THE EFFECT OF HIGH SPINAL ANESTHESIA ON THE RENAL HEMODYNAMICS AND THE EXCRETION OF ELECTROLYTES DURING OSMOTIC DIURESIS IN THE HYDROPENIC NORMAL PREGNANT WOMAN 1

Abstract

The effect of autonomic blockade on the renal hemodynamics and the excretion of electrolytes was studied on 5 normotensive pregnant subjects. These patients were selected because a marked drop in blood pressure occurred following the blockade. Osmotic diuresis with mannitol loading was used because water diuresis proved to be unsatisfactory for study in the pregnant woman. Spinal anesthesia was induced with 0.2% and l%procaine solutions. Spinal levels up to C-4 were obtained. The results showed a marked reduction in renal plasma flow and glomerular filtration rate following the injection of the spinal anesthetic. This reduction approx. paralleled the drop in blood pressure. Arterial renal resistance was increased after the blockade. A reduction in the excretion of Na and Cl was also observed following the spinal blockade. The changes in K excretion were variable. The alteration in the excretion of electrolytes did not bear any time relationship with the drop in glomerular filtration. The authors conclude that the changes in renal hemodynamics and the excretion of electrolytes observed following spinal blockade in the pregnant woman are primarily due to the drop in blood pressure and cardiac output. A compensatory renal vasoconstriction of humoral nature might also be operating.