title: Association of intraoperative hypotension with acute kidney injury after elective noncardiac surgery.
abstract: BACKGROUND
  Intraoperative hypotension (IOH) may be associated with postoperative acute kidney injury (AKI), but the duration of hypotension for triggering harm is unclear. The authors investigated the association between varying periods of IOH with mean arterial pressure (MAP) less than 55, less than 60, and less than 65 mmHg with AKI.
  
  
  METHODS
  The authors conducted a retrospective cohort study of 5,127 patients undergoing noncardiac surgery (2009 to 2012) with invasive MAP monitoring and length of stay of 1 or more days. Exclusion criteria were preoperative MAP less than 65 mmHg, dialysis dependence, urologic surgery, and surgical duration less than 30 min. The primary exposure was IOH. The primary outcome was AKI (50% or 0.3 mg/dl increase in creatinine) during the first 2 postoperative days. Multivariable logistic regression was used to model the exposure-outcome relationship.
  
  
  RESULTS
  AKI occurred in 324 (6.3%) patients and was associated with MAP less than 60 mmHg for 11 to 20 min and MAP less than 55 mmHg for more than 10 min in a graded fashion. The adjusted odds ratio of AKI for MAP less than 55 mmHg was 2.34 (1.35 to 4.05) for 11- to 20-min exposure and 3.53 (1.51 to 8.25) for more than 20 min. For MAP less than 60 mmHg, the adjusted odds ratio for AKI was 1.84 (1.11 to 3.06) for 11- to 20-min exposure.
  
  
  CONCLUSIONS
  In this analysis, postoperative AKI is associated with sustained intraoperative periods of MAP less than 55 and less than 60 mmHg. This study provides an impetus for clinical trials to determine whether interventions that promptly treat IOH and are tailored to individual patient physiology could help reduce the risk of AKI.
authors.affiliation: From the Department of Anesthesia, Toronto General Hospital and University of Toronto, Toronto, Ontario, Canada (L.Y.S., D.N.W., G.A.T., W.S.B.); Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Ontario, Canada (D.N.W.); Institute of Health Policy Management and Evaluation, Toronto, Ontario, Canada (D.N.W.); and Cardiovascular Research Program, Institute for Clinical Evaluative Sciences, Totonto, Ontario, Canada.
authors.forename: Louise Y
authors.initials: LY
authors.lastname: Sun
authors.forename: Duminda N
authors.initials: DN
authors.lastname: Wijeysundera
authors.forename: Gordon A
authors.initials: GA
authors.lastname: Tait
authors.forename: W Scott
authors.initials: WS
authors.lastname: Beattie
mesh_terms: D058186:Acute Kidney Injury / Q000175:diagnosis* / Q000209:etiology; D000368:Aged; D015331:Cohort Studies; D017558:Elective Surgical Procedures / Q000009:adverse effects* / Q000639:trends; D005260:Female; D006801:Humans; D007022:Hypotension / Q000150:complications / Q000175:diagnosis*; D007431:Intraoperative Complications / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D011183:Postoperative Complications / Q000175:diagnosis* / Q000209:etiology; D011446:Prospective Studies; D012189:Retrospective Studies