CASE 8 —2000 Intraoperative Bispectral Index Monitoring and Early Extubation After Cardiac Surgery in Patients With a History of Awareness Under Anesthesia

A 68-year-old, 84-kg man with unstable angina presented for coronary artery bypass graft surgery. Cardiac catheterization showed triple-vessel disease and good left ventricular function. Past history included an episode of awareness during a previous general anesthetic for orthopedic surgery several years earlier, in which the patient had vivid recollections of severe pain and of overhearing staff conversations. In anticipation of an uneventful intraoperative course and in accordance with usual practice, the use of short-acting anesthetic agents was planned to allow early extubation and discharge from the intensive care unit (ICU). The patient was premedicated with oral lorazepam, 2 mg, and intramuscular papaveratum, 20 mg; and scopolamine, 0.4 mg. In the operating room, intravenous midazolam was titrated (total dose 8 mg) to provide sedation during insertion of intravascular catheters (intravenous, arterial, and pulmonary artery catheters). Bispectral index (BIS) monitoring (Aspect Medical Systems, MA) was used to measure depth of anesthesia and to guide anesthetic drug titration. BIS electrodes were placed on the patient’s forehead according to the manufacturer’s instructions. The BIS reading was 94 immediately before induction. The patient was induced with propofol, administered by a target-controlled infusion device to a target concentration of 3.0 g/mL, and remifentanil, which was started at an initial rate of 1.5 g/kg/min. Once the eyelash reflex was lost and the BIS had decreased to 40, pancuronium, 8 mg, was administered, and the patient’s trachea was intubated. Anesthesia was maintained at a BIS value of 35 to 40 by titrating the propofol target concentration between 2.6 and 3.0 g/mL (infusion rate approximately 60 to 100 g/kg/ min), whereas remifentanil was maintained at 0.5 g/kg/ min. Nitroglycerin was administered at 20 g/min. The patient had a stable hemodynamic profile before cardiopulmonary bypass (CPB) with a systolic blood pressure between 120 and 90 mmHg and heart rate between 50 and 65 beats/min. Once CPB was established and the BIS decreased into the low 30s, the propofol target concentration was decreased to 2.0 g/mL. Four vessels were grafted with a cross-clamp time of 42 minutes and a total CPB time of 71 minutes. On rewarming, the BIS increased from 33 to 38, and the propofol target concentration was increased to 3.0 g/mL. CPB was terminated uneventfully with no inotropic support. Once the sternum was closed, the patient received intravenous ketorolac, 10 mg, and a morphine infusion was started at 5 mg/h after an initial 5-mg bolus. At the completion of surgery, neuromuscular blockade was reversed, a forced air warming device was applied, propofol was stopped, and the remifentanil infusion was reduced to 0.1 g/kg/min. Over the next 10 minutes, the BIS increased into the 90s, and the patient resumed spontaneous ventilation, although still unresponsive. The remifentanil infusion was then stopped. After a further 20 minutes, the patient awoke, his trachea was extubated, and he was transferred to the ICU. Flumazenil, 500 g, was administered in the ICU because the patient remained excessively drowsy. He spent an uneventful night in the ICU and was transferred to the ward the next morning. On direct questioning on the day after surgery, the patient’s last memory of the procedure was of being transferred into the operating room. His next recollection was his time in the ICU, and he had no recall during surgery. He made an uneventful recovery and was extremely satisfied with his anesthesia care.