Neuroprotection During Open Heart Surgery

The aim of the study is to evaluate neuroprotective effect of mixture of propofol and ketamine (ketofol) as compared to propofol after open heart surgery. Induction; * Pre-oxygenation with100% O2 for 3 min. * Morphine 0.1-0.15 mg/kg * Fentanyl, dose 3-5 mcg/kg. * hypnotic agent differs for each group: * Propofol group: Propofol, dose 0.5-2 mg/kg. * Ketofol group: Ketofol,( dose 0.25-1 mg/kg propofol plus 0.25-1 mg/kg ketamine diluted in normal saline with maintained 1:1 ratio between propofol and ketamine. ) Catheterization: 1. Central venous catheter: A suitable central venous catheter will be inserted into Right subclavian vein under complete aseptic technique using seldinger technique. 2. Jugular bulb catheterization: Patients is placed in supine position with mild neck extension. The head is placed in neutral position with mild tilt to the opposite side of insertion. Under complete aseptic conditions, the anatomical landmarks for the right internal jugular vein will be identified (at the level of cricoid cartilage, medial to the sternomastoid muscle and lateral to a palpable internal carotid artery). The internal jugular vein will be then cannulated by retrograde insertion of a catheter for sampling of the jugular venous bulb blood. Catheter will be advanced till resistance of the skull base is reached then withdrawn about 1 to 2 mm. Position of the catheter will be confirmed by antero-posterior and lateral neck C-arm x-ray to verify the correct placement of the catheter tip in the will be sutured to the skin and dressed with sterile gauze