Metabolic acidosis and organ dysfunctions in critically ill patients

Objective

Metabolic acidosis (MA) is common in critically ill patients. We characterize MA, analyse two methods of evaluation and correlate it with multiple organ dysfunction using the highest value of the Sepsis-related Organ Failure Assessment score of 5 days (SOFAm).

Methods

We evaluated 29 patients at admission and 24 hours later. Vital signs and laboratorial values were recorded and analysed through the classic methods and Stewart's method. The anion gap (AG), strong ion gap (SIG) and base excess (BE) were correlated with the SOFAm using univariate and multivariate methods. Medians, interquartile ranges and a Bland–Altman diagram were used.

Results

The Acute Physiology and Chronic Health Evaluation II score was 16 (13,19). Lactate represented 8–21% of anions. The AG correlated with the SIG (r = 0.98, P < 0.001), but the Bland–Altman bias was 7.9. The SIG and AG at entrance did not correlate with the SOFAm (r = 0.364 and r = 0.352, P < 0.05). BE at entrance and 24 hours later demonstrated inverse correlation with the SOFAm (r = -0.670 and r = -0.620, P < 0.001). Multivariate analyses demonstrated that BE at entrance was the best predictor of multiple organ dysfunction (coefficient β = -0.416, P = 0.017).

Conclusions

Lactic acidosis is not the major factor responsible for MA in critically ill patients. BE is the best predictor of multiple organ dysfunction when compared with the other methods used, and is less demanding.