Ketamine-lidocaine Versus Ketamine-fentanyl for Induction of Anesthesia in Patients With Left Ventricular Systolic Dysfunction Undergoing Elective Coronary Artery Bypass

Cerebral oximetry monitoring using Near-Infrared Spectroscopy (NIRS) Resting baseline rSO2 values will be obtained

in all patients, ketamine will be injected slowly at 1.5 mg/kg in 0.25 mg/kg increments until clinical loss of consciousness. After loss of consciousness, atracurium 0.5 mg/kg will be administered to facilitate tracheal intubation. Tachycardia and hypertension, (20% increase heart rate, blood pressure from baseline reading) will be managed by a 25 mcg-bolus of Fentanyl. Anesthesia will be maintained by isoflurane (adjusted to maintain end-tidal minimal alveolar concentration of 1-1.2 %) in oxygen/air mixture. Mechanical ventilation will be adjusted to maintain end-tidal CO2 of 35-40 mmHg Any episode of hypotension (defined as mean arterial pressure [MAP] < 70% of the baseline reading and/or MAP <65mmHg, will be managed by 5 mcg norepinephrine (which could be repeated if hypotension persists for 1-min, NE infusion will be started if persisted after 3 boluses). Ephedrine bolus will be give if hypotension was associated with bradycardia.

Inclusion criteria

• patients with coronary artery disease
• with moderate to severe left ventricular dysfunction (ejection fraction < 40%),
• scheduled for elective CABG surgery

Exclusion criteria

• associated chronic stroke, TIA , carotid occlusive disease( due to abnormal vasomotor activity), patients with known neurological impairment (cerebral infarction , dementia ), significant carotid artery stenosis ,
• valvular heart disease,
• persistent arrhythmias,
• congestive cardiac failure,
• on mechanical ventilation,
• intra-aortic balloon pump,
• emergency surgery,
• and those with known allergy to any of the study's drugs,
• severe systemic non-cardiac disease and
• patients with baseline NIRS reading < 60%
• Patients with dementia or visual or auditory impairment