The effects of positive end-expiratory pressure at different levels on postoperative respiration parameters in patients undergoing laparoscopic cholecystectomy

From June 2013 to March 2014, 105 consecutive patients undergoing elective laparoscopic cholecystectomy were included in this study. Preoperatively, physical examination of the patients was performed by an anaesthesiologist and all patients received detailed information about the respiratory function test and spirometry. Before the operation, respiratory function was evaluated using spirometry (Vitalograph micro. 63000 Series, Ennis, Ireland) by an anaesthesiologist blinded to the group assignment. Before entering the operating room, all patients received 500 mL of colloids via intravenous (IV) cannula and premedication was provided with intramuscular (im) 0.1 mg/kg midazolam for all patients before induction of anaesthesia. Standard monitoring including non-invasive arterial pressure, electrocardiography and pulse oximetry was established in the operating room. Before the operation, heart rate (HR), peripheral oxygen saturation (SpO2), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) values were recorded. Patients were randomly allocated into one of the three groups after induction of general anaesthesia using a computer generated random number table. Group I (n=35) did not receive PEEP whereas group II (n=35) received PEEP as 5 cmH2O and group III received PEEP as 8 cm H2O in mechanical ventilation during laparoscopic procedure . Same anaesthesia protocol was applied for all patients. Anaesthesia induction was provided with IV 2. microg/kg fentanyl, IV 2mg/kg propofol and 0.5-1 mg/kg rocuronium. All patients received colloids at a rate of 3-5 ml/kg/h during operation. Tracheal intubation was performed and anaesthesia was maintained with sevoflurane 1-2%, air (50%), oxygen (50%) and remifentanyl infusion at a rate of 0.15-0.25 microg/kg/min. During anaesthesia, all patients were ventilated with a Datex- Ohmeda anaesthetic machine (Madison WI 53707, USA). The ventilator mode was standardized in all patients (tidal volume of 8ml/kg, a respiratory rate of 12 bpm and I:E time = 1:2). The patients' ventilatory parameters were set to maintain a goal end-tidal carbon dioxide between 30-35 mmHg. In addition to basic ventilation settings, patients in group I did not receive PEEP, patients in group II received PEEP as 5 cmH2O and patients in group III received PEEP as 8 cmH2O in mechanical ventilation during laparoscopic procedure. While the patient was in the supine position, the abdominal cavity was inflated with CO2, the intra-abdominal pressure did not exceed 12 mmHg. Patient was then enrolled in trendelenburg position and the same position was maintained during operation. Intra-abdominal pressure was kept at 12-15 mmHg automatically during surgery.After the completion of surgery, remifentanyl infusion was stopped; lungs were ventilated with 100% O2 manually until the spontaneous respiration was observed. Neuromuscular block was reserved with neostigmine (0.04 mg kg-1, IV) and atropine (0.02 mg kg-1, IV). After sufficient muscle strength was obtained, extubation was carried out. After extubation, all patients were transferred to the recovery room. All patients received standard postoperative care. Postoperative analgesia was provided with tramadol 1mg/kg, IV (Contramal, Abdi Ibrahim, Turkey) and postoperative nausea-vomiting was treated with metoclopramide in all patients. The patients with Aldrete score above 8 were transferred to the service. Measurements with spirometry were taken 1 hour before the operation (T1) and, 1 (T2), 6 (T3) and 24 hours (T4) after extubation by an anaesthetist blinded to intraoperative group assignment. All measurements were performed in upright sitting position according to the American Thoracic Society guidelines. All measurements were only performed while patients had a pain score at rest under 4 (0, no pain; 10, maximum pain). The test was ended when the patient got tired or did not want to go on the test or a failure occurred, although it was repeated mostly 8 times. Forced expiratory volume (FEV1), forced vital capacity (FVC) and peak expiratory flow (PEF) were measured three times at each time point and highest values were recorded for analysis. Socio-demographic characteristics of the patients (age, gender, weight, height and BMI) and HR, SpO2, SBP, DBP and MAP parameters at each time point were also recorded.