From the Guidelines
In patients with hypertrophic obstructive cardiomyopathy (HOCM), the standard adrenaline (epinephrine) dose for anaphylaxis should be reduced to 0.3mg of 1:10,000 concentration (0.3mL of 1:1,000) administered intramuscularly. This modified dosing is crucial because HOCM patients have increased sensitivity to catecholamines due to their cardiac pathophysiology, as noted in the guidelines for anaphylaxis management 1. Standard anaphylaxis doses could potentially worsen left ventricular outflow tract obstruction, trigger dangerous arrhythmias, or cause severe hypertension followed by hypotension.
When administering epinephrine to HOCM patients, close cardiac monitoring is essential, and the medication should be given slowly while observing for adverse effects, as recommended in the practice parameters for anaphylaxis diagnosis and management 1. If multiple doses are needed, they should be administered with caution and longer intervals between doses. The benefit of treating anaphylaxis generally outweighs the risks, as untreated anaphylaxis is life-threatening, but the modified approach helps minimize cardiac complications in this vulnerable population.
Healthcare providers should also be prepared with beta-blockers to counteract excessive cardiac stimulation if needed, considering the potential for severe adverse effects from epinephrine administration, such as ventricular arrhythmias, angina, myocardial infarction, pulmonary edema, sudden sharp increase in BP, and intracranial hemorrhage, as highlighted in the guidelines for anaphylaxis management 1. The most recent and highest quality study on this topic, published in 2010, emphasizes the importance of early epinephrine administration in anaphylaxis and provides guidance on dosing and administration routes 1.
Key considerations in managing anaphylaxis in HOCM patients include:
- Close cardiac monitoring during epinephrine administration
- Slow administration of epinephrine while observing for adverse effects
- Preparedness with beta-blockers for potential excessive cardiac stimulation
- Awareness of the potential for severe adverse effects from epinephrine
- Individualized approach based on patient's specific condition and response to treatment, as recommended in the practice parameters for anaphylaxis diagnosis and management 1.
From the Research
Effect of Adrenaline (Epinephrine) on HOCM Patients
- The administration of adrenaline (epinephrine) in patients with Hypertrophic Obstructive Cardiomyopathy (HOCM) who are experiencing anaphylaxis can have significant effects on their cardiovascular system 2.
- In a case report, a patient with HOCM who developed anaphylaxis during surgical septal myectomy did not respond to epinephrine administration, and instead, experienced worsening of left ventricular outflow tract obstruction (LVOTO) 2.
- The anaesthetic goals in patients with HOCM are to maintain preload and afterload and avoid stimulation of inotropy and chronotropy to prevent left ventricular outflow obstruction 2.
- In patients with anaphylaxis and HOCM, maintaining these haemodynamic goals becomes more challenging, and special consideration may be warranted for the need to have extracorporeal life support to treat refractory hypotension 2.
General Treatment of Anaphylaxis
- Epinephrine remains the drug of choice for the treatment of anaphylaxis and should be administered intramuscularly as soon as the diagnosis is suspected 3, 4, 5, 6.
- The initial recommended adult dose of epinephrine is 0.3-0.5 mg, injected intramuscularly in the anterolateral aspect of the mid-thigh 4.
- Antihistamines and corticosteroids are second-line medications and should never be given in lieu of, or prior to, epinephrine 3, 5, 6.
- Patients with severe anaphylaxis may require additional treatment, such as supplemental oxygen, intravenous fluids, and supportive care for their airway, breathing, and circulation 3, 6.