Hydroxocobalamin for Smoke Cyanide
Objective: Link closed-space smoke plus unexplained lactic-looking shock or arrest to cyanide suspicion, and know what hydroxocobalamin is for — without delaying airway and destination.
Why This Is Hard
Pulse ox lies in CO, and cyanide does not have a field test. Crews treat “just smoke inhalation” while the patient is vasodilated, seizing, or in PEA. AHA 2025 special circumstances: for suspected cyanide poisoning (including smoke), hydroxocobalamin is the antidote many EMS systems carry. It is not a reason to skip the airway clock or a burn center.
- Closed-space fire, soot in airway, altered, seizure, unexplained hypotension or arrest — think cyanide plus CO.
- High-flow oxygen. Airway as indicated (see smoke-inhalation lesson). Hydroxocobalamin IV/IO if protocol and supply allow.
- It turns mucous membranes and urine red and can interfere with some lab colorimetric tests. Tell the ED you gave it.
Street Sequence
- Remove from the environment. Oxygen. ABCs. Stop the burning clothes.
- If they are crashing out of proportion to visible burns: cyanide is on the table.
- Hydroxocobalamin per protocol (typical adult teaching dose is a 5 g vial infused as labeled — verify your kit). Do not wait for a hospital cyanide level.
- Airway swelling still has its own clock. Destination: burn/critical care capable. CO may still need a center that can manage it.
Field Rules (Education)
- Suspicion, not a lab: you will not confirm cyanide on the truck. The picture is smoke + coma/shock/arrest/seizure without another story.
- Hydroxocobalamin binds cyanide to form cyanocobalamin. It is preferred over older nitrite kits in many EMS systems because it does not induce methemoglobinemia on top of CO.
- Not a pulse-ox fix: treat CO and cyanide as a pair in enclosed-fire victims. See the CO lesson.
- Tell the hospital: the red fluids confuse labs and the chart. Name the drug and the time.
- Closed-space smoke — CO and cyanide both on the table
- Oxygen and airway first
- Hydroxocobalamin if protocol and we have it
- ED: Cyanokit given at __ — labs may be color-interfered
Field Pitfalls
- Waiting for a cyanide level that does not exist in the field.
- Giving the antidote and forgetting the swelling airway.
- Using a nitrite-based kit on a CO-poisoned patient if your protocol has moved to hydroxocobalamin.
Practice
60-second drill
Apartment fire, found unresponsive in a bathroom, soot, BP 78, no major burns. Three treatments in order. What do you tell the ED about the urine?
Related: Smoke Inhalation & the Airway Clock, Carbon Monoxide.
Sources & Further Study
Named guidelines for further study. They are not clinical orders and do not replace your protocol or medical direction.
- NASEMSO National Model EMS Clinical Guidelines (2022) — smoke inhalation / cyanide pathways; protocol owns the kit
- AHA 2025 Part 10: Special Circumstances — suspected cyanide including smoke — hydroxocobalamin as EMS antidote
Education only. Apply learning within your protocols and medical direction. This is not clinical care guidance.
Check Your Understanding
Street decisions from this lesson only. After you check, the key is highlighted. Education practice — not a certification exam.