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

We measured continuously cerebral venous oxyhaemoglobin saturation (Sjvo(2)) using a 4F fibreoptic catheter in 11 patients scheduled for elective myocardial revascularisation. The aims of this study were to assess the Oximetrix 3 computer and Opticath 40 cm catheter during moderate hypothermic cardiopulmonary bypass, and identify epochs of cerebral hypoperfusion (Sjvo(2) < 54%). Radial artery pressure, brain electrical activity, arterial and cerebral venous oximetry (dual oximetry), end-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 additionally taken. The mean difference between the catheter Sjvo(2) and the in vitro laboratory derived value was 0.34%, with a 95% confidence interval -3.2% to 2.4%. In 10 patients Sjvo(2) decreased below normal at rewarming and myocardial reperfusion: mean lowest value 37%, range 19%-55%. Reduced Sjvo(2) were associated with a decrease in perfusion pressure (r = 0.292, 80 DF, p = 7.7*10(-3)), and with an increase in nasopharyngeal temperature (r = -0.46, 115 DF, p = 2.7*10(-7)) after moderate hypothermia. The Oximetric 3 computer and Opticath 40 cm catheter provided reliable and accurate continuous monitoring of Sjvo(2) during nonpulsatile cardiopulmonary bypass involving hypothermia with haemodilution and identified rewarming as the period of greatest risk of global cerebral hypoperfusion.