Cyanide antidotal therapy

Saincher A, Swirsky N, Tenenbein M. 1994. Cyanide overdose Survival with fatal blood concentration without antidotal therapy. JEmergMed 12(4) 555-557. 

Patients who are critical and do not satisfactorily respond to supportive therapy should be administered specific cyanide antidotes as outlined in Table 19.5. Cyanide antidotes have been classified into three main groups based on their mechanism of action (1) methemoglobin inducers, (2) sulfur donors, and (3) cobalt compounds. The definitive treatment of cyanide poisoning differs in various countries due to different medical practices and guidelines. The safety... 

TABLE 19.5. Supportive therapy and specific antidotal therapy for acute cyanide poisoning... 

Amyl nitrite, sodium nitrite, and sodium thiosulfate are commercially available in standard doses in the Pasadena Cyanide Antidote Kit. This kit is not widely distributed in Department of Defense medical channels. No antidote kits are provided to naval personnel far forward. However, should a person be exposed to a lethal dose of the agent and not receive therapy immediately, death is certain. 

In addition to antidotal therapy, administration of 100% oxygen can help with cyanide detoxification, possibly by affecting the binding of cyanide to cytochrome oxidase (13). Hyperbaric therapy may be considered, but only after standard treatment has failed, or if the patient has concurrent carbon monoxide poisoning (13). 

Possibly the most important elements of therapy are general supportive actions, which, by themselves, can effect the recovery of most casualties without further risk from specific antidotal therapy.41 They are probably the only indicated therapies for casualties of cyanide poisoning who arrive conscious at the emergency medical treatment station. 

Casualties with advanced toxicity from a large amount of cyanide may require specific antidotal therapy in addition to the vigorous supportive therapy outlined above. The recommended agents or components of specific antidotal therapies for cyanide... 

Binenfeld Z. Antidote therapy in cases of poisoning by some heavy metals and cyanides and its risks. Farm Gias. 1971 27 1-6. 

Cyanide poisoning. Empiric antidotal therapy with sodium thiosulfate (see p 505) and (if available) hydroxocobalamin (p 453) is recommended for patients with altered mental status, hypotension, or acidosis. Use of sodium nitrite is discouraged because it may cause hypotension and aggravate methemoglobinemia. 

A 41-year-old woman became weak and had difficulty breathing after ingesting 30 apricot kernels (estimated total, 15 g) purchased at a health food store. She became comatose and hypothermic but responded promptly to antidotal therapy for cyanide poisoning (Suchard et al. 1998). 

Patients who are in critical condition and do not satisfactorily respond to supportive therapy should be administered specific cyanide antidotes as outlined in Table 23.5. Cyanide antidotes have been classified into... 

Based on the avidity of cobalt for cyanide ions, intravenous injection of the cobalt EDT A complex has been recommended as being the best antidote in cyanide poisoning73). Earlier therapy was based on sodium nitrite and sodium thiosulphate, with partial conversion of haemoglobin to methaemoglobin. 

Blood gases and serum electrolytes should be monitored and corrected as needed (Hall and Rumack, 1986 Vogel et al, 1981). Blood cyanide levels can confirm exposure, but due to the time needed to get the results, they are not clinically useful. Provide supplemental oxygen with assisted ventilation as indicated. Animal study results for hyperbaric oxygen therapy have been questionable (Way et al, 1972). Acidosis (pH <7.1) should be corrected with intravenous sodium bicarbonate, but acidosis may not resolve until after the administration of antidotes (Hall and Rumack, 1986). Benzodiazepines or barbiturates can be used to control seizures. 

Irrespective of the antidote treatment available, treatment will always consist of supportive therapy (Rotenberg, 2003a). Supportive therapy alone may reverse the effects of cyanide even in the face of apnea (Rotenberg, 2003a Baskin... 

Other than for chelation therapy, in which the ligand is generally administered by slow, intravenous infusion, EDTA has been used in creams and ointments, pharmaceuticals, oils, soaps, bath preparations, cosmetics, and in hair dyes and permanent waving solutions. A novel application of an EDTA chelate is the use of the dicobalt chelate (dicobalt edetate) as an antidote in cyanide poisoning the CN ion forms a strong ionic complex with the Co ions in the chelate to form a relatively non-toxic and readily excretable species. 

Cyanide casualties present the triage officer with few problems. In general, a person exposed to a lethal amount of cyanide will die within 5 to 10 minutes and will not reach the MTF. Conversely, a person who does reach the MTF will not require therapy and will probably be in the minimal group, able to return to duty soon. If the exposure occurs near the treatment area, a severely exposed casualty might appear for treatment. He will be unconscious, convulsing or postictal, and apneic. If the circulation is still intact, the antidotes will restore the casualty to a reasonably functional status within a short period of time. The triage officer, however, must keep in mind that it takes 5 to 10 minutes to... 

A casualty from exposure to a lethal amount of cyanide will die within a few minutes if he receives no therapy. If antidotes are given in time, he will recover with no serious adverse effects or sequelae to interfere with wound care. One of the antidotes, sodium nitrite, causes vasodilation and orthostatic hypotension, but these effects are short and should not be factors in overall patient care. If a casualty with a conventional wound and severe effects from cyanide poisoning presented at the unit-level MTF (or even at a major hospital), the procedure would be to give the antidote immediately. If the effects of cyanide are reversed, he should receive further care. Incapacitating Agents... 

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