Monday August 10, 2009
Quick and Dirty on Vasopressors and Inotropes



Vasopressor activity on the following receptors are agonistic:

• a1 receptors-- peripheral arteries-- peripheral vasoconstriction
• b1 receptors-- coronary smooth muscle-- increased heart rate and contractility
• b2 receptors—smooth muscle—increases force of contractility in the heart
• DA1 receptors-- renal, mesenteric, and coronary beds-- vasodilation and increase urine output.
• V1, receptors-- vascular smooth muscle--vasopressor;
• V2 receptors-- renal collecting duct system--natural diurectic
  

Vasopressors:

• Dopamine: receptor action is dependent on dose… DA1 1-5 microgram/kg/min + HR; b1 5-10 microgram/kg/min, ++ HR, + MAP, + CO; a1 > 10 microgram/kg/min + SVR, + MAP, + HR, +CO
• Epinephrine: b1 >> a1 1-20 microgram/min ++ SVR, +MAP, +HR, +CO
• Norepinephrine: a1 > b1 1-80 microgram/min, ++ SVR, ++MAP , ?+HR, ?+CO
• Phenylephrine: a1 2-200 micrograms/min; ++SVR, +MAP, ?+HR, ?+ CO
• Vasopressin: V1 V2 0.04 units/min ++SVR, +MAP, ?+HR, ? +CO
  
  

Inotropes:

• Dobutamine: b1, b2 2-20 microgram/kg/min ááCO áHR âSVR ?âMAP
• Milrinone: PDE inhibitor in vascular and cardiac smooth muscle which improves calcium handling causing dilation. In cardiac muscle, the inhibition of phosphodiesterase results in increased levels of cAMP, resulting in increased chronotropic and inotropic effects.
  

Reference:

Dellinger RP. Crit Care Med 2008;36(1):296