EFFECTS OF PROPOFOL VS ISOFLURANE ON RESPIRATORY GAS-EXCHANGE DURING LAPAROSCOPIC CHOLECYSTECTOMY

Background: Respiratory function and pulmonary gas exchange are affect ed in laparoscopic procedures where a pneumoperitoneum is introduced u sing CO2. Previous studies have shown differing results concerning pul monary gas exchange during laparoscopic procedures: Whereas in patient s undergoing isoflurane anaesthesia decreases in PaO2 are demonstrated , this factor remains unchanged in patients undergoing propofol anaest hesia. In the present study, the effects of propofol on pulmonary gas exchange were compared with those of isoflurane in patients undergoing elective laparoscopic cholecystectomy in a prospective randomised man ner. Methods: Twenty ASA patients with physical status I and II were d ivided randomly between isoflurane (IG) and propofol groups (PG). Afte r induction of anaesthesia patients were moderately hyperventilated. R espirator settings remained unchanged during pneumoperitoneum (PP) unt il 10 min after deflation of the peritoneal cavity. Blood gas analyses were performed at 5 time points: 15 min after induction of anaesthesi a (giving pre-PP values), immediately before carbon dioxide insufflati on (0 min PP), after both 30 and 60 min of PP and 10 min post PP. Insp iration plateau pressure (P-plat), compliance of the respiratory syste m, and both ins-and expiratory gas concentrations were continuously re corded by an Ultima V (R) monitor (Datex Corp., Helsinki, Finland). Th e difference between arterial and end-tidal CO2 partial pressure (P(a- et)CO2) was calculated so as to allow assessment of physiological dead space by the modified Bohr equation. Results: Pulmonary gas exchange differed significantly after 30 min of PP between the IG and the PG. A t this time, PaO2 was 19.5 +/- 2.9 kPa (mean +/- SD) in the IG and 23. 1 +/- 1.8 kPa in the PG (P < 0.01), whereas PaCO2 was 5.5 +/- 0.37 kPa in the IG and 4.9 +/- 0.27 kPa in the PG (P < 0.01). These discrepanc ies remained until after carbon dioxide desufflation. At 10 min post P P, PaO2 was 18.3 +/- 2.6 kPa in the isoflurane group and 21.9 +/- 2.2 kPa in the propofol group (P < 0.01), whereas PaCO2 was 5.4 +/- 0.46 k Pa in the IG and 4.8 +/- 0.22 kPa in the PG (P < 0.01). During carbon dioxide insufflation the P(a-et)CO, increased significantly in the IG from 0.47 +/- 0.13 kPa to 0.76 +/- 0.37 kPa (P < 0.05), while the valu es in the PG remained constant. Conclusion: This study demonstrates th at pulmonary gas exchange in patients with laparoscopic cholecystectom y is affected by the choice of anaesthetic procedure. During and after laparoscopic cholecystectomy using isoflurane as the anaesthetic, the PaCO2 is significantly higher and the PaO2 significantly lower than t hey are with propofol. (C) Acta Anaesthesiologica Scandinavica 42 (199 8).