Circadian variation affects atherosclerosis at many levels, including a circadian outcome in the treatment of myocardial infarction by angioplasty and thrombolysis.This has not been studied in the surgical patient. The circadian variation in mortality dependant on the time of surgery was examined in patients undergoing coronary artery bypass surgery (CABG).
A 4 year retrospective review of all CABG patients (n=3140) from 1999 to 2002 at a single institution with an accreditated training program was undertaken. The patients were divided into elective, urgent and emergency cases. The cases were subdivided according to the start time of the operation as morning (7am-2pm =AM), afternoon (2pm-8pm=AF) and night (8pm-7am =NT) and as weekday (Monday to Friday =WD) or weekend (WE) cases. The outcome was mortality within 30 days and compared for 4 different time frames: (1) AM vs. AF (2) AM vs. NT (3) AF vs. NT (4) WD vs. WE for each prioritized group. Risk factors and number of anastamoses were compared for each group. Sigma Statistical package and z-test for 2 group comparison were used for analysis. T-test was used to compare age and ejection fraction.
No statistically significant difference in mortality was observed for the elective and urgent groups for each of the time periods compared (Table). The emergency cases had significantly increased deaths in the AM and NT compared to the AF (p<0.01 and p<0.05 respectively). There was no statistically significant difference with respect to age, gender, number of anastamoses performed, ejection fraction and preoperative risk factors between groups.
The mortality for non-emergent CABG is independent of the timing of surgery. Circadian variation does not influence the outcome in cardiac surgical patients.
This study demonstrates that the biological effect of circadian variation and environmental factors (eg. surgeon fatigue) has no effect on mortality in cardiac surgery. This reassures surgeons and patients alike that the outcome is independant of the time of the procedure.This should be noted prior to further work hour legislation being introduced.
Mortality (Deaths/Cases)AMAFNTWDWEElective16/6372/2010/1018/8350/13 CABG2.51%0.995%0%2.16%0%Urgent48/151223/6740/3166/20605/152 CABG3.17%3.41%0%3.20%3.29%Emergency6/231/375/18AM vs AF: p<0.0110/692/9 CABG26.09%2.70%27.78%AF vs NT: p<0.0514.49%22.22%
Ajay Dhadwal, None.