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Conduct of the Anesthetic

 

Does the type of anesthetic influence the cardiac outcome?

For many years anesthesiologists have argued in regards to whether or not the type of anesthetic influenced outcome. Years ago we assumed the discussion was closed. However, with the emergence of the concept of ischemic pre-conditioning, the issue may be re-emerging and is important to our discussion. The inhalational anesthetics are thought to possess ischemic pre-conditioning properties(31). The mechanism is thought to be through the activation of an ATPase. Although most investigations of anesthetic ischemic preconditioning have been done in cardiac anesthesia, the potential effects in high-risk cardiac patients having non-cardiac surgery deserves comment. In a meta-analysis of 19 studies including 20,000 patients, there was no net reduction in the in-hospital myocardial infarction rate. However, there was significant heterogeneity in the analysis. Two agents, enflurane and halothane, were associated with increased myocardial infarctions. When enflurane and halothane are excluded from the meta-analysis, isoflurane, sevoflurane and desflurane collectively showed a 38% reduction in myocardial infarction. This preliminary work requires more investigation.

Two independently conducted RCT’s(33-35) have shown that nitrous oxide increases the incidence of perioperative and postoperative myocardial ischemia. Furthermore, nitrous oxide increases homocystiene levels for over 72 hours post-operatively. This may influence both platelet reactivity and endothelial function. Nitrous oxide has the added distinction of doubling the incidence of post-operative nausea and vomiting. Since nitrous oxide is a poor anesthetic agent, there is no reason to use it in patients at high risk for post-operative cardiac complications.

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