Challenges in the diagnosis of acute cyanide poisoning

The aim of this systematic review was to identify isolated acute cyanide poison cases and to identify reported signs, symptoms, and laboratory findings.

We searched MEDLINE, Cochrane Reviews, and Web of Science case reports and series using a number of MeSH descriptors pertaining to cyanide, toxicity, and poisonings. We excluded studies on plants, laboratory analyses, smoke inhalation poisonings, animals as well as non-English language articles and those in which data were not available. Data extracted included demographics, exposure characteristics, acute signs/symptoms, and medical management and outcome.

From the initial 2976 articles retrieved, 65 articles (52 case reports, 13 case series) met inclusion criteria and described 102 patients. Most patients were unresponsive (78%), hypotensive (54%), or had respiratory failure (73%); other signs and symptoms included cardiac arrest (20%), seizures (20%), cyanosis (15%), cherry red skin (11%), and had an odor present (15%). Medical management included cyanide antidote kit (20%), sodium thiosulfate (40%), and hydroxocobalamin (29%). The majority of cases (66%) required intubation with mechanical ventilation and a substantial number (39%) developed refractory hypotension requiring vasopressor support.

Contrary to general reviews published on cyanide toxicity, reports of cherry red skin and bitter almond odor were rare among published cyanide cases. Consistent with other studies, metabolic acidosis with significant lactic acidosis were the laboratory values consistently associated with cyanide toxicity. Healthcare providers may overlook cyanide toxicity in the differential diagnosis, if certain expected characteristics, such as the odor of almonds or a cherry red color of the skin are absent on physical examination.