From the Guidelines
Phenylephrine is the recommended vasopressor starting with P for reversing ischemia. It is typically administered as an intravenous infusion starting at 0.5–2.0 mcg/kg/min, as indicated in the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1. Phenylephrine works as a pure alpha-1 adrenergic receptor agonist, causing peripheral vasoconstriction without direct cardiac effects, which increases systemic vascular resistance and blood pressure. This mechanism helps improve perfusion pressure to ischemic tissues without increasing heart rate or myocardial oxygen demand, making it particularly useful in scenarios where tachycardia would be detrimental. Some key points to consider when using phenylephrine include:
- Monitoring for reflex bradycardia, excessive hypertension, and reduced cardiac output
- Using it cautiously in patients with severe hypertension, ventricular tachyarrhythmias, or when increased afterload might worsen cardiac function
- Being aware of its typical starting dose and titration range, as outlined in the guidelines 1 Overall, phenylephrine's profile makes it a suitable choice for managing ischemia by improving blood pressure and perfusion to critical tissues, as supported by the guidelines 1.
From the FDA Drug Label
Phenylephrine hydrochloride Injection is an alpha-1 adrenergic receptor agonist indicated for the treatment of clinically important hypotension resulting primarily from vasodilation in the setting of anesthesia Phenylephrine hydrochloride injection can cause excessive peripheral and visceral vasoconstriction and ischemia to vital organs.
The recommended vasopressor starting with P for reversing ischemia is Phenylephrine. However, it is essential to note that phenylephrine can cause excessive peripheral and visceral vasoconstriction and ischemia to vital organs, which may exacerbate ischemia in some cases.
- Key considerations: Correct intravascular volume depletion and acidosis before administration, as acidosis may reduce the effectiveness of phenylephrine.
- Dosage: The recommended initial dose is 40 to 100 mcg administered by intravenous bolus, with additional boluses every 1-2 minutes as needed, not to exceed a total dosage of 200 mcg. For continuous intravenous infusion, the recommended rate is 10 to 35 mcg/minute, titrating to effect, not to exceed 200 mcg/minute 2 2.
From the Research
Vasopressor Ischemia Reversal Agent Starting with P
- Phenylephrine is a selective alpha(1) adrenergic receptor agonist that increases arterial blood pressure by peripheral vasoconstriction 3
- It has been shown to ameliorate cerebral cytotoxic edema and reduce cerebral infarction volume in a rat model of complete unilateral carotid artery occlusion with severe hypotension 3
- Phenylephrine may be a rational pharmacologic choice in specific instances such as critical aortic stenosis, tetralogy of Fallot, and hypotension during cesarean delivery 4
- The use of phenylephrine before ischemia is protective and similar to that obtained with ischemic preconditioning 5
- Phenylephrine, mediated by alpha-1 agonism, significantly improves postischemic left ventricular dysfunction without worsening the overall myocardial metabolic state 6
Key Findings
- Phenylephrine increases arterial blood pressure and improves cerebral blood flow 3
- It reduces cerebral infarction volume and ameliorates cytotoxic edema 3
- Phenylephrine may be beneficial in specific clinical settings such as critical aortic stenosis and tetralogy of Fallot 4
- The timing of phenylephrine administration is crucial, with pre-ischemic administration being protective 5
- Phenylephrine improves postischemic left ventricular dysfunction and cardiac efficiency 6