Comparison of the effects of different PEEP (positive end-expiratory pressure) levels on cerebral oxygen saturation in patients undergoing laparoscopic cholecystectomy

One hundred and five patients between the ages of 18-60 yr, ASA physical status I and II, scheduled to undergo routine laparoscopic cholecystectomy under general anesthesia, were studied. The patients were randomized, by using a computer-generated block randomisation, into 3 groups: Group I (n=35) with no external PEEP, Group II (n=35) with external PEEP of 5 cmH2O, Group III (n=35) with external PEEP of 10 cmH2O. Routine monitors (consisting of a pulse oximeter, 3-lead ECG and a non-invasive blood pressure cuff ) and BIS monitoring were applied. In addition to this monitoring cerebral oximeter sensors were attached to frontotemporal areas (both right and left). Fasting periods were in accordance with ASA guidelines, and no one premedicated. Anesthesia was induced with propofol (2 mg/kg) and fentanyl (1-2 microg/kg), and endotracheal intubation was facilitated using rocuronium. After induction, volume- controlled mechanical ventilation (tidal volume adjusted to 8 mL/kg with no application of PEEP in Group I, 5 cmH2O in Group II, 10 cmH2O in Group III and respiratory rates were adjusted to achieve an end-tidal carbon dioxide of 30 to 35 mmHg) was initiated. All patients were ventilated with the same anesthetic machine. Anaesthesia was maintained using sevoflurane 1–2% in an oxygen / air mixture and remifentanil (0,25 microg/kg/min) accompanied by BIS monitoring. The CO2 pneumoperitoneum (PP) was introduced with a closed Veress needle technique, and the intraa-bdominal insufflation pressure was limited to 10-12 mmHg. After introduction of the four trocars and insufflation of CO2, the patient was placed in the reverse Trendelenburg position, using up to 30 degree of head-up tilt. HR, MBP, oxygen saturation (SpO2) and rSO2 values were continuously recorded from awake status to tracheal extubation (basal, after induction, after intubation, immediately after pneumoperitoneum, every 5 minutes during pneumoperitoneum, immediately after desufflation of CO2, at the end of surgery, after). ETCO2, peak inspiratory pressure (PIP) (after intubation, immediately after pneumoperitoneum, every 5 minutes during pneumoperitoneum, immediately after desufflation of CO2, at the end of surgery, after), operation time, PP time and intraoperative fluid administration were also recorded.