Objectives: To compare the postoperative effects of three anesthetic agents, fentanyl, halothane and isoflurane, on recovery from anesthesia, changes in arterial blood gases, and tests of liver and kidney function in morbidly obese patients recovering from vertical ring gastroplasty.
Material and methods: Thirty-three patients were studied, randomly distributed into three groups of 11. Induction for all was with atracurium (5 mg), 2.5% thiopentone sodium (5-6 mg.kg-1), succinylcholine (1.5 mg.kg-1) and orotracheal intubation. Anesthesia was maintained with intermittent doses of fentanyl (group F), 2% halothane (group H) or 2.5% isoflurane (group I). All patients received a 50% O2/N2O mixture at a minute volume calculated on ideal weight. Muscle relaxation was achieved by continuous perfusion of atracurium. Postoperative analgesia was by morphine chloride through a lumbar epidural catheter. Time of eye opening and time of extubation were recorded. Arterial blood gas measurements were taken and the results of liver and kidney function tests were recorded until the 7th day after surgery.
Results: Eye opening after awakening was earlier in the fentanyl group (6 +/- 5 min), but no differences were found for time of extubation. Blood gas measurements for the 33 patients revealed a significant decrease in PaO2 (58 +/- 14 mmHg), a slight increase of PaCO2 (40 +/- 6 mmHg) and a lower pH (7.32 +/- 0.04) immediately after surgery. On day seven, PaO2 had not yet reached preoperative levels (p < 0.01). These results were independent of anesthetic agent used. Kidney function tests showed significant rises in SGOT (81 +/- 36 U/l), SGPT (150 +/- 110 U/l) and bilirubin (Bil: 15 +/- 5 mmol/l) and decreases in prothrombin activity (PT: 73 +/- 11%) 24 hours after surgery, with later normalization. Urea fell significantly throughout the seven-day period (3.2 +/- 1.3 mmol/l). These results were also independent of the anesthetic agent used.
Conclusions: Morbidly obese patients undergoing gastroplasty recover from anesthesia in the same way regardless of the agent used. The early postoperative period is characterized by severe hypoxemia and transitory changes in kidney function tests. Neither of these findings is dependent on the agent used.