Prospective randomized control trial to compare the relationship between cerebral oxygen saturation and mild hypercapnia in patients undergoing off- pump Coronary Artery Bypass Grafting

A thorough pre-anaesthetic check-up will be done prior to surgery. Patients will be educated briefly about the anaesthesia procedure. All patients will be kept nil by mouth for 6 hours prior to surgery. Written and informed consent will be taken from all patients participating in the study. Patient’s confidentiality will be maintained at all times and patients will be duly informed about the study through patient information sheet before signing the informed consent.

On arrival to the operating room, monitors including five lead electrocardiogram, pulse oximeter  , capnography  will be connected. An intravenous access with 16G/18G cannula and a radial arterial line under local anaesthesia shall be achieved for IABP monitoring and for ABG sampling. Prior to induction of anaesthesia, cerebral oximetry sensors placed bilaterally over the fronto temporal area, and the baseline rSO2 values will be measured. The patient shall be given Inj Midazolam 0.3mg/kg, Inj Fentanyl 5-10 microgram/kg body weight and Inj vecuronium 0.1 mg/kg body weight shall be used for induction. The patient will be pre oxygenated for 3 minutes and then intubated with appropriate size endotracheal Tube. A 7 fr central line will be secured for administration of drugs (infusion of   Dobutamine /Milirinone,  Noradrenaline, Nitroglycerine) and for CVP monitoring. Anaesthesia will be maintained with fentanyl and sevoflurane in oxygen, air mixture. Muscle relaxant will be maintained with vecuronium boluses.

After induction patient will be  randomised to either targeted mild hypercapnia (TMH) or targeted normocapnia  (TN) group. Minute ventilation will be adjusted to maintain an end tidal carbon dioxide concentration of 45-55 mm Hg  just before LIMA harvesting in targeted mild hypercapnia (TMH) group and 35-40 mm Hg in targeted normocapnia (TN) group. Inj heparin 100 units/kg to maintain ACT level around 250.The fluid will be given as per CVP . The ionotrope will be decided by pre op or intra op condition of heart and hemodynamics.

The cerebral oxygen saturation (rSO2), heart rate (HR), Mean Arterial Pressure (MAP), end tidal CO2, , peripheral oxygen saturation (SPO2) monitoring done as baseline i.e before induction,  after LIMA harvesting, at each grafting proximal and distal, after protamine,  after shifting in ICU. ABG will be taken before induction, after LIMA harvesting, at each grafting proximal  and distal, after protamine, after shifting to ICU, 4,12, 24 hrs and 48  hrs after extubation.  The Standardized Mini-Mental State Examination (SMMSE) will be  performed preoperatively, at 8, 12 & 24 hrs post-extubation.