An anesthesiologist’s perspective on inhaled anesthesia decision-making

Abstract

To describe the culture and content of anesthesia practice; the stages, types, and goals of anesthesia; nomenclature and factors that can affect dosing of inhaled anesthesia; basis for anesthesiologist choices among inhaled anesthesia agents; and special considerations in using inhaled anesthesia in bariatric surgery patients, pediatric patients, and cardiac surgery patients; and to provide insights into myths associated with inhaled anesthesia. The practice of anesthesiology requires complex monitoring, detailed knowledge of pharmacology, and the ability to make quick decisions about patient management. Four stages of anesthesia have been characterized on the basis of patient responsiveness to surgical stimuli. The second stage ("excitement") occurs during induction of or emergence from anesthesia; patients in this stage are particularly vulnerable to problems with laryngospasm, airway obstruction, uncontrolled motor movements, regurgitation, vomiting, and aspiration. In the United States, most general anesthesia involves inhaled agents. The minimum alveolar concentration (MAC) of inhaled anesthetic agents, which anesthesiologists use in dosing these drugs, can be affected by age, a variety of medications, and other patient-specific factors. MAC can be thought of as a measure of drug potency. Both MAC and solubility in blood and tissues differ among inhaled anesthetic agents. Agents with low solubility have a rapid onset and offset of effect and may allow for faster recovery. The choice among inhaled anesthetic agents may depend on their solubility, as well as the propensity to cause airway irritation and coughing, drug cost, and characteristics such as patient age, obesity, and duration of surgery. Anesthesia care providers' experience and habits may also influence drug choice. Emergence delirium (i.e., agitation) can occur with all three inhaled anesthetic agents in common use (isoflurane, desflurane, and sevoflurane). Other potential issues such as hepatotoxicity and nephrotoxicity are of minimal concern with these agents. Using low flow rates of fresh gas is one strategy for minimizing inhaled anesthesia costs, but it is not always feasible. Experience and careful consideration of the characteristics of inhaled anesthesia agents and surgery- and patient-specific factors allow anesthesia care providers to meet the rapidly changing needs of patients receiving inhaled anesthesia in a safe and cost-effective manner.