Early Postoperative Hyperlactatemia After Extracorporeal Circulation: The Role of Standard Base Excess and Anion Gap in Differential Diagnosis

Objectives: This study aimed to determine whether follow-up with standard base excess (SBE) and anion gap (AG) aids in the differential diagnosis of early postoperative hyperlactatemia, specifically in distinguishing between low cardiac output and lactate washout.
Methods: The study involved 1203 patients who underwent isolated coronary bypass surgery with the help of Extracorporeal Circulation (ECC). These patients were divided into two groups based on their cardiac index (CI): Group 1 consisted of 1162 patients with CI ≥ 1.8 L/min/m², while Group 2 had 41 patients with CI<1.8 L/min/m². Blood gas measurements were taken at five different time points to examine the correlation between lactate, SBE, and AG.
Results: The correlation between lactate and SBE in Group 1 was weak (r=-0.07, p<0.001). Similarly, the correlation between lactate and anion gap was weak (r=0.08, p=0.005). On the other hand, in Group 2 (CI<1.8 L/min/m²), a much stronger correlation was observed between lactate and SBE (r=-0.49, p<0.001). However, there was no correlation between lactate and anion gap (r=-0.007, p=0.964).
Conclusion: Relying solely on SBE (standard base excess) and anion gap to distinguish hyperlactatemia is limited because they depend on various variables. Therefore, we recommend assessing hyperlactatemia by examining the patient's clinical condition, other tissue perfusion parameters, flow measurements, plasma chloride, and albumin values.