Cerebral hypoperfusion after cardiac surgery and anesthetic strategies: a comparative study with high dose fentanyl and barbiturate anesthesia.

BACKGROUND

Postoperative delirium is a common sequel of cardiopulmonary bypass that is hard to diagnose correctly, difficult to predict and almost impossible to prevent and to treat. The aim of this study is to evaluate the frequency of postoperative cognitive disorders and cerebral hypoperfusion in patients receiving either high dose fentanyl or thiopentone anesthesia in cardiac surgery.

METHODS

50 unpremedicated patients, Class IIb-NYHA (25 patients in each group suffering from single critical LAD disease) undergoing elective coronary artery bypass grafting surgery were randomly allocated into two groups either to receive fentanyl 50 microg/kg with diazepam 0.1 mg/kg (Group 1) or thiopentone 7 mg/kg (Group 2) for the induction of anesthesia. Anesthesia was maintained with fentanyl 2 microg/kg/hr and diazepam 0.05 mg/kg/hr infusion in Group 1 throughout the procedure. In Group 2, it was maintained with enflurane 0.7-1.5% before and after cardiopulmonary bypass (CPB) and with thiopentone 3 mg/kg/hr infusion during CPB. Neuropsychiatric evaluation (STAI-T, min mental state examination-MMSE and Zung tests), EEG and SPECT rCBF (Single Photon Emission Computed Tomography Regional Cerebral Blood Flow) studies were performed preoperatively, early and late postoperatively. The patients that were diagnosed to have postoperative cerebral hypoperfusion also underwent computed tomography scanning postoperatively.

RESULTS

Eleven patients (9 from fentanyl and 2 from thiopentone group) were diagnosed to have cerebral hypoperfusion with respect to SPECT rCBF studies. Seven of these patients (5 from fentanyl and 2 from thiopentone) were diagnosed to be in a state of delirium clinically with MMSE tests.

CONCLUSION

High dose fentanyl anesthesia causes significant predisposition to postoperative cerebral hypoperfusion when compared with barbiturate anesthesia in cardiac surgery. Hypoperfusion as demonstrated by SPECT rCBF studies may play an important role in the pathophysiology of mental disorders, i.e., postoperative delirium.