Endotoxin adsorption by polymyxin B immobilized fiber column in patients with systemic inflammatory response syndrome: The Japanese experience

The polymyxin B immobilized fiber column (PMX) has been used to treat septic shock patients since 1994 under the Japanese health insurance system. In 1997, the results of the first multicenter clinical study enrolling 42 patients were published, showing a significant reduction in the plasma endotoxin level of the survivors, whilst there was no change with the non-survivors, following treatment with PMX. Body temperature, blood pressure and hemodynamic abnormalities were significantly improved after PMX treatment. The second multicenter study enrolling 88 patients demonstrated that in the survivors, the plasma level of mediators such as TNF-alpha, IL-6, IL-10 and plasminogen activator inhibitor-1 (PAI-1) was significantly decreased following treatment with PMX. Recent studies investigating the mechanisms of PMX treatment have indicated that various mediators other than endotoxin might be adsorbed by PMX. Possible mediators include endogenous cannabinoids, such as macrophage-derived anandamide, and platelet-derived 2-arachidonyl glyceride (2-AG) and tetrahydrobiopterin (BH4), an essential cofactor for inducible NO synthase. The interaction between PMX and activated monocytes may suggest an alternative mechanism for the improvement in patient condition following PMX treatment. Further studies are needed to clarify the mechanisms of PMX treatment and to strengthen the scientific basis of this treatment.