Neil Goldsack,
respiratory specialist registrar
Chest Clinic,
North Middlesex Hospital,
London
David Howell,
Medical Research Council fellow
Richard Marshall,
Wellcome fellow
Hugh Montgomery, cardiology specialist registrar
University College and Middlesex Hospital,
London

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In the fourth part of our emergency series, Neil Goldsack, Hugh Montgomery, Richard Marshall, and David Howell tell you how to treat patients with anaphylactic shock

Introduction
Anaphylaxis can be one of the most frightening and dramatic acute medical emergencies. It is, however, fortunately an uncommon emergency to be called to as a house officer but is more likely when you become a senior house officer in the casualty department. There it is a comparatively common emergency that occurs in a number of situations. Among the most common are of course allergies to bee and wasp stings, and to nuts. Remember that people who are allergic to nuts will try all they can to avoid exposure to nuts, but when they eat in restaurants they may become inadvertently exposed. During your time as a house officer, anaphylaxis has normally been effectively dealt with before you arrive. The time you may experience it is on a medical ward, after a dose of penicillin has been given and the patient suddenly becomes extremely short of breath. Alternatively, it can be seen after the administration of blood products or intravenous immunoglobulins. In these settings it is important that you can recognise the main features and deal with it in an efficient manner.

Wasp stings can result in anaphylactic shock
Photo: NILE ROOT/CUSTOM MEDICAL STOCK PHOT/SPL

When anaphylaxis is first experienced it can be terribly worrying for the new house officer. If you follow a few simple rules, however, a life can be easily saved. This is a real acute emergency and must be dealt with immediately.

The symptoms and signs of this condition are usually obvious (see box 1). The patient initially flushes, then the face and tongue begin to swell, and the patient experiences breathing difficulties because of laryngeal swelling and bronchospasm. This can happen over the space of a few seconds. In extreme cases the intense vasodilation that occurs can result in acute cardiorespiratory shock and cardiac arrest. We will deal with this situation later.

Box 1: Symptoms and signs of acute anaphylaxis Erythema Urticaria Conjunctival injection (redness)   Facial swelling   Lip swelling   Tongue swelling   Rhinitis   Choking (laryngeal obstruction)   Bronchospasm   Tachycardia   Hypotension   Shock

Dealing with anaphylaxis is comparatively easy if you proceed sensibly. The most important problem in treating these patients is the fact that their cardiac and respiratory systems can be rapidly compromised by the developing anaphylaxis. Deal with these effectively, and you have dealt with the problem.

Management
You should be able to initiate the management of anaphylaxis on your own. You should, however, also shout for help and ask for the immediate attendance of senior colleagues, including your registrar and an anaesthetist. The management of this condition has to be committed to memory as do the doses of drugs, and in particular adrenaline, that need to be given.

Light micrography of crystalline adrenaline
Photo: DAVID PARKER/SPL (X100 MAGNIFICATION)

Emergency management and exam answers
The management of this condition can be split into two stages (see box 2).

 

Management of acute anaphylactic shock First line treatment   Call for help   Give high flow oxygen   Give 0.5 mg intramuscular adrenaline (0.5 ml of 1:1000 solution). Aliquots of intravenous adrenaline (0.5 ml of 1:10 000) can be given in severe precipitous anaphylaxis   Give intravenous fluids (crystalloid or colloid)   Give nebulised salbutamol or adrenaline Second line treatment   Give 200 mg intravenous hydrocortisone   Give 10 mg intravenous chlorpheniramine (Piriton)   Consider intravenous glucagon in patients who are taking ß blockers

Stage 1: first line treatment
High flow oxygen should be administered to the patient through a non-rebreathing bag.

Adrenaline - 0.5 ml of a 1:1000 solution (0.5 mg) should be injected intramuscularly. This is kept on the resuscitation trolley. Note that the dose to be given is 0.5 mg as a 1:1,000 solution. On the cardiac arrest trolley there is also a solution of 1:10,000. These two must not be mixed up as trying to inject 5 ml of 1:10,000 intramuscularly (0.5 mg) will be extremely uncomfortable and also ineffective. The muscle used should be a well vascularised muscle, usually the deltoid or the quadriceps. Adrenaline can be given every 10 minutes should the need arise. In exceptional circumstances, when the patient is about to have a cardiac arrest (profound hypotension, low saturations), adrenaline can be given intravenously. In this case, the 1:10 000 adrenaline can be given in boluses of 0.5 ml. Again, this can be repeated as necessary.

Treat circulatory shock. After administering the adrenaline you should rapidly gain good venous access, usually through a large venflon (grey or brown) into an antecubital vein. This allows you to give intravenous fluids as appropriate. Either crystalloid or colloid can be given, and large volumes are often necessary. Be guided by the blood pressure. If the patient remains hypotensive (systolic blood pressure <100 mm Hg), continue to give intravenous fluids rapidly.

Nebulised treatment. These patients will often have severe bronchospasm that will require the nebulisation of 5 mg of salbutamol. This should be given with oxygen as the driving gas and not air. If the patient has stridor and bronchospasm, then nebulised adrenaline should be given instead of salbutamol. Again, the driving gas should be oxygen.

Stage 2: second line (additional) treatment
200 mg hydrocortisone can also be given intravenously. However, this is only effective 4-6 hours later and plays no part in the initial improvement of the patient.

10 mg chlorpheniramine (Piriton) should be given intravenously. This can be given by a bolus push. This antihistamine is again stocked on the resuscitation trolley.

1 mg glucagon can be given intravenously. This can be useful in patients who are taking ß blockers and are refractory to the treatment above.

If at this point there is no improvement in the patient or significant bronchospasm is still present then the patient should be intubated. There is no point in holding off at this stage as the patient will rapidly deteriorate, and intubation will become more difficult through the oedematous vocal cords. If this becomes necessary the anaesthetist will inform you of the drugs that are needed. It is worth giving further intravenous fluids at this stage as the patient will be hypotensive to some degree, which will only be exacerbated by the anaesthetic drugs. Once intubated, the patient should be transiently managed on the intensive care unit.

Further management
The more likely scenario is that, after initial treatment has been given, there is a rapid improvement in the patient's condition and the situation becomes less worrying. You should, however, be aware that patients may deteriorate again, and so you should remain with them. It is always valuable to continue to give the patient some intravenous fluids at this stage as the intense vasodilation is associated with hypotension to some degree, and this will persist. You should ask the nurse to put a saturation probe on to measure a patient's O2 level and also measure the blood pressure. On most occasions this is all that is necessary in the acute situation.

Anaphylactic cardiorespiratory arrest
This should be dealt with like any other cardiac arrest (see cardiac arrest). So check that the patient has had an arrest by observing that he or she does not respond and there is no chest movement or respiratory effort. Call for help and give two ventilations. Then check for a pulse; if this is absent begin cardiac massage. As people arrive, secure venous access and continue advanced life support as you would usually. Your registrar will run the arrest and will tell you what you should do.

Aftercare of anaphylaxis patients
If we now assume that the patient has improved from his or her anaphylactic shock and is getting better on the ward or in the casualty department, there are a few other important things that you should do.

Find out from the patient exactly what they are allergic to and write this clearly - in red - both inside and on the front of the medical notes. In the event of a drug allergy this should be written clearly on the front of the drug chart in red.

Furthermore, in the event of a drug allergy make sure that the offending drug is erased from the drug chart. It is amazing how often this is forgotten and what disasters it can lead to. It is also important that the allergy is explained to the patient so he or she can avoid similar problems in the future. Remember that in the case of penicillin allergy there is a 7-10% crossover with cephalosporins. So before prescribing another antibiotic check that it is necessary and seek senior advice.

If the patient is on the ward after an allergic reaction to bees, wasps, or nuts etc, get the nurses to teach the patient how to inject subcutaneously and give the patient an adrenaline syringe to take home and carry at all times (it is amazing how often patients are given adrenaline for home use and this last point is forgotten). Subcutaneous adrenaline can be life saving in this situation. Make sure that patients are also told that if they do use this adrenaline then they must call 999 immediately and come to casualty. as they may still require further treatment.

Conclusion
Anaphylactic shock can present in the most dramatic fashion but can be treated extremely effectively in only a few minutes. Memorise the treatments and don't be scared to call for expert help at an early stage.

 

Things to be aware of (1)   I well remember someone giving a dose of hydrocortisone to manage a patient who had become breathless after being given a dose of antibiotics. This, of course, will be of no acute help to the patient. When a patient is dead in the mortuary you may see some benefit a few hours later!! Always give oxygen and adrenaline first. (2)   I can also recall a doctor giving intravenous ranitidine. There are two types of histamine blockers. One is useful, the other is useless. H2 blockers are useless.

Next month - how to treat people who have taken a drug overdose.