ABSTRACT
For the past three decades, signs of circulatory insufficiency in horses with a variety of gastrointestinal diseases have been linked with the term endotoxemia. This association between the translocation of bacterial endotoxins (lipopolysaccharides) from the gastrointestinal tract into the circulation, and the subsequent development of clinical signs referable to endotoxemia, initially was based on the detection of lipopolysaccharides in the circulation of approximately 30% to 40% of horses presented to a variety of university veterinary clinics.1-3 The strength of this association was increased by the results of experimental studies in which the cardiovascular effects of the intravenous administration of purified lipopolysaccharides were noted to be similar to the derangements in cardiovascular function encountered in horses with gastrointestinal diseases characterized by loss of integrity of the intestinal wall.4-6 However, differences between experimentally induced endotoxemia and the clinical syndrome of endotoxemia were recognized by veterinary clinicians. For example, the profound neutropenia and febrile responses classically reported to occur after intravenous administration of purified lipopolysaccharides often were absent in many horses described as being endotoxemic. During the same time frame, a similarly confusing situation existed in human medicine, especially when the terms sepsis, septic shock, and sepsis syndrome were used interchangeably. As a result of this confusion, in the early 1990s the term “systemic inflammatory response syndrome” was coined to account for the clinical response of human patients to a nonspecific insult (i.e., in the absence of a documented infection).7 Whereas this systemic inflammatory response can be triggered by lipopolysaccharides, similar responses occur to other stimuli perceived to be dangerous by the host. The current knowledge regarding the systemic inflammatory response to bacterial ligands provides the basis for reconsidering the widespread usage of the term endotoxemia in equine clinical practice.
