Abstract
Cyanide concentrations in plasma and red blood cells during hypotension induced by sodium nitroprusside and a nitroprusside-trimetaphan mixture were studied in 29 male rabbits under halothane anesthesia. The rabbits were randomly divided into three groups: nitroprusside (group S; n=10) ; nitroprusside-trimetaphan mixture (group M; n=10) ; Controls (group C; n=9) . Group C received no vasodilator therapy and served as controls. Group S received an infusion of 0.05% nitroprusside solution, and group M received an infusion of a nitroprusside-trimetaphan mixture (0.02% nitroprusside and 0.2% trimetaphan) . Mean arterial pressure was decreased and was maintained at 60 mmHg for 60 minutes in groups S and M. No change was noted in plasma or red blood cell cyanide concentration in group C throughout the experiment. During and after induced hypotension in group S, plasma cyanide concentration was significantly higher than that of control value. The maximum increase occurred 60 min after induction of hypotension and the highest concentration of plasma cyanide was six times the control value. In group M, plasma cyanide concentration was unchanged from the control value. However, during and after induced hypotension, cyanide concentrations in red blood cells of group S and group M were significantly higher than those in control values. Concentrations of cyanide in red blood cells increased for 30 and 60 min during induced hypotension in group S (27.11±3.9μg/ml, P<0.001, 46.73±4.7μg/ml, P<0.001, respectively) and in group M (0.31±0.05μg/ml, P<0.05, 0.29±0.03μg/ ml, P<0.01, respectively) . In conclusion, the data suggest that a nitroprussidetrimetaphan mixture is a safe method to prevent cyanide toxicity for hypotensive anesthesia.
