The primary outcome was a composite of death from any cause by day 28 and the presence of at least one organ failure at day 7. In the a-priori defined stratum of patients enrolled with acute kidney injury and Acute Kidney Injury Network (AKIN) scores of 2 or 3, the primary outcome occurred in 82% (74/90) of those in the control group and 70% (64/92) of those in the bicarbonate group (absolute difference estimate −12.3%, 95% CI −26.0 to −0.1; p=0.0462).
The authors note that despite the frequency of its use in ICUs across the world, the effect of sodium bicarbonate infusion for the treatment of metabolic acidaemia on clinical outcomes is unknown. Although its use was not associated with a statistically significant effect on the primary outcome, the positive results of the subgroup of patients with acute kidney injury, and for some secondary outcomes (e.g. need for renal replacement therapy), are noted.
According to a related commentary, the lack of benefit on the primary outcome is consistent with the results of previous studies, and has been largely attributed to two adverse effects of bicarbonate infusion: a pH-dependent decrease in the concentration of ionised calcium, and intracellular acidification due to tissue accumulation of carbon dioxide. In this regard, the use of central venous blood gases to assess tissue acid–base status could have identified the frequency and magnitude of intracellular acidification, likely to be common because large amounts of sodium bicarbonate were infused in patients with severe circulatory compromise. They say the lower incidence of the primary outcome in patients with advanced acute kidney injury receiving sodium bicarbonate treatment is intriguing, and requires further study.