Circulatory shock in horses

Abstract

Circulatory shock can be defined as an acute circulatory failure with an inadequate tissue delivery of oxygen and nutritive substrates to the tissues, resulting in generalised cellular hypoxia. Shock can be classified as cardiogenic, obstructive, hypovolaemic, or distributive. The pathophysiologic consequences of inadequate tissue perfusion are directly related to cell ischemia, inadequate O₂ delivery, and the production of proinflammatory mediators. If abnormalities of tissue perfusion are allowed to persist, the function of vital organs will be impaired. The subsequent reperfusion will exacerbate organ dysfunction and, in severe cases, may culminate in multiple organ dysfunction syndrome. Early recognition of equine that are shocked and immediate provision of effective circulatory support is therefore essential. In all cases the objective is to restore oxygen delivery to the tissues while correcting the underlying cause. Delays in making the diagnosis and initiating treatment, as well as suboptimal resuscitation, contribute to the development of peripheral vascular failure and irreversible defects in oxygen use which can culminate in vital organ dysfunction.