Differential Impact of Polymyxin B Hemadsorption on Long‐Term Mortality in Septic Shock: A Retrospective Analysis of Intra‐Abdominal Versus Extra‐Abdominal Infections

The long-term benefit of polymyxin B hemadsorption (PMX-HA) in septic shock patients remains unclear and may depend on the site of infection. We evaluated the association between PMX-HA use and 1-year mortality in patients with intra-abdominal infection (IAI) and extra-abdominal infection (EAI). We retrospectively analyzed adult patients with septic shock (Sepsis-3) admitted to an ICU between January 2017 and July 2023. Patients were categorized as IAI or EAI and further stratified by PMX-HA use. One-year mortality was assessed using Kaplan-Meier analysis, multivariable Cox regression (adjusted for age, sex, and SOFA score), and inverse probability of treatment weighting (IPTW), balancing age, sex, SOFA, CRRT use, and with or without surgical and/or radiological interventions. Among 182 patients (98 IAI, 84 EAI), PMX-HA was administered to 71 IAI and 32 EAI patients. In the IAI group, PMX-HA was associated with significantly lower 1-year mortality (32.3% vs. 59.2%, p = 0.005), supported by Cox regression (adjusted HR: 0.485; 95% CI: 0.252-0.935; p = 0.031) and IPTW (weighted HR: 0.415; 95% CI: 0.215-0.787; p = 0.007). In contrast, in the EAI group, 1-year mortality was similar between the non-PMX and PMX groups (44.4% vs. 56.6%, p = 0.516), with no significant association in Cox analysis (adjusted HR: 0.790; 95% CI: 0.404-1.543; p = 0.49) or IPTW (weighted HR: 0.85; 95% CI: 0.446-1.617; p = 0.62). PMX-HA was significantly associated with a lower risk of 1-year mortality in patients with IAI, but not in those with EAI.