[Respiratory changes during laparoscopic cholecystectomy. A comparative study of three techniques]

To analyze the repercussions of CO2 pneumoperitoneum on the ventilation of healthy patients undergoing laparoscopic cholecystectomy; to assess the influence of anesthetic technique and determine whether duration of procedure or CO2 volume are relevant factors.

Prospective study of 132 patients undergoing laparoscopic cholecystectomy. The patients were selected based on disease and level of anesthetic risk and then randomly assigned to three groups to receive anesthesia with oxygen/nitrous oxide (group I), isoflurane in O2 and air (FIO2 0.4) (group II) or propofol in continuous infusion with O2 and air (FIO2 0.4) (group III). Analgesia and muscle relaxation were the same in all groups. Monitoring included blood pressure (BP), heart rate (HR), electrocardiography (ECG), central venous pressure (CVP), capnography (PETco2), pulse oximetry (SaO2), peak airways pressure (PAP), FIO2, intra-abdominal pressure (IAP), volume in insufflated CO2 and serial gasometry. Readings were taken before pneumoperitoneum after 20 minutes and every 30 minutes until end of surgery. After surgery parameters were recorded four more times at intervals of 30 minutes.

The groups were homogeneous. pneumoperitoneum caused a decrease in PaO2 (p < 0.001) and SaO2 and increases in PaCO2, PETco2 and CVP, although levels later stabilized. No relation was found between duration of pneumoperitoneum or CO2 volumen and any of the changes observed. Group I had the lowest mean PaO2 before pneumoperitoneum and 60 minutes later (p < 0.05). Group II had the smallest increase in PaCO2, although the difference was non significant.

CO2 pneumoperitoneum caused ventilatory changes dependent on uptake and increased abdominal pressure. The duration and volume of CO2 used did not influence the parameters studied. The clinical significance of these changes is slight in the healthy patient. The anesthetic agents used did not have substantial effects.