Use of inotropes and vasopressor agents in critically ill patients

Abstract

Inotropes and vasopressors are biologically and clinically important compounds that originate from different pharmacological groups and act at some of the most fundamental receptor and signal transduction systems in the body. More than 20 such agents are in common clinical use, yet few reviews of their pharmacology exist outside of physiology and pharmacology textbooks. Despite widespread use in critically ill patients, understanding of the clinical effects of these drugs in pathological states is poor. The purpose of this article is to describe the pharmacology and clinical applications of inotropic and vasopressor agents in critically ill patients. LINKED ARTICLESThis article is commented on by Bracht et al., pp. 2009 and De Backer and Scolletta, pp. 2012-2014 ]i, Intracellular calcium concentration; ATP, adenosine triphosphate; cAMP, cyclic adenosine monophosphate; CPR, cardiopulmonary resuscitation; DO2, systemic oxygen delivery; GPCR, G-protein coupled receptor; GTP/GDP, guanosine triphosphate/diphosphate; PKA/PKC, protein kinase A/C; PLC, phospholipase C; SvO2, mixed/central venous oxygen saturation; TNF-a, tumour necrosis factor alpha; VO2, oxygen consumption IntroductionInotropes are agents administered to increase myocardial contractility whereas vasopressor agents are administered to increase vascular tone. The use of these potent agents is largely confined to critically ill patients with profound haemodynamic impairment such that tissue blood flow is not sufficient to meet metabolic requirements. Examples include patients with severe heart failure and septic or cardiogenic shock, as well as patients undergoing major surgery and victims of major trauma. They are generally administered via a large central vein and, in some specific situations, via a peripheral vein. These agents have a diverse range of actions including metabolic and immune effects, many of which are poorly understood. The objective of this review is to describe the underlying cardiovascular mechanisms that clinicians seek to influence through the use of inotropic agents, to describe the basic pharmacology of those drugs in common use and, finally, to explore the evidence base for specific approaches to inotrope and vasopressor therapy in clinical practice. As many of the commonly used agents exert both inotropic and vasopressor effects, the term 'inotrope' will be generally used in this review to describe agents with a spectrum of actions. The physiological basis for the actions of inotropic agentsMyocyte excitation and contraction. Cardiac muscle fibres contract through the sliding filament mechanism. Actin and myosin filaments are propelled past each other through repeated cross-bridge linking and unlinking. Each cardiac action potential results in the opening of voltage-gated myocyte calcium channels and a rise in intracellular calcium concentration ([Ca 2+ ]i). This triggers a further release of calcium from the sarcoplasmic reticulum, which accounts for around three quarters of the total increase in [Ca 2+ ]i (Levick, 2003...

Inotropes and vasopressors

“…Other relevant receptors are dopaminergic receptors (DA) and vasopressin receptors. There are five types of DA which are divided into two groups, DA1 and DA2 receptors (1,5,7). Both groups are G-protein related receptors.…”

“…Both of those are further divided into subtypes (1,5). α1 receptors are mostly found in blood vessels and their activation is mainly responsible for vasoconstriction.…”

“…Inotropes are agents used to increase myocardial contractility, while vasopressors are administered to increase vascular tone (1). Their use ismostly confined to critically ill patients whose hemodynamic impairment is such that tissue perfusion is insufficient to meet metabolic requirements (2).…”

Experience using high-dose glucose-insulin-potassium (GIK) in critically ill patients

“…Once stabilised, the frequency of monitoring could be reduced. When stopping the GIK infusion, insulin should be reduced to half its previous infusion rate at [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] hourly intervals.…”

“…Other options for treating low cardiac output states include phosphodiesterase inhibitors such as enoximone or calcium sensitizers such as levosimendan. Both agents can sometimes cause excessive vasodilation [8], while phosphodiesterase inhibitors have been associated with worse outcomes [9,10].…”