Intraoperative base excess and carbon dioxide gap predict length of intensive care stay after cardiac surgery

Introduction

Perfusion parameters are goals of standard treatment in shock states and have prognostic significance in critically ill patients. After cardiac surgery, factors such as a low ejection fraction, longer duration of pump and perioperative ischemia may prolong the stay in the ICU. We sought to determine whether perfusion parameters as lactate and base excess may predict duration of stay in the ICU after cardiac surgery.

Methods

We performed a consecutive observational study in a university hospital. A total of 98 patients undergoing elective coronary artery bypass graft surgery were evaluated. Samples of lactate, arterial gases, and central venous saturation (ScVO₂) were collected 60 minutes after the beginning of surgery (initial) and at the end of procedure (final). Perfusion parameters were analyzed: central venous saturation (low <70%, normal >70%), base excess (low <-3 mol/l, normal >-3 mol/l), lactate (high >2.2 mmol/l, normal <2.2 mmol/l), carbon dioxide gap (abnormal >5, normal <5). A long ICU stay was considered more than 7 days. Univariate and multivariate analyses were performed.

Results

Risk factors for a longer time of ICU stay were a high initial carbon dioxide gap (P = 0.004) and a low level of initial base excess (P = 0.004). In a multivariate analysis, a low level of initial base excess is an independent predictor of a longer time of ICU stay after cardiac surgery (OR = 4.7; 95% CI, 3.45–47). Neither lactate nor ScVO₂ showed correlation with longer duration of ICU stay after cardiac surgery.

Conclusion

In this observational study, high postoperative carbon dioxide gap and low base excess predicted the length of ICU stay after cardiac surgery. These findings suggest that these parameters may be markers of prognosis after cardiac surgery and support the role of hemodynamic optimization in reducing complications.