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) bilaterally (CASMED, Module series Fore-sight Elite, [SN]1931030) will be applied to all patients.

Resting baseline rSO2 values will be obtained after waiting at least 1 min after placement of sensors once values had stabilized. Bispectral index (BIS) will be applied.

The baseline data for the heart rate, systolic, diastolic, and mean systemic arterial pressures will be recorded from the average ward measurement the day before surgery.

in all patients, ketamine will be injected slowly at 1.5 mg/kg in 0.25 mg/kg increments until clinical loss of consciousness. Clinical loss of consciousness (defined as no response to auditory command) will be assessed by asking the patients repeatedly to open their eyes. 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 50 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