Influence of dietary sodium on renin activity and arterial pressure during anesthesia

The effect of pentobarbital anesthesia on plasma renin activity (PRA) and mean arterial pressure (MAP) was studied in chronically catheterized dogs maintained on normal or low-sodium intake. Within 1 min of administration, pentobarbital caused a rapid fall in MAP which was followed by a restoration of MAP toward control within 5 min. Thirty minutes after induction of anesthesia, PRA was unchanged in sodium-replete dogs and elevated two-fold in sodium-depleted dogs. MAP was significantly lowered (20 mmHg) in normal salt dogs and only slightly decreased in low-salt dogs 30 min after pentobarbital. MAP returned to preanesthetic control value in dogs given converting enzyme inhibitor before anesthesia. Surgical stress or cutaneous electrical stimulation causey hexamethonium. These results indicate that change in PRA and MAP of pentobarbital-anesthetized dogs is significantly influenced by the sodium intake of the animal and by the degree of surgical stress.