Background: Perioperative acute kidney injury (AKI) is common and increases risk of morbidity and mortality. The study objectives were to determine the impact of preoperative risk factors and intraoperative events, with special focus on hypotension, on the risk of perioperative AKI.
Methods: In this observational cohort study, patients undergoing major elective noncardiac surgery who were scheduled for an overnight admission to the postoperative unit at the Karolinska University Hospital, Stockholm, Sweden, Oct 2012 to June 2013 and Jan 2015 to April 2016, were included. Preoperative risk factors (comorbidities), intraoperative events (hypotension defined as a percentage decrease in systolic blood pressure relative each patient’s baseline lasting > 5 min) and postoperative data were collected from medical records. Plasma creatinine were measured before, on the first, second and third day after surgery; AKI was determined according to the KDiGO criteria. Data were analysed with STATA version 14.2; the Mann–Whitney U-test or the chi-square test were used for continuous and categorical variables in the bivariate analyses, multivariable logistic regression, sensitivity analysis and tests of interaction were also performed.
Results: Of the final cohort of 470 patients, 127 (27%) developed AKI in the perioperative period. The AKI patients were more often men, had a higher ASA class, a higher frequency of treated hypertension and higher preoperative creatinine. During anaesthesia and surgery, the AKI subgroup had more hypotensive events and blood loss. In the postoperative phase positive fluid balance was more common among AKI patients, as was myocardial damage and 30-day mortality. Intraoperative hypotension was frequent; 286 patients (61%) had a 40%, and 68 patients (14%) a 50%, reduction from preoperative baseline. Multivariate analyses demonstrated that an intraoperative hypotensive event >50% was associated with a more than doubled risk of AKI (adjusted OR 2.46, CI 1.31-4.62).
Conclusions: In patients undergoing noncardiac surgery there was a high incidence of perioperative AKI. Intraoperative avoidance of hypotension may decrease the risk of AKI substantially.

Intraoperative hypotension is associated with acute kidney injury in non-cardiac surgery