[The influence of aging on cerebral blood flow and oxygen metabolism during moderate hypothermic cardiopulmonary bypass--a clinical study by means of transcranial Doppler ultrasound].

The purpose of this study was to determine the influence of aging on cerebral blood flow and oxygen metabolism during moderate hypothermic cardiopulmonary bypass (CPB) in 25 patients undergoing open heart surgery. the patients were subdivided into one of two groups according to their age (the cut off value was 40 years for males and 50 years for females). Ten patients were included in group A (YOUNG group), and 15 patients were included in group B (OLD group). In these 25 patients, blood flow velocity in the middle cerebral artery (MCAv) was measured by means of transcranial Doppler ultrasound, and cerebral oxygen consumption was estimated by relating the arterio-venous oxygen content difference to flow velocity (D-CMRO2) during surgery. MCAv and D-CMRO2 were expressed as percent of the values determined at 30 minutes before CPB. High dose fentanyl anesthesia was employed and alpha-stat strategy (uncorrected for body temperature), moderate hemodilution and nonpulsatile flow pattern were maintained during CPB with moderate hypothermia. In both groups, MCAv and D-CMRO2 changed in parallel in proportion to the change in body temperature during the procedure. Thus, there was a good correlation between flow velocity and D-CMRO2 during CPB (group A: r = 0.648, p < 0.001, B: r = 0.636, p < 0.001). This result suggests that the coupling between cerebral blood flow and oxygen consumption was maintained throughout CPB in spite of aging. In group B, however, the usual of significant increase in the flow velocity and D-CMRO2 from the rewarming to the weaning stage of CPB tended to be delayed and suppressed.(ABSTRACT TRUNCATED AT 250 WORDS)