Pharmacological modulation of cardiac function and blood vessel calibre

Inadequate end organ perfusion and tissue hypoxia is an end point of many disease processes in critical illness. Maintenance of blood flow and hence tissue oxygenation is critical to the management of intensive care patients. End organ blood flow is determined by a balance of myocardial factors (stroke volume and heart rate) and vascular factors (vasodilation and constriction). Global blood flow is determined by a balance of neurohormonal factors, with local autoregulation ultimately determining regional flow. Pharmacological manipulation of both the myocardium and vasculature at the level of the autonomic nervous system (via α or β adrenoceptors), myocardium (e.g. calcium sensitization via levosimendan), or locally (e.g. via sympathectomy) is commonly used in anaesthesia to mitigate the effects of critical illness and to maintain organ perfusion, either through increasing vascular tone or cardiac output. This article considers the global control of the system through to local and regional regulation of blood flow, and how the system may be manipulated at every stage.