Blood Pressure Support during General Anesthesia in a Renin-dependent State in the Rat

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Abstract
To investigate the renin-angiotensin system with increased PRA [plasma renin activity] 25 rats were fed a low-Na diet for 5 to 7 days and divided into 4 groups: awake; halothane, 1.26 vol %; enflurane, 1.75 vol %; ketamine, 125 mg/kg, i.m. The protocol consisted of a 2 h awake period, then an h of stable anesthesia, followed by 30 min infusion of saralasin, an angiotensin II competitive inhibitor. An additional 18 rats had PRA measured by radioimmunoassay before and after an h of stable anesthesia. Stable anesthesia decreased mean arterial pressure from 122 .+-. 2 to 69 .+-. 4 torr for the halothane group, 70 .+-. 3 torr for the enflurane group, and 103 .+-. 7 torr for the ketamine group. When saralasin was infused for 30 min, blood pressure decreased to 100 .+-. 3 torr for the awake group, 40 .+-. 1 torr for the halothane group, 44 .+-. 2 torr for the enflurane group, and 73 .+-. 3 torr for the ketamine group. PRA increased from 4.3 .+-. 0.5 ng per ml/hr for Na replete rats to 12.9 .+-. 1.7 ng per ml/hr for Na depleted rats. After an h of stable anesthesia, PRA increased in all the anesthetized groups. The anesthetic agents studied increase renin release in the Na depleted rat. The initial renin level might be important in determining whether changes in renin release occur with anesthetic agents.

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