Assessment of sublingual PCO2 during selective cerebral perfusion

: We monitored sublingual tissue PCO2 (PSLCO2) continuously with an ISFET (ion-sensitive field effect transistor) based PCO2 sensor during and after surgical treatment for descending aortic aneurysm. Using femoro-femoral bypass and a beating heart technique, distal end of aneurysm was clamped and then selective cerebral perfusion was performed into the left subclavian and left common carotid arteries. Aneurysmectomy and reconstructive surgery were carried out with proximal end of the left common carotid artery being clamped. Upon starting selective cerebral perfusion, PSLCO2 increased abnormally. PSLCO2 increased from 38 mmHg just after induction of anesthesia to the maximum value of 87 mmHg during selective cerebral perfusion. Three hours after arriving in the intensive care unit, the patient developed convulsion and anisocoria and the computed tomography showed cerebral infraction. Since the blood flow to the tongue is fed through the internal and external carotid arteries, the increase in PSLCO2 is supposed to be caused by the decrease of blood flow to the tongue during selective cerebral perfusion. The monitoring of PSLCO2 may be a useful method to estimate the brain blood flow during selective cerebral perfusion.