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.