What is the incidence of delayed respiratory depression following high-dose fentanyl anesthesia in patients undergoing aortocoronary artery bypass?
High-dose fentanyl anesthesia during cardiac surgery can cause life-threatening delayed respiratory depression 2 to 6 hours postoperatively, which is reversible with naloxone or muscle relaxants.
High-dose fentanyl anesthesia is widely used in cardiac surgery. Its immediate side-effects are well known. However, its late adverse effect manifested by extreme truncal rigidity, decreased chest wall compliance, hypoventilation, respiratory acidosis and hemodynamic instability is not sufficiently appreciated. Of 380 patients who underwent aortocoronary artery bypass under high-dose (100 micrograms/kg) fentanyl anesthesia, 29 (7.6%) developed the sudden onset of extreme thoracic and abdominal rigidity, leading to respiratory depression 2 to 6 h postoperative, after an apparently normal recovery from the anesthesia. In 15 patients, a high plasma level of fentanyl (5.2 to 7.8 ng/ml) correlated with the clinical events. Administration of naloxone or a muscle relaxant rapidly reversed this late complication of fentanyl, thought to be due to re-entry of fentanyl into plasma from deposits in adipose tissue, muscle and the GI tract, leading to a secondary peak in plasma fentanyl. It is more likely to be encountered when hypothermia, rewarming, and acidosis occur in the postoperative period. Awareness of this life-threatening complication is critical in patients undergoing surgery with fentanyl anesthesia.
Caspi et al. (Tue,) studied this question.
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