Immunotherapy Safety for the Primary Care ... - U.S. Coast Guard

Antihistamines
H1 antihistamines (Benadryl) Further therapy can be provided by an Hi antihistamine;
however this drug is not a substitute for epinephrine.
• Dose: 1-2 mg/kg (Max:’ 50 mg)
IV (slowly over 5-10 minutes), IM, or P0 (depending on the severity)
• Other antihistamines (Atarax) can be substituted for oral therapy.
H2 antihistamines. (Cimetidine/Ranitidine) Although pruritus, wheal and flare reactions,
and angioedema reactions are primarily Hi receptor mediated, histamine induced
hypotension and cardiac arrhythmias can be mediated by both Hi and H2. receptors.
Therefore, though has not been proven to be of benefit for anaphylaxis, H2
antihistamine can be added.
• Dose: 4 mg/kg Cimetidine IV (slowly over 5 minutes)
• Exception: beta-blockers. In this setting, cimetidine could decrease clearance of
the beta-blocker and thus perpetuate its action.
Upper Airway Obstruction
• Epinephrine
• Oxygen
• Racemic epinephrine: 0.3 ml in 3 ml saline (or nebulized epinephrine)
• Intubation or cricothyrotomy
Lower Airway Obstruction
Managed with a stepwise approach similar to that used for severe asthma.
• Epinephrine
• Oxygen
• Nebulized beta-agonists
• Aminophylline bolus/infusion
• Endotracheal intubation
Late-phase reactions It is important to realize that some patients will resolve their anaphylaxis
only to have a spontaneous recrudescence 8 to 24 hours later. This is the so-called late
phase response.
• Bronchodilators prevents the early, but not the late phase.
• Corticosteroids prevents the late, but not the early phase.
• Cromolyn prevents both the early and late phase.
• The prospective study by Dr. Sullivan of anaphylaxis in 25 consecutive patients noted
three distinct clinical patters:
Uniphasic: 52%
Biphasic: 20%
Protracted: 28% (hypotension or respiratory distress lasting 5 to 32 hours despite
aggressive therapy).
• Contrary to expectations, glucocorticoid therapy introduced during the initial phase of
anaphylaxis did not prevent the appearance of recurrent or protracted anaphylaxis.