Racemic epinephrine is an inhaled medication used in specific medical emergencies involving significant swelling of the upper airway. It is a fast-acting treatment administered almost exclusively in a hospital or paramedic setting to rapidly relieve breathing difficulties. The primary purpose of this intervention is to provide temporary relief, allowing time for other medications, such as corticosteroids, to produce a more sustained effect.
Medical Uses for Racemic Epinephrine
The most common reason for administering racemic epinephrine is to treat moderate to severe croup. Croup is a viral infection that primarily affects young children, causing inflammation and swelling around the larynx (voice box) and trachea (windpipe). This swelling narrows the airway and leads to a distinctive “barking” cough, hoarseness, and a high-pitched, noisy breathing sound called stridor. In severe cases where a child has stridor even while calm, this medication is used to quickly reduce swelling and ease breathing distress.
It is also used to manage post-extubation stridor. This condition can occur in both children and adults after a breathing tube (endotracheal tube) is removed following a period of mechanical ventilation. The presence of the tube can irritate and inflame the upper airway tissues, leading to swelling and potential obstruction once it is taken out. Nebulized racemic epinephrine can be used to alleviate the swelling and prevent the need for re-intubation.
Mechanism of Action
Racemic epinephrine works by interacting with specific sites on cells called adrenergic receptors. Its main therapeutic benefit comes from stimulating alpha-adrenergic receptors located in the smooth muscle of blood vessels lining the upper airway. This stimulation causes the blood vessels to constrict, or tighten, which reduces local blood flow and fluid leakage into the surrounding tissues, directly decreasing the swelling that narrows the airway.
Simultaneously, the medication also stimulates beta-adrenergic receptors. This action primarily affects the lower airways, causing the smooth muscles of the bronchi to relax in a process called bronchodilation, which can further help improve overall airflow. The effects have a relatively short duration, typically lasting about one to two hours.
The Treatment Process
The administration of racemic epinephrine is done through a nebulizer, a device that converts the liquid medication into a fine mist. The patient breathes this mist in through a mask or mouthpiece over a period of about 10 to 15 minutes. Treatment is often combined with a steroid like dexamethasone, which has a longer-lasting anti-inflammatory effect.
As the epinephrine is absorbed from the lungs into the bloodstream, it can cause systemic side effects. Patients often experience an increased heart rate, and may feel jittery, anxious, or appear pale. Other possible side effects include headache, nausea, and tremors. Due to these effects, patients are monitored closely during and after treatment, sometimes with continuous cardiac monitoring.
Following treatment, a mandatory observation period is required. This period typically lasts between two and four hours to watch for a phenomenon known as the “rebound effect.” As the medication’s vasoconstrictive effects wear off, the airway swelling can return, sometimes becoming as severe as or worse than it was before treatment. Medical staff monitor the patient for any recurrence of stridor or breathing difficulty to determine if another dose is needed or if the patient can be safely discharged.