title: The association between perioperative hemoglobin and acute kidney injury in patients having noncardiac surgery.
abstract: BACKGROUND
  Acute kidney injury (AKI) is a common complication of noncardiac surgery and is associated with excess morbidity and mortality. Perioperative hemoglobin concentrations are strongly associated with surgical mortality, but little is known about their relationship with AKI. We studied hemoglobin concentration before and 24 hours after surgery and its association with AKI.
  
  
  METHODS
  We performed a single-center observational cohort study using clinical and administrative data from the Cleveland Clinic, Cleveland, OH. In patients with normal preoperative renal function, we examined the association between the outcome of AKI and the exposures of preoperative hemoglobin concentration and decrements in hemoglobin concentration in the first 24 hours after surgery using logistic regression and controlling for important confounding variables.
  
  
  RESULTS
  We included 27,381 patients who had 33,330 noncardiac surgeries. AKI developed in 2478 (7.4%) surgeries. Preoperative hemoglobin concentrations were <12.0 g/dL in 9566 (29%) patients. Hemoglobin concentrations decreased by >4.0 g/dL in 10,808 (32%) patients. Compared with patients with a preoperative hemoglobin >12.0 g/dL, the adjusted odds ratio (OR) for AKI was 2.01 (95% confidence interval [CI], 1.8-2.3) for those with a preoperative hemoglobin between 10.1 and 12.0 g/dL and was 3.7 (95% CI, 2.6-5.4) for those with a preoperative hemoglobin <8.0 g/dL. Compared with patients who did not have a decrease in postoperative hemoglobin, a decrement of 1.1 to 2.0 g/dL was associated with an adjusted OR of 1.51 (95% CI, 1.15-1.98), and a decrement of >4.0 g/dL with an OR of 4.7 (95% CI, 3.6-6.2) for AKI.
  
  
  CONCLUSIONS
  Low preoperative and early postoperative decrements in hemoglobin concentrations are strongly associated with postoperative AKI in a graded manner. Given the frequency of low perioperative hemoglobin and decreases in hemoglobin concentration, research is needed to determine whether there are safe treatment strategies to mitigate the risk of AKI.
authors.affiliation: From the Departments of Medicine and Clinical Epidemiology and Biostatistics, McMaster University; Population Health Research Institute, McMaster University and Hamilton Health Sciences, Hamilton; Department of Medicine, Western University, London, Ontario, Canada; and Departments of General Anesthesiology and Outcomes Research, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Michael
authors.initials: M
authors.lastname: Walsh
authors.forename: Amit X
authors.initials: AX
authors.lastname: Garg
authors.forename: P J
authors.initials: PJ
authors.lastname: Devereaux
authors.forename: Maged
authors.initials: M
authors.lastname: Argalious
authors.forename: Hooman
authors.initials: H
authors.lastname: Honar
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Sessler
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood* / Q000175:diagnosis* / Q000601:surgery; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019990:Perioperative Care / Q000639:trends; D011183:Postoperative Complications / Q000097:blood* / Q000175:diagnosis*; D012307:Risk Factors
chemical_list: D006454:Hemoglobins
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