Push-Dose Pressors

General Info/Intro

Vasopressors are medications well known to the critical care and emergency medicine communities. Useful for raising blood pressure and cardiac contractility and therefore improving cardiac output and tissue perfusion, they are used in the treatment of severe sepsis and other forms of shock. In treating shock, continuous infusions of these medications are required, and when refractory, multiple and/or large doses of vasopressors may be necessary. Due to the vasoactive properties of these drugs, they can only be safely delivered through a central line. However, if a patient’s hypotension is expected to be transient, placing a central line and starting an infusion of vasopressors may be undesirable and unnecessary.

In the field of anesthesiology, there currently exists a large amount of literature supporting the use of bolus-dose, or push-dose, pressors in the operating room. Most of the literature examines boluses of ephedrine and phenylephrine to reverse or prevent transient and recurrent hypotension induced by spinal anesthesia during caesarean delivery.^1,2,3,4 The literature generally shows excellent response in patients with regard to improvement in blood pressure and prevention of hypotension when used prophylactically.

Despite the multitude of studies, the excellent results, and the commonplace use by anesthesiologists for decades, the use of push-dose pressors has not yet made its way into standard emergency medicine practice. There currently are no studies that show the benefit of push-dose pressors in the emergency department. However, Scott Weingart, MD, an emergency department intensivist, advocates for their use in the ED.⁵

Recap Basics

Indications for push-dose pressors include transient hypotension — when the clinician anticipates that the patient’s blood pressure will improve if given some time — but the current blood pressure is dangerously low, as may occur post-intubation or during procedural sedation. Another indication is as a temporizing measure until a central line can be placed, infusion vasopressors can be mixed up and received, or patient adequately resuscitated with crystalloid fluids.

How to Prepare Push Doses of Vasopressors

Epinephrine

• Obtain a 10 mL syringe and fill it with 9 mL of sterile normal saline
• Into the syringe, draw up 1 mL of epinephrine 1:10,000 (from a cardiac arrest amp)
• Concentration of epinephrine 1:10,000 is 100 mcg/mL (or 1 mg in 10 mLs, which is one amp)
• The concentration of epinephrine in the syringe is now 1:100,000, or 10 mcg/mL

Dose: 0.5-2 mL every 2-5 minutes (5-20 mcg). This is equivalent to dose of epinephrine given via infusion (5-20 mcg/min).
Onset: 1 minute
Duration: 5-10 minutes

• Epinephrine has both α- and β-adrenergic activity and will therefore stimulate the heart in addition to causing vasoconstriction. Consider phenylephrine if patient has significant tachycardia or any tachyarrhythmia.

Phenylephrine

• Draw up 1 mL of phenylephrine from a vial (contains 10 mg/mL) into a 3 mL syringe
• Inject this into a 100 mL bag of normal saline; bag now contains 100 mcg/mL of phenylephrine
• Draw up 10 mLs of this solution into 10 mL syringe

Dose: 0.5-2 mL every 2-5 minutes (50-200 mcg). This is equivalent to dose of phenylephrine given via infusion (50-200 mcg/min).
Onset: 1 minute
Duration: 5-10 minutes

• Phenylephrine solely has α-adrenergic activity and therefore has no effect on the heart. Use when patient is tachycardic. May cause reflex increase in parasympathetic tone and therefore cause a decrease in heart rate.

Bottom Line/Pearls & Pitfalls

• Ensure you use the correct dosage of epinephrine.
• Do not bolus cardiac arrest doses of epinephrine (1:10,000) unless the patient is pulseless.
• The concentration of push-dose epinephrine, properly mixed up, will be the same as that contained in lidocaine preparations used in local analgesics — 1:100,000. Knowing this, if the push-dose epinephrine were to extravasate, it would be equivalent to injecting 0.5-2 mL of lidocaine with epinephrine subcutaneously.

Further Reading