Predictors of Outcome in Infrainguinal Bypass for Trauma
Hunter M Ray, Harleen K Sandhu, Charles C Miller, Edmundo Dipasupil, Rana O Afifi, Ali Azizzadeh, Kristofer Charlton-Ouw
The University of Texas Medical School at Houston, Houston, TX
Trauma remains a leading cause of morbidity and mortality worldwide, with vascular injuries present in 1-2% and with the majority of injuries occurring to the extremities. This study aims to determine predictors of poor outcome in infrainguinal bypasses performed for traumatic arterial injury.
Patients admitted between September 1999 and July 2015 who underwent infrainguinal arterial bypass for trauma at a single level one trauma center were included for analysis. Poor outcome was defined as a composite comprised of thrombosis leading to graft abandonment, reoperation, major amputation or death. Data were analyzed by stratified Kaplan-Meier and multiple Cox regression analysis using SAS v9.4 (SAS Institute, Cary, NC).
During the study period, 108 patients had infrainguinal arterial bypass for traumatic arterial injury, composed of 45 end-to-side and 63 interposition bypasses. Mean age was 35±17 years-old; 17/108 (16%) were female; median Injury Severity Score (ISS) was 12 (IQR 9-18); admission glomerular filtration rate (GFR) was 77.5 (IQR 59-92); median Mangled Extremity Severity Score (MESS) was 6 (IQR 5-7); median injury-to-surgery time was 5.1 hours (IQR 2-24); 39/108 (36%) had blunt injury; 30/108 (28%) had crush injury; 39/108 (36%) had motor vehicle collision (MVC); 10/108 (10%) had diabetes mellitus (DM); and 76/108 (70%) had an infrageniculate target for bypass.
Univariate risk factors for poor outcome include age >40 years (48% vs 21%, p<0.01); MESS>7 (51% vs 14%, p<0.01); blunt mechanism (39% vs 15%, p<0.01); diabetes (70% vs 27%, p<0.01); and infrageniculate target vessel (37% vs 16%, p<0.03). Popliteal artery injury (38% vs 21%, p<0.06) and concomitant orthopedic injuries (35% vs 17%, p<0.06) had worse outcomes, yet were not statistically significant. Baseline renal function, injury-to-surgery time, surgeon’s specialty, and associated venous injuries were not significantly predictive of poor outcome. MESS was strongly predictive of poor outcome, with probability rising as high as 95% when MESS reached 12 (Figure 1). A MESS score >7 was 73% sensitive and 70% specific to predict poor outcomes.
Age (OR 1.03/year, p<0.04) and MESS >7 (OR 3.8, p<0.02) were persistent predictors of poor outcome in multivariable analysis. In stratified analysis, interposition grafts fared worse only in penetrating injuries with composite poor outcome in 0/13 (0%) in end-to-side vs. 6/26 (23%) in interposition bypass (RR 1.3; 95% CI 1.1-1.6; p<0.03).
Poor outcome in infrainguinal bypass for trauma is predicted by age >40 years, MESS>7, blunt mechanism of injury, infrageniculate target as well as history of DM. Interestingly, interposition bypasses had worse outcomes compared to end-to-side bypasses only in penetrating injures.
Figure 1: Logistic Regression plot demonstrating poor predicted outcome with increasing Mangled Extremity Severity Score (MESS) with 95% probability of poor outcome predicted when MESS reached 12.
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