Effects of verapamil on thermal trauma depressed cardiac output in the anaesthetized dog.

Thermal trauma to the anaesthetized dog results in an immediate, significant decrease in cardiac output, an increase in peripheral resistance and no significant change in mean arterial blood pressure. The administration of verapamil 1.0 mg/kg by slow intravenous injection produced a rapid increase in cardiac output and a decrease in peripheral resistance. Mean arterial pressure fell and returned to or nearly to pre-injection values within 30 min. The duration of the increase in cardiac output after a single dose of verapamil was approximately 1.5-2.0 h. Administration of a second 0.5 mg/kg dose of verapamil, 1.5 h after the first dose, increased cardiac output and decreased peripheral resistance. After the second dose of verapamil, cardiac output was significantly greater and peripheral resistance was significantly less than in untreated animals for at least 2 h.