Postoperative blood urea nitrogen is associated with stroke in cardiac surgical patients

Abstract

Background: This case-control study identified perioperative risk factors associated with postoperative stroke risk after all cardiac surgical procedures.

Methods: Among 5498 adults 18 to 90 years old who underwent cardiac surgical procedures from 2005 to 2010, we identified 180 patients who suffered a stroke within 10 days postoperatively. Controls were randomly selected and frequency matched for sex and age-band to cases. Univariate and multivariate logistic regression analyses were performed to ascertain risk factors for postoperative stroke.

Results: Emergency surgical procedures (odds ratio [OR], 3.04; 95% confidence interval [CI], 1.80 to 5.10), current smoking (OR, 1.97; 95% CI, 1.29 to 3.00), peripheral vascular disease (OR, 2.80; 95% CI, 1.41 to 5.53), and previous stroke with residual paralysis (OR, 4.27; 95% CI ,1.18 to 15.38) were associated with increased stroke risk. Preoperative blood pressures were higher in patients with cases than in controls (p < 0.0001). Log of immediate postoperative blood urea nitrogen (BUN) was higher in patients with cases than in controls (p < 0.0001). In adjusted multivariable logistic regression, postoperative BUN was associated with increased odds of stroke (OR, 2.37 per 25% increase in BUN, p < 0.0001). Postoperative stroke risk was also predicted by emergency surgical procedures (OR, 2.70, p = 0.014), current smoking (OR, 2.82, p = 0.002), and preoperative diastolic blood pressure (DBP) (OR, 1.77 for every 10-point increase in DBP, p < 0.0001). Receiver operator characteristic curves indicated that postoperative BUN (area under the curve, 0.855) largely explained the increased postoperative stroke risk.

Conclusions: In these analyses, we identified BUN as a marker of heightened postoperative stroke risk after cardiac surgical procedures. Postoperative risk markers may improve assessment of delayed postoperative strokes.