Nomograms Predict Risk of Postsurgical Blood Clots

A new study provides a tool that may help clinicians determine which patients are at highest risk of postsurgical venous thromboembolism (VTE).

Researchers at the University of California Davis (UCD; Sacramento, USA) reviewed and analyzed the American College of Surgeons (ACS) National Surgical Quality Improvement Program database, identifying 471,867 patients who underwent inpatient abdominal or thoracic operations between 2005 and 2010; the researchers excluded primary vascular and spine operations. They then built logistic regression models using stepwise model selection. The results were used to create nomograms for VTE and VTE after hospital discharge (VTEDC), with statistically significant covariates.

The results showed that the overall, unadjusted, 30-day incidence of VTE and VTEDC was 1.5% and 0.5%, respectively; annual incidence rates remained unchanged over the study period. On multivariate analysis, age, body mass index (BMI), presence of preoperative infection, cancer surgery, procedure type, multivisceral resection, and nonbariatric laparoscopic surgery were significant predictors for VTE and VTEDC. Other significant predictors for VTE, but not VTEDC, included a history of chronic obstructive pulmonary disease (COPD), disseminated cancer, and emergent operation. The nomograms demonstrated concordance indices for VTE and VTEDC of 0.77 and 0.67, respectively.

The researchers found that the risks indicated by the study deviated sharply from current US Joint Commission (Oakbrook Terrace, IL, USA) risk appraisals. For example, based on the study’s findings, a patient who is having his colon partially removed laparoscopically to treat recurrent cancer has a 10% for VTE. Meanwhile, a patient having an emergency hernia repair has less than a 5% risk. Under current guidelines, however, both patients would be treated as having equal risk. Using the nomogram to calculate risk could allow clinicians to more precisely respond to each patient’s individual risk factors. The study was published ahead of print on January 2, 2013, in the Journal of Surgical Research.

“A multitude of factors go into whether a patient is at risk for VTE, as well as how to prevent it. Prior to this study, no one had ever looked at so many of these factors so comprehensively,” said lead author professor of surgery Robert Canter, MD, of the UCD Comprehensive Cancer Center. “The standard preventive measure is heparin; however, there are many questions surrounding its use. What type of heparin should be administered? What dosage? Should we give it to patients before or after surgery? By identifying patients who are at higher risk for VTE, we attempt to answer many of these questions and help to personalize treatment.”

Related Links:
University of California Davis
US Joint Commission