The effect of labetalol on urinary prostacyclin secretion during surgery

The effects of labetalol on the secretion of prostacyclin and plasma-renin activity (PRA) were evaluated, relative to a control group in 24 patients undergoing hip osteotomy. They were randomly assigned to two groups (G-I and G-II) with 12 patients each. Patients allocated to both groups received standard anaesthesia (thiopentone, pancuronium, fentanyl and nitrous oxide). Patients belonging to Group II were given labetalol at a dose of 0.8 mg kg-1. The stable metabolite of PGI2, 6-keto-PGF1 alpha was quantified from urine samples by radioimmunoassay (RIA). Cortisol, PRA and aldosterone were determined from blood samples. A significant increase in 6-keto-PGF1 alpha elimination was observed in G-I. Labetalol administration partially but significantly inhibited this increase. We believe that prostacyclin is involved not through the beta 1 but through the alpha 1 receptors in the secretion of renin.