The cited research reported that the most common post-operative complication was post-operative infections (Weekend 30% vs. Weekday 20%). However, there was also an increased risk of need for repeat laparotomy, mechanical wound complications, and pulmonary complications. Of note, there was no difference in disease severity between weekend and weekday groups.
Oddly, this increase in complications did not occur with Crohn's disease patients.
Although these findings can not and should not generalize to other surgical procedures, the following logistical issues ARE present when decision for urgent surgery is made after hours or on weekends.
The following issues are probably what prompts this type of research to occur in the first place.
During such off-periods, there are no surgical support staff present in the hospital. They need to be called in from home. As such, there may be a slightly higher time delay before surgery begins. Furthermore, the surgical tech that assists the surgeon may be unfamiliar with the surgery as well as instruments used leading to a surgical procedure that may be "inefficiently" performed.
For example, if I need to take a child back to the OR who is suffering from excessive bleeding after a tonsillectomy, the surgical technician who may be assisting me may be an orthopedic technician unfamiliar with ENT instruments as well as unfamiliar with how the procedure is performed.
Although one may like to select who assists in the surgery, unfortunately, the patient nor the surgeon gets to choose who their surgical support staff is. It is whoever happens to be on-call when the need for urgent surgery arises. You get who you get...
However, during the weekday, the surgical support staff helping with the surgery is the team that does that particular surgery all the time... the "A" team so to speak.
The other factor is the surgeon himself. During the weekday, the patient will most likely have surgery performed by "their" surgeon who knows and is already familiar with the patient.
After-hours or on the weekend, the patient may or may not get the surgeon who knows the patient personally. It would be whoever the on-call surgeon is.
So now you know...
Now to be fair, there have been studies that both support as well as refute the assertion that weekend surgeries/admissions place patients at elevated risk of complications.
Weekends Worse for Surgery. New York Times. 3/22/13
Weekend hospitalisations and post-operative complications following urgent surgery for ulcerative colitis and Crohn's disease. AP&T Article first published online: 4 MAR 2013. DOI: 10.1111/apt.12272