Intraoperative hypotension is associated with acute kidney injury in noncardiac surgery
BACKGROUND: Perioperative acute kidney injury (AKI) is common and increases the risk of morbidity and mortality. OBJECTIVES: To determine the association between intraoperative hypotension, defined as an individual decrease from baseline and the risk of perioperative AKI. DESIGN: Observational cohort study. SETTING: Karolinska University Hospital, Stockholm, Sweden, from October 2012 to May 2013 and October 2015 and April 2016. PATIENTS: All adult patients undergoing major elective noncardiac surgery who were scheduled for an overnight admission in the postoperative unit were included. Patients undergoing phaeochromocytoma surgery were excluded. DATA COLLECTION: Preoperative risk factors (comorbidities), intraoperative events (hypotension defined as a more than 40 or 50% decrease in SBP relative to each patient's baseline and lasting more than 5 min) and postoperative data were collected from medical records. MAIN OUTCOME MEASURES: AKI within the first two postoperative days. RESULTS: Of the final cohort of 470 patients, 127 (27%) developed AKI in the perioperative period. AKI was associated with male sex [(66 vs. 48%) P < 0.001], a higher preoperative creatinine (81 vs. 73 μmol l, P = 0.003), American Society of Anaesthesiologists class more than two (54 vs. 42%, P = 0.014) and preoperative hypertension (54 vs. 40%, P = 0.005). During surgery, the AKI subgroup had more hypotensive events (>40%, 70 vs. 57%, P = 0.013; >50%, 20 vs. 12%, P = 0.024) and greater blood loss (800 vs. 400 ml, P < 0.001). Postoperatively, in AKI patients a positive fluid balance was more common (3123 vs. 2700 ml, P < 0.001), as was 30-day mortality (4 vs. 1%, P < 0.005). Multivariate analyses demonstrated that an intraoperative reduction of SBP more than 50% was associated with a more than doubled risk of AKI, adjusted odds ratio 2.27; 95% CI, 1.20 to 4.30, P = 0.013. CONCLUSION: In patients undergoing noncardiac surgery, there was a high incidence of perioperative AKI. Intraoperative avoidance of hypotension may decrease the risk of AKI.