Effects of alpha-adrenergic blockade on renal function in hemorrhagic shock.

This study was undertaken to determine whether alpha-adrenergic blockade would reverse the altered kidney function in hemorrhagic shock. Urinary excretion of Na+, K+, and total solute were studied in 10 anesthetized dogs before and after administration of phenoxybenzamine (PBZ) in shock. Five of the 10 dogs were used to evaluate the effect of shock on renal hemodynamics. Another group of five dogs was used as controls. Normovolemic shock caused a reduction in renal blood flow (RBF) from 9.0 +/- 1 to 6.0 +/- 0.6 ml/min per kg, and an increase in renal vascular resistance (RVR) (P less than .05). When compared to the untreated shock animals, phenoxybenzamine caused an 83% increase in RBF and a 53% decrease in RVR. Treatment of control animals with phenoxybenzamine resulted in a 10-fold increase in urinary [Na+], while urinary [K+] remained unchanged. Neither urinary [K+] nor urinary [Na+] was affected significantly by PBZ in the shock group. Although the excretion rate for Na+ was increased severalfold in the untreated shocked animals when compared to controls (14.0 +/- 3 vs. 1.7 microneq/min) the excretion rates for K+ (P less than .05) and total osmotically active substances (P less than .01) diminished. Phenoxybenzamine caused significant increases in the excretion rates for Na+ and K+ in both the control and shocked dogs. The observed changes in excretion rates when PBZ was given most likely reflect drug-induced changes in renal hemodynamics.