From the Guidelines
Phenylephrine (Neosinephrine) should be administered intravenously at a dose of 0.5–2.0 mcg/kg/min, as indicated in the most recent guidelines 1. This dosing is recommended for treating severe hypotension, particularly when a low total peripheral resistance is present.
- The medication works as a pure alpha-1 adrenergic receptor agonist, causing peripheral vasoconstriction, which increases systemic vascular resistance and blood pressure.
- It has minimal beta effects, making it particularly useful when tachycardia is undesirable.
- When administering phenylephrine, blood pressure should be monitored continuously, and the dose should be adjusted based on patient response.
- Caution is warranted in patients with severe hypertension, ventricular tachycardia, or hyperthyroidism, and the drug should be used carefully in patients with coronary artery disease as it may reduce cardiac output.
- According to the Surviving Sepsis Campaign guidelines 1, phenylephrine is not the first-line treatment for septic shock, but it may be considered in specific circumstances, such as when norepinephrine is associated with serious arrhythmias or when cardiac output is high and blood pressure is persistently low.
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 dosing for phenylephrine (a possible alternative to neosinephrine) in treating 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 Both should be titrated to effect 2
From the Research
Neosinephrine Dosing for Hypotension
The recommended dosing for phenylephrine (neosinephrine) in treating hypotension is not directly addressed in the provided studies, as they primarily focus on the use of norepinephrine and epinephrine in various clinical settings. However, some studies provide information on the use of phenylephrine:
- A scoping review 3 mentions the use of push-dose phenylephrine as a common practice among anesthesiologists, but it does not provide specific dosing recommendations.
- There is no direct evidence in the provided studies to support the use of neosinephrine (phenylephrine) for hypotension, and the studies primarily focus on norepinephrine and epinephrine.
Alternative Vasopressors
The studies provide information on the dosing of alternative vasopressors, such as norepinephrine:
- A randomized controlled trial 4 compared three infusion rates of norepinephrine (0.025 μg · kg(-1) · min(-1), 0.050 μg · kg(-1) · min(-1), and 0.075 μg · kg(-1) · min(-1)) for prophylaxis against postspinal hypotension during cesarean delivery.
- A pilot randomized controlled trial 5 used a peripheral low-concentration (10 µg/mL) norepinephrine infusion to prevent hypotension during major noncardiac surgery.
- A study 6 used iv infused norepinephrine (0.5 to 1 microgram/kg X min) to treat hyperdynamic vasodilated septic patients who remained hypotensive despite iv volume expansion and antimicrobial and dopamine therapy.
Key Findings
Some key findings from the studies include:
- Norepinephrine was found to be safe and effective in various clinical settings, including septic shock 6 and postspinal hypotension during cesarean delivery 4.
- The use of push-dose norepinephrine was found to be safe and effective, with favorable hemodynamic markers compared to other agents 3.
- The optimal dose of norepinephrine for prophylaxis against postspinal hypotension during cesarean delivery was found to be 0.050 μg · kg(-1) · min(-1) or 0.075 μg · kg(-1) · min(-1) 4.