Acute Anaphylaxis
Clinical features
- In severe reactions IM adrenaline (0.01mg/kg) 0.5mg IM is the
initial treatment
- Anaphylaxis has a broad range of presentations from a rash to full cardiorespiratory
arrest. It may present de novo from the community or be as a result of drugs administered
in the Emergency Department.
- Precipitants are varied and frequently cannot be identified. Often in ED the
precipitant is of little clinical relevance. Antibiotics are the most commonly identified
cause. Don’t agonise over the cause; the treatment is what counts.
Life threats
- Life-threatening events can be manifested in the following ways:
- Airway - angioedema - lip, tongue, throat swelling
- Breathing - bronchospasm leading to respiratory arrest
- Circulation - profound hypotension, cardiogenic shock,
circulatory collapse
- Mucocutaneous involvement of the skin (urticaria) and gut (vomiting, abdominal pain,
diarrhoea) can also occur.
Initial Management
- Administer oxygen and establish IV line (in
moderate/severe reactions)
- Lay supine if hypotensive (and does not compromise respiration)
| SEVERITY OF REACTION |
CLINICAL EXAMPLE |
INITIAL MANAGEMENT |
| Mild |
Urticaria only |
Promethazine
(1mg/kg) 25mg PO or IM |
| Moderate |
Angioedema without stridor Mild/Moderate bronchospasm |
Adrenaline 6mg/6ml neb
+/-
Adrenaline (0.01
mg/kg) 0.5mg IM |
| Severe |
Angioedema with stridor Severe bronchospasm
Hypotension |
Adrenaline (0.01
mg/kg) 0.5mg IM
(if impeding or complete airway obstruction consider sublingual injection)
+/-
Saline/Gelofusin 500ml IV stat (if shocked)
|
Special cases - C1 esterase deficiency - FFP 2 units
* note that ACE-I induced angioedema often poorly responsive to conventional
measures
Ongoing Management
Adrenaline
For moderate to severe cases which are not responding
- Adrenaline neb 6mg/6ml can be repeated immediately
- Adrenaline 5-20mcg/min IV
Otherwise
- Adrenaline IM 0.5mg can be repeated after 5 min
- Adrenaline 10-50mcg as IV bolus repeated every 3 min (NB
arrhythmogenicity is enhanced in
anaphylaxis)
Fluids
- Repeated Fluid bolus for refractory shock
Anti-histamines
Promethazine 25mg PO or IV/IM
- Slow IV (Beware of hypotension, give when stable)
- IM (equivalent onset to IV but less side effects)
- PO (unreliable absorption if GI involvement)
Ranitidine 50mg 8/24 IV
- Limited evidence
- Possible benefits via H2 cardiac receptors
Steroids
All moderate to severe cases receive steroids on arrival and for 3 days (minimum)
- Prednisolone 50mg PO
- Hydrocortisone 100-200mg 6/24 hrly IV (if gut involvement)
Disposal
Observe all moderate/severe cases for 6 hrs. If stable then discharge with
referral to Allergist/Immunologist ELSE admit.
Consider discharge with self-administered adrenaline pen (and instructions on use)
| SEVERITY |
TREATMENT |
| Mild |
Promethazine 10mg qid PO (3 days) |
| Moderate/Severe |
as above + prednisolone 50mg daily PO (3 days) |