The use of bolus-dose vasopressors in anesthesiology and other areas of critical care medicine is well known. This common medical intervention, however, is not often employed in emergency medicine (EM). Bolus-dose vasopressors are defined as the administration of small bolus doses of vasopressor agents, such as epinephrine or phenylephrine, to patients with compromised perfusion who continue to have a pulse (ie, these patients are not in cardiac arrest). This intervention is considered as a temporizing measure for transient hypotension or as a bridge to more definitive therapy.
Bolus-dose vasopressive therapy is also referred to as push-dose pressor (PDP) therapy—a term coined by Weingart.1-3 Theoretically, any vasopressor could be used in a mini-dose, bolus fashion, though in current clinical practice, anesthesiologists primarily employ ephedrine, epinephrine, and phenylephrine. Two of these agents are likely more appropriate for the ED, including epinephrine and phenylephrine. Both of these agents have a short half-life and therefore an abbreviated period of effect. In addition, dosing and related administration of epinephrine and phenylephrine is relatively straightforward. Moreover, most emergency physicians and nurses are quite familiar with both agents.
With respect to ephedrine, due to its longer half-life, complex dosing regimen, and associated higher-incidence of cardiovascular (CV) complications, its use is likely not appropriate in the ED as a bolus-dose vasopressor.
Epinephrine and Phenylephrine
Epinephrine is a potent sympathomimetic agent with alpha- and beta-receptor activity. In addition to its vasopressor effects, epinephrine is also an inotropic and chronotropic agent, increasing cardiac output, heart rate (HR), and systemic vascular resistance, which can markedly improve perfusion. Epinephrine also can be given to patients with hypoperfusion and/or shock due to low-cardiac output with or without vasodilation, lacking significant tachycardia.
Phenylephrine is a pure alpha agonist and therefore does not appreciably affect cardiac output and HR, but does significantly increase systemic vascular resistance and thus systemic perfusion. Phenylephrine can be used to treat patients with hypoperfusion and/or shock states due to vasodilation with coexistent, significant tachycardia.
Preparation and Administration
The preparation and dosing of push-dose epinephrine and phenylephrine are not particularly complex. Many clinicians recommend the pre-mixed, manufacturer-prepared agents for PDP therapy. These premixed formulations not only facilitate administration, but also reduce the chance of a preparation error that can result in incorrect dosing.3-5 If pre-mixed formulations are not available, clinicians can readily prepare epinephrine and phenylephrine for PDP use.
Push-Dose Epinephrine. Clinicians can prepare epinephrine for push-dose administration as follows:1-3
- Obtain 1 mL of epinephrine 1:10,000 (ie, 0.1 mg/mL or 100 mcg/mL);
- Obtain a 10 mL syringe of normal saline and remove 1 mL;
- Inject the 1 mL of epinephrine 1:10,000 (100 mcg/mL) into this syringe containing 9 mL of normal saline; and
- Result: 10 mL of epinephrine (10 mcg/mL), with each 1 mL of this solution containing 10 mcg of epinephrine.
Administration of push-dose epinephrine (10 mcg/mL) produces effect within 1 minute of use with a duration of approximately 5 to 10 minutes. Dosing at this concentration ranges from 0.5 to 2.0 mL every 2 to 5 minutes, delivering 5 to 20 mcg.1-3Push-Dose Phenylephrine. To prepare phenylephrine for push-dose administration, clinicians may use the following approach:1-3
- Obtain 1 mL of phenylephrine (10 mg/mL concentration);
- Inject this 1 mL of phenylephrine (10 mg/mL) into a 100 mL bag of normal saline; and
- Result: 100 mL of phenylephrine (100 mcg/mL), with each 1 mL of this solution containing 100 mcg of phenylephrine.
Administration of push-dose phenylephrine (100 mcg/mL) produces effect within 1 minute of use with a duration of approximately 10 to 20 minutes. Dosing at this concentration ranges from 0.5 to 2.0 mL every 2 to 5 minutes, delivering 50 to 200 mcg.1-3Alternative Push-Dose Preparations for Phenylephrine. Two other methods of preparing phenylephrine for bolus-dose administration include the following: (1) the addition of phenylephrine 20 mg to a bag of 250 cc of normal saline, resulting in an 80 mcg/mL concentration; and/or (2) phenylephrine (20 mg) is commercially available for continuous infusion in a 250 mL bag of normal saline, yielding the same concentration of 80 mcg/mL; in either case, medication can be drawn up and administered. Dosing at this concentration ranges from 0.5 to 2.5 mL every 2 to 5 minutes, delivering 40 to 200 mcg. Lastly, phenylephrine is also commercially available in pre-made mixtures, specifically manufactured for bolus-dose therapy.