Cyanide Gas in a Plating Room: Three Victims, Four SCBA, No Antidote at the Hospital
Two workers at a plating shop collapse minutes after a bucket of sodium cyanide crystals is dumped into an acid pickling bath in a 10 m by 12 m room with one door and no local exhaust. The first is unresponsive, apneic, and has a pulse of 40; bystanders report a 'bitter almond' smell. The second is confused and vomiting. A coworker who tried to drag them out is now sitting against the doorframe inside the room, dizzy and nauseated. Your engine arrives with four SCBA and a four-gas meter; at the doorway it reads O2 20.9%, LEL 0%, CO 0, H2S 0. Your paramedic unit carries hydroxocobalamin, sodium thiosulfate, and a nitrite-based antidote kit. The receiving hospital is 20 minutes out and confirms it has no cyanide antidote in stock. Additional engine and medic units are 8 minutes away.
1. Lay out your rescue plan with the resources on scene, including how you handle the third victim and what the meter readings do and do not tell you.
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Acid plus cyanide salt releases hydrogen cyanide, a gas with an IDLH of 50 ppm that kills within minutes at high concentration. Your meter tells you almost nothing: it has no HCN sensor, and a normal oxygen, LEL, CO, and H2S reading does not exclude an IDLH cyanide atmosphere. Treat the room as IDLH and uncharacterized.
Plan:
Command, and stop the rescue impulse. No one enters without SCBA. The bystanders who tried to help have already created a third victim; do not let that become a fourth.
Commit only what you can back up. With four SCBA you can field a two-person entry team and a two-person backup; that is the minimum. Push for the additional engine and medic units immediately, and stage a rapid intervention team.
Rescue in order of reachability and survivability. The coworker at the doorframe is nearest the exit and can be dragged out by the entry team in seconds, which clears the doorway. Then remove the two inside. Extraction, not treatment, is the hot-zone task; do not attempt prolonged care in the room.
Ventilate on the way out. Open the door, use positive-pressure ventilation from outside once victims are clear, and keep the area isolated.
Move patients to the warm zone for decon and treatment. The apneic patient needs ventilation with a bag-valve mask immediately - not mouth-to-mouth - and CPR if there is no pulse. Recheck that pulse of 40 carefully; cyanide bradycardia can be mistaken for arrest.
2. Choose the antidote regimen for the apneic patient and the confused patient, and explain why the nitrite kit is the wrong choice here.
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Cyanide blocks cytochrome oxidase, so cells cannot use oxygen; the patient is profoundly hypoxic at the tissue level while the field oxygen reading and the pulse oximeter look normal. Oxygen and ventilation are the foundation, and the antidote is an adjunct to them, not a substitute.
First-line: hydroxocobalamin 5 g IV over about 15 minutes for the adult, repeated if the response is inadequate. It binds cyanide to form cyanocobalamin, which is excreted in the urine. It does not cause methemoglobinemia or hypotension, which is exactly why it is preferred in a rescue setting. Add sodium thiosulfate 12.5 g IV as a sulfur donor to support rhodanese-mediated detoxification. Give the same regimen empirically to the confused, vomiting patient - vomiting and confusion are consistent with significant cyanide exposure, and this is not a situation to wait for a lab result.
Why not the nitrite kit: amyl nitrite and sodium nitrite work by inducing methemoglobinemia, which pulls cyanide off cytochrome oxidase. That deliberately reduces the blood's oxygen-carrying capacity and causes hypotension. In any patient with possible concurrent carbon monoxide exposure, or with hypotensive or cardiovascularly unstable patients, that trade can be lethal. In this case you have no fire and no CO reading, but the patient is bradycardic and unstable, and hydroxocobalamin is available and superior. Reserve the nitrite kit for a situation with no hydroxocobalamin and a stable patient.
Warn the receiving facility that hydroxocobalamin turns urine red and interferes with colorimetric lab assays.
3. Describe the decontamination and transport plan for all three patients, and explain what the 'bitter almond' report does and does not establish.
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Decontamination: hydrogen cyanide is a gas, so the dominant exposure route is inhalation and clothing removal plus a shower is generally enough for the two who were only in the vapour. The patient who may have contacted the cyanide salt or the bath liquid needs more care: strip and double-bag all clothing, wash skin with soap and water, and flush eyes if there was splash. Protect the ambulance crew - the patient's breath and clothing will continue to off-gas cyanide, so ventilate the patient compartment, keep the stretcher away from the medics' breathing zone, and wear gloves. Do not delay transport for extensive decon on a patient in respiratory arrest; do the clothing removal, package, and go.
Transport: the apneic patient goes first with continuous bag-valve ventilation, oxygen, cardiac monitoring, and IV access. If an ALS unit can rendezvous, do it - the hospital has no antidote, so the hydroxocobalamin and thiosulfate on your medic unit must travel with the patient, and the receiving facility needs that information before arrival. Pre-alert with patient count, estimated exposure, antidote administered and dose, and ETA. The confused patient and the would-be rescuer both go for evaluation; the rescuer is a victim with the same exposure and should be treated as such.
The 'bitter almond' report proves little. A large fraction of the population cannot detect hydrogen cyanide by smell, and the odour threshold is well below hazardous concentrations anyway, so absence of odour does not mean absence of exposure and its presence does not confirm it. Rely on the mechanism of generation - acid plus cyanide salt in a confined space - which is enough on its own.