Anaphylaxis definitions:

·       Any acute onset illness with typical skin features (urticarial rash or erythema/flushing, and/or angioedema)

·       With or without involvement of respiratory and/or cardiovascular and/or persistent severe gastrointestinal symptoms

or

·       Any acute onset of hypotension or bronchospasm or upper airway obstruction where anaphylaxis is considered possible, even if typical skin features are not present.

The most common triggers of anaphylaxis (severe allergic reaction) are foods, insect stings and drugs (medications).

Signs and symptoms of allergic reactions: -

1)  Mild or moderate reactions:

•  Swelling of lips, face, eyes

•  Hives or welts

•  Tingling mouth

• Abdominal pain, vomiting (these are signs of anaphylaxis for insect sting or injected drug (medication) allergy

2)  Anaphylaxis – Indicated by any one of the following signs:

•  Difficult/noisy breathing

•  Swelling of tongue

•  Swelling/tightness in throat

•  Difficulty talking and/or hoarse voice

•   Wheeze or sudden persistent cough which is sudden onset unlike cough in asthma

•  Persistent dizziness or collapse

•  Pale and floppy (young children)

•   Abdominal pain, vomiting (for insect sting or injected drug (medication) allergy).

3)  Immediate actions to be taken:

·    Remove allergen (if still present).

·    Call for assistance.

·     Lay patient flat. Do not allow patient to stand or walk. Do not hold infants upright. If breathing is difficult, allow the patient to sit.

·     Give INTRAMUSCULAR (IM) INJECTION ADRENALINE (epinephrine) into outer mid-thigh without delay using an adrenaline autoinjector if available OR adrenaline ampoule and syringe.

·     Give oxygen.

·     ALWAYS give adrenaline FIRST, then asthma reliever if someone with known asthma and allergy to food, insects or medication has SUDDEN BREATHING DIFFICULTY (including wheeze, persistent cough* or hoarse voice) even if there are no skin symptoms.

*Unlike the cough in asthma, the onset of coughing during anaphylaxis is usually sudden.

•  If required at any time, commence cardiopulmonary resuscitation (CPR).

Adrenaline administration and dosages according:

·      Adrenaline (epinephrine) is the first line treatment of anaphylaxis and acts to reduce airway mucosal oedema, induce bronchodilation, induce vasoconstriction and increase strength of cardiac contraction.

·      Give INTRAMUSCULAR (IM) INJECTION OF ADRENALINE (1:1000) into outer

mid-thigh (0.01mg per kg up to 0.5mg per dose) without delay using an adrenaline autoinjector if available OR adrenaline ampoule and syringe, as follows.

Note:

·       If multiple doses are required for severe reactions (e.g. 2-3 doses administered at 5 minutes intervals), consider adrenaline infusion.

·       For emergency treatment of anaphylaxis, ampoules of adrenaline 1:1000 should be used for both IM doses and infusion if required.

·       IV adrenaline infusions should be used with a dedicated line, infusion pump and anti-reflux valves wherever possible

·       Infants with anaphylaxis may retain pallor despite 2-3 doses of adrenaline, and this can resolve without further doses. More than 2-3 doses of adrenaline in infants may cause hypertension and tachycardia.

·       Pregnant women experiencing anaphylaxis need to be treated without delay and there are no absolute contraindications to adrenaline use in anaphylaxis. If clinical judgement deems that there is a risk of maternal death or foetal compromise due to inadequately treated anaphylaxis, then in pregnant women weighing > 50kg, consider giving 500 mcg IM adrenaline.

Positioning of patients:

·      Laying the patient flat will improve venous blood return to the heart.

·      By contrast, placing the patient in an upright position, including holding infants upright over a shoulder, can impair blood returning to the heart, resulting in insufficient blood for the heart to circulate and low blood pressure.

·      The left lateral position is recommended for patients who are pregnant to reduce the risk of compression of the inferior vena cava by the pregnant uterus and thus impairing venous return to the heart.

·      Fatality can occur within minutes if a patient stands or sits suddenly. For mainly respiratory reactions, the patient may prefer to sit and this may help support breathing and improve ventilation. BEWARE that even sitting may trigger hypotension. Monitor closely. Immediately lay the patient flat again, if there is an alteration in conscious state or drop in blood pressure.

·      If vomiting, lay the patient on their side (recovery position).

·      Patients must not be walked to/from the ambulance, even if they appear to have recovered.

Supportive management:

·      Check level of consciousness

·      Check pulse, blood pressure, ECG, pulse oximetry

·      Give high flow oxygen and airway support if needed

·      Obtain IV access in adults and hypotensive children

·       If hypotensive, give IV normal saline 20mL/kg rapidly and consider additional wide bore IV access

Additional measures to consider if IV adrenaline infusion is ineffective:

Antihistamines and corticosteroids:

Antihistamines-

·       Antihistamine therapy considered to be adjunctive to epinephrine so not to be administered alone

·       Combination of H1 blocker and an H2 blocker considered to be superior to an H1 blocker alone in relieving the histamine-mediated symptoms.

·       Diphenhydramine and ranitidine are an appropriate combination. IV administration ensures that effective dosing is not impaired by hemodynamic compromise, which adversely affects gastrointestinal (GI) or IM absorption. However, oral or IM administration of antihistamines may suffice for milder anaphylaxis.

Corticosteroids-

·       Intravenous Corticosteroid recommended for all patients with anaphylaxis and to be administer early to prevent a potential late-phase reaction (biphasic anaphylaxis).

·       Patients with asthma or other conditions recently treated with a corticosteroid may be at increased risk for severe or fatal anaphylaxis and may receive additional benefit if corticosteroids are administered to them during anaphylaxis.

Patient to be observed for at least 4 hours after last dose of adrenaline: Relapse, protracted and/or biphasic reactions may occur. Patients require overnight observation if they-

·       Had a severe or protracted anaphylaxis (e.g. required repeated doses of adrenaline or IV fluid resuscitation), OR

·       Have a history of asthma or severe/protracted anaphylaxis, OR

·       Have other concomitant illness (e.g. asthma, history or arrhythmia), OR

·       Live alone or are remote from medical care, OR

·       Present for medical care late in the evening.

(True biphasic reactions are estimated to occur following 3-20% of anaphylactic reactions).

Preparation:

Equipments required for acute management of anaphylaxis-

·       Adrenaline 1:1000 (consider adrenaline autoinjector availability, particularly in rural locations, for initial administration by nursing staff)

·       1mLor 2mL syringes

·       Oxygen

·       Airway equipment, including nebuliser and suction

·       Defibrillator

·       Manual blood pressure cuff

·       IV access equipment (including large bore canulae)

·       At least 3 litres of normal saline

·       A hands-free phone in resuscitation room, to allow health care providers in remote locations to receive instructions by phone whilst keeping hands free for resuscitation.

Advanced Acute Management of Anaphylaxis:

Supportive management-

·       Monitor pulse, blood pressure, respiratory rate, pulse oximetry, conscious state.

·       Give high flow oxygen (6-8 L/min) and airway support if needed.

·       Supplemental oxygen should be given to all patients with respiratory distress, reduced conscious level and those requiring repeated doses of adrenaline.

·       Supplemental oxygen should be considered in patients who have asthma, other chronic respiratory disease, or cardiovascular disease.

·       Obtain intravenous (IV) access in adults and in hypotensive children.

·       If hypotensive:

– Give intravenous normal saline (20 mL/kg rapidly under pressure), and repeat bolus if hypotension persists.

– Consider additional wide bore intravenous access.

(During severe anaphylaxis with hypotension, marked fluid extravasation into the tissues can occur so DO NOT FORGET FLUID RESUSCITATION)

Assess circulation to reduce risk of overtreatment:

·     Monitor for signs of overtreatment (especially if respiratory distress or hypotension were absent initially) – including pulmonary oedema, hypertension.

·    In this setting (anaphylaxis) it is recommended that, if possible, a simple palpable systolic blood pressure (SBP) should be measured:

·    Attach a manual BP cuff of an appropriate size and find the brachial or radial pulse.

·    Determine the pressure at which this pulse disappears/reappears (the "palpable" systolic BP).

·    This is a reliable measure of initial severity and response to treatment

·    Measurement of palpable SBP may be more difficult in children.

(Note: If a patient is nauseous, shaky, vomiting, or tachycardic but has a normal or elevated SBP, this may be adrenaline toxicity (side effects) rather than worsening anaphylaxis.)

The protocol for 1000 mL normal saline is as follows:

·       Mix 1 mL of 1:1000 adrenaline in 1000 mL of normal saline.

·       Start infusion at ~5 mL/kg/hour (~0.1 microgram/kg/minute).

·       If you do not have an infusion pump, a standard giving set administers

~20 drops per mL, therefore, start at ~2 drops per second for an adult.

·       Titrate rate up or down according to response and side effects.

·       Monitor continuously – ECG and pulse oximetry and frequent non- invasive blood pressure measurements as a minimum to maximise benefit and minimise risk of overtreatment and adrenaline toxicity.

Note:

·       This protocol is intended for temporary use, when no infusion pump is available.

·       Most anaphylactic reactions settle with only 1 mg adrenaline in 1 litre.

·       Indefinite continuation of low concentration infusion increases risk of fluid overload.

·       Caution - Intravenous boluses of adrenaline are NOT recommended due to risk of cardiac ischaemia or arrhythmia UNLESS the patient is in cardiac arrest.

Additional measures:

Advanced airway management:

·       Oxygenation is more important than intubation per se.

·       Always call for help from the most experienced person available.

·       If airway support is required, first use the skills you are most familiar with (e.g. jaw thrust, Guedel or nasopharyngeal airway, bag-valve-mask with high flow oxygen attached). This will save most patients, even those with apparent airway swelling (these patients have often stopped breathing due to circulatory collapse rather than airway obstruction and can be adequately ventilated with basic life support procedures).

·       DO NOT make prolonged attempts at intubation (since the patient is not getting any oxygen while intubation is being attempted)

·       If unable to maintain an airway and the patient's oxygen saturation is falling further approaches to the airway (e.g. cricothyrotomy) should be considered in accordance with established difficult airway management protocols.

Special situation: Overwhelming anaphylaxis (cardiac arrest)- Key points:

·       Massive vasodilatation and fluid extravasation.

·       Unlikely that IM adrenaline will be absorbed in this situation due to poor peripheral circulation.

·       Even if absorbed, IM adrenaline on its own may be insufficient to overcome vasodilatation and extravasation.

·       Need both IV adrenaline bolus (cardiac arrest protocol, 1 mg every 2-3 minutes)

·       Aggressive fluid resuscitation in addition to CPR (Normal Saline 20mL/kg stat, through a large bore IV under pressure, repeat if no response).

·       Do not give up too soon - this is a situation when prolonged CPR should be considered, because the patient arrested rapidly with previously normal tissue oxygenation, and has a potentially reversible cause.

·       Consider extracorporeal membrane oxygenation (ECMO) if resource is available.