The effects of anesthesia on antidiuretic hormone

Arginine vasopressin, the antidiuretic hormone in man, in low concentrations increases reabsorption of water in the collecting ducts of the kidney, producing a concentrated urine. It is also a potent vasoconstrictor because of its direct effect on arteriolar smooth muscle, particularly the splanchnic, renal, and coronary vascular beds. This appears to be a dose-dependent response. In very high concentrations it is capable of producing a diuresis with increased urinary sodium excretion. The preponderance of evidence today has failed to show any significant increase in antidiuretic hormone levels with anesthesia alone, provided significant hemodynamic changes do not occur. It seems unlikely, then, that the inhalation anesthetics or high-dose narcotic anesthesia are a direct stimulus to ADH release. If a decrease in urine flow does occur, it is more likely caused by either the renal hemodynamic effects of the anesthetic or a secondary release of ADH. Surgical stimulation is capable of significantly increasing ADH levels. This apparently is a stress response that can be attenuated by the depth of anesthesia. Such a response to operation may produce ADH levels that can indeed decrease urinary flow, but more importantly may succeed in achieving levels that can exert a significant vasopressor effect. In unusual circumstances, vasopressin levels can occur that are capable of producing a diuresis and increased urine sodium excretion.