Cardiovascular System

The understanding of how the heart works is fundamental for our intensivist to provide cardiovascular support. 

Inotropes are pharmalogical agents that increase force of ventricular contraction, usually ß-effect

Vasopressor constricts blood vessels, α-effect.

Chronotrope increases heart rate, ß-effect.

Adrenaline

• both α and ß-effect.
• inotope, vasopressor and chronotrope
• ß2 effect at low doses causing vasodilatation in skeletal muscle thus lowering SVR.
• α-vasoconstrictor effect at higher doses will increase SVR and myocardial oxygen demands, with adverse effect on cardiac output.

Noradrenaline

• α-effect, vasopressor
• indicate din septic shock when hypotension is due because of massive peripheral vasodilatation which will persist despite fluid/volume resuscitation.

Dobutamine

• ß1 and ß2 effect. 
• Inotrope, vasodilator
• ß1 effect increases heart rate and force of contraction
• ß2 causes mild vasodilatation
• This is the first choice of inotropes in cardiogenic shock due to left ventricular dysfunction.
• Dobutamine and low dose dopamine in conjunction used in cardiogenic shock to increase blood pressure by increasing cardiac contractility and urinary output (UO). This will increase renal perfusion.