Comparison of nitrite treatment and stroma-free methemoglobin solution as antidotes for cyanide poisoning in a rat model

Combined carbon monoxide and cyanide poisoning: a place for treatment

During fires, victims can inhale significant carbon monoxide (CO) and cyanide (CN) gases, which may cause synergistic toxicity in humans. Oxygen therapy is the specific treatment for CO poisoning, but the treatment of CN toxicity is controversial. To examine the indication for treatment of CN toxicity, we have established a canine model to delineate the natural history of combined CO and CN poisoning. In seven dogs (24 +/- 3 kg), CO gas (201 +/- 43 mL) was administered by closed-circuit inhalation. Then, potassium CN was intravenously (i.v.) infused (0.072 mg.kg-1.min-1) for 17.5 +/- 3.0 min. Cardiorespiratory measurements were conducted before and after these toxic challenges. Despite significant CO poisoning (peak carboxyhemoglobin fractions [COHb] = 46% of total hemoglobin [Hb]; elimination t1/2 = 114 +/- 42 min) with attendant decrease in blood O2 content, CO had essentially little effect on any hemodynamic or metabolic variable. On the other hand, CN severely depressed most hemodynamic and metabolic functions. Compared to baseline values, CN caused significant (P < 0.01) decreases in cardiac output (6.4 +/- 2.0 to 3.1 +/- 0.5 L/min) and heart rate (169 +/- 44 to 115 +/- 29 bpm) and decreases in oxygen consumption (VO2) (133 +/- 19 to 69 +/- 21 mL/min) and carbon dioxide production (VCO2) (128 +/- 27 to 103 +/- 22 mL/min). However, these critical hemodynamic and metabolic variables recovered to baseline values by 15 min after stopping the CN infusion, except lactic acidosis which persisted for at least 25 min after the CN infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Hospital treatment of victims exposed to combustion products

Combustion toxicology is complex so, although victims exposed to combustion products are mainly treated symptomatically, it is important to identify those situations when specific therapeutic measures might be of importance. Victims presenting respiratory symptoms including severe cough, bronchoconstriction, hypoxia and respiratory distress should be given oxygen and ventilatory assistance or support. Furthermore, bronchoconstriction should be treated with bronchodilators (beta-2-adrenoreceptor agonists, theophylline). Corticosteroids should be considered both for inhalation and systemically due to the risk of developing toxic pulmonary oedema that may appear after a symptom-free interval that might last up to 48-72 h. Victims with impaired consciousness should be regarded as being exposed to carbon monoxide and cyanides. Apart from oxygen and optimal symptomatic treatment hyperbaric oxygen therapy should be considered in carbon monoxide poisoning. Certain cyanide antidotes, namely those with low intrinsic toxicity (as sodium thiosulphate, hydroxocobalamin) should be given liberally in these situations. Other specific therapeutic measures that might be considered when appropriate are administration of organophosphate antidotes (atropine, oximes), heavy metal chelators (e.g. dimercaptopropane sulfonate, dimercaptosuccinic acid) and methemoglobinemia antidotes (methylthionine, toluidine blue). Inhalation of hot fumes may cause upper respiratory tract oedema (e.g. laryngeal oedema) necessitating orotracheal intubation and ventilatory support.

Cyanide poisoning successfully treated without 'therapeutic methemoglobin levels'

A 24-year-old woman ingested an unknown amount of potassium cyanide in a suicide attempt. Coma and metabolic acidosis developed. Administration of the Lilly Cyanide Antidote kit (Eli Lilly and Co, Indianapolis) resulted in prompt resolution of symptoms and full recovery. Whole blood cyanide level was 13 micrograms/mL approximately one hour after ingestion. The highest measured methemoglobin level after sodium nitrite administration was 9.2%, demonstrating that attaining a "therapeutic methemoglobin level" of 25% is unnecessary to insure a satisfactory clinical outcome. Because severe hypotension or excessive methemoglobinemia can be caused by the sodium nitrite component of the Lilly kit, only enough to produce an acceptable clinical response should be administered.