title: Does sodium bicarbonate infusion really have no effect on the incidence of acute kidney injury after cardiac surgery? A prospective observational trial.
abstract: BACKGROUND
  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?
  
  
  METHODS
  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 CPB-dependent hemolysis. The definition of AKI was acquired by applying the AKI-network (AKIN) classification over the course of five postoperative days.
  
  
  RESULTS
  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 (<3 Thakar points), the incidence of AKI 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.
  
  
  CONCLUSIONS
  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 low-risk patients while there was no statistically significant difference in the high-risk patient cohort.
  
  
  BACKGROUND
  DRKS00007616, Registered 12 December 2014.
authors.affiliation: Department of Anesthesiology, Emergency and Intensive Care Medicine, University of Goettingen, Robert-Koch-Str. 40, Goettingen, 37075, Germany. anna.wetz@med.uni-goettingen.de.
authors.forename: Anna J
authors.initials: AJ
authors.lastname: Wetz
authors.affiliation: Department of Anesthesiology, Emergency and Intensive Care Medicine, University of Goettingen, Robert-Koch-Str. 40, Goettingen, 37075, Germany. abraeue@gwdg.de.
authors.forename: Anselm
authors.initials: A
authors.lastname: Bräuer
authors.affiliation: Department of Anesthesiology, Emergency and Intensive Care Medicine, University of Goettingen, Robert-Koch-Str. 40, Goettingen, 37075, Germany. mquintel@med.uni-goettingen.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Quintel
authors.affiliation: Department of Anesthesiology, Emergency and Intensive Care Medicine, University of Goettingen, Robert-Koch-Str. 40, Goettingen, 37075, Germany. dheise1@gwdg.de.
authors.forename: Daniel
authors.initials: D
authors.lastname: Heise
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D058186:Acute Kidney Injury / Q000209:etiology / Q000517:prevention & control; D002315:Cardiopulmonary Bypass; D013504:Cardiovascular Surgical Procedures / Q000009:adverse effects; D015994:Incidence; D007262:Infusions, Intravenous; D011446:Prospective Studies; D018570:Risk Assessment; D017693:Sodium Bicarbonate / Q000627:therapeutic use
chemical_list: D017693:Sodium Bicarbonate