Minimum Alveolar Concentration of Sevoflurane as a Single Hypnotic Agent to Maintain BIS Below 50 in Patients During Normothermic Cardiopulmonary Bypass.

OBJECTIVES: Minimum alveolar concentration (MAC) of volatile anesthetic agents to maintain bispectral index (BIS) below 50 in 50% of patients was defined as MACBIS50. The primary objective of this study was to determine the minimum alveolar concentration of sevoflurane as a single hypnotic agent to maintain BIS below 50 in patients during normothermic cardiopulmonary bypass. DESIGN: Prospective and observational study. SETTING: Dante Pazzanese Institute of Cardiology, Brazil. PARTICIPANTS: Eighteen consecutive patients scheduled for elective coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) under general anesthesia, American Society of Anesthesiologists physical status classes III and IV, between the ages of 40 and 70, were included in the study. METHODS: All patients underwent inhalation induction with facial mask using sevoflurane (Cristália) in 100% oxygen, pancuronium (Cristália) 0.1 mg/kg, and sufentanil (Cristália) 0.5 µg/kg intravenously (IV) administered. A single bolus dose of sufentanil, 1.0 µg/kg IV, was administered before surgical incision. MACBIS50 was calculated using the midpoint concentration of patients involving a crossover (BIS < or ≥50) according to Dixon's Up-and-Down method. The Up-and-Down sequence also was analyzed by probit test that enabled the authors to obtain the effective dose 50 (ED50) and effective dose 95 (ED95) of sevoflurane to maintain a BIS value <50, with a 95% confidence interval (95% CI) of the mean. RESULTS: A total of 15 patients were analyzed in this study. MACBIS50 of sevoflurane as a single hypnotic agent was 0.82% (95% CI 0.47-1.16) in patients aged 40 to 70 undergoing CABG during normothermic CPB. The ED50 and ED95 of sevoflurane to maintain a BIS value <50 for the same context were 0.73% (95% CI 0.45-1.00) and 1.39 (95% CI 0.42-2.37) by means of probit analysis, respectively. CONCLUSION: MACBIS50 of sevoflurane as a single hypnotic agent was 0.82% in patients undergoing CABG during normothermic CPB.

Tricks, tips, and literature review on the adapted vaporize system to deliver volatile agents during cardiopulmonary bypass.

BACKGROUND: Recently, evidence of cardio-protection and reduction in mortality due to the use of volatile agents during cardiac surgery led to an increase in their use during cardiopulmonary bypass (CPB). These findings seem to be enhanced when the volatile agents are used during all the surgical procedure, including the CPB period. AIMS: Since the administration of volatile agents through CPB can be beneficial to the patients, we decided to review the use of volatile agents vaporized in the CPB circuit and to summarize some tricks and tips of this technique using our 10-year experience of Brazilian and Italian centers with a large volume of cardiac surgeries. STUDY SETTING: Hospital. METHODS: A literature review. RESULTS: During the use of the volatile agents in CPB, it is very important to analyze all gases that come in and go out of the membrane oxygenators. The proper monitoring of inhaled and exhaled fraction of the gas allows not only monitoring of anesthesia level, but also the detection of possible leakage in the circuit. Any volatile agent in the membrane oxygenator is supposed to pollute the operating theater. This is the major reason why proper scavenging systems are always necessary when this technique is used. CONCLUSION: While waiting for industry upgrades, we recommend that volatile agents should be used during CPB only by skilled perfusionists and physicians with the aim to reduce postoperative morbidity and mortality.