Individuals at risk of anaphylaxis are often prescribed adrenaline (epinephrine) autoinjectors such as EpiPens. A recent review published in Clinical & Experimental Allergy finds that these autoinjectors, which people use to self-administer adrenaline into the muscle, can deliver high doses of adrenaline into the blood, but these levels are short-lived and may not be sufficient to save lives in cases of fatal anaphylaxis.
Anaphylaxis is an acute systemic hypersensitivity reaction to an allergen or trigger, typically associated with skin reactions, nausea/vomiting, difficulty breathing, and shock.
Investigators noted that data from animal and human studies suggest that intravenous adrenaline infusions delivered directly into the blood can prevent fatal anaphylaxis, but adrenaline autoinjectors may have little impact in such deadly cases.
“For effective management of the most severe allergic reactions, adrenaline given by continuous intravenous infusion, with appropriate fluid resuscitation, is likely to be required—how this is safely achieved in the pre-hospital setting remains to be determined,” the authors wrote. This challenge stems from the fact that fatal anaphylaxis is unpredictable and fast. Fortunately, fatality is rare, with a population incidence of 0.03–0.51 per million per year.
Earlier adrenaline treatment during a cardiac arrest is linked to better recovery compared to later treatment, according to preliminary research to be presented at the American Heart Association’s Resuscitation Science Symposium (ReSS) 2021.
“Our study’s findings should guide emergency medical services professionals towards earlier administration of epinephrine [adrenaline] during out-of-hospital cardiac arrest management,” said lead study author Shengyuan Luo, MD, MHS, an internal medicine resident physician at Rush University Medical Center in Chicago.
Previous research found that only about 1 in 5 people survive a cardiac arrest outside of the hospital and those who do survive often have long-term impairment in the ability to perform daily living tasks.
During a cardiac arrest, immediate CPR (cardiopulmonary resuscitation) is critical. For some types of cardiac arrest, an AED (automated external defibrillator) also is used to deliver an electric shock through the chest to the heart to restore a heartbeat. For these ‘shockable’ cardiac arrests, adrenalineis injected to help restore blood flow. Previous research indicated that adrenaline should be given after three unsuccessful electric shocks with an AED, however, it was unclear whether it should be given even earlier – such as after the first electric shock.
To compare the effects of earlier versus later administration of adrenaline, the researchers examined medical records to compare epinephrine timing to patient recovery. Study subjects included 6416 multi-ethnic adults across North America who had an out of hospital cardiac arrest with shockable initial rhythm from 2011-2015. They were an average age of 64 years, and most were men.
Overall, adrenaline administration within four minutes after the first shock from an AED was associated with greater chances of recovery, while administration after four minutes was associated with reduced chances. Specifically, people who received adrenaline after four minutes were nearly half as likely to have heartbeat and blood flow restored before hospital admittance and half as likely to survive to hospital discharge or be able to perform daily tasks, as measured by a standard test, at discharge. Additionally, the risks of later adrenaline treatment rose with each minute of delayed treatment.
“It is crucial that whenever a cardiac arrest event is suspected, the emergency medical system be notified and activated immediately, so that people with cardiac arrest receive timely, life-saving medical care,” Dr Luo said.
These findings support the latest American Heart Association CPR and Emergency Cardiovascular Care Guidelines, which were released in October 2020. The guidelines indicate adrenaline should be administered as early as possible to maximise good resuscitation outcome chances. The guideline recommendation was based on previous observational data that suggest better outcomes when adrenaline is given sooner.
