Delirium Reduction by Volatile Anesthesia in Cardiac Surgery

Overview

Parallel group, prospective, randomized, controlled, single-blinded trial. The aim of our study is to test the hypothesis that volatile anesthesia would reduce the incidence of early postoperative delirium in patients undergoing cardiac surgery with CPB as compared to TIVA.

Delirium is a common neurologic complication after cardiac surgery. Up to 52% of postoperative cardiac surgery patients have delirium. The occurrence of postoperative delirium is associated with worse outcomes, including prolonged length of stay in the ICU and hospital, increased morbidity and mortality, compromised long-term cognitive function and physical ability, and elevated medical care costs. Morbidity of postoperative cognitive dysfunction and delirium mostly common in patients with age more than 60 years. Several factors including cerebral anoxia, embolism, excessive excitatory neurotransmitter release, systemic inflammatory response, electrolyte and metabolic disorders and hemodynamic changes have been demonstrated to contribute to postoperative neurological dysfunction and delirium. Previous studies have shown that inhalation anaesthesia and total intravenous anaesthesia (TIVA) may produce different degrees of cerebral protection in these patients. Effects of this two types of anaesthesia in cardiac surgery with CPB remain controversial and much debated. Inhalation agents depress glucose metabolism, decrease cerebral metabolic rate and oxygen consumption. They also partially uncouple the reactivity of cerebral blood flow to CO2. The changes in cerebral blood flow (CBF) depend on the changes in cerebral metabolism and on direct vasodilatory effects. Cerebral autoregulation is dose-dependently altered. Volatile anaesthetics have been shown to initiate early ischemic preconditioning in neurons, but models of focal brain ischemia suggest it can take 24 h for preconditioning to develop fully. Propofol is a well-known potentiator of GABAA receptors, it reduces cerebrovascular resistance, CBF and cerebral oxygen delivery during cardiopulmonary bypass. A neuroprotective effect of propofol has been shown to be present in many in vitro and in vivo established experimental models of mild/moderate acute cerebral ischemia. In recent meta-analysis of 13 randomized controlled studies Chen et al compared the neuroprotective effects of inhalational anesthesia and those of total intravenous anesthesia (TIVA) in cardiac surgery with cardiopulmonary bypass. They have shown that anesthesia with volatile agents appeared to provide better cerebral protection than TIVA. As this meta-analysis had several limitations (small sample size of included studies, high heterogenity, etc.), further studies with larger clinically relevant sample-sizes are needed to demonstrate which anesthetics are more beneficial in terms of brain protection in cardiac surgery.

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