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

Overview

There is no consensus on the ideal induction technique for patients with coronary artery disease and left heart dysfunction. Induction for cardiac surgery focuses on maintaining hemodynamic stability, optimizing myocardial oxygen balance, and minimizing the intubation stress response. Ketamine provides stable hemodynamics in patients with impaired ventricular function, though combining it with opioids to blunt the intubation response may increase post-induction hypotension. Systemic lidocaine has anesthetic-sparing properties and has been shown to potentiate agents such as thiopentone, propofol, and midazolam. The ketamine-lidocaine combination has also demonstrated favorable hemodynamic effects in septic shock. 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.

Upon arrival to the operating room, initial monitoring will include five lead electrocardiograms, non-invasive blood pressure, and pulse oximetry. At the attending anesthetist's discretion, intravenous midazolam will be administered for anxiolytics. Under local anesthesia, an arterial line will be placed in the radial artery of the non-dominant hand and central venous line will be placed in the right internal jugular vein. Cerebral oximetry monitoring using Near-Infrared Spectroscopy (NIRS) bilaterally (CASMED, Module series Fore-sight Elite, \[SN\]1931030) will be applied to all patients. After cleansing of the adjacent skin area with alcohol, an adhesive optode pad was placed over each fronto-temporal area. 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.