Vasopressors

Question 1

Norepinephrine

Mechanism?

Physiological effect?

Starting dose?

Dose range?

Answer 1

Strong alpha-1 agonist, weak beta-1 agonist

Increases SVR/venoconstriction (preload)

0. 1mcg/kg/min
1. 01-1mcg/kg/min

Question 2

Adrenaline/Epinephrine
Mechanism?

Physical effects (3)

Effect on lactate?

Starting dose?

Dose range?

Answer 2

Alpha-1 agonist (high doses) , beta-1 agonist (low doses)

Increases chronotropy/inotropy

Increases SVR/venoconstriction (preload)

Stabilises mast cells

Beta-2 agonism causes aerobic lactate production in the liver

0. 05mcg/kg/min
1. 01-1mcg/kg/min

Question 3

Vasopressin

Mechanism?

Physical effects?

Dose?

Answer 3

Stimulates V1 and V2 receptors, causing vasoconstriction and renal water retention.

Increases SVR/venoconstriction. Can reduce cardiac output. May preferentially cause vasoconstriction of efferent arteriole improving renal function.

0.1-0.06 units/min

Question 4

Phenylephrine

Mechanism?

Physiologic effect?

Common side effect?

Strength relative to norad?

Dose?

Answer 4

Pure alpha-agonist, causes arterial and venous vasoconstriction.

Increase SVR/venocontriction (preload). Will increase CO if preload responsive (not systolic HF)

Can cause reflex bradycardia (HR reduces to lower BP - BP =HRxSVxSVR)

Around 10x less potent than norad.

50-300mcg/kg/min

Question 5

Dobutamine

Mechanism?

Primary effect? Secondary effect?

Starting dose?

Dose range?

Answer 5

Mainly beta-1

Positive inotropy with positive chronotropy (increasing cardiac output). Secondary effect is peripheral vasodilation. Effect on BP is unpredictable.

Starting dose: 2.5 mcg/kg/min

1-10 mcg/kg/min