Effects of Head Position on Cerebral Oxygenation and Blood Flow Velocity During Thyroidectomy.

OBJECTIVE Determining the blood flow through intra and extra-cranial arteries during neck extension may be helpful but is a controversial issue. We aimed to elucidate the changes in cerebral blood flow related to head positioning during thyroid surgery by carotid Doppler examination and regional oxygen saturation variations. METHODS Thirty patients were recruited to the study. Patients were positioned with a final position of thyroidectomy consisting a 30° semi Fowler with the extension of neck and head. Values of peak systolic velocity, average velocity, arterial diameter and blood flow volume of the common carotid artery were calculated. Bilateral regional cerebral oxygen saturation were monitored continuously. RESULTS At the end of the operation, peak systolic velocity, average velocity and blood flowvolume of the common carotid artery decreased significantly compared to the baseline measurement (p<0.001). Both left and right cerebral oximetry measurements showed a significant increase after induction and the increased oxymetric values persisted at the end of the operation (p<0.001). Age, body mass index, surgical duration and anaesthesia duration were found not to be correlated with the changes occurred in the values of peak systolic velocity, average velocity, arterial diameter, blood flow volume of the common carotid artery, left and right regional cerebral oxygen saturation after induction and at the end of surgery. CONCLUSION The head and neck extension given for thyroidectomy negatively affect carotid blood flow and cerebral oxygenation gradually and become pronounced especially at the end of surgery. In conclusion, it is important to maintain the cerebral perfusion pressure and cerebral blood flow.