[Effect of intramuscular pethidine on cardiovascular and endocrine functions in dogs]

Effect of intramuscular administration of pethidine on cardiovascular and endocrine functions were studied as judged by cardiac variables and plasma hormone levels in dogs under 1% enflurane anesthesia. Twenty-four mongrel dogs were divided into three groups. Seven dogs receiving physiological saline only served as the control group. Pethidine 2 mg.kg-1 was given to each of nine dogs (2 mg.kg-1 group), and in the remaining eight dogs 6 mg.kg-1 of the drug was administered (6 mg.kg-1 group). Swan-Ganz catheter was used for measurement of cardiac variables such as central venous pressure, cardiac output, pulmonary capillary wedge pressure and etc. In the 6 mg.kg-1 group, mean arterial pressure, heart rate and cardiac index decreased significantly, but no significant changes in cardiac variables were observed in the 2 mg.kg-1 group. Plasma levels of cortisol and ACTH decreased significantly in the 6 mg.kg-1 group and tended to decrease in the 2 mg.kg-1 group. No significant changes were observed in plasma levels of catecholamines, aldosterone, renin activity, antidiuretic hormone and insulin in both groups. These findings suggest that in dogs under 1% enflurane anesthesia intramuscular administration of pethidine 6 mg.kg-1 would depress cardiac functions and intramuscular administration of pethidine more than 2 mg.kg-1 would also depress adrenocortical function.