk should inform decisions about tracheostomy timing in patients expected to require many trips to the operating room.

Temperature Management

Thermoregulatory failure is an intrinsic consequence of major burns due to loss of the skin's insulating function, and perioperative hypothermia is associated with coagulopathy, impaired wound healing, and increased infection risk. An international survey of 148 clinicians across the UK, Australia, and New Zealand revealed that 38% reported no local thermoregulation protocol and 22% were unaware of any existing protocol ^[2]. Hypothermia was more likely than hyperthermia to cause surgical delays, with 35 degrees C cited as the most common threshold. High-complexity burn services tolerated wider temperature ranges during surgery compared to lower-complexity services ^[2].

Regional Anesthesia

Regional anesthesia techniques can reduce opioid requirements and improve postoperative pain control in burn patients undergoing limb surgery. A retrospective study of 25 patients undergoing lower-limb escharectomy and autologous skin grafting under a dual-block protocol (ultrasound-guided sciatic popliteal block plus adductor canal block with ropivacaine 0.375% and clonidine) demonstrated effective postoperative analgesia with only 16% of patients requiring rescue opioids ^[1]. The technique is limited by burn extent (coagulated or infected tissue at potential needle insertion sites) but holds promise for unburned extremities and donor sites.

Controversies and Evidence Gaps

No randomized trial has compared general anesthetic techniques head-to-head in burn populations. The optimal volatile agent for prolonged burn surgery is undefined. The role of total intravenous anesthesia versus balanced anesthesia in the hypermetabolic burn state has not been studied. Temperature thresholds for delaying surgery vary widely and lack evidence-based standardization. The long-term effects of cumulative anesthetic exposure across dozens of procedures on neurocognitive outcomes in burn survivors are unknown.

References

[1] Coppolino F et al. "Postoperative Pain and Opioid Use Following Lower-Limb Escharectomy and Skin Grafting Under a Standardized Regional Anesthesia Protocol: A Retrospective Study." Life (Basel) 2026;16(2). PMID: 41752840 [2] Stanley GHM et al. "optiTHERMM: A trainee-led international collaborative survey on perioperative patient body temperature monitoring and management for major burn injuries." Burns 2025;52(2):107817. PMID: 41455304 [3] Kopanczyk R et al. "Volatile Anesthetics: A Comprehensive Review of Pharmacology, Delivery Systems, and Safety Considerations for ICU Practitioners." Crit Care Med 2026;54(4):926-938. PMID: 41556744 [4] Martyn JA, Richtsfeld M. "Succinylcholine-induced hyperkalemia in acquired pathologic states: etiologic factors and molecular mechanisms." Anesthesiology 2006;104(1):158-69. PMID: 16394702 [5] Gronert GA, Theye RA. "Pathophysiology of hyperkalemia induced by succinylcholine." Anesthesiology 1975;43(1):89-99. PMID: 1147311 [6] Jaehde U, Sörgel F. "Clinical pharmacokinetics in patients with burns." Clin Pharmacokinet 1995;29(1):15-28. PMID: 7586895 [7] Bittner EA, Shank E, Woodson L, Martyn JA. "Acute and perioperative care of the burn-injured patient." Anesthesiology 2015;122(2):448-64. PMID: 25485468 [8] Prakash S, Mullick P. "Airway management in patients with burn contractures of the neck." Burns 2015;41(8):1627-1635. PMID: 25868969 [9] Gupta R, Sahni A. "Is video laryngoscopy easier than direct laryngoscopy for intubation in patients with contracture neck?" Saudi J Anaesth 2020;14(2):206-211. PMID: 32317876 [10] Zhen E et al. "Long-Term Laryngotracheal Complications After Inhalation Injury: A Scoping Review." J Burn Care Res 2023;44(2):381-392. PMID: 35486925