What is the emergency management for a patient exposed to toxic gas fumes, including possible carbon monoxide or cyanide poisoning?

Emergency Management of Toxic Gas Fume Exposure

Immediately administer 100% oxygen via non-rebreather mask or endotracheal tube to all patients with suspected toxic gas exposure, particularly carbon monoxide or cyanide poisoning, without waiting for laboratory confirmation. 1, 2, 3

Immediate Resuscitation and Decontamination

Airway and Breathing

• Secure the airway early if signs of thermal injury are present (hoarseness, dysphagia, drooling, stridor, carbonaceous sputum, singed facial/nasal hairs) as airway obstruction can develop rapidly 1
• Perform rapid sequence intubation with modified technique if airway compromise is imminent; consider videolaryngoscopy to improve success rates 1
• Initiate 100% oxygen immediately via non-rebreather mask (15 L/min) or endotracheal tube for all suspected inhalation injuries 1, 2, 3
• Continue oxygen therapy until carboxyhemoglobin normalizes (<3%) and symptoms resolve, typically requiring approximately 6 hours 1, 2

Decontamination (for chemical gas exposures like chlorine)

• Remove patient from exposure source and strip all contaminated clothing and jewelry outside the medical facility to prevent secondary contamination 4
• Irrigate exposed skin with copious running water for at least 15 minutes 4
• Healthcare personnel must wear organic vapor cartridge respirators or powered air-purifying respirators with acid-gas filters 4

Diagnostic Evaluation

Carbon Monoxide Assessment

• Obtain carboxyhemoglobin level via CO-oximetry on venous or arterial blood to confirm diagnosis 2, 3
• Do not rely on pulse oximetry, as it will show falsely normal SpO2 readings even with COHb levels as high as 25% 1, 2
• Recognize that COHb levels may be low or normal if several hours have elapsed since exposure or if oxygen has already been administered 2, 3
• COHb levels correlate poorly with symptoms or prognosis and serve primarily to confirm exposure, not guide treatment intensity 1, 2

Cyanide Poisoning Assessment

• Suspect concomitant cyanide poisoning in all house fire victims, as synthetic materials release hydrogen cyanide when burned 2, 5, 6
• Check arterial blood gas and lactate levels: plasma lactate ≥10 mmol/L in fire victims without severe burns or ≥8 mmol/L in pure cyanide poisoning indicates cyanide intoxication 2, 7
• Severe metabolic acidosis (pH <7.20) with elevated lactate suggests cyanide toxicity 2, 7
• Carbon monoxide and cyanide act synergistically, effectively lowering the lethal doses of both toxins 8, 9

Additional Monitoring

• Obtain 12-lead ECG and initiate continuous cardiac monitoring for all patients with moderate to severe poisoning 2
• Assess for thermal airway injury with fiberoptic bronchoscopy if upper airway obstruction is suspected 5
• Check for coingestions in intentional poisoning cases (present in up to 44% of cases) 3

Specific Antidote Therapy

Cyanide Antidotes

Administer hydroxocobalamin as first-line antidote for suspected cyanide poisoning due to its superior safety profile 7, 6

Hydroxocobalamin Dosing

• Acts immediately by binding cyanide and converting it to cyanocobalamin (vitamin B12), which is renally excreted 7, 6
• Safe in fire victims with or without confirmed cyanide poisoning 7
• Only reported side effect is red coloration of skin and urine 7
• Do not administer hydroxocobalamin and sodium thiosulfate via the same IV line, as they are chemically incompatible 10

Sodium Thiosulfate (Alternative/Adjunctive)

• Adults: 50 mL (12.5 grams) IV immediately following sodium nitrite administration 10
• Children: 1 mL/kg (250 mg/kg or 30-40 mL/m² BSA) IV, not to exceed 50 mL total dose 10
• Acts by converting cyanide to thiocyanate, which is renally excreted 10, 7
• Efficient and safe but acts with delay compared to hydroxocobalamin 7
• Consider continuous infusion in massive cyanide poisoning due to limited potency of hydroxocobalamin alone 7

Empiric Treatment Indications

• Administer cyanide antidote empirically if arterial pH <7.20 or plasma lactate >10 mmol/L in fire victims 2, 7
• Do not delay treatment while awaiting laboratory confirmation, as acute cyanide toxicity can become fatal within minutes 6

Redosing Protocol

• If signs of cyanide poisoning reappear, repeat treatment using one-half the original dose of both sodium nitrite and sodium thiosulfate 10
• Monitor blood pressure continuously during treatment 10

Hyperbaric Oxygen Therapy Considerations

Indications for HBO Therapy

Consider hyperbaric oxygen therapy for carbon monoxide poisoning if any of the following high-risk features are present: 2, 3

• Loss of consciousness during or after exposure
• Neurological deficits
• Ischemic cardiac changes on ECG
• Significant metabolic acidosis
• COHb level >25%
• Pregnancy with any symptoms of CO poisoning

HBO Protocol

• Administer at 2.5-3.0 atmospheres absolute pressure 2, 3
• Reduces COHb half-life from 74 minutes (on 100% normobaric oxygen) to approximately 20 minutes 2, 3
• Persistently symptomatic patients may benefit from up to three treatments 3
• May also help displace cyanide in combined poisoning 8

Follow-Up Care

Short-Term Follow-Up

• Schedule clinical follow-up in 4-6 weeks (1-2 months) to screen for delayed neurological sequelae in accidental poisoning cases 2, 3
• Assess for memory disturbance, depression, anxiety, calculation difficulties, vestibular problems, motor dysfunction, and sleep disorders 3
• Refer patients not recovered to baseline functioning for formal neuropsychological evaluation 3
• Provide appropriate cardiology follow-up for patients with evidence of cardiac damage 3

Long-Term Considerations

• Recognize that CO poisoning survivors have increased long-term mortality (up to 3-fold) compared to unexposed individuals, suggesting possible residual brain injury 2, 3
• Delayed neurological sequelae occur in 12-68% of poisoned patients 3
• Mandatory psychiatric follow-up required for intentional CO poisoning due to high risk of subsequent suicide 3

Critical Pitfalls to Avoid

• Never delay oxygen therapy while awaiting laboratory confirmation of CO or cyanide poisoning 1, 2, 3
• Never withhold hyperbaric oxygen solely because a patient appears clinically stable, as delayed neurological sequelae can still occur 3
• Never use standard pulse oximetry to rule out CO poisoning, as it provides falsely reassuring readings 1, 2
• Never discharge patients without identifying and eliminating the CO exposure source to prevent re-exposure 1, 3
• Never use inadequate personal protective equipment (ordinary surgical masks are insufficient for chlorine vapor protection) 4
• Always consider cyanide poisoning in house fire victims, as it is present in an estimated 35% of all fire victims upon ED arrival 6