Abstract 16974: Sex Paradox: Greater Hemodilution Yet Lower Rate of Acute Kidney Injury in Women Compared with Men Undergoing On-Pump Cardiac Surgery
Background: Women undergoing cardiac surgery (CS) have lower baseline hematocrit (HCT) and due to their smaller body surface area are more prone to severe hemodilution (lower nadir HCT) on cardiopulmonary bypass (CPB) compared with men. Lower nadir HCT on CPB is also a well known risk factor for Acute Kidney Injury (AKI) after CS. Whether women because of lower baseline and nadir HCT on CPB are more prone to AKI after CS remains unknown.
Methods and results: We evaluated 13,274 patients (31.3% women) undergoing CS on CPB (6/1/2001-12/31/2011) at our institution to study the association of HCT and sex with post-CS AKI (>2X increase in baseline creatinine and post-CS creatinine >2 mg/dl). Women having CS were older (68±12 vs. 65±12 yrs, p<.01) with more comorbidities. Baseline (37.4±4.4 vs. 39.8±4.6%, p<.01) and nadir (24.5±3.5 vs. 27.4±3.6%, p<.01) HCT were lower, whereas change in HCT on CPB (baseline-nadir, 12.9±4.3 vs. 12.4±4.2%, p<.01) was greater in women. Yet despite this, AKI rates were similar in women and men (4.1 vs. 4.0%, p=.97). While nadir HCT was inversely related to AKI in both sexes, women had 21% lower relative risk of AKI than men for any given value of nadir HCT (adjusted OR 0.79, 95% CI 0.64-0.98, p=.035, Fig).
Conclusions: Both men and women undergoing CS on CPB were prone to the deleterious effects of hemodilution on renal function. Yet, despite greater hemodilution, women had significantly lower relative risk of AKI for any given nadir HCT on CPB than men. Whether different thresholds for RBC transfusions (i.e. lower HCT than in men) may help not only avoid unwarranted and deleterious effects of blood, but also help further decrease AKI rates and improve outcomes in women undergoing CS on CPB remains to be studied in future.
- © 2012 by American Heart Association, Inc.