Last updated 12/11/23

Anaphylaxis

Anaphylaxis is a severe and extreme life-threatening allergic reaction affecting the whole body. It often occurs within minutes of exposure to the substance which causes the allergic reaction (the allergen), but occasionally may not occur for several hours.

Essential Points

  • Symptoms and signs often follow very soon after contact with a trigger, and sometimes within seconds if the allergen is injected e.g. sting.
  • Anaphylaxis affects the whole body, but what makes it life-threatening is respiratory compromise and cardiovascular collapse.
  • Cardiac arrest can occur within minutes of exposure to the allergen.
  • Whilst it can be useful for the hospital to know if a particular trigger is suspected, diagnosis and treatment is based on the presenting symptoms and signs.
  • Speed of response and treatment are the key to survival.
  • If the signs and symptoms of anaphylaxis are present, you should treat it immediately, as soon as you encounter them as you work through primary survey, even if there is no known contact with a possible trigger.
  • The treatment is to REMOVE THE PRECIPITATING CAUSE (if possible, e.g. bee sting) AND ADMINISTER IM ADRENALINE WITH THE INJECTOR PEN (Jext), possibly repeating every five minutes, until the signs and symptoms have subsided.
  • If an injector pen is not available or malfunctions, give 0.5ml adrenaline from a 1 ml ampoule (full details below).


 

Anaphylaxis is ALWAYS life threatening
If untreated, the time between allergen contact and death
ranges from less than 1 minute after an insect bite or injected drug
to 35 mins after food 

Time to cardiac arrest after exposure to allergen.PNG

Anaphylaxis should be identified and treated in the Primary Survey. Perform a rapid ABC and treat anaphylaxis as soon as you find it.
Asthmatics are more prone to anaphylaxis and have more severe reactions to triggers (their mortality rate is higher).

Clinical diagnosis

The following criteria have been validated as being reliable. Anaphylaxis is highly likely when TWO or MORE of the following are present:

  • Acute onset of illness (usually minutes, but can be several hours) especially if exposure to a substance to which the person is known to be allergic

  • Involvement (swelling) of the skin, lining of the mouth, or both

Facial Swelling

Uticaria

  • Difficulty in breathing

  • Fall in blood pressure sufficient to produce symptoms such as reduced conscious level. Note: in susceptible people, the extreme fall in BP can trigger an attack of angina or cause an abnormal heart rhythm (can even be extremely slow)

  • Gastrointestinal symptoms e.g diarrhoea, stomach pain

Also look for:

  • Rapid heart rate

  • Generalised flushing.

  • Nettle rash (hives) or a skin rash (urticaria) which spreads quickly, is raised and itchy with pinkish edges and paler centres.

Do not mistake anaphylaxis for asthma as this will delay treatment.

 

 

 

History

Typical Allergens

Take a history to establish the diagnosis ASAP (do not let this delay treatment), do a quick SAMPLE and ask if:

  • it’s happened before

  • they carry an Jext, EpiPen or similar device

  • they have any know triggers (are sensitised) or

  • have come into contact with a trigger for them or any commonly-known triggers.

Common triggers include:

  • bee and wasp stings,

  • foods e.g. peanuts and shellfish

  • drugs e.g. antibiotics and NSAIDs (Aspirin, Diclofenac, Ibuprofen)

  • latex


A full history is very important in aiding the hospital’s investigations, but must not delay treatment.

If symptoms are present, treat first and ask questions later.

 

Management 

Remove the trigger if it is still in contact e.g. remove bee sting. Do NOT squeeze the bee whilst removing as this will force more toxin into the victim.

Intramuscular adrenaline is the ONLY recognised treatment.


Other measures are considered complementary and are used AFTER adrenaline has been given.

  • Delaying administration of adrenaline will reduce the effectiveness of the treatment.

  • The sooner it’s given after the onset of anaphylaxis, the more effective it will be.

Adrenaline relieves the symptoms of anaphylaxis by constricting blood vessels which helps to bring up the blood pressure, strengthens the heart beat, and opens the breathing airways. However, it does NOT remove the cause. As the effects of adrenaline wear off, the symptoms can return. In these instances repeated doses will be necessary until the symptoms stop returning.

Remember - The dose may have to be repeated multiple times, at intervals of 5 minutes if necessary. Therefore, think ahead and ask following team members to bring additional drug boxes to increase the number of JEXT pens and adrenaline ampules available. This will ensure there is a good supply of adrenaline available in an easy-to-use form.

We have two methods of giving adrenaline available to us, the Jext auto-injector and intramuscular injection.

Due to the speed of preparation, the Jext is our first route of administration.  To use:

  • Remove the device from it’s protective tube.

  • Remove yellow safety cap. Warning – the device is now primed and ready to fire.

  • Place against the casualty’s thigh at 90°. The JEXT needle is only 16mm long. Therefore to maximise the chance of the adrenaline being injected into the muscle and not into the fatty tissue overlying it, if possible inject directly into skin, rather than through the clothing.

  • Push hard into the thigh until the auto-injector mechanism functions and you hear a click.

  • Hold in place for 10 seconds then remove and massage the area for several seconds.

  • Although a shield extends over the needle to prevent accidental injury, discard the used device using a sharps bin.


If an Jext is unavailable or malfunctions, give adults 0.5mg of adrenaline by IM injection:  

  • Draw up 0.5 ml adrenaline from a 1 ml ampoule in the Drugs Box

  • Inject that IM using a green needle into the outer aspect of the thigh (in the same place you would inject with the Jext).

  • Remember to draw back before injecting. Do NOT inject if the needle is in a vein. Unlike morphine, if you accidentally give 0.5 mg adrenaline intravenously, this can cause abnormal heart rhythms.

  • We don’t draw back with the Jext pen, partly because it isn’t designed for that, but mainly because Jext delivers a smaller dose.

  • See Drugs Crib for children’s dosage and side effects.



WARNING – the adrenaline ampoules we carry contain 1 mg i.e. TWICE the dose for treating anaphylaxis

ONLY GIVE HALF AN AMPOULE AT A TIME

 NB: Severe anaphylaxis in patients taking beta-blocker drugs (used for heart rate control and occasionally high blood pressure) may not respond to adrenaline. Glucagon, if available, may be effective in these cases by increasing heart rate and blood pressure.

Subsequent management
 

  • Oxygen high flow at 15L/min via a non-rebreathing mask.

  • Monitor SpO2 regularly and consider using a lower oxygen flow rate if the available supply will not last throughout the evacuation.

  • Lie them down and raise legs unless they are so breathless they need to sit up. Do not stand the casualty up this can cause cardiac arrest. NB if the casualty is well on in pregnancy lie on their left side not on their back.

  • If BP is low and a suitably qualified casualty carer is available give 1 Litre of saline as fast as possible

  • If wheezing is present you can try nebuliser salbutamol +/- atrovent

  • Be prepared for cardiac arrest

  • Evacuate ALL casualties straight to hospital, even if they improve. 25% will have a recurrence over the following few hours and will need further intervention including adrenaline.

 

Signs of Improvement

Monitor continually and look for:

  • Reduced feeling of breathlessness.

  • Breathing pattern normalises.

  • Casualty feels better.

  • Heart rate reduces towards normal.

  • Blood pressure stabilises and rises towards normal.

  • Swelling and rash subside will take longer to subside

Remember - symptoms may return as the effects of adrenaline wear off.  Be prepared to resume treatment, do not stop monitoring until the casualty has been handed over to the ambulance service.

Snakebites

Note that the adder is the only indigenous venomous snake in this country. It will generally bite the hand, foot or Achilles as it can’t open it mouth wide enough to bite anywhere else. A snake bit can cause anaphylaxis.

Treatment

  • ABCD

  • Manage anaphylaxis.

  • Do not agitate wound, cover with sterile dressing.

  • Hospitalise ASAP with as little movement as possible.

  • Phone ahead to warn the hospital so they can prepare, because snake bites are rare

  • If possible, get details of snake for identification (but do not get too close).

    Excellent article by L. Brotherton attached is a good summary of the issues and management.