Plasma Antidiuretic Hormone Levels in Cardiac Surgical Patients during Morphine and Halothane Anesthesia

The effects of halothane and morphine anesthesia on plasma antidiuretic hormone (ADH) levels and urinary flow were determined in 18 patients undergoing elective open-heart operations. Patients were divided into three groups of six each: Group I, halothane, 0.5 per cent; Group II, morphine, 1 mg/ kg; Group til, morphine, 2 mg/kg. In addition, all patients received nitrous oxide - oxygen, 50 per cent each. Measurements of mean blood pressure; heart rate; urinary flow, osmolality and electrolytes; and plasma ADH (by radioimmunoassay) we remade prior to induction of anesthesia, 15 and 30 min after induction, and 15 and 30 min after surgical incision. Control values for ADH were comparable in all groups (about 3 pg/ml). There was no significant change in any group after induction of anesthesia. After surgical incision ADH levels increased significantly in Group I (102 ± 29 pg/ml), and Group II (42.6 ± 25 pg/ml), but not in Group III (14.5 ± 7 pg/ml). The increase of plasma ADH was significantly higher in Group I than in Group II or III. Variations in urinary (low were not significant throughout the study. These data demonstrate that neither morphine nor light halothane anesthesia stimulates high levels of ADH secretion. They suggest that the increase in ADH with surgical stimulation is a stress response that can be attenuated by deeper morphine anesthesia. The ADH levels arc beyond the physiologic range for antidiuretic action on the kidney, and may represent a vasopressor response. Variations in urinary flow were not ADH-related.