Cerebral Oximetry in Cardiac Surgery

INTERVENTION: 4 groups, with blinded or unblinded operator with respect to cerebral oximetry monitor and unblinded operator with respect to rewarming rate. Group 1: Standard rewarming with blinded near infrared spectroscopy (control) Group 2: Standard rewarming with interventional near infrared spectroscopy Group 3: Slow rewarming with blinded near infrared spectroscopy Group 4: Slow rewarming with interventional near infrared spectroscopy Cerebral monitoring occurs from time immediately prior to intubation to the time the patient is extubated (12‐15 hr). Standard rewarming is when the patient is rewarmed at a maximum rate of 1 degree per minute, slow rewarming is when the patient is rewwarmed at a maximum rate 0.5C per minute. INVOS Cerebral Oximeter interventions include increasing flow, gas sweep rates, cardiac output, oxygen saturation and hematocrit. Blinded near infrared spectroscopy is when the perfusionist is unaware of what the spectrocopy results are during the oepration (equivalent to current practice), interventional is when the perfusionist uses the interventiones noted above to manage the perfusion based upon the near infra red spctrcopy results. The device is called teh INVOS cerebral oximeter, details are avaialble on the follwoing website http://www.somanetics.com/invos.htm. INVOS means "In‐Vivo Optical Spectroscopy". CONDITION: Patients cerebral oxygenation during cardiopulmonary bypass PRIMARY OUTCOME: Neuropsychological outcome measures (including Employment Status; Edinburgh Handedness; Orientation;California Verbal Learning Test‐II; Purdue Pegboard ; Verbal Fluency (COWAT); Trails Making Test A & B; Symbol Digit; Boston Naming Test short form: or Cognitive Drug Research test battery) SECONDARY OUTCOME: In addition Short Portable Mental Status Questionnaire, Medical Outcome Short Form 36 Health Survey, Delerium Symptom Interview, Depression Anxiety Sress Scale, Mood Anxiety Sress‐Questionairre, Mini International Neuropsychiatirc Interview and a clinical assessment are performed at discharge, 6, 12 and 24 months. ; ; A clinical assessment is the routine morbidity and health examination that is performed on all patients prior to discharge. Secondary outcomes 1: combined clinical endpoint, a composite endpoint based on the presence of 30‐day mortality or a major morbidity (permanent stroke, renal dysfunction or failure, cardiac surgery reoperation, prolonged ventilation, deep sternal wound infection) occurring during the period of hospitalisation. INCLUSION CRITERIA: The patient sample: will consist of participants of both gender, requiring elective isolated coronary artery bypass graft surgery at Flinders Medical Centre; The patient is willing to participate and has signed a consent form.