Airway management in burn patients

Overview

Airway management in burn patients is a time-sensitive clinical challenge driven by progressive edema, direct thermal or chemical injury to the upper airway, and the potential for rapid deterioration from a manageable airway to a surgical emergency ^[7]. The biphasic nature of airway compromise (early edema followed by late mucosal sloughing) demands anticipatory decision-making rather than reactive intervention ^[7].

Burns create multiple overlapping mechanisms of airway difficulty: facial and neck edema distorts landmarks, fluid resuscitation exacerbates tissue swelling, and inhalation injury causes supraglottic edema ^[1][7]. Chronic burn contractures can further restrict mouth opening and neck extension ^[2]. These factors make burn patients among the highest-risk populations for difficult intubation.

Indications for Intubation

Early intubation is recommended when clinical signs suggest upper airway involvement. Waiting for objective airway compromise (stridor, desaturation) risks converting a difficult intubation into a failed airway ^[6]. Accepted indications include ^[6][7]:

• Stridor or hoarseness
• Facial or oropharyngeal burns
• Singed nasal vibrissae
• Carbonaceous sputum or oropharyngeal soot
• History of enclosed-space fire with altered mental status
• Progressive facial or neck edema
• Burns greater than 40-50% TBSA (anticipatory, due to resuscitation-related edema)
• Respiratory distress or failure

A retrospective analysis of 1,272 patients intubated before arrival at a burn center found that 11.9% were extubated on the day of admission and 21.3% on postburn day 1, suggesting that a proportion of prehospital intubations may not have been necessary ^[6]. However, no patients extubated on postburn day 1 or 2 required reintubation, supporting the safety of early extubation after reassessment at a burn center ^[6].

Approach to the Burn Airway

Acute Burns

In the acute setting, airway difficulty is driven by edema. Key principles include ^[1][7]:

• Assess before sedation. Evaluate the airway before administering paralytic agents when possible. If mask ventilation is uncertain, maintain spontaneous ventilation.
• Video laryngoscopy as first-line. Video laryngoscopy provides improved glottic visualization in the presence of edema and blood. It should be the default approach rather than a rescue technique ^[1].
• Prepare for surgical airway. Have cricothyrotomy equipment immediately available. Progressive edema can render both direct and video laryngoscopy impossible within hours of injury ^[4].
• Avoid nasal intubation in facial burns. Nasal routes risk contamination and are difficult to secure in the setting of facial edema and burns.

Burn Contractures

Patients with healed burn contractures of the neck and face present a distinct set of airway challenges ^[2][3]:

• Reduced mouth opening from perioral scarring
• Limited neck extension from anterior cervical contractures
• Distorted laryngeal anatomy from scar tissue
• Restricted mandibular mobility

The recommended approach for moderate to severe neck contracture is awake fiberoptic intubation with maintenance of spontaneous ventilation ^[2][3]. Alternatives include use of an intubating laryngeal mask airway and pre-induction contracture release under local anesthesia or ketamine sedation followed by direct or video laryngoscopy ^[2].

Difficult Airway Prediction

Standard difficult airway prediction tools (Mallampati, thyromental distance) have limited sensitivity in burn patients because the primary mechanism of difficulty (edema) is dynamic and may not be present at initial assessment ^[1]. The HEAVEN criteria (Hypoxemia, Extremes of size, Anatomic abnormalities, Vomit/blood/fluid, Exsanguination, Neck mobility issues) may be more applicable to emergency intubation in burn and trauma settings, with validation showing an inverse relationship between HEAVEN criteria present and first-attempt success ^[5].

Laryngeal Injury

A systematic review of laryngeal inhalational injuries found that airway stenosis was more common in patients who were intubated before airway evaluation (50% vs 5.2%) and posterior glottic involvement was identified only in patients intubated prior to laryngeal assessment ^[3]. These findings, while subject to confounding, support early otolaryngology referral for thermal injuries occurring in enclosed spaces. The study identified that closed-space exposure was universal among patients in whom airway intervention preceded laryngeal evaluation ^[3].

Extubation Considerations

Extubation in burn patients carries risk of reintubation in the setting of ongoing edema. Standard approaches include:

• Assessment of air leak around a deflated cuff (cuff leak test)
• Direct visualization of the airway with a flexible bronchoscope or video laryngoscope before extubation
• Staged extubation over an airway exchange catheter when reintubation risk is high
• Ensuring peak edema (typically 24-48 hours post-injury and resuscitation) has resolved VERIFY

Controversies and Evidence Gaps

• The threshold for prophylactic intubation in large burns without signs of inhalation injury is undefined. Overintubation exposes patients to ventilator-associated complications, while delayed intubation risks emergency surgical airway ^[6].
• No prospective study has compared video laryngoscopy versus direct laryngoscopy as the primary technique in acute burn intubation VERIFY.
• The role of awake fiberoptic intubation in acute (non-contracture) burn patients with anticipated difficult airway has not been systematically studied ^[2].
• Optimal criteria for safe extubation after burn-related intubation lack standardization VERIFY.

References

[1] Somwaru B, Grossman D. "Intubating Special Populations." Emerg Med Clin North Am 2022;40(3):443-458. PMID: 35953210. [2] Prakash S, Mullick P. "Airway management in patients with burn contractures of the neck." Burns 2015;41(8):1627-1635. PMID: 25868969. [3] Tang JA et al. "Laryngeal inhalational injuries: A systematic review." Burns 2021;48(1):23-33. PMID: 33814215. [4] Greathouse JS et al. "Difficult airway management following severe gasoline burn injury: a case report." AANA J 2012;80(4):268-72. PMID: 23251995. [5] Kuzmack E et al. "A Novel Difficult-Airway Prediction Tool for Emergency Airway Management: Validation of the HEAVEN Criteria in a Large Air Medical Cohort." J Emerg Med 2018;54(4):395-401. PMID: 29331494. [6] Eastman AL et al. "Pre-burn center management of the burned airway: do we know enough?" J Burn Care Res 2010;31(5):701-5. PMID: 20634705. [7] Foncerrada G et al. "Inhalation Injury in the Burned Patient." Ann Plast Surg 2018;80(3 Suppl 2):S98-S105. PMID: 29461292.