8.4 Inhalation Injury, Escharotomy & Burn Wound Care
Key Takeaways
- Standard pulse oximetry cannot distinguish oxyhemoglobin from carboxyhemoglobin, yielding false-normal SpO2 readings in carbon monoxide poisoning that require definitive co-oximetry blood gas analysis.
- Carbon monoxide poisoning mandates immediate treatment with 100% high-flow normobaric oxygen via a non-rebreather mask to reduce CO-Hb half-life from 320 minutes to 60–90 minutes.
- Cyanide poisoning in smoke inhalation causes cellular asphyxiation by inhibiting cytochrome c oxidase, treated definitively with intravenous hydroxocobalamin (Cyanokit).
- Circumferential full-thickness burns of the trunk or extremities require urgent escharotomy when chest wall compliance is severely restricted or distal vascular perfusion is lost.
- Topical antimicrobial selection requires matching clinical goals: Silver Sulfadiazine is widely used for partial-thickness burns, whereas Mafenide Acetate penetrates thick eschar but carries a risk of carbonic anhydrase inhibition and metabolic acidosis.
Inhalation injury, circumferential eschar constriction, and burn wound infection represent major causes of morbidity and mortality in burn trauma. Comprehensive nursing care requires early airway stabilization, rapid toxicological intervention, prompt surgical escharotomy, and evidence-based topical antimicrobial therapy.
Inhalation Injury Pathophysiology & Airway Management
Inhalation injury is categorized into upper airway (supraglottic) thermal injury and lower airway (infraglottic) chemical injury.
Supraglottic Thermal Injury
Direct heat transfer to the pharynx and larynx causes rapid mucosal erythema, edema, and progressive airway occlusion. Because upper airway edema peaks between 12 and 24 hours post-injury, early elective endotracheal intubation is mandatory before anatomical landmarks are distorted.
Clinical indications for immediate endotracheal intubation include:
- Facial burns and soot deposits around the mouth and nares.
- Singed facial and nasal hairs.
- Carbonaceous (sooty) sputum.
- Hoarseness, brassy cough, or stridor.
- Blistering or edema of the posterior pharynx and soft palate.
Infraglottic Chemical Injury
Inhalation of toxic combustion products—such as aldehydes, sulfur dioxide, chlorine, and ammonia—causes mucosal necrosis, bronchospasm, loss of ciliary action, and pulmonary microvascular leak. Sloughed bronchial mucosa and inflammatory debris form thick bronchial casts, causing segmental atelectasis, non-cardiogenic pulmonary edema, and Acute Respiratory Distress Syndrome (ARDS).
Carbon Monoxide (CO) & Cyanide Poisoning
Smoke inhalation in enclosed spaces frequently results in systemic chemical asphyxiation from carbon monoxide (CO) and hydrogen cyanide (HCN) gas.
Carbon Monoxide Poisoning & Co-Oximetry Diagnostic Pitfall
Carbon monoxide binds to hemoglobin with an affinity 200 to 250 times greater than oxygen, forming carboxyhemoglobin (CO-Hb). CO-Hb shifts the oxyhemoglobin dissociation curve to the left, impairing tissue oxygen delivery.
CRITICAL DIAGNOSTIC PITFALL: Standard two-wavelength pulse oximeters (SpO2) cannot distinguish carboxyhemoglobin from oxyhemoglobin. The pulse oximeter will display a falsely reassuring 100% SpO2 reading despite fatal carboxyhemoglobin concentrations. Diagnosis requires an arterial blood gas (ABG) analyzed via direct co-oximetry.
| CO-Hb Level | Clinical Manifestations | Therapeutic Management |
|---|---|---|
| <3% (Up to 10% in smokers) | Asymptomatic | None required |
| 10–20% | Mild headache, dyspnea on exertion | 100% High-Flow Normobaric O2 via NRB mask |
| 20–30% | Severe throbbing headache, dizziness, nausea, confusion | 100% High-Flow O2; monitor cardiac status |
| 30–50% | Severe disorientation, syncope, tachycardia, seizures | 100% O2; evaluate for Hyperbaric Oxygen (HBO) |
| >50% | Coma, fatal ventricular arrhythmias, cardiac arrest | Emergent HBO therapy / Advanced Life Support |
Administering 100% High-Flow Oxygen via a non-rebreather mask (NRB) reduces the elimination half-life of carboxyhemoglobin from 320 minutes on room air down to 60–90 minutes. Hyperbaric Oxygen (HBO) therapy further reduces CO-Hb half-life to 15–30 minutes and is indicated for CO-Hb levels >25% (>15% in pregnant patients), loss of consciousness, neurological deficits, or acute myocardial ischemia.
Cyanide Poisoning & Hydroxocobalamin Antidote
Combustion of synthetic materials (plastics, polyurethane, nylon) generates hydrogen cyanide gas. Cyanide binds to the ferric (Fe3+) ion in mitochondrial cytochrome c oxidase, blocking the electron transport chain and halting aerobic ATP production.
Patients present with profound, unexplained metabolic acidosis, markedly elevated serum lactate (>10 mmol/L), and elevated central venous oxygen saturation (due to cellular inability to extract oxygen).
The primary antidote is Hydroxocobalamin (Cyanokit, 5 g IV over 15 minutes). Hydroxocobalamin neutralizes cyanide by forming non-toxic cyanocobalamin (Vitamin B12), excreted harmlessly in urine (causing transient reddish discoloration of skin and urine).
Circumferential Full-Thickness Burns & Escharotomy
Full-thickness burns form a tough, rigid, unyielding eschar. As sub-eschar tissue edema accumulates during fluid resuscitation, structural compartment pressures elevate dramatically.
- Circumferential Torso Burns: Constrict chest wall expansion, producing hypoventilation, decreased tidal volume, elevated peak airway pressures (>40 cm H2O), and respiratory failure.
- Circumferential Limb Burns: Compromise vascular perfusion, causing distal arterial thrombosis, compartment syndrome, and tissue necrosis.
Indications & Technique for Bedside Escharotomy
Urgent escharotomy is indicated for:
- Impaired chest wall compliance causing respiratory distress.
- Absent distal Doppler arterial signals, prolonged capillary refill (>3 seconds), paresthesias, or severe ischemic pain in a circumferential extremity burn.
Escharotomy involves longitudinal surgical incisions extending through the full thickness of the dead eschar down to subcutaneous fat (without cutting underlying muscle fascia). Incisions are performed along the mid-medial and mid-lateral axial lines of extremities and the anterior chest wall. Because full-thickness eschar is insensate, bedside escharotomy is performed without general anesthesia.
Burn Wound Care & Topical Antimicrobial Agents
The goal of burn wound care is debridement of necrotic tissue, prevention of invasive wound sepsis, and preparation of the wound bed for autografting.
| Topical Antimicrobial | Clinical Indications | Major Advantages | Key Disadvantages & Nursing Considerations |
|---|---|---|---|
| Silver Sulfadiazine (Silvadene 1%) | Partial- and full-thickness burns | Painless application; broad spectrum antibacterial | Poor eschar penetration; causes transient leukopenia; contraindicated in sulfa allergy or face |
| Mafenide Acetate (Sulfamylon) | Thick eschar; ear/nose cartilage burns | Penetrates deep eschar; potent against Pseudomonas | Painful application; carbonic anhydrase inhibitor causing severe metabolic acidosis |
| Silver Nitrate (0.5% solution) | Exudative burn wounds; graft beds | Broad spectrum; non-allergenic | Stains skin and environment black; causes severe hyponatremia and hypochloremia |
| Silver-Impregnated Dressings | Partial-thickness burns; donor sites | Sustained silver release over 3–7 days; reduces dressing changes | Requires moist activation; higher initial material cost |
A firefighter exposed to dense smoke inside a structure fire arrives in the emergency department alert with facial soot and a complaint of a severe headache. Pulse oximetry displays 99% SpO2 on room air. ABG reveals a pH of 7.31, PaCO2 of 36 mmHg, PaO2 of 95 mmHg, and carboxyhemoglobin (CO-Hb) of 28%. What explains the discrepancy between the pulse oximeter reading and the patient's actual oxygenation status?
A patient rescued from a house fire involving burning synthetic furniture presents with profound metabolic acidosis, a serum lactate of 14 mmol/L, and cardiovascular instability despite 100% high-flow oxygen. Cyanide poisoning is suspected. Which antidote should be administered immediately?
An adult patient with a 45% TBSA burn involving circumferential full-thickness burns to both upper extremities is receiving Parkland fluid resuscitation. Four hours into resuscitation, the patient develops absent radial pulses by Doppler, cold pale hands, and worsening paresthesias. What emergency bedside surgical procedure is indicated?