SOME PHYSIOLOGICAL AND METABOLIC EFFECTS OF SODIUM NITROPRUSSIDE AND CYANIDE IN THE DOG

The cardiovascular and acid-base changes following equivalenti.v. bolus doses of sodium nitro-prusside (SNP) and potassiumcyanide (KCN) have been studied in two groups of anaesthetizeddogs. In a third group, the metabolic changes produced by i.v.infusion of SNP 1.5 mg kg^–1 at a constant rate over 1h have been studied. In contrast to a decrease in arterial pressurefollowing SNP, hypertension and tachycardia occurred after theadministration of KCN, with hyperventilation and an increasein packed cell volume. During infusion of SNP, increases inplasma cyanide concentrations were associated with an increasein arterial base deficit, plasma lactate and excess lactateand a decrease in oxygen consumption. The occurrence of lacticacidosis with SNP 1.5 mg kg^–1 suggests that this may bethe maximum safe dose for short term infusion. However, allthese changes reversed spontaneously following discontinuationof SNP, indicating that base deficit is an adequate metabolicmonitor during administration of SNP.