Effect of sodium nitrite on cyanide ion concentration in rabbit blood during cyanide poisoning

Cyanide was separated from acidified blood by aeration and determined colorimetrically by pyridine-barbituric acid reagent. Ten min after rabbits were injected iv KCN 0.7 mg/kg, the blood con-centration of CN- was 0.55 ug/ml. When NaN02 20 mg/kg and KCN 0.7 mg/kg were injected iv simultaneously to rabbits, the blood CN- was c 4.02 ug/ml 10 min after the iv. When NaN02 was given iv to rab-bits following iv KCN, the CN- concentra-tion in the blood was found to be 2.47 vg/ml 20 min after iv NaN02. These results suggest that cytochrome oxidase in tissues compete with methemoglobin in blood for cyanide. When KCN 0.7mg/kg and increasing doses of NaN02 were injected, the amount of CN- liberated from tissues into blood was directly proportional to the dose of NaNOz up t0 20 mg/kg. In the treatment with NaNOz, it took about 20 min to mobilize the tissue CI\T-into blood. The rate of elimination of CN- from blood coincided with first-order equation. The rate constants were 3.80 xl0-2/min (KCN iv) and 3.22 X10-2/min (KCN and NaN02 iv simultaneously).