By Christina Frangou

A risk assessment model has found several modifiable intraoperative practices that increase risk for surgical site occurrences after open ventral hernia repair.

These practices include use of skin flaps, single-stage repairs for hernias that are actively infected and improper placement of mesh.

“High-risk patients undergoing complex ventral hernia repairs are probably enduring one of the hardest and most difficult surgeries that they will ever experience in their lives,” said senior author Mike Liang, MD, assistant professor of surgery, Baylor College of Medicine, Houston. “Patients in this high-risk group may benefit from a modified surgical technique.”

Rachel Berger, a student for a master of public health degree, presented the findings at the 2013 annual meeting of the Surgical Infection Society, held in Las Vegas.

This is one of the first studies to address the incidence and risk factors, including intraoperative factors, for surgical site occurrences following open ventral hernia repair.

Donald E. Fry, MD, executive vice president of Michael Pine and Associates and adjunct professor of surgery at Chicago’s Northwestern University, said the study “will hopefully provide us with some direction on how we are going to be able to optimize outcomes for quite a morbid operation.”

More research is needed, he added, to assess all factors that play into infection risk, particularly admission laboratory results. The risk assessment model will require validation at other institutions.

Dr. Fry, an expert in risk assessment modeling, said the study represents some of the highest-quality research to address infections in ventral hernia.

Previous projects from the Ventral Hernia Working Group, a corporate-sponsored group of hernia experts in the United States, and the National Nosocomial Infections Surveillance system identified multiple factors predicting patients at higher risk for surgical site occurrences or infections. These risk assessment tools, however, were incomplete, said Dr. Liang. They were not based on direct patient data, not specific to ventral hernias or failed to provide adequate stratification of hernia patients.

Dr. Liang and his colleagues set out to create a prognostic ventral hernia risk score based on direct patient data. They conducted a retrospective study of 888 patients who underwent open ventral hernia repair at a single institution between 2000 and 2010. Their study examined all surgical site occurrences to ensure all wound complications were captured.

Surgical site occurrences were defined as surgical site infections; formations of a seroma, hematoma or fistula; or wound dehiscences.

In all, one-third of the patients developed 415 unique surgical site occurrences. The most common occurrence was a surgical site infection (21.6%), followed by seroma (12.1%), wound dehiscence (7.1%), hematoma (3.0%) and fistula (1.4%).

The investigators conducted a multivariate analysis using internal resampling to identify independent risk factors for surgical site occurrences. Their methodology ensured greater external validity and applicability of the model to external data sets. Each risk factor was assigned a numeric value based on the odds ratio, and a clinical risk score for each patient was calculated based on these factors.

The presence of a class 4 wound significantly increased risk for surgical site occurrence, with an odds ratio of 8.7 (95% confidence interval [CI], 3.7-24.1; P<0.001). Investigators assigned nine points to the presence of a class 4 wound, making it the most important factor in the Ventral Hernia Risk Score. (In the National Nosocomial Infection Surveillance risk index, a class 4 wound is worth only one point, making it the same as the American Society of Anesthesiologists' score 3.)

Three other variables were found to significantly increase ventral hernia risk: the creation of skin flaps, incidental or concomitant hernia repair and the implantation of mesh. Each of these variables was worth two points in the risk score.

The investigators grouped patients into three categories based on their risk score: Class I, zero points; Class II, 2 to 4 points; and Class III, three or more points. Nearly 80% of patients categorized as Class III in the study developed a surgical site occurrence, compared with 49.6% of patients in Class II and 17.8% in Class I.

Dr. Liang said he and his colleagues now use the risk score in their assessment of patients with ventral hernia. They employ preoperative and intraoperative techniques to reduce the risk in patients likely to develop a surgical site infection or an occurrence.

Patients are encouraged to lose weight, stop smoking and improve diabetes control. In patients with wound class 4, surgeons attempt to reduce the pathology and stage repairs rather than perform single-stage repairs. They avoid use of skin flaps whenever possible, Dr. Liang said. They carefully select mesh, “as the mesh will invariably come into contact with bacteria in complicated ventral hernia repair.”

Some patients should be considered for watchful waiting instead of surgery, Dr. Liang said.

The authors used a receiver operating characteristic analysis to compare the Ventral Hernia Risk Score with the risk assessment tools from the Ventral Hernia Working Group and the National Nosocomial Infection Surveillance system index. The analysis showed the Ventral Hernia Risk Score for accurately predicting surgical site occurrence exceeded other tools.

The investigators are organizing follow-up studies to externally validate their results.

Dr. Liang disclosed that he receives a LifeCell research grant and unrestricted educational grants. Dr. Fry disclosed that he is on the speakers’ bureau for Merck, and has served as a consultant for Ethicon.