Effects of ephedrine on renal function in patients after major vascular surgery

The haemodynamic and renal effects of ephedrine were studied in 11 mechanically ventilated patients on the first day after major vascular surgery. Ephedrine, a sympathomimetic agent with alpha-1, beta-1, and beta-2 agonistic activity, was infused into 11 patients to achieve a 20% rise in systolic blood pressure. The doses used were 2-6 micrograms/kg/min, and in six of these 11 patients the dose was then doubled, 4-12 micrograms/kg/min for another renal function test. Blood pressure, heart rate, and cardiac output increased at both dose-ranges. Systolic pulmonary arterial pressure increased by 10% at the first dose-range. Systemic vascular resistance was unchanged and plasma catecholamine levels were unaltered in the present study. Plasma renin activity diminished by 18% and 6%, respectively. Clearance of para-aminohippuric acid increased by 20% and 6%, at the two dose-ranges, while clearance of inulin and urine flow rate increased by 24% and 29%, respectively, at the first dose-range, without further increase during the second dose-range. Fractional chloride excretion, and fractional osmolar clearance were unaltered. Fractional Na+ clearance rose by 30% and 36%, respectively. Fractional free water clearance diminished by 8% at the second dose-range. When comparing the two dose-ranges, HR, systolic and mean BP rose by 8%, 13% and 11%, respectively. Fractional K+ excretion diminished by 30%. We conclude that ephedrine given as a continuous infusion seems to have beneficial effects on renal function in patients after elective major vascular surgery.