What is the treatment for a patient with suspected cyanide poisoning and profound vasoplegia using Cyanokit (hydroxocobalamin)?

Hydroxocobalamin (Cyanokit) for Profound Vasoplegia in Suspected Cyanide Poisoning

Administer hydroxocobalamin 5 g IV immediately for suspected cyanide poisoning with profound vasoplegia, escalating to 10 g IV if the patient is in cardiac arrest, without waiting for laboratory confirmation. 1, 2

Immediate Treatment Protocol

Dosing Strategy

• Standard dose: 5 g IV infused over 15 minutes for suspected cyanide poisoning with severe manifestations including shock or cardiovascular collapse 2
• Cardiac arrest dose: 10 g IV when the patient has progressed to cardiac arrest from cyanide toxicity 2
• The rapid hemodynamic response is remarkable—vasopressors can typically be discontinued within 40 minutes of hydroxocobalamin administration 3

Clinical Indicators for Immediate Treatment

Do not delay treatment waiting for confirmatory testing; treat based on clinical suspicion alone 1, 2. Key indicators include:

• Fire or smoke exposure with cardiovascular collapse or shock 2
• Profound vasoplegia with metabolic acidosis and elevated lactate (≥10 mmol/L in fire victims without severe burns, or ≥8 mmol/L in pure cyanide poisoning) 2, 4
• Normal arterial oxygen saturation despite hemodynamic instability—cyanide paralyzes cellular respiration, creating a narrowed arteriovenous oxygen gradient despite adequate arterial oxygenation 5, 6
• Depressed mental status, seizures, or coma in the appropriate exposure context 2

Why Hydroxocobalamin is Preferred Over Alternatives

Hydroxocobalamin is the first-line antidote because it does not cause hypotension or impair oxygen-carrying capacity, making it ideal for patients with profound vasoplegia and potential carbon monoxide co-poisoning 1, 2, 5. This is critical because:

• Sodium nitrite (the alternative antidote) induces methemoglobin formation, which further impairs oxygen delivery and can worsen outcomes in smoke inhalation victims with concurrent carbon monoxide exposure 7, 4
• Experimental data showed increased mortality in carbon monoxide- and cyanide-poisoned animals treated with methemoglobin-forming agents 4
• Hydroxocobalamin acts immediately by binding cyanide to form non-toxic cyanocobalamin, which is renally excreted 6, 4

Adjunctive Therapy

Sodium Thiosulfate

• Add sodium thiosulfate 12.5 g IV following hydroxocobalamin to enhance cyanide elimination 2, 5
• Sodium thiosulfate acts with delay but provides persistent effect by serving as a substrate for enzymatic conversion of cyanide to thiocyanate 7, 4, 8
• The combination may have synergistic effects: hydroxocobalamin provides immediate action while sodium thiosulfate offers delayed but sustained benefit 8

Oxygen Therapy

• Administer 100% oxygen concurrently, even if arterial saturation appears normal 2, 5
• Oxygen counteracts cyanide's mitochondrial effects and accelerates carboxyhemoglobin elimination in co-poisoned patients 2, 4

Critical Pitfalls and Monitoring

Hemodialysis Interference

• Hydroxocobalamin causes false blood leak alarms in hemodialysis machines, which can delay or prevent dialysis treatment 3, 9
• If renal replacement therapy is needed, consider continuous renal replacement therapy (CRRT) instead of intermittent hemodialysis to overcome this interference 9
• The red coloration from hydroxocobalamin interferes with the blood leak detector's optical sensors 3, 9

Renal Monitoring

• Monitor renal function for oxalate nephropathy, a potential complication of hydroxocobalamin 2

Laboratory Interference

• Hydroxocobalamin causes red discoloration of skin, urine, and plasma 4
• This can interfere with certain laboratory analyses, including urinary thiocyanate measurements 3

Pediatric Considerations

• For children: 70 mg/kg IV (maximum 5 g) for moderate to severe cyanide poisoning 2
• Sodium thiosulfate dosing: 250 mg/kg IV for children 2