Introduction: Polymyxin B-immobilized fiber column hemoperfusion (PMX-DHP) improves hemodynamics and pulmonary oxygenation in patients with septic shock. However, optimal duration time for PMX-DHP remains unclear. Methods: This retrospective cohort study conducted in a single hospital between February 2004 and March 2010 included all patients with septic shock who required PMX-DHP. All patients were principally treated according to the strategy of Surviving Sepsis Campaign Guidelines. In conventional 2-hour group, PMX-DHP was performed for 2 hours (and then the second PMX-DHP was performed 24 hours after the end of the first treatment). The endpoint for continuous long-duration (>12hours) PMX-DHP (by a change of column approximately every 24 hours, if necessary) was determined by improvement of MAP (>65mmHg), normalization of lactate levels (<2mmol/L) and withdrawal in vasopressor/inotropic agents in each individual patient. Univariate differences between groups were assessed using Mann-Whitney U test. Multivariable regression analysis was used to develop propensity score-based models adjusted for baseline characteristics between two groups. Primary endpoint was 28-day mortality. Results: 101 patients (males 60%, mean age 70.7 years: 47 in the continuous long-duration group and 54 in the conventional 2-hour group) were treated with PMX-DHP for septic shock (abdomen, lung, urinary tract, soft tissue and others). Endotoxin levels were measured. Isolated microorganisms and sites were obtained. Baseline characteristics (group A vs. group B): mean age 73.0 vs. 68.7 P=0.24, males 62% vs. 59% P=0.80, gram negative infection 74% vs. 76% P=0.87, abdominal surgery 34% vs. 76% P<0.001, abdominal infection 43% vs. 80% P<0.001, malignancy 23% vs. 15% P=0.27, chronic dialysis 11% vs. 7% P=0.57, APACHE II score 27 (25-33) vs. 25 (23-29) P=0.002, SOFA score 9 (8-12) vs. 9 (7-10) P=0.08, PaO2/FiO2 ratio 227 (151-309) vs. 264 (183-377) P=0.203, MAP (mmHg) 53 (50-60) vs. 61 (56-75) P<0.001, catecholamine index (CAI) 11(8-15) vs. 9 (8-12) P=0.34, lactate levels (mmol/L) after fluid resuscitation 4.3 (2.3-5.9) vs. 2.7 (1.8-4.2) P=0.024, RRT 49% vs. 28% P=0.029. Total duration time (hours) was 38 (21-48) vs. 3.0 (2.1-5.0) (p<0.001). Crude 28-day mortality was 25.5% vs. 35.2% (HR 0.65 [95%CI 0.31-1.34] P=0.24). After adjustment for these baseline imbalances, multivariable Cox regression analysis identified continuous long-duration PMX-DHP (adjusted HR 0.25 [95%CI 0.11-0.59] P=0.002), malignancy (adjusted HR 2.75 [95%CI 1.20-6.30] P=0.02), abdominal infection (adjusted HR 0.38 [95%CI 0.17-0.86] P=0.02) and RRT (adjusted HR 3.46 [95%CI 1.56-7.64] P=0.002) as independent predictors of 28-day mortality. Propensity score for receiving continuous long-duration PMX-DHP was calculated by using multivariable logistic regression and included three independent variables comprising abdominal infection (adjusted odds ratio 0.13 [95%CI 0.04-0.37] P<0.001), MAP (adjusted odds ratio 0.90 [95%CI 0.85-0.95] P<0.001) and CAI (adjusted odds ratio 0.88 [95%CI 0.79-0.99] P=0.038). Propensity score analysis identified continuous long-duration PMX-DHP as an independent predictor of 28-day mortality (propensity score-matched analysis (PS±0.03) HR 0.18 [95%CI 0.04-0.82] P=0.013, regression adjustment with propensity score HR 0.27 [95%CI 0.11-0.65] P=0.003, inverse-probability-of-treatment-weighted (IPTW) HR 0.29 [95%CI 0.13-0.68] P=0.016, standardized mortality ratio-weighted (SMRW) HR 0.24 [95%CI 0.11-0.52] P=0.011. Multiple regression analysis revealed that duration time for PMX-DHP could be formulated as follows: Duration time (hours) = 64 - 0.85 x MAP + 2.24 x lactate levels (R 20.21). The significant side effects in continuous long-duration PMX-DHP were not shown. Conclusions: Continuous long-duration PMX-DHP improves 28-day mortality compared with conventional 2-hour PMX-DHP for septic shock. Optimal duration time for PMX-DHP can be predicted from MAP and lactate levels before PMX-DHP.
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