Indications for Pressor and Why

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Indications for Pressor and Why?

• Taimur Khan

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Vasopressors

• Dopamine
• Norepinephrine
• Phenylephrine
• Epinephrine
• Dobutamine
• Amrinone/Milrinone

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Dopamine

• At low doses dopamine receptor activation and
  renal, mesenteric, cerebral circulations
  increased dose usually set at 3 µg/kg/min
• At doses between 4-7 µg/kg/min, ß stimulation and
  augmentattion of cardiac output occurs
• At doses above 8 µg/kg/min, progressive
  vasoconstriction is dominant feature
• Pressor effects are milder as compared to
  Norepinephrine and Phenylephrine, can be
  initially used for pressure support but if no
  response present switch to more potent pressors

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Norepinephrine

• Mainly an a receptor agonist theat promotes
  widespread vasoconstriction
• In cases of hypotension refractory to dopamine,
  it can be added as a second agent
• Dose dependent increase in SVR, and also can
  stimulate ß receptors, thus causing tachycardia
• Cardiac output increased only at low doses
• Range of dose 2-12 µg/min usual dosage rate 2-4
  µg/min

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Phenylephrine

• Primarily a- receptor agonist and causing
  peripheral vasoconstriction
• Some ß effects can occur at higher doses
• Primary effects, include peripheral
  vasoconstriction with resultant increase in
  diastolic and systolic blood pressures, small
  decreases in cardiac output and an increase in
  circulation time. A reflex bradycardia can occur
• May be a good choice when tachyarrhythmias limit
  therapy with other vasopressors.

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Epinephrine

• Primarily ß receptor agonist at low doses and an
  a receptor agonist at high dose
• Vasopressor range 0.01 0.1 µg/kg/min
• Uses include cardiac arrest associated with
  pulseless ventricular tachycardia and ventricular
  fibrillation, aystole and pulseless electrical
  activity
• Not recommended as first line agent for routine
  management of low cardiac output or circulatory
  shock

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Dobutamine

• Primarily a ß1- receptor agonist (cardiac
  stimulation), but also a mild ß-2 effect
  (vasodialtrion)
• Dose dependent increase in Stroke volume (SV),
  accompanied by decrease in cardiac filling
  pressures
• Increase in SV also accompained with decrease in
  systemic vascular resistance (SVR) (baroreceptor
  medicated) thus arterial BP remains unchanged.
• Effective on both right and left sided heart
  failure
• Dosage can range from 5-15 µg/kg/min. Between 4-7
  µg/kg/min, ß receptor stimulation and
  augmentation of cardiac output occurs
• Not indicated for monotherapy in patients with
  cardiogenic shock

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Amrinone/Milrinone

• Phosphodiestrase inhibitor that has both positive
  ionotropic and vasodilator actions
• Combined actions of amrinone produce and increase
  in cardiac stroke output without increase in
  cardiac stoke work
• Unlike dobutamine, the actions are not attenuated
  by ß receptor antagonists
• Can be effective as single agent for low output
  states due to systolic hear failure however
  mostly used as a second agent that is added to
  dobutamine in cases of refractory heart failure