Abstract W P156: Perioperative Low Arterial Oxygenation is Associated With Increased Risk of Stroke After Cardiac Surgery
Background: Postoperative stroke occurs in up to 5% of cardiac surgery patients, contributing significantly to mortality and morbidity. Patient characteristics as well as intraoperative factors have been associated with a higher risk of stroke. We hypothesized that poor systemic blood oxygenation in the perioperative period is associated with increased risk of stroke following cardiac surgery.
Methods: This was a case-control study of 311 adult patients who underwent cardiac surgical procedures at a single center from 2003-6. Patients having a postoperative stroke were matched 1:2 with controls. Minimum and average pO2 values, as measured from arterial blood gas values during and up to 24 hours after the start of surgery, were recorded and evaluated as continuous and categorical (in quartiles) predictors. Conditional logistic regression models adjusted for hypertension, diabetes, hyperlipidemia, cardiopulmonary bypass time, and prior stroke were used to evaluate associations between minimum and average pO2, each, and stroke status.
Results: Lower nadir pO2 values were significantly associated with postoperative stroke. Per 10 mm Hg decline in nadir pO2, odds of stroke increased nearly 25% (OR 1.23, 95% CI 1.09-1.39). Nonlinear models of oxygen levels predicting stroke were explored (figure) but results remained similar; the linear model had the best statistical fit. Each equivalent decrease in mean pO2 was associated with smaller but significantly increased odds of stroke (OR 1.08, 95% CI 1.01-1.15). Having a nadir pO2 value in the lowest vs highest quartile was associated with 3.3-fold increased odds of stroke (95% CI 1.51-7.23).
Conclusion: Odds of stroke after cardiac surgery is significantly increased in patients with a low minimum or average pO2 within 24 hours of surgery. This relationship is independent of other potential confounders of operative outcome.
Author Disclosures: A.M. Miller: None. M. Grega: None. G.M. McKhann: None. O.A. Selnes: None. W. Baumgartner: None. R.F. Gottesman: None.
- © 2014 by American Heart Association, Inc.