II. Indications: Hypotension (intravenous)
- Emergency Resuscitation for cardiovascular collapse while performing other interventions
- Example: Septic Shock refractory to fluid Resuscitation, temporizing while obtaining central access
- Can be used via peripheral IV for hours until central access is available for other Vasopressors (e.g. Norepinephrine)
-
Conscious Sedation
- Commonly used by anesthesiology for Hypotension secondary to Propofol and other agents
III. Contraindications
- Severe Coronary Artery Disease (or other severe Cardiomyopathy)
IV. Mechanism: Intravenous
- Direct selective alpha-Adrenergic Agonist
-
Push Dose Pressor (Bolus Phenylephrine)
- Vasopressor without direct inotropic (contractility) or chronotropic (Heart Rate) activity
- Increases cardiac perfusion via Vasoconstriction and secondary increase in venous return
V. Pharmacokinetics: Intravenous
- Onset: 1 minute
- Duration: 10-20 minutes
VI. Adverse Effects: Intravenous
- Local infiltration effects (extravasation)
- Risk of tissue ischemia, necrosis and gangrene
- Less local toxicity to tissue and vascular structures compared with other pressors
- Reflex Bradycardia
- Unlikely to occur during cardiovascular collapse in which adrenergic response is expected to be strong
- Baroreceptor reflex to increasing BP is typically outweighed by a stronger adrenergic response
VII. Medications: Intravenous
- See Push Dose Pressor
- Precautions
- Limit Push Dose Pressors to emergency use
- Mixing errors are common (Exercise caution)
- When adequate time is available, pharmacy prepared solutions are preferred
- Push Dose Pressors are a temporizing measure to stabilize Hypotension
- In some cases, Push Dose Pressor alone may be sufficient (e.g. Propofol induced Hypotension)
- Prepare for Vasopressor infusion (e.g. Norepinephrine, Epinephrine) if expected persistent Hypotension
- Preparation
- Dilute 1 ml (10 mg) from Phenylephrine vial (10 mg/ml) in Normal Saline 100 ml bag
- Resulting solution: Phenylephrine 100 mcg/ml
- Draw solution into labeled syringe for use as Push Dose Pressor
VIII. Dosing: Adult
- Phenylephrine IV bolus
- Bolus (100 mcg/ml) 50 to 200 mcg (0.5 to 2 ml) IV bolus as needed every 10 to 15 min
- May initially be needed every 2-5 minutes in severe Hypotension
- Phenylephrine IV Infusion
- Prepare 20 mg Phenylephrine in 250 ml D5W (80 mcg/L)
- Start 100 to 180 mcg/min (75 to 135 ml/h)
- Maintain typically at 40 to 60 mcg/min
IX. Dosing: Child (off label)
- Phenylephrine IV bolus
- Bolus (100 mcg/ml) 5 to 20 mcg/kg IV bolus as needed every 10 to 15 min
- Phenylephrine IV Infusion
- Prepare 20 mg Phenylephrine in 250 ml D5W (80 mcg/L)
- Infuse 0.1 to 0.5 mcg/kg/min IV, titrating to target Blood Pressure and perfusion
X. Resources
- EM-Crit Blog (Scott Weingart)
- Phenylephrine Injection Solution (DailyMed)
XI. References
- Hamilton (2020) Tarascon Pharmacopoeia, Jones and Bartlett, Boston
- Mattu and Weingart in Majoewsky (2013) EM:Rap 13(4): 9-10
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