Introduction: Perioperative neurological and neuro-physiologic dysfunctions are of great importance, as they influence both the patient's quality of life and the usage of economic resources. In experimental animal studies; when volatile anaesthetics were administered during ischaemic states, they have prevented or reduced brain damage. The aim of our study was to see whether sevoflurane improves neurological outcome after coronary artery bypass surgery (CABG) or not.
Method: 42 patients; aged 42-65, ASA II-III, undergoing CABG, were selected for the study. Patients were randomly divided into two groups as either sevoflurane or total intravenous anaesthesia (TIVA). Anaesthesia was maintained by fentanyl, midazolam and pancuronium in the TIVA group and by fentanyl, sevoflurane and pancuronium in the sevoflurane group. Middle cerebral artery blood flow rates were measured by transcranial Doppler; before induction of anaesthesia, 10 minutes after induction of anaesthesia, after aortic cannulation, 20 minutes after the beginning of CPB and at the end of the surgery. Samples for S100β protein measurements were taken; before induction of anaesthesia, at the end of the CPB and postoperative 24th hour. Serial Digit Learning (SDL) test and Raven's Standard Progressive Matrices (SPM) test, were done; 1 day before the operation and 10 weeks after the operation.
Results: In the TIVA group, mean arterial pressure (MAP) and mean middle cerebral arterial flow rates (Vmean) both decreased after the induction of anaesthesia. In the sevoflurane group, MAP and Vmean changes showed a parallel progress in all measurement periods. Statistical analysis made with neurocognitive test scores showed a decrease only in TIVA group's SPM test (P < 0.05). All of the S100β protein values which were measured before and 24 hours after the operation were below the pathological level. Measurements made at the end of CPB showed a statistically significant increase above the pathological level but there were no significant difference between the groups.
Discussion: Progression of MAP and Vmean changes during operation make us think that sevoflurane disturbs the cerebral autoregulation. In this situation, cerebral blood flow becomes dependent on systemic arterial blood pressure. On the contrary, neurocognitive tests for systematic and accurate intelligence evaluation did not change in isoflurane patients, but decreased in TIVA patients. In conclusion, further investigations should focus on whether cerebral autoregulation should be maintained or not.
1 Kudo M, Aono M, Lee Y, et al. Effects of volatile anesthetics on N-methyl-D-aspartate excitotoxicity in primary rat neuronalglial cultures. Anesthesiology