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Adult Anaphylaxis

Anaphylaxis should be suspected in patients showing typical signs and symptoms shortly after (seconds to minutes, rarely hours) exposure to a known allergen. Death can occur within minutes and usually occurs due to cardiovascular or respiratory compromise. 1 Typical signs and symptoms are: 1 2 3

 

            R          Respiratory Distress                                           present in up to 70% of patients

            A          Abdominal Symptoms                                      present in up to 45% of patients

            S          Skin/mucosal symptoms                                    present in up to 90% of patients

            H          Hypotension (or altered conscious state)        present in up to 45% of patients

 

Note that hypotension does not always occur early in the course of anaphylaxis, clinicians must not wait until its presence to confirm the diagnosis.  Persistent asthma, other respiratory diseases, cardiovascular disease and acute infection are important comorbid risk factors which increase death due to anaphylaxis and should be assessed for early in the evaluation of the acute patient. 1 

 

Patients with anaphylaxis should be treated as follows:

AIRWAY

  • All anaphylactic patients require diligent and ongoing monitoring of airway patency.

  • Patient’s with a current or threatened compromised airway (respiratory arrest, stridor, obvious swelling/oedema, voice alteration) should be endotracheally intubated. 

BREATHING

  • Dyspneic patients may prefer to sit high fowlers; ensure adequate BP is maintained 3

  • SpO2 and EtCO2 monitoring should be initiated and maintained 3

  • Positive pressure ventilation may be required to support adequate gas exchange 4

CIRCULATION

  • ECG monitoring should be initiated and maintained 3

  • Two large bore IVs should be initiated and maintained 5

  • In the normotensive patient, IVs should be maintained at a ‘to keep vein open’ (only) rate.  In the hypotensive patient, IV fluid bolus is appropriate (see below, under TREATMENT)

  • Pregnant patients should be placed left lateral to avoid compression of the inferior vena cava 3

  • Non pregnant patients should be supine with legs elevated, if not contraindicated 5 (e.g. as long as airway is non-oedematous and there is no trauma, elevated intracranial pressure, etc.)

OTHER

  • Appropriately remove the allergen (if possible) at the soonest opportunity

  • Patients should not be asked to ambulate at all, even if they do not appear distressed or symptomatic 3 6

  • All patients should be transported to definitive, ongoing care due to the risk of relapse or biphasic anaphylaxis.  Do not ‘treat and release’ the anaphylactic patient. 2 3 7 8
     

 

TREATMENT

  1. Adrenaline 3 4 6 7 8

    1. Early IM adrenaline should be administered into a large muscle mass – the anterior/lateral thigh is the preferred location. 

    2. Paramedics should have a low threshold for initiating adrenaline treatment.  If in doubt, administer adrenaline. Delayed administration is associated with increased fatalities. 5

    3. Initial IM dosage is: 5

      1. 25-50 kg = 0.3 mg (0.3 mL of a 1mg/mL preparation)

      2. >50 kg =    0.5 mg (0.5 mL of a 1mg/mL preparation)

    4. IM adrenaline can be repeated at 5-15 minute intervals as necessary.  Up to 35% of patients may require more than one dose. 5

    5. Intravenous bolus of adrenaline is not recommended.

    6. A slow intravenous infusion of adrenaline may be required in patient’s refractory to IM adrenaline plus normal saline fluid bolus.  In this case a starting dose of 0.1 mcg/kg/minute is recommended, with increases of roughly half the starting dose (0.05 mcg/kg/minute) every two to three minutes, titrating to effect.

      1. To deliver this an infusion pump is preferred.

      2. If an infusion pump is unavailable add 1 mg of adrenaline to 1 litre of normal saline solution.  Using a macrodrip start the infusion at 2 drops per second and titrate to effect.

    7. Nebulized adrenaline may be considered for ongoing upper airway oedema refractory to IM/IV adrenaline administration or for patients with angioedema. 2 3 7 8

  2. Oxygen 3 6

    1. Normoxia and normocarbia should be maintained.  Initial, aggressive treatment with oxygen in the hypoxic patient is a priority.  Subsequent to the attainment of normoxia, titrate dosage appropriately.

  3. Normal saline 3 5 6

    1. Administer 20 mL/kg of fluid as an initial bolus to any patient who remains hypotensive subsequent to an initial dose of adrenaline.  This may be repeated as necessary. Continue to assess blood pressure and to auscultate breath sounds between administrations.  Several litres of fluid may be required.

  4. Other vasopressors

    1. In the absence of an appropriate therapeutic response to repeated doses of adrenaline and repeated boluses or normal saline, other vasopressors may be attempted.  The first choice should be a non-adrenergic vasopressor such as vasopressin.  Other adrenergic vasopressors such as noradrenaline and dopamine are secondary options.

  5. Salbutamol and Ipratropium Bromide 3 5 6

    1. Salbutamol and Ipratropium Bromide should be used secondarily to treat severe bronchospasm that is refractory to adrenaline.  These are not first line agents for bronchospasm in anaphylaxis and treatment with adrenaline remains the priority.

  6. Glucocorticoids 3 7 8

    1. There is no evidence in the literature of additional benefit from glucocorticoid administration in anaphylaxis 5, however some Australasian paramedic services do recommend their use. 3

  7. Antihistamine  3 7 8

    1. There is no evidence to suggest that H1 antihistamines are useful in the treatment of any airway swelling, hypotension, or shock, and they do not contribute to mast or basophil stabilisation in anaphylaxis 5, however they may be useful in non-rapidly addressing cutaneous symptoms. H2 antihistamines are not indicated in anaphylaxis.

    2. Treatment with antihistamines is not a priority and must take delay primary treatment of the ABCs, or administration of adrenaline and fluid therapy.

  8. Glucagon 3

    1. Glucagon may be used as a second line treatment for patient’s refractory to adrenaline, as glucagon has inotropic and chronotropic effects that are not mediated by beta receptors. Administer 1 to 2 IU by slow IV over 5 minutes.  This may be followed by an infusion of 5-15 mcg/minute, titrated to effect. 3 5

 

 

References:

 

1.        Campbell, R. L. & Kelso, J. M. Anaphylaxis: Acute diagnosis. UpToDate (2019). Available at: https://www.uptodate.com/contents/anaphylaxis-acute-diagnosis.

2.        Ambulance Victoria. Clinical Practice Guidelines for Ambulance and MICA Paramedics. https://www.ambulance.vic.gov.au (2018).

3.        Queensland Ambulance Service Clinical Quality and Patient Safety Unit. Clinical Practice Guidelines: Medical/Anaphylaxis and severe allergic reaction. https://www.ambulance.qld.gov.au (2019). Available at: https://www.ambulance.qld.gov.au/docs/clinical/cpg/CPG_Anaphylaxis and allergy.pdf.

4.        South Australia Ambulance Service Clinical Performance and Safety Unit. Anaphylaxis and Allergy. (2015).

5.        Campbell, R. L. & Kelso, J. M. Anaphylaxis: Emergency treatment. UpToDate (2018). Available at: https://www.uptodate.com/contents/anaphylaxis-emergency-treatment.

6.        ACT Ambulance Service. Clinical Management Guideline 29 - Allergic and Anaphylactic Reactions. December 2016. https://esa.act.gov.au (2016). Available at: https://esa.act.gov.au/sites/default/files/wp-content/uploads/CMG-29-ALLERGIC-AND-ANAPHYLACTIC-REACTIONS-top-Dec-2016.pdf. (Accessed: 14th July 2019)

7.        St John Ambulance, N. Z. Clinical Procedures and Guidelines, 2019-2021. (2019).

8.        Wellington Free Ambulance. Clinical Procedures and Guidelines. 146–180 doi:10.1016/B978-141604485-7.50013-5