DETECTION OF CEREBRAL HYPOPERFUSION DURING CARDIOPULMONARY BYPASS - CONTINUOUS MEASUREMENT OF CEREBRAL VENOUS OXYHEMOGLOBIN SATURATION DURING MYOCARDIAL REVASCULARIZATION

We measured continuously cerebral venous oxyhaemoglobin saturation (Sj vo(2)) using a 4F fibreoptic catheter in 11 patients scheduled for ele ctive myocardial revascularisation. The aims of this study were to ass ess the Oximetrix 3 computer and Opticath 40 cm catheter during modera te hypothermic cardiopulmonary bypass, and identify epochs of cerebral hypoperfusion (Sjvo(2) < 54%). Radial artery pressure, brain electric al activity, arterial and cerebral venous oximetry (dual oximetry), en d-tidal CO2 and nasopharyngeal temperature were recorded continuously in each patient. Following in vivo calibration of 11 continuous Sjvo(2 ) catheters and monitor, 57 simultaneous, paired recordings were addit ionally taken. The mean difference between the catheter Sjvo(2) and th e in vitro laboratory derived value was 0.34%, with a 95% confidence i nterval -3.2% to 2.4%. In 10 patients Sjvo(2) decreased below normal a t rewarming and myocardial reperfusion: mean lowest value 37%, range 1 9%-55%. Reduced Sjvo(2) were associated with a decrease in perfusion p ressure (r = 0.292, 80 DF, p = 7.710(-3)), and with an increase in na sopharyngeal temperature (r = -0.46, 115 DF, p = 2.710(-7)) after mod erate hypothermia. The Oximetric 3 computer and Opticath 40 cm cathete r provided reliable and accurate continuous monitoring of Sjvo(2) duri ng nonpulsatile cardiopulmonary bypass involving hypothermia with haem odilution and identified rewarming as the period of greatest risk of g lobal cerebral hypoperfusion.