What is the recommended dose of phenylephrine (PE) for treating hypotension?

From the Guidelines

For the treatment of hypotension, phenylephrine should be administered at a typical starting dose of 0.5–2.0 mcg/kg/min, which translates to 35–140 mcg/min in a 70-kg adult, and then titrated to effect. This recommendation is based on the guidelines provided by the American Heart Association for cardiopulmonary resuscitation and emergency cardiovascular care 1. The use of phenylephrine is particularly indicated for severe hypotension, such as a systolic blood pressure of 70 mm Hg, and in cases of low total peripheral resistance.

Key Considerations for Phenylephrine Administration

• Phenylephrine works as a pure alpha-1 adrenergic receptor agonist, causing peripheral vasoconstriction and increasing systemic vascular resistance, which raises blood pressure without significant direct effects on heart rate or cardiac contractility.
• It is particularly useful for hypotension associated with vasodilation, such as in sepsis, anaphylaxis, or neurogenic shock, or during anesthesia.
• Monitor blood pressure frequently during administration and be aware that reflex bradycardia may occur due to the increase in blood pressure.
• The dose should be titrated based on the patient's blood pressure response, aiming to achieve an adequate blood pressure while minimizing potential side effects.

Comparison with Other Vasoactive Drugs

• Other vasoactive drugs like epinephrine, norepinephrine, dopamine, dobutamine, and milrinone have different indications and effects on the cardiovascular system, as outlined in the guidelines 1.
• The choice of drug should be based on the specific clinical scenario, including the underlying cause of hypotension, the presence of other hemodynamic abnormalities, and the patient's overall clinical condition.

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Dosing for Perioperative Hypotension • Intravenous bolus administration: 50 mcg to 250 mcg • Intravenous continuous infusion: 0.5 mcg/kg/minute to 1.4 mcg/kg/minute titrated to effect Dosing for Patients with Vasodilatory Shock • Intravenous continuous infusion: 0.5 mcg/kg/minute to 6 mcg/kg/minute titrated to effect

The recommended dose of phenylephrine for hypotension is:

• Intravenous bolus administration: 50 mcg to 250 mcg
• Intravenous continuous infusion:
  • For perioperative hypotension: 0.5 mcg/kg/minute to 1.4 mcg/kg/minute
  • For vasodilatory shock: 0.5 mcg/kg/minute to 6 mcg/kg/minute, titrated to effect 2

From the Research

Phenylephrine Dose for Hypotension

• The ideal dose of phenylephrine for hypotension is not explicitly stated in the provided studies, but its efficacy in treating peri-intubation hypotension is discussed in 3.
• According to 3, bolus-dose phenylephrine was effective in increasing systolic and diastolic blood pressure in hypotensive patients during the peri-intubation period.
• However, the study also notes that the use of phenylephrine was not systematic, and its timing varied greatly, which may lead to inadvertent negative effects.
• In contrast, 4 mentions that other vasopressor drugs such as epinephrine and phenylephrine may be similar in efficacy to noradrenaline, but experience and available data with their use are limited.
• 5 classifies phenylephrine as a pure vasoconstrictor and notes that it can be used to increase mean arterial pressure by augmenting vascular tone.

Comparison with Other Vasopressors

• 4 suggests that noradrenaline is a safe and effective choice for treating hypotensive vasodilatation, and that the addition of other vasopressors such as vasopressin may be helpful in individual patients.
• 6 compares the use of epinephrine and norepinephrine in cardiac arrest patients with post-resuscitation shock, and finds that norepinephrine is associated with lower mortality rates.
• 5 notes that norepinephrine may be preferred as a first-line therapy for a broad range of shock states, including septic shock.