Vasodilators in critical illness
Vasodilators are commonly used in the intensive care unit (ICU) to control arterial blood pressure, unload the left or the right heart, control pulmonary artery pressure, and improve microcirculatory blood flow. Vasodilator refers to drugs acting directly on the smooth muscles of peripheral vessel walls and drugs are usually classified based on their mechanism (acting directly or indirectly) or site of action (arterial or venous vasodilator). Drugs that have a predominant effect on resistance vessels are arterial dilators and drugs that primarily affect venous capacitance vessels are venous dilators. Drugs that interfere with sympathetic nervous system, block renin-angiotensin system, phosphodiesterase inhibitors, and nitrates are some examples of drugs with indirect effect. Vasodilator drugs play a major therapeutic role in hypertensive emergencies, primary and secondary pulmonary hypertension, acute left heart, and circulatory shock. This review discusses the main types of vasodilators drugs commonly used in the ICU.