ABSTRACT
Support of the Cardiovascular System The cardiovascular system is key to survival of horses with acute abdominal disease. Abdominal disease can lead to profound cardiovascular changes, principally through loss of water and electrolytes from the circulation to the gastrointestinal tract and by absorption of toxins. The principal toxin involved is endotoxin, a component of the cell wall of gram-negative bacteria. This toxin interacts with immune-series cells to cause the synthesis and release of a cascade of soluble mediators, including the cytokines IL-1 and TNF-alpha. These mediators, in turn, cause profound changes in both the contractility of the heart and the resistance of the blood vessels to blood flow. Both the effects of the toxins and loss of water from the circulation can severely reduce progressive blood flow through the capillary beds in the organs. The principal job of the blood flow through the organs is to deliver oxygen to the individual cells. As capillary blood flow is reduced, the metabolic processes of these cells are severely curtailed, and they may die. This, in turn, leads to organ failure and, ultimately, death.
