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National Advisory Committee on Immunization (NACI)
ANAPHYLAXIS: STATEMENT ON INITIAL MANAGEMENT IN NON-HOSPITAL SETTINGS
This statement is updated from the version published in the Canadian
Immunization Guide (4th edition, 1993). Dosage guidelines for epinephrine
have been modified to better suit pre-adolescents.
This statement is intended to be a guide for initial management of patients
in a public health clinic or similar non-hospital setting. In a patient with
severe, life-threatening anaphylaxis, establishment of intravenous access
for drug and fluid administration will be necessary and endotracheal intubation
and other maneuvers may be required. These interventions are ordinarily best
performed in a hospital's emergency room.
Anaphylaxis is a rare and potentially life-threatening allergic complication
of immunization that should be anticipated in every vaccinee. Prevention is
the best approach. Pre-vaccination screening should include questions about
possible allergy to any component of the product(s) being considered to identify
this contraindication. As avoidance is not always possible, every vaccine
provider should be familiar with the symptoms of anaphylaxis and be ready
to administer appropriate medications. Vaccine recipients should be kept under
supervision for at least 15 minutes post-immunization.
Anaphylaxis is one of the rarer events reported in the post-marketing surveillance
system for vaccine adverse events. Based on the last 5 years of complete national
data, the annual rate of anaphylaxis ranges from 0.11 to 0.31 reports per
100,000 doses of vaccines distributed.
Anaphylaxis must be distinguished from fainting (vasovagal syncope), which
is a more common and benign reaction. Fainting is simply managed by placing
the patient in a recumbent position. Rapidity of onset is a key differentiator.
With fainting, the subject changes from a normal to an unconscious state within
seconds. Fainting is sometimes accompanied by brief clonic seizure activity
but this generally requires no specific treatment or investigation. With anaphylaxis,
changes develop over several minutes, may involve multiple body systems (skin,
respiration, circulation) and may progress to unconsciousness only as a late
event in severe cases. Rarely is unconsciousness the sole manifestation of
anaphylaxis.
Anaphylaxis usually begins a few minutes after injection of the offending
substance and is usually evident within 15 minutes. Symptoms can include sneezing,
coughing, itching, "pins and needles" sensation of the skin, flushing, facial
edema, urticaria, anxiety, respiratory difficulties and hypotension, which
may progress to shock and collapse. Cardiovascular collapse can occur without
respiratory symptoms. Early recognition and treatment of anaphylaxis is vital.
Measures outlined here are appropriate for initial management in non-hospital
settings.
1. Place the patient in a recumbent position (elevating the feet if
possible).
2. Establish an oral airway if necessary.
3. Place a tourniquet (when possible) above the site of vaccination.
Release for 1 minute every 3 minutes.
4. Promptly administer 0.01 mL/kg (maximum 0.5 mL) of aqueous epinephrine
1:1,000 by subcutaneous or intramuscular injection in the opposite limb to
that in which the immunization was given.
The subcutaneous route of epinephrine injection is appro-priate
for mild or early cases. Severe cases should receive intramuscular injections
because they lead more quickly to generalized distribution of the drug. A
single subcutaneous injection is usually sufficient for mild or early anaphylaxis.
Dosing can be repeated twice at 20-minute intervals, if necessary. Severe
reactions could require these repeat doses to be given at shorter intervals
(10 to 15 minutes).
Speedy intervention is of paramount importance: failure to use epinephrine
promptly is more dangerous than using it improperly.
Epinephrine dosage should be carefully determined. Calculations based on
body weight are preferred when weight is known. Recording the weight of children
prior to routine immu-nization is recommended when feasible. Excessive dosages
of epinephrine can add to subjects' distress by causing palpitations, tachycardia,
flushing and headache. Although unpleasant, such side effects pose little
danger. Cardiac dysrhythmias may occur in older adults but are rare in otherwise
healthy children.
When body weight is not known the dosage of epinephrine 1:1,000 can be
approximated from the subject's age as follows:
| 2 to 6 months* |
0.07 mL |
(0.07 mg) |
| 12 months* |
0.1 mL |
(0.1 mg) |
| 18 months* to 4 years |
0.15 mL |
(0.15 mg) |
| 5 years |
0.2 mL |
(0.2 mg) |
| 6 - 9 years |
0.3 mL |
(0.3 mg) |
| 10 - 13 years |
0.4 mL |
(0.4 mg) |
| >= 14 years |
0.5 mL |
(0.5 mg) |
| * Dosage for children between the ages shown should be approximated,
choosing dose volumes intermediate between those shown or the next larger
dose, depending on practicability. |
The anaphylactic state in patients on beta adrenergic antagonist therapy (for
elevated blood pressure) will be more resistant to epinephrine therapy.
Since anaphylaxis is rare, epinephrine vials and other emergency supplies
should be checked on a regular basis and replaced if outdated.
5. If the vaccine was injected subcutaneously, an additional dose of
0.005 mL/kg (maximum 0.3 mL) of aqueous epinephrine 1:1,000 can be injected
in the vaccination site to slow absorption. Local injection of epinephrine
into an intramuscular vaccination site is contraindicated because it dilates
vessels and speeds absorption.
6. As an adjunct to epinephrine, a dose of diphenhydramine hydrochloride
(Benadryl ® ) can be given. It should be reserved for patients not
responding well to epinephrine or to maintain symptom control in those who
have responded (epinephrine being a short-acting agent), especially if transfer
to an acute care facility cannot be effected within 30 minutes. Oral treatment
is preferred for conscious patients who are not seriously ill because Benadryl
® is painful when given intramuscularly. This drug has a high safety margin
making precise dosing less important.
The approximate dosages of diphenhydramine HCI (Benadryl ® for injection
50 mg/mL solution) are shown in the following table:
| < 2 years |
0.25 mL |
(12.5 mg) |
| 2 - 4 years |
0.5 mL |
(25 mg) |
| 5 - 11 years |
1.0 mL |
(50 mg) |
| >= 12 years |
2.0 mL |
(100 mg) |
7. Arrange for rapid transport to an emergency room. For all but the
mildest cases of anaphylaxis, patients should be hospitalized overnight or
monitored for at least 12 hours.
Reference
1. Thibodeau JL. Office management of childhood vaccine-related anaphylaxis.
Can Fam Phys 1993;40:1602-10.
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