Effects of polymyxin B haemoperfusion on septic shock caused by Gram-positive bacteria

Polymyxin B haemoperfusion is commonly used to adsorb endotoxins in septic shock caused by Gram-negative bacterial infections. Polymyxin B haemoperfusion has been reported to improve hypotension in Gram-positive bacterial infections; however, its efficacy and mechanism in treating such cases are unclear. We hypothesised that polymyxin B haemoperfusion would be equally effective in improving haemodynamics during Gram-positive bacterial infections as in Gram-negative bacterial infections. We conducted a retrospective study that included patients with septic shock admitted to the intensive care unit. The patients were divided into two groups according to bacterial culture results: Gram-negative rod (GNR) and Gram-positive coccus (GPC). We calculated the vasoactive inotropic score (VIS) before (0 h) and 2, 6, 12 and 24 h after polymyxin B haemoperfusion therapy. Data were analysed using two-way analysis of variance and post hoc tests for the associations between infection type and treatment time. Overall, 157 patients with septic shock were enrolled in the study: 81 and 76 patients were treated or not treated with extracorporeal haemoperfusion therapy, respectively. Although there was no significant difference in the VIS in polymyxin B haemoperfusion between patients with GNR and GPC infections, there was a significant decrease in the VIS over time, even when GPC was the causative organism. In addition, the degree of reduction in the VIS was significantly different in both the GNR and GPC groups compared with that in the non-extracorporeally treated group. Thus, polymyxin B haemoperfusion for septic shock caused by GNR reduced the VIS and could be effective even in cases of GPC infection.