The Effect of PEEP, Zero PEEP and Intraabdominal Pressure Levels on Cerebral Oxygenation (rso2) in the Morbidly Obese Undergoing Sleeve Gastrectomy

60 morbidly obese patients which planned sleeve gastrectomy procedures under general anestesia (ASA 2-3 status) were included in this study. Patients were devided into 2 groups which was ventilated with no positive end expiratory pressure (Group 5PEEP n=30), and 5 cmH2O positive and expiratory pressure (Group ZEEP n=30). All the patients were right hand dominate.Two patient in Group 5 PEEP were excluded because of the haemodynamic instability during procedure.

Exclusion criteria: Documented coronary or periferally arteryel disease, unregulated diabetes mellitus, history of smoking, symptoms of bowel or urinary bladder obstruction, preoperative systolic pressure grater than 170 mmHg, diastolic arterial pressure grater than 90mmHg, pregnancy, anemia (haematocrit levels under %30), and symptoms of increased intracranial pressure, significant stenosis of the carotid arteries. In all anesthetised patients were monitorised with 3 leads electrocardiography(ECG), pulse oxymetry (sPO2),invasive blood pressure(IBP), end-tidal carbondioxide (EtCO2),intraabdominal pressure levels (IAP)with intravesical urinary catheter, peak inspiratuar pressure (PIP), laparoscopic pressure (LP), regional cerebral oxygen saturation(rSO2) continuously. rSO2 values were measured with near infrared spectroscopy (NIRS) technique by cerebral oximeter (INVOS 4100, Somanetics, Covidien) measurements recorded as basal values; after induction; before 15 minute of insufflation; after 15 minute of insufflation; 30, 45, 60 after induction; before 15 minute of desufflation; after 15 minute of desufflation. Arterial blood samples were collected and performed before 15 minute of insufflation; after 15 minute of insufflation; after 15 minute of desufflation. Partial oxygen pressure(PaO2), partial carbondioxide pressure( PaCO2), peripheric oxygen saturation (SaO2), bicarbonate (HCO3), aside- base status (pH), haematocrit (Htc) haemoglobin(Hb) levels were recorded and evaluated those three time periods which explained above. Cerebral oximeter was placed skin of the patients forehead after clean special skin-prep pad. The skin sensors were applied on the right and left sides of the forehead. The medial margin of the sensor was at the midline of the forehead and lateral margin 2 cm above the eyebrows.

After induction of anesthesia a 20 gauge intraarterial cannula was placed in to left radial artery and recorded 5 minute periods.

Anesthetic procedures and measured parameters were administered same ways except of PEEP levels.

All patients were received midazolam 2mg intravenously (IV) about five minute before induction. Anesthesia was induced with fentanyl( 1-3 mcgr/kg), propofol (2-3mg/kg), rocuronium (0,6 mg/kg). After intubation anesthesia was maintained with sevoflurane 2-3 % volume (to improve MAC 1 levels for sevoflorane). Remifentanyl was given continuously during surgery at a rate of 0.05-2 mcg/kg/min) (IV). Rocuronium was administered at a rate of 30 min time intervals during the anesthesia. Sugammadex was administered at the end of the surgery for reversing the neuromuscular blockage. Tramadol 1mg/kg, 40 mg meperidine and paracetamol 1g were administered for postoperative analgesia after trochars were removed. The concentration of volatile anesthetic was monitored with GE anesthesia machine. Patients were ventilated 6 lt/dk gas flow (50% oxygen with 50% air mixture). 6-8 ml/kg tidal volume, inspiration/ expiration rate 1/2 was maintained. Respiratory rate was 8-12 breaths. EtCO2 was kept within the range 35-45 mmHg. 5mmHg PEEP was administered in Group 5 PEEP, no PEEP was administered Group ZEEP. Fluid balance and blood replacement was maintained with %0.09 NaCl and ringer or colloid(Voluven Fresenius Kabi, Graz, Austria) solution IV. Body temperature was maintained normothermic by upper body forced air and warming pads. Laparoscopic pressure was maintained at below 14mmHg throughout the operation. Intraabdominal pressure was measured in mililitres of mercury through a Foley bladder catheter with 3 stopcocks connected to infusion set and pressure transducer. IT connected to the electronic monitor of anesthesia machine. (Datex -Ohmeda S/5 Compact, GE Healthcare, Finland) . After clamping the tube 100 ml Saline solution was injected in to the bladder. The transducer was replaced and zeroed to the urinary bladder level whenever the position changes throughout the procedure. Oscillation test was performed before started the IAP measurements. This measurements was performed into two position: basal, after induction, before insuflation, after insuflation, before desuflation, after desuflation values were measured in supine position; 30min, 45 min, 60min measurements in 30 degree reverse trendelenburg position (head of the bed elevated to 30 degree). Intraabdominal hypertension was defined as an IAP of 12 mmHg or higher, according to the consensus definations of the World Society for The Abdominal Compartment Syndrome.