Acute intravenous administration of potassium chloride to furosemide pretreated dogs.

Twelve male mongrel dogs were used for this study; six were untreated (control) and six were given intravenous furosemide (1 mg/kg) daily for seven consecutive days before each study. Each animal received intravenous KCl 0.8, 1.6 or 3.2 mMol/kg/hr for one hour, but only one dose for each study and at least seven days were allowed between studies. The animals were given thiopentone for tracheal intubation and mechanically ventilated, maintaining a PaCO2 of 4.0 to 4.5 kPa (30-35 torr) and anaesthetized with nitrous oxide-oxygen and halothane. Daily administration of furosemide reduced serum potassium from 4.48 to 4.09 mMol/1 with no significant change in serum sodium. A greater number of furosemide-pretreated animals (6 vs 3) developed cardiac dysrhythmias during non-lethal intravenous KCl at 0.8, 1.6 mMol/kg/hr. The furosemide-pretreated group tended to succumb at a lower serum potassium concentration (12.2 vs 13.8 mMol/I, P less than 0.05) and developed earlier onset (44 vs 54 min, P less than 0.05) of cardiac standstill or ventricular fibrillation following intravenous KCl at 3.2 mMol/kg/hr. Cardiac output, heart rate and mean arterial pressure were significantly elevated during serum concentrations of 6.9-9.1 mMol/1, while no statistically significant changes were observed for stroke volume and peripheral resistance. There were no significant differences of urinary potassium excretion between the untreated and treated groups when like doses of KCl were infused. These data suggest that acute infusion of KCl in furosemide-pretreated dogs may not be an effective means of treating hypokalaemia and could be hazardous.