Arachidonylethanolamide (AEA) and 2-arachidonylglycerol (2-AG) are endocannabinoids involved in septic shock, and 8-epi prostaglandin F2alpha (F2-isoprostane) is a biomarker of oxidative stress in biological systems. Because the antibiotic polymyxin B absorbs endocannabinoids as well as endotoxins, direct hemoperfusion therapy with polymyxin B-immobilized fibers (PMX-DHP) decreases serum levels of endocannabinoids. To investigate the features of sepsis and determine the proper use of PMX-DHP, we measured the changes in levels of endocannabinoids and F2-isoprostane in patients with septic shock. Twenty-six patients with septic shock, including those with septic shock induced by peritonitis, underwent laparotomy for drainage. Endocannabinoids absorption with PMX-DHP was examined in two groups of patients: patients whose mean arterial blood pressure (mABP) had increased more than 20 mm Hg (responder group; N = 13); and patients iwhose mABP did not increase or had increased no more than 20 mm Hg (non-responder group; N = 13). Levels of AEA did not change after PMX-DHP in either the non-responder or responder groups, whereas levels of 2-AG decreased significantly after PMX-DHP in the responder group, but not in the non-responder group. F2-isoprostane gradually increased after PMX-DHP treatment; on the other hand, levels of F2-isoprostane remained constant in the responder group. Patients with septic shock are under considerable oxidative stress, and 2-AG plays an important role in the cardiovascular status of these patients. The removal of 2-AG by PMX-DHP benefits patients with septic shock by stabilizing cardiovascular status and decreasing long-term oxidative stress.