Association of Preoperative Pulse Pressure and Oxygen Delivery Index During Cardiopulmonary Bypass With Postoperative Acute Kidney Injury

Abstract

Objective: To investigate if oxygen delivery index during cardiopulmonary bypass (DO₂I) was more strongly associated with acute kidney injury (AKI), the higher the patient's preoperative pulse pressure (PP).

Design: Retrospective cohort of 1064 patients undergoing cardiac surgery.

Setting: Single academic healthcare center.

Participants: Adult patients undergoing coronary artery bypass grafting, valve, aortic, or combined surgery requiring cardiopulmonary bypass.

Interventions: Hemoglobin, arterial oxygen saturation, and pump flow recorded no fewer than every 30 min were extracted from the patients' perfusion records, and DO₂I was calculated. The AKI was assessed from the pre- and postoperative creatinine and urine output values using the Acute Kidney Injury Network criteria. The sample was stratified in 5 categories of progressively higher PP. The patient characteristics and intraoperative variables were evaluated in univariate analysis for a relationship with AKI. The significant risk factors from the univariate analysis then were evaluated in a multivariate analysis and assessed for logistic fit with respect to AKI.

Primary outcome: The AKI assessed as a binary outcome.

Measurements and main results: Age, body surface area, DO₂I, history of heart failure, and baseline creatinine were associated significantly with AKI, as was an interaction term between the PP category and DO₂I (p = 0.0067). The higher the PP category, the stronger the observed association between DO₂I and AKI, and the higher the variability in the predicted risk of AKI dependent on DO₂I.

Conclusions: A lower DO₂I during cardiopulmonary bypass appeared more strongly associated with a higher likelihood of developing AKI, the higher the patient's preoperative pulse pressure.

Keywords: Acute kidney injury; Cardiopulmonary bypass; Oxygen delivery index; Pulse pressure.