Phenylephrine (Neosynephrine)
Anesthesia Implications
Therapeutic Effects: Raises blood pressure/treats hypotension
Anesthesia Implications
Used as one of the first-line treatments of intraoperative hypotension. Often causes a baroreceptor reflex (which can lead to bradycardia). For this reason, if the patient has bradycardia, an agent such as ephedrine would be considered. Avoided in patients having flap/skin surgery as it reduces perfusion to the new flap. Use is rare with pediatric patients.
Phenylephrine is just as effective as ephredrine at maintaining placental perfusion. Recent evidence suggests that infants had less acidosis when the mothers hypotension was treated with phenylephrine (versus ephedrine).
Contraindications
Bradycardia, pheochromocytoma, hypertension,
IV push dose
40 – 100 mcg is the typical starting dose. Needs to be titrated to effect. This drug usually comes in a 10 mg vial and has to be diluted. Typical dilution is as follows for the 10mg (1ml) vial:
Add the contents of the vial to a 100ml saline bag to dilute to 100 mcg/ml.
Add the contents of the vial to a 250ml saline bag to dilute to 40 mcg/ml.
Peds: 0.5-10 mcg/kg (rare use)
IV infusion dose
40-80 mcg/min START, titrated to effect. 100-200 mcg/min is the higher end of the spectrum. Peds: 0.1-0.5 mcg/kg/min (rare use)
Classification: Alpha-1 agonist, Vasopressor, Sympathomimetic
Time to Onset: 30-60 seconds
Time to Peak: 1-2 minutes
Duration: 15-20 minutes
Method of Action: Vasoconstrictor of both arterial and venous blood vessels
Metabolism: Hepatic
Barash. Clinical anesthesia. 7th edition. 2013.
Nagelhout. Nurse anesthesia. 5th edition. 2014.