Mortality for intra-abdominal infection is associated with intrinsic risk factors rather than the source of infection

Intra-abdominal infections (IAIs) are an important cause of mortality and morbidity. Nosocomial IAIs (NIAIs) have been associated with higher mortality than community-acquired IAIs (CIAIs). We hypothesized that intrinsic risk factors were a better predictor of mortality than the type of infection.

Patients with IAI treated at a single urban academic hospital over 8 years (June 1999-June 2007) were retrospectively reviewed. Data collected included demographics, comorbidities, source of infection, type of infection (community vs nosocomial), type of intervention (operation versus percutaneous drainage), and postoperative complications. Charlson Comorbidity Index and multiple organ dysfunction (MOD) scores were evaluated at admission and on postoperative day 7 (POD-7).

There were 452 patients; 234 (51.8%) had CIAI and 218 (48.2%) had NIAI. The mean age was 51.3 +/- 0.8. The most common source of CIAI was the appendix (n = 129, 28.5%); 137 patients with NIAI had postoperative infections (30.3%). When patients with appendicitis were excluded, there was no difference in mortality or complications between patients with CIAI and NIAI. Logistic regression analysis demonstrated catheter-related bloodstream infection (P < .001; OR 7.3, 95% CI, 2.5-22.2), cardiac event (P < .001; OR 6.0, 95% CI, 2.3-16.1), and age > or = 65 (P = .009; OR 3.8, 95% CI, 1.4-8.8) to be independent risk factors for mortality. Among patients who failed initial therapy, a non-appendiceal source of infection (P < .001; OR 4.7, 95% CI, 2.3-9.8) and a Charlson score > or =2 (P = .033; OR 1.6, 95% CI, 1.0-2.6) were determined to be independent risk factors. Non-appendiceal source of infection (P = .001, OR 3.3, 95% CI, 1.6-7.0) and POD-7 MOD score > or =4 (P < .001; OR 3.4, 95% CI, 1.9-6.0) were found to be independent predictors for re-intervention.

These results suggest mortality from IAI is strongly related to age and organ dysfunction; however, catheter-related bloodstream infection and postoperative cardiac events have a greater effect on outcome.