Surgical Mortality Subject to Daily, Weekly, and Seasonal Variability

A new study suggests that the risk of death following surgery is highest in the afternoon, at weekends, and during the month of February.

Researchers at Charité University Medicine (Charité, Berlin, Germany) conducted a retrospective analysis of 218,758 patients who underwent surgery between 2006 and 2011 at the two University Hospital campuses of Charité. The data was then modeled to work out cyclical patterns and investigate the daily, weekly, and seasonal variability of mortality in patients after surgery, since while hospital mortality is known to be subject to variability, it has not yet been shown in patients after surgery.

The results showed that hospital mortality showed variability over the course of the day, during different weekdays, and on different months. Surgery conducted in the afternoon was associated with 21% increased risk of death, compared with surgery conducted at other times. Surgery at the weekend was associated with a 22% increased risk of death, compared with surgery on weekdays. February was the highest risk month for surgery, with surgery in February associated with a 16% increased risk of death compared with surgery in all other months. The study was presented at Euroanaesthesia 2014, held during May-June 2014 in Stockholm (Sweden).

“Several factors may have influenced this outcome. For example, it may be that standard of care differs throughout the day and between weekdays and weekends,” concluded study authors and presenters Felix Kork, MD, and Prof. Claudia Spies, MD, from the department of anesthesiology and intensive care. “And although we controlled for risk factors including emergency surgery in our study, it may very well be that the patients treated in the afternoon and on the weekends were more severely ill.”

The results are supported in part by another study—also presented at Euroanaesthesia 2014—conducted by researchers from Tohoku University (Japan), who reviewed data from 72 different studies covering more than 55 million patients worldwide. Their conclusion was that the weekend effect on hospital death rates is international, and the most likely explanation for the results was poorer quality care at weekends. However, their results do not support the Charité surgical data, suggesting that postoperative care in critical care units might dilute any effect of increased weekend mortality in postsurgery patients.

Related Links:
Charité University Medicine
Tohoku University