The molecular basis for toxicity of surfactants in surgical wounds: 1. EO:PO Block Polymers

Abstract

The purpose of this study was to ascertain how molecular variations in a homologous series of polymeric nonionic surfactants affect their tissue toxicity. The results of these structure-toxicity studies serve to identify nontoxic surfactants for use in surgical scrub solutions. Structure-toxicity studies were undertaken with a family of nonionic surfactants, Pluronic polyols, whose composition can be easily altered to form an almost unlimited number of nonionic surfactants. Pluronic polyols are a series of block copolymers that consist of water-soluble poly (oxyethylene) groups at both ends of a water-insoluble poly (oxypropylene) chain. Pluronic polyols of varying molecular weight with a wide range of ethylene oxide content were used for this study. The effect of topical application of solutions of Pluronic polyols on the wound's resistance to infection was used as a measure of toxicity. The molecular weight of the Pluronic polyol was found to be an unimportant determinant of the toxicity of these surfactants in the surgical wounds. The incidence of gross infection in contaminated wounds after the application of a polyol with a high molecular weight differed insignificantly from the infection rate of wounds treated with a polyol with a lower molecular weight. The ethylene oxide content in the Pluronic polyol was an important causal factor of toxicity. Contaminated wounds treated with a polyol with a high ethylene oxide content (80% by weight of total molecule) exhibited a lower incidence of infection than wounds receiving a polyol with a lower ethylene oxide content (20–50% by weight of total molecule). Surfactants with a high ethylene oxide content failed to impair the wound's resistance to infection. The gross infection scores for contaminated wounds treated with the polyols with a high ethylene oxide content differed insignificantly from the incidence of infection of wounds subjected to 0.9% sodium chloride. The use of a nontoxic surfactant has improved the therapeutic value of surgical scrub solutions in the treatment of the contaminated wound. A polyol with a high ethylene oxide content, Pluronic F68, has been utilized with an iodophor, polyvinylpyrrolidone-iodine, in the preparation of a new surgical scrub solution. The therapeutic value of this solution was compared to another surgical scrub solution containing polyvinylpyrrolidone-iodine and an anionic surfactant. The incidence of gross infection after treatment with the mixture of the Pluronic polyol and the iodophor was significantly less than the infection rates of wounds subjected to a surgical scrub solution containing an iodophor and an anionic surfactant. The results of the study provide compelling reasons for further experimental and clinical investigations to assess the potential of this nontoxic surfactant in the treatment of the contaminated wound.