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TREATING ANAPHYLAXIS
In the emergency setting, anaphylaxis is a dangerous, life threatening condition that must
be treated in an aggressive and timely fashion. Anaphylaxis is a condition related to
acute allergic reactions. Following the body’s exposure to the offending allergen,
there are common systemic reactions. The most serious reactions involve the respiratory
and cardiovascular systems, but the gastrointestinal, dermatologic, and genitourinary
systems are often involved causing varied symptoms such as urticaria, flushing,
angioedema, bronchospasm, hypotension, cardiac arrythmias, nausea, intestinal cramps,
pruritus, and finally uterine cramps. (Physician Assistant, 8/94) The above list is by no
means exhaustive, specific symptoms vary from person to person. The same person suffering
from several anaphylactic reactions can also present with differing symptoms.
Physiologically speaking, the two main effects of the body’s released mediators (IgE)
during an anaphylactic reaction are smooth muscle contraction and vasodilatation, which
cause most of the body’s adverse symptoms. (JAMA, 11/26/82) Since the most life
threatening reactions usually involve the respiratory and cardiovascular systems, that is
where emergency treatment is focused. In the cardiovascular system, a combination of
vasodilatation, increased vascular permeability, tachcycardia, and arrhythmias can lead to
severe hypotension. In the respiratory system, the swelling of tissues along with
bronchospasm and increased mucus production are the main cause of death. So, if untreated,
anaphylaxis can be fatal as a result of the body’s going into what is essentially
shock, while simultaneously (and more importantly) being deprived of the oxygen needed to
sustain life.
As of today there is one universally accepted treatment for acute anaphylaxis.
Epinephrine. Epinephrine is both an alpha and a beta agonist. This makes it the drug
optimally suited to treat anaphylaxis. "Epinephrine will increase vascular
resistance, reduce vascular permeability, produce bronchodilation and increase cardiac
output." (Emergency, 10/93)
Epinephrine will directly counteract the potentially life threatening aspects of
anaphylaxis. Epinephrine can , and is, used in the both the pre-hospital environment as
well as in definitive care institutions. Epinephrine is widely administered by ALS
providers the world over. The drug is so effective that and relatively simple to use that
"…subcutaneous administration of epinephrine by EMT-B’s trained in
recognition … of anaphylaxis… is safe." (Annals of Emergency Medicine,
6/95)
Following the administration of epinephrine, antihistamines such as diphenhydramine,
hydroxyzine, and promethazine can be administered. These agents block the harmful effects
of histamine, a mediator associated with allergic reactions, and while not displacing
histamine from receptors, they compete with histamine for receptor cites and therefore
block additional histamine from binding. (JEMS, 4/95)
Patients taking beta adrenergic blocking agents will have limited benefits from the
administration of epinephrine (it being a beta agent), as well potentially unopposed alpha
adrenergic effects that could result in severe hypertension. (Physician Assistant, 8/94)
In such cases norepinepherine and dopamine may be necessary to treat systemic anaphylaxis.
Glucagon which increases cAMP, is a bronchodilator, and stimulates cardiac output, can be
very useful, even in the presence of beta blockers. (Physician Assistant, 8/94)
Inhaled bronchodilators are useful for the treatment of respiratory complications
associated with anaphylaxis. There is a wide variety of acceptable agents.
Sympathomimetics such as albuterol, and metaproterenol will relax the smooth muscle in the
respiratory tract. Anticholinergic agents such as ipratropium bromide can also decrease
bronchospasm. Aminophylline, a bronchodilator and diuretic can also increase intracellular
cAMP levels, as well as potentiating catecholamines and stimulating their release; these
effects make it a useful tool in dealing with persistent bronchospasm. (Physician
Assistant, 8/94)
Even though steroids (glucocorticosteroids) have some potentially beneficial effects for
the relief of bronchospasm and hypotension, they are not recommended for the treatment of
acute anaphylactic symptoms due to the fact that it takes four to six hours for them to be
effective. (JAMA, 11/26/82) But, steroids such as methylprednisolone and hydrocortisone,
are useful in shortening the duration of, and reducing the severity of prolonged
anaphylactic reactions, as well as preventing the recurrence of delayed symptoms.
(Physician Assistant, 8/94)
The above agents are all widely used to treat anaphylaxis. But there are studies and
experiments underway that are looking at alternative, or additional treatments. Naloxone
and thyrotropin-releasing hormone (TRH) are both being looked at in the possible treatment
of anaphylaxis as well as traumatic shock. "Naloxone improves cardiovascular function
in a variety of animal models of shock caused by…and anaphylaxis. Administration of
TRH …also has pressor effects in these shock models." (Annals of Emergency
Medicine, 8/85)
"TRH has been shown to increase mean arterial pressure during anaphylactic
shock." (Annals of Emergency Medicine, 5/89) In animal studies of anaphylaxis the use
of TRH, epinephrine, and normal saline were compared. TRH treated rabbits responded
slightly better than those treated with epinephrine (the study focused on cardiovascular
and respiratory parameters.) (Annals of Emergency Medicine, 5/89)
I started this project with the aim of identifying alternative treatments for anaphylaxis.
I had mistakenly assumed that there are a host of viable and effective treatment regiments
for anaphylactic shock. What I discovered was that as of today, the only universally
accepted therapy for acute anaphylaxis is… epinephrine. Due to it’s alpha and
beta adrinergic effects epinephrine is miraculously suited for anaphylaxis. It almost
seems to be a natural antidote, a wonder drug with singular abilities in the treatment of
anaphylaxis.
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