The risk of coronary artery surgery in women: A matched comparison using preoperative severity of illness scoring

Objective: To evaluate the effect of gender on outcomes of coronary artery bypass surgery using a weighted preoperative severity of illness scoring system. Design: Retrospective database review. Setting: Tertiary care teaching hospital. Participants: The patient population consisted of 2,800 consecutive coronary artery bypass graft (CABG) patients (658 women, 2,142 men), with or without concurrent procedures, operated on between January 1, 1993 and March 31, 1994. Measurements and Main Results: Patients were stratified for severity of illness using a 13-element scoring system. The distribution of severity of illness scores and severity of illness-stratified morbidity, hospital mortality, and intensive care unit (ICU) length of stay were compared by chi-square and Fischer's exact test where appropriate. Median duration of intubation and median duration of ICU length of stay were examined by the median test. Female versus male unadjusted mortality (4.9% v 3.0%), total morbidity (15.0% v 9.2%), and average initial ICU length of stay (92.62% v 60.56 hours) were statistically different. Female patients also had significantly more of the following postoperative morbidities: central nervous system complications (focal neurologic deficits, patients ≤65 years 3.20% v 1.54%; global neurologic deficits, patients ≤65 years 2.76% v 1.25%), duration of perioperative ventilation that includes the intubation time in the operating room until extubation in the ICU (average = 77.36 hours v 49.20 hours; median = 21.87 v 20.26 hours), and average initial ICU length of stay (average = 92.62 hours v 60.56 hours; median = 42.33 hours v 27.91 hours). However, distribution of severity scores was also different. Women had significantly more preoperative risk factors (p < 0.05): age 65 to 74 years (45.1% v 36.6%), age ≤75 years (21.3% v 11.9%), chronic obstructive pulmonary disease (10.8% v 6.4%), hematocrit less than 34% (21.9% v 5.5%), diabetes (34.8% v 21.8%), weight less than 65 kg (37.4% v 6.2%), and operative mitral valve insufficiency (9.6% v 6.0%). Stratified by severity, no statistically significant gender differences were found for mortality, morbidity, or ICU length of stay. Conclusions: Gender does not appear to be an independent risk factor for perioperative morbidity, mortality, or excessive ICU length of stay when patients are stratified by preoperative risk in this severity of illness scoring system.