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

Objective: To investigate if oxygen delivery index during cardiopulmonary bypass (DOI) 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 DOI 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, DOI, history of heart failure, and baseline creatinine were associated significantly with AKI, as was an interaction term between the PP category and DOI (p = 0.0067). The higher the PP category, the stronger the observed association between DOI and AKI, and the higher the variability in the predicted risk of AKI dependent on DOI.

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