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

A Comparison Between the Effect of Ketamine-lidocaine Versus Ketamine-fentanyl for Induction of Anesthesia on Cerebral Perfusion Guided by Near Infra-red Spectroscopy in Patients With Coronary Artery Disease and Left Ventricular Systolic Dysfunction Undergoing Elective Coronary Artery Bypass Graft Surgery: (A Randomized Controlled Study)

This study compares ketamine/fentanyl versus ketamine/lidocaine in term of their impact on cerebral perfusion during CABG. No prior data address these effects, and the goal is to identify the induction regimen that better preserves cerebral oxygenation.

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