Lengthy surgery increases blood clot risk

A new study published online has reported that the risk of developing blood clots appears to increase with surgery that has a longer-than-average duration.

Longer surgical procedures have had an association with negative health outcomes such as blood clots, but this has not been supported by research previously.

The researchers the Northwestern University Feinberg School of Medicine in Chicago, IL,  examined the link between blood clots - also known as venous thromboembolisms (VTE) - and surgery duration for the study, published by JAMA Surgery.

According to the researchers, there is a widely accepted association between longer surgical procedures and death, as well as blood clots, but this association had yet to be assessed quantitatively using a sufficiently strong database.

VTEs are a serious medical condition. Doctors often use VTE to describe two conditions occurring simultaneously: deep vein thrombosis (DVT) and pulmonary embolism (PE).

DVT occurs with the formation of a blood clot in at least one of the body's deep veins, typically in the legs. Clots can then break free and travel through the bloodstream to other parts of the body. PE occurs when one of the pulmonary arteries in the lungs is blocked, usually by a blood clot. Each year, over 500,000 hospitalizations and 100,000 deaths are associated with blood clots.

Further assessment of the link between surgical time and VTEs would enable more informed medical and surgical decision making while improving patient health outcomes, write the authors.

Increase in VTE likelihood with longer surgery

For the study, data was analyzed from the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) - a database that includes information from 2005 to 2011 for over 1.7 million patients across surgical disciplines in more than 300 health institutions.

A total of 13,809 patients were found to have had a postoperative VTE, 10,198 patients developed DVT and 4,772 patients developed PE.

In comparison with operations of average duration, patients undergoing lengthier procedures had a 1.27-fold increase in their likelihood of developing a VTE. In contrast, patients undergoing quicker procedures had lower odds of VTE development.

For three of the most common operations - appendectomy, gall bladder removal and gastric bypass - surgical time was found to be a risk factor for the development of VTE.

'Validation of a widely held belief'

The authors believe that their findings suggest risk assessments should analyze the length of surgery more thoroughly. Quantifying the risk of VTE could help reduce complications following surgery that can lead to readmissions and increasing health care costs.

"This study provides quantitative validation of the widely held, but not previously substantiated, belief that longer operations are associated with a higher risk of VTE. These findings may improve VTE risk modeling, enhance existing prophylaxis guidelines and better inform surgical decision making," write the authors.

The observational nature of the study limits the findings, as it means the researchers are unable to definitively conclude that the association between surgical duration and VTE incidence is a cause-and-effect relationship.

However, the authors argue that other potential confounders such as surgeon skill and the extent of the disease being treated are inextricably tied up with surgery duration. A particularly skilled surgeon would naturally be able to perform a procedure in a quicker time than a less-skilled one, for example.

"In addition to playing a role in postoperative risk assessment," the authors state, "our findings can provide a useful benchmark for VTE rates, helping to assess the efficacy of future risk-reduction initiatives."

Previously, another team of researchers reported on a study that found an increased risk of VTE among users of non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin and ibuprofen.

References:

1. Surgical duration and risk of venous thromboembolism, John Y. S. Kim, et al., JAMA Surgery, doi:10.1001/jamasurg.2014.1841, published online 3 December 2014, abstract.
2. JAMA news release, accessed 3 December 2014.
3. Additional source: Mayo Clinic Deep vein thrombosis (DVT) - definition, accessed 3 December 2014.
4. Additional source: Mayo Clinic Pulmonary embolism - definition, accessed 3 December 2014.