Cardiopulmonary bypass (CPB) required for cardiac surgery presents unique challenges to the cardiac anesthesiologist responsible for providing the 3 most basic facets of any
anesthetic:
amnesia,
analgesia, and muscle relaxation. Unique pathophysiologic changes during CPB result in pharmacokinetic alterations that impact the serum and tissue concentrations of IV and volatile
anesthetics. Similarly, CPB causes pharmacodynamic alterations that impact
anesthetic efficacy. The clinical significance of these alterations represents a "moving target" as practice evolves and the technology of CPB circuitry advances. In addition, perfusionists choose, modify, and maintain the CPB circuitry and
membrane oxygenator. Thus, their significance may not be fully appreciated by the anesthesiologist. These issues have a profound impact on the
anesthetic state of the patient. The delivery and maintenance of
anesthesia during CPB present unique challenges. The perfusionist may be directly responsible for the delivery of
anesthetic during CPB, a situation unique to the cardiac suite. In addition, monitors of
anesthetic depth-assessment of clinical signs, hemodynamic indicators, the
bispectral index monitor, end-tidal
anesthetic concentration, or twitch monitoring-are often absent, unreliable, or directly impacted by the unique pathophysiology associated with CPB. The magnitude of these challenges is reflected in the higher incidence of
intraoperative awareness during cardiac surgery. Further complicating matters are the lack of specific clinical guidelines and varying international policies regarding medical device specifications that add further layers of complexity and introduce practice variability both within institutions and among nations. We performed a systematic survey of the literature to identify where
anesthetic practice during CPB is evidence based (or not), identify gaps in the literature to guide future investigations, and explore the implications of evolving surgical practice, perfusion techniques, and national policies that impact
amnesia,
analgesia, and muscle relaxation during CPB.