Is the venoarterial carbondioxide gradient and lactate predictor of inadequate tissue perfusion during cardiopulmonary bypass?

Abstract

Background: In this study, we aimed to investigate the possible relationship between the venoarterial gradient of carbon dioxide (Dv-a PCO2) and lactate during cardiopulmonary bypass (CPB). Methods: Sixty consecutive patients (35 males, 53 females; mean age 64 years; range 38 to 78 years) who were scheduled for elective isolated coronary artery bypass graft (CABG) surgery were included in the study after obtaining their informed consent and the approval of the ethics committee of the hospital. All patients were followed up by the same surgical and anesthesia team. The adequacy of tissue perfusion during CPB was evaluated by the venoarterial partial carbon dioxide gradient, lactate level, measurement of arterial and venous blood gas, urinary flow rate, and hemodynamic parameters. The measurements were performed in four periods: before CPB (T1), at the beginning of CPB (T2) at 36 ºC and 32 ºC of hypothermia (T3) and at the end of rewarming (T4) at 37 ºC. The relationship between tissue perfusion parameters was assessed by Pearson’s correlation analysis. Results: There was a significant correlation between Dv-aPCO2 and the venous lactate level (r=0.54, p=0.046) as well as between Dv-aPCO2 and the arterial lactate level (r=0.55, p=0.042) during the T2 a nd T 4 periods of CPB. There was also a significant correlation between Dv-aPCO2 and arterial base excess (BE) (r=0.64, p=0.013) and between Dv-aPCO2 a nd a rterial H CO3 (r=0.54, p=0.048) during the T3 and T4 periods. Conclusion: Our study results suggest that in the hypothermia period, the increase in the venoarterial carbon dioxide gradient (Dv-aPCO2) is not inversely associated with insufficient blood flow during CPB and there was a significant correlation between Dv-aPCO2 and the tissue perfusion parameters during the periods other than hypothermia.