Effects of sodium bicarbonate infusion on mortality in medical-surgical ICU patients with metabolic acidosis-A single-center propensity score matched analysis.

OBJECTIVE:Metabolic acidosis is associated with high mortality. Despite theoretical benefits of sodium-bicarbonate (SB), current evidence remains controversial. We investigated SB-related effects on outcomes in ICU patients with metabolic acidosis. DESIGN:Retrospective analysis. SETTING:Academic medical center. PATIENTS OR PARTICIPANTS:971 ICU patients with metabolic acidosis defined as arterial pH<7.3 and CO2<45mmHg treated between 2012 and 2016. A propensity score (PS) was estimated using logistic regression. Patients were matched in pairs using the PS. INTERVENTIONS:441 patients were treated with SB 8.4% (SB-group) and n=530 patients were not (control group). MAIN VARIABLES OF INTEREST:Primary outcome was all-cause mortality at ICU-discharge. Average Treatment Effect (ATE), Average Treatment effect in Treated (ATT), and estimated relative survival effects at 20 days were computed. RESULTS:In the full cohort, we observed considerable differences in pH, base excess, additional acidosis-related indices, and ICU mortality (controls 31% vs. SB-group 56%, p<.001) at baseline between the two groups. After PS-matching (n=174 in each group), no significant difference in ICU mortality was observed (controls 32% vs. SB-group 41%; p=.07). Odds ratios (OR) for ATE and ATT showed no association with ICU mortality (OR ATE: 1.08, 95%-CI 0.99-1.17; p=.08; OR ATT 1.09; 95%-CI 0.99-1.2; p=.09). Hazard ratios at 20-days (multivariable HR, matched sample n=348: 1.16, 95%-CI 0.86-1.56, p=.33) showed similar survival in the two study groups. CONCLUSIONS:We did not observe effects of SB infusion on all-cause mortality in critically ill patients with metabolic acidosis.