Does sodium bicarbonate infusion really have no effect on the incidence of acute kidney injury after cardiac surgery? A prospective observational trial

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Wetz AJ, Bräuer A, Quintel M, Heise D
Crit Care 22;19(1):183.

Postoperative acute kidney injury (AKI) is a frequently observed phenomenon after cardiac
surgery with cardio-pulmonary bypass (CPB); this severe complication is associated with
adverse patient outcomes. There are multiple mechanisms involved in AKI during cardiac
surgery, including CPB-dependent hemolysis. An IV infusion of sodium bicarbonate, which
leads to urine alkalization, may play a role in preventing AKI. Recently, several trials have investigated the effect of sodium bicarbonate and reported controversial results. The purpose of this investigation was to investigate the following question. Under what circumstances can sodium bicarbonate prevent postoperative AKI?
We analyzed data from 342 patients undergoing CPB surgery at the University Hospital
Goettingen, Germany. A total of 174 patients received a preemptive dose of sodium
bicarbonate. Directly after the induction of anesthesia, the continuous infusion of 0.15
mmol/kg body weight/h was started and continued until 2 pm on the first postoperative day.
Patients who were not treated with sodium bicarbonate formed the control group (n = 168).
To verify the AKI risk configuration of each group, we surveyed risk factors and determined
the commonly used clinical predictive score according to Thakar and colleagues. We
recorded the concentration of free hemoglobin (fhb) to estimate the amount of CPBdependent
hemolysis. The definition of AKI was acquired by applying the AKI-network
(AKIN) classification over the course of five postoperative days.
Patients who received the sodium bicarbonate infusion showed a significantly lower
incidence (35.6 vs. 50%) of AKI than that of patients who did not receive the infusion (p =
0.01). AKIN levels 2 and 3 were also more frequent when sodium bicarbonate was not
administered. Particularly, in the low-risk cohort ( was significantly reduced (26 vs. 46%) when patients received sodium bicarbonate (p = 0.01), whereas in the high-risk patients, no significant reduction was observed.
In this study, we observed that low-risk patients particularly benefited from the preventive treatment with sodium bicarbonate. The incidence of AKI was significantly reduced in lowrisk patients while there was no statistically significant difference in the high-risk patient cohort.