Accurate Risk Stratification for Development of Organ/Space Surgical Site Infections after Emergent Trauma Laparotomy

Shuyan Wei; John Harvin; Lillian Kao; Charles Green; Van Thi Thanh Truong; Charles Wade; Brandy Padilla-Jones

Organ/space surgical site infection (OS-SSI) develops frequently after trauma laparotomies and is associated with significant morbidity. Currently, no valid model exists to accurately risk stratify the probability of OS-SSI development after emergent laparotomy. Risk stratification for OS-SSI in these patients could guide promising, but unproven, interventions for OS-SSI prevention, such as more frequent dosing of intraoperative antibiotics or direct peritoneal resuscitation.

We hypothesize that in trauma patients who undergo emergent laparotomy, probability of OS-SSI can be accurately estimated using patient data available during the index operation.

Retrospective review was performed of a prospectively maintained database of emergent trauma laparotomies from 2011-2016. Patient demographics and risk factors for OS-SSI were collected. We performed Bayesian multilevel logistic regression to develop the model based on a 70% training sample. Evaluation of model fit using area under the curve (AUC) was performed on a 30% test sample. A Bayesian model was chosen in the setting of a low ratio of observed events to predictors, which permits estimation of probabilities when sample size is small.

1,308 patients underwent laparotomy, of which 165 (13%) developed OS-SSI. Variables included in the model and their contribution to the model are presented in the Table. Three variables that contributed most to OS-SSIs were damage control laparotomy, colon injury, and colon resection. The AUC of the predictive model validated on the test sample was 0.80 (95% CI 0.73-0.86). An example of how the model can be used to calculate the probability of OS-SSI are also presented (Table). 

Using a combination of factors available to surgeons prior to the end of an emergent laparotomy, the probability of OS-SSI could be accurately estimated using this retrospective cohort. A web-based calculator is under design to allow the real-time estimation of probability of OS-SSI intraoperatively. The calculator could be used to improve intra- or post-operative management of moderate and high risk patients. Prospective validation of its generalizability to other trauma cohorts and of its utility at the point-of-care is required.