• Vikhyat S Bebarta, Rebecca L Pitotti, Patricia Dixon, Julio R Lairet, Anneke Bush, and David A Tanen.
• Wilford Hall Medical Center/Brooke Army Medical Center, the Department of Emergency Medicine, San Antonio, TX, USA. vikbebarta@yahoo.com
• Ann Emerg Med. 2012 Jun 1;59(6):532-9.

Study ObjectiveWe compare the efficacy of hydroxocobalamin to sodium thiosulfate to reverse the depressive effects on mean arterial pressure in a swine model of acute cyanide toxicity and gain a better understanding of the mechanism of action of the hydroxocobalamin in reversal of the toxicity.MethodsSwine were intubated, anesthetized, and instrumented with central arterial and venous lines and a pulmonary artery catheter. Animals (n=36) were randomly assigned to one of 3 groups: hydroxocobalamin alone (150 mg/kg), sodium thiosulfate alone (413 mg/kg), or hydroxocobalamin (150 mg/kg)+sodium thiosulfate (413 mg/kg) and monitored for 60 minutes after the start of antidotal infusion. Cyanide was infused until severe hypotension developed, defined as blood pressure 50% of baseline mean arterial pressure. Repeated-measures ANOVA was used to determine statistically significant changes between groups over time.ResultsTime to hypotension (25, 28, and 33 minutes), cyanide dose at hypotension (4.7, 5.0, and 5.6 mg/kg), and mean cyanide blood levels (3.2, 3.7, and 3.8 μg/mL) and lactate levels (7, 8.2, 8.3 and mmol/L) were similar. All 12 animals in the sodium thiosulfate group died compared with 2 of 12 in the hydroxocobalamin/sodium thiosulfate group and 1 of 12 in hydroxocobalamin group. No statistically significant differences were detected between the hydroxocobalamin and hydroxocobalamin/sodium thiosulfate groups for carbon monoxide, mean arterial pressure, cyanide levels, or mortality at 60 minutes. Lactate level (2.6 versus 2.1 mmol/L), pH (7.44 versus 7.42), and bicarbonate level (25 versus 26 mEq/L) at 60 minutes were also similar between groups.ConclusionSodium thiosulfate failed to reverse cyanide-induced shock in our swine model of severe cyanide toxicity. Further, sodium thiosulfate was not found to be effective when added to hydroxocobalamin in the treatment of cyanide-induced shock. Hydroxocobalamin alone was again found to be effective for severe cyanide toxicity.Copyright © 2012. Published by Mosby, Inc.

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