Background: Central nervous system dysfunction after cardiopulmonary bypass (CPB) is frequent and can be caused by inadequate cerebral perfusion and oxygenation or microembolism. We studied the evaluation of the arterial and jugular venous blood gas analysis and the factors that affect these parameters during hypothermic CPB.

Methods: This prospective study was carried out on total 20 patients (11 coronary bypass and 9 valve replacement) operated electively in our department. To evaluation the effectiveness of cerebral autoregulation during CPB, we calculated changes in the cerebral blood flow from changes in the jugular venous oxyhemoglobine saturation (SjvO₂) of the rewarming speed periods during moderate hypothermia.

Results: While the value of jugular venous oxyhemoglobine saturation increased during CPB, it decreased to the values of pre-pump during heating. Statistically a significant increase between pre-pump period and the value in pump (p = 0.001), and a significant decrease between pump time and the values of heating period were determined. Increasing the cerebral blood flow induced parallel increases in the SjvO₂. In observing the difference between arterial oxygen content (CaO₂) and venous oxygen content (CvO₂), we determined that CaO₂ and CvO₂ difference significantly decreased during pump and increased with heating period.

Conclusion: We determined that SjvO₂ values increased in CPB with hypothermia but the difference of CaO₂ and CvO₂ decreased and in re-heating period SjvO₂ decreased but CaO₂2 and CvO₂ tend to increase. The most important factors on this change are hypothermia, pump flow rate and re-heating rate.

Keywords : Cardiopulmonary bypass, vena jugularis, oxyhemoglobine saturation, and cerebral blood flow