Association between peripheral perfusion index and postoperative acute kidney injury in major noncardiac surgery patients receiving continuous vasopressors: a post hoc exploratory analysis of the VEGA-1 trial

Background: The peripheral perfusion index is the ratio of pulsatile to nonpulsatile static blood flow obtained by photoplethysmography and reflects peripheral tissue perfusion. We investigated the association between intraoperative perfusion index and postoperative acute kidney injury in patients undergoing major noncardiac surgery and receiving continuous vasopressor infusions. Methods: In this exploratory post hoc analysis of a pragmatic, cluster -randomised, multicentre trial, we obtained areas and cumulative times under various thresholds of perfusion index and investigated their association with acute kidney injury in multivariable logistic regression analyses. In secondary analyses, we investigated the association of timeweighted average perfusion index with acute kidney injury. The 30 -day mortality was a secondary outcome. Results: Of 2534 cases included, 8.9% developed postoperative acute kidney injury. Areas and cumulative times under a perfusion index of 3% and 2% were associated with an increased risk of acute kidney injury; the strongest association was observed for area under a perfusion index of 1% (adjusted odds ratio [aOR] 1.32, 95% confidence interval [CI] 1.00 - 1.74, P = 0.050, per 100%*min increase). Additionally, time -weighted average perfusion index was associated with acute kidney injury (aOR 0.82, 95% CI 0.74 - 0.91, P < 0.001) and 30 -day mortality (aOR 0.68, 95% CI 0.49 - 0.95, P = 0.024). Conclusions: Larger areas and longer cumulative times under thresholds of perfusion index and lower time -weighted average perfusion index were associated with postoperative acute kidney injury in patients undergoing major noncardiac surgery and receiving continuous vasopressor infusions. Clinical trial registration: NCT04789330.