Welcome to UH EMS-I’s Pharmacy Phriday. In this installment, we will review the use of racemic epinephrine for cases of respiratory distress caused by upper airway diseases. We will also review the alternative treatment listed in the UH Protocols when racemic epi is not available.
Racemic epi is a medication that is slightly different chemically from the epinephrine we carry for IV, IO, or IM administration, and is thus often referred to as an isomer of epinephrine. This medication is typically provided in our UH drug boxes for the treatment of upper airway diseases, such as croup. It is significantly more concentrated than other epinephrine concentrations we carry. The medication is typically provided as a single unit dose of 0.5 ml of a 2.25% concentration. The 2.25% concentration equals 22.5 mg/ml. With the 0.5 ml dose, the provider is administering a dose of 11.25 mg. It is indicated for nebulized administration to the pediatric patient in cases of moderate to severe upper airway distress, with croup being the most common. It is also indicated in the adult protocols for respiratory distress caused by asthma or chronic obstructive pulmonary disease, and if the patient has severe distress along with stridor.
As you may recall, croup is a common childhood viral illness characterized by a barky cough, stridor, hoarseness, and respiratory distress. Children with severe croup have a high risk of needing intubation, so early treatment is essential. Croup causes upper airway obstruction through edema of the upper airway. Nebulized epinephrine, via its Alpha effect of vasoconstriction, reduces edema associated with the disease process. Epinephrine also has a Beta-2 effect of smooth muscle relaxation that is beneficial in these cases. The result of the racemic epinephrine nebulizer should be decreased edema and bronchospasm.
Differentiating upper and lower airway obstruction and understanding the actions of inhaled medications are fundamental in the treatment of these emergencies. Albuterol, often used for lower airway disease, has no real effect on the upper airway swelling and thus is an ineffective treatment. In fact, its Beta effect could potentially cause vasodilation and theoretically worsen upper airway edema.
UH protocols refer to two distinct differences that can assist in determining which protocol to follow. Stridor and/or the “seal bark cough” is often related to an upper airway obstruction, and in cases of moderate to severe distress, can be present even at rest. Racemic epi is the treatment of choice in these cases following initial assessment, airway control, and oxygen. When one encounters wheezing, the provider is directed to the “Respiratory Distress Lower Airway” protocol, which indicates the use of albuterol or a DuoNeb.
When administering racemic epi, the provider is directed to administer the 0.5 ml dose of the 2.25% concentration, mixed in 3 ml of normal saline via the nebulizer. The medication is administered only once and is not repeated in the prehospital setting. Side effects may include tachycardia, agitation, and hypertension, so the patient should be monitored carefully. This is also a reason the provider is cautioned about its use with the geriatric or cardiac patient.
A precaution that is sometimes mentioned with the use of racemic epi is the phenomenon of “rebound worsening” after the initial administration. Literature seems to suggest this is a rare event and is more likely a “re-emergence” of symptoms as the medication’s effects wear off (the duration being about 1-3 hours normally). It is also suggested that the re-emergence is less pronounced in patients who have had steroids administered as well, which are also indicated within our protocols (see methylprednisolone in your protocol pharmacy section).
In cases of shortages of the racemic epi, an acceptable alternative can include the nebulized treatment with the 1 mg/ml epinephrine (0.1%) carried in our drug boxes. The dosing in those cases would be 3 ml of the 1 mg/ml concentration for a pediatric patient less than 10 kg, or 5 ml for the pediatric patient greater than 10 kg. The 5 ml dose is also the appropriate dose for the adult patient. These doses would not be diluted before administration.
Remember: In cases when the patient does not respond to these treatments, symptoms return, or symptoms worsen, and the patient exhibits signs of respiratory failure, the provider must be prepared to assist ventilations with a BVM.
As always, stay safe!
Sincerely,
The UH EMS-I Team
University Hospitals
Download a PDF of this email HERE.