SODIUM-NITROPRUSSIDE METABOLISM IN CHILDREN DURING HYPOTHERMIC CARDIOPULMONARY BYPASS

Ten children, aged 1-7 yr, presenting for repair of complex congenital heart lesions, were prospectively studied. A ketamine, halothane/isof lurane, and fentanyl anesthetic was used. After initiation of hypother mic cardio-pulmonary bypass, sodium nitroprusside (SNP) was titrated a s necessary to maintain a target mean arterial blood pressure of 35-60 mm Hg. Blood samples drawn immediately prior to starting SNP infusion , every 15 min during infusion, and at 1, 4, and 24 h postinfusion wer e analyzed for whole blood cyanide (CN-) and serum thiocyanate (SCN-). Blood gas analysis was performed every 30 min during SNP infusion. A maximum CN- level greater than or equal to 1.0 mu g/mL was observed in two children; four others had maximum CN- levels between 0.5 mu g/mL and 1.0 mu g/mL (normal, <0.2 mu g/mL). No child had a clinically impo rtant increase of SCN- subsequent to SNP Infusion, There was substanti al variability in observed CN- accumulation during SNP infusion. CN- l evels during the first 60 min correlated with the average SNP rate of administration (P = 0.02). Cyanide levels rapidly decreased after term ination of SNP infusion and were undetectable 4 h postinfusion. Despit e the short-term increase of CN- level, no child showed biochemical si gns of toxicity (acidosis or increased mixed venous oxygen tension).