Effect of sodium pentobarbital anesthesia on plasma volume of adrenalectomized dogs

¹ Biological Laboratory, Princeton University, Princeton, New Jersey

Pentylenetetrazol-shocked, adrenalectomized dogs are unable to raise their lowered plasma volumes when fed a low-sodium diet despite administration of large doses of deoxycorticosterone. The plasma volume rises to preshock levels following injection of glucocorticoids or when the animals are anesthetized with pentobarbital. The plasma volume again decreases to shock levels on recovery from the anesthetic. Dogs exhibiting symptoms of adrenal insufficiency react similarly; the volume rises to normal level under barbiturate anesthesia and falls to the insufficiency level when the anesthetic wears off. Although the plasma volume returns to normal under anesthesia, the arterial pressure of the adrenal-insufficient dogs continues to fall and the plasma potassium to rise. Plasma volume changes evidently have no survival value unless accompanied by increased cardiac and renal efficiency and a sustained blood pressure such as occurred in the deoxycorticosterone-treated animals. Increased plasma volume induced by pentobarbital is apparently due to strong vasodilating properties of the drug. Presumably it relieves the vasoconstriction and opens large areas of closed microcirculatory beds thereby releasing sequestered plasma dammed up at the periphery of the vascular tree.