Longer Surgery, Greater Risks

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Under the American College of Surgeons’ National Surgical Quality Improvement Program from 2005 to 2011, more than 1.4 million patients undergoing surgery at US hospitals were observed to see if lengthier surgery durations would affect the risk of developing a blood clot, or venous thromboembolism (VTE). We’ve known that being bound to a hospital bed (common after surgery) is a risk factor for VTEs, but this is the first evidence that surgery duration is a risk factor as well.

Doctors fear venous thromboses because they often break into fragments called emboli that are then carried back to the heart by the blood stream. Emboli can eventually obstruct the smaller blood vessels in the lungs, hindering oxygenation. The hypoxemia (low oxygen) can ultimately lead to death.

In the hospital we give patients anticoagulants like heparin to prevent VTEs and recommend wearing sequential compression devices (SCDs) on the calves. SCDs intermittently inflate causing increased blood flow through the veins, which means less opportunity for VTEs to develop.  There are also studies that suggest a molecular mechanism for SCDs role in anticoagulation.

The authors looked at rates of blood clots in patients that occurred within 30 days of surgery and found that those who had longer surgery duration were at greater risk (1.27 times greater for the lengthiest surgeries). This is true of even the most common general surgeries including laparoscopic cholecystectomy, appendectomy, and gastric bypass.

500,000 Americans are hospitalized due to VTEs every year, which means that reducing post-surgical VTE risk has impressive implications in terms of reducing patient mortality and costs of care. It’s also important for hospitals that are institutionally incentivized by the Patient Protection and Affordable Care Act to drive down readmissions for surgical complications.

This study stands out because it demonstrates an avenue for improving patient safety and reducing medical costs. For example, evidence-based protocols might be developed to routinely screen patients who had the lengthiest surgery durations for VTEs. Noentheless, more research is still needed. We need to see that these findings are reproducible in different populations, begin to define “lengthiest surgery duration”, and create a model that can reliably stratify multifactorial risk.