LAKSHMAN KARALLIEDDEOCTOBER 2011
A precise definition of anaphylaxis is not important for the emergency treatment ofan anaphylactic reaction.Thereis no universally agreed definition.The European AcademyofAllergologyand Clinical Immunology NomenclatureCommittee proposedthe following broad definition:Anaphylaxis is a severe, life-threatening,generalisedor systemichypersensitivity reaction.Thisischaracterisedby rapidly developing life-threatening airway and/or breathingand/or circulation problems usually associated with skin and mucosal changes.
Anaphylaxis is a life-threatening type of allergic reaction
Canoccur at anytime.Risksinclude a history of any type of allergic reaction.
Anaphylaxisis asevere, whole-body allergic reactionto a chemicalthat hasbecome anallergen.
INCIDENCE1million cases of venom anaphylaxis0.4 millioncases of nut anaphylaxis up to age 44 years worldwide.Approximately 20 anaphylaxis deaths reported each year in the UK(specific causes of anaphylaxis -prevalence and severity data available)
PROGNOSISOverallprognosis of anaphylaxis isgood.Casefatality ratio of lessthan 1% reported in most population-basedstudies.Riskof death is,however, increasedin thosewith pre-existingasthma, particularly if the asthma ispoorly controlledorInasthmatics who fail to use, or delay treatmentwith adrenaline.
Anaphylaxis can occur in response to any allergen.Common causes include:Drug allergiesFood allergiesInsect bites/stingsPollens and other inhaled allergens rarely cause anaphylaxis.Some people have an anaphylactic reaction with no known cause.
SymptomsA. develop rapidly- often within seconds or minutes.May include thefollowing:Abdominalpain or cramping-Diarrhoea, Nausea,VomitingDifficultybreathing- Abnormal (high-pitched) breathing sounds-WheezingCoughFainting,light-headedness,dizziness,Anxiety,Confusion, Slurred speechDifficulty swallowingSkin redness,Hives, itchinessNasal congestionPalpitations
SignsInclude:Abnormal heart rhythm (arrhythmia),Low blood pressure, RapidpulseWheezing, Fluid in the lungs (pulmonary edema)Hives, Skin that is blue from lack of oxygen or pale fromshockMentalconfusionSwelling (angioedema) in the throat that may be severe enough to block the airwaySwelling of the eyes or faceWeakness
Life-threatening problemsAirway:swelling, hoarseness,stridorBreathing:Rapid breathingWheezeFatigueCyanosis,SpO2< 92%ConfusionA warning sign of dangerous throat swelling is a very hoarse or whispered voice, or coarse sounds when the person is breathing in air.Circulation:Pale clammy skin/extremetiesLowbloodpressureFaintnessDrowsy/coma
EMERGENCYTREATMENT OF ANAPHYLACTICREACTIONS-Resuscitation Council (UK)•EstablishairwayHighflowoxygenIVfluidchallengeChlorphenamine((IM or slow IV) (IM or slow IV)-Adult or child more than 12 years 10 mgChild 6 - 12 years 5 mgChild 6 months to 6 years 2.5 mgChild less than 6 months 250 micrograms/kg 25mgHydrocortisone((IM or slow IV) (IM or slow IV)Adult or child more than 12 years -200mgChild 6 - 12 years 100 mgChild 6 months to 6 years 50 mgChild less than 6 months 25mg
Monitor-Oxygen saturation- PulseoximetryBlood PressureECG
EpidemiologyOne of the problems is that anaphylaxis is not alwaysrecognised.Further,the criteria for inclusion varyin differentstudies and countries.IncidencerateThe American College of Allergy, Asthma and Immunology Epidemiology ofAnaphylaxis Working group summary:overallfrequencyof episodesof anaphylaxis-between30 and 950 cases per100,000 persons per year.Lifetimeprevalencebetween 50and 2000episodes per 100,000personsor 0.05-2.0%.Lifetimeage-standardised prevalence of arecorded diagnosisof anaphylaxisof75.5 per 100,000 in 2005.Calculationsbasedon thesedata indicate that approximately 1 in 1,333 of the English populationhave experiencedanaphylaxis at some point in their lives
DO NOT: -Assumethat any allergy shots the person has already received will provide complete protection.Place a pillow under the person's head if he or she is having trouble breathing. This can block the airways.Give the person anything by mouth if the person is having trouble breathing.Paramedics or physicians may place a tube through the nose or mouth into the airways (endotracheal intubation) or perform emergency surgery to place a tube directly into the trachea (tracheostomyor cricothyrotomy).
DO : -Take steps to prevent shock.Have the person lie flat, raise the person's feet about 12 inches (Do NOT place the person in this position if a head, neck, back, or leg injury is suspected or if it causes discomfort.Cover with coat or blanket.
Outlook (Prognosis)Anaphylaxis is a severe disorder that can be life-threatening without prompt treatment.However, symptoms usually get better with the right therapy, so it is important to act right away.Possible ComplicationsAirwayblockageCardiacarrest (no effectiveheartbeat)Respiratoryarrest(nobreathing)Shock
TriggersAnaphylaxiscan be triggered by any of a very broad range of triggers.Those most commonly identified includeFoodDrugsVenom.Food - particularly important in childrenMedicinal products being much more common triggers in older people.Virtually any food or class of drug can be implicated, although the classesof foods and drugs responsible for the majority of reactions are well described.Of foods- nuts are the most common causeDrugs: muscle relaxants, antibiotics, NSAIDs and aspirin are most commonlyimplicatedIn many cases, no cause can be identified.Asignificant number of cases of anaphylaxis are idiopathic (non-IgE mediated).
TRIGGERS IIStings 47 -29 wasp, 4 bee, 14 unknownNuts 32 -10 peanut, 6 walnut, 2 almond, 2 brazil, 1 hazel,11 mixed or unknownFood 13 -5 milk, 2 fish, 2 chickpea, 2 crustacean, 1 banana,1 snailFood possible cause 17-5 during meal, 3 milk, 3 nut, 1 each - fish, yeast,sherbet, nectarine, grape, strawberryAntibiotics 27-11 penicillin, 12 cephalosporin, 2 amphotericin,1 ciprofloxacin, 1 vancomycinAnaesthetic drugs 39-19 suxamethonium, 7 vecuronium, 6 atracurium,7 at inductionOther drugs 24-6 NSAID, 3 ACEI, 5 gelatins, 2 protamine, 2 vitamin K, 1 each - etoposide, acetazolamide, pethidine, local anaesthetic, diamorphine,streptokinaseContrast media 11-9 iodinated, 1 technetium, 1 fluoresceinOther 3-1 latex, 1 hair dye, 1 hydatid
Time course for fatal anaphylactic reactionsWhen anaphylaxis is fatal, death usually occurs very soon after contact with the trigger.From a case-series, fatal food reactions cause respiratory arrest typically after 30–35 minutesInsect stings cause collapse from shock after 10–15 minutesDeaths caused by intravenous medication occur most commonly within five minutes.Death never occurred more than six hours after contact with the trigger
Anaphylaxis is likely when all of the followingcriteriaaremet:Sudden onset and rapid progression of symptomsLife-threatening Airway and/or Breathing and/or Circulation problemsSkin and/or mucosal changes (flushing, urticaria, angioedema)The following supports the diagnosis:Exposure to a known allergen for the patientRemember:Skin or mucosal changes alone are not a sign of an anaphylactic reaction. Skin and mucosal changes can be subtle or absent in up to 20% of reactions (some patients can have only a decrease in blood pressure, i.e., a Circulation problem)There can also be gastrointestinal symptoms (e.g. vomiting, abdominal pain, incontinence)
Sudden onset and rapid progression of symptomsThe patient will feel and look unwell.Most reactions occur over several minutes.Rarely, reactions may be slower in onset.The time of onset of an anaphylactic reaction depends on the type of trigger.An intravenous trigger will cause a more rapid onset of reaction than stings-which, in turn, tend to cause a more rapid onset than orally ingested triggersThe patient is usually anxious and can experience a “sense of impendingDoom”
Life-threatening Airway and/or Breathing and/or CirculationproblemsPatients can have either an A or B or C problem or any combination.Use the ABCDE approach to recognise these.Airway problems:Airway swelling, e.g., throat and tongue swelling (pharyngeal/laryngealoedema). The patient has difficulty in breathing and swallowing and feels that the throat is closing up. Hoarse voice.Stridor – this is a high-pitched inspiratory noise caused by upper airway obstruction.Breathing problems:Shortness of breath – increased respiratory rate.Wheeze.Patient becoming tired.Confusion caused by hypoxia.Cyanosis (appears blue) – this is usually a late sign.Respiratory arrest.There is a range of presentation from anaphylaxis-anaphylaxis with predominantly asthmatic features- to a pure acute asthma attack with no other features of anaphylaxis. Life-threatening asthma with no features of anaphylaxiscan be triggered by food allergy.Anaphylaxis can present as a primary respiratory arrest.
Circulation problemsSigns of shock – pale, clammy.Increased pulse rate (tachycardia).Low blood pressure (hypotension) – feeling faint (dizziness), collapse.Decreased conscious level or loss of consciousness.Anaphylaxis can cause myocardial ischaemia and electrocardiograph (ECG) changes even in individuals with normal coronary arteries.Cardiac arrest.Circulation problems (referred to as anaphylactic shock) can be caused by direct myocardial depression, vasodilation and capillary leak, and loss of fluid from the circulation.Bradycardia (a slow pulse) is usually a late feature, often preceding cardiac arrest.The circulatory effects do not respond or respond only transiently to simple measures such as lying the patient down and raising the legs. Patients with anaphylaxis can deteriorate if made to sit up or stand up.A, B and C problems can all alter the patient’s neurological status (Disability problems) because of decreased brain perfusion. There may be confusion, agitation and loss of consciousness. Patients can also have gastro-intestinal symptoms (abdominal pain, incontinence, vomiting).
Skin and/or mucosal changesThese should be assessed as part of theExposurewhen using the ABCDEapproach.They are often the first feature and present in over 80% of anaphylactic reactions.They can be subtle or dramatic (just skin, just mucosal, or both skin and mucosal changes).There may be erythema – a patchy or generalised, red rash.There may be urticaria (also called hives, nettle rash, weals or welts), which can appear anywhere on the body.The weals may be pale, pink or red, and may look like nettle stings.They can be different shapes and sizes, and are often surrounded by a red flare.They are usually itchy.
Angioedema is similar to urticaria but involves swelling of deeper tissues,most commonly in the eyelids and lips, and sometimes in the mouth andthroat.Although skin changes can be worrying or distressing for patients and those treatingthem, skin changes without life-threatening airway, breathing or circulation problemsdo not signify an anaphylactic reaction.Reassuringly, most patients who have skin changes caused by allergy do not go on to develop an anaphylactic reaction.Differential diagnosisLife-threatening conditions:Anaphylactic reaction can present with symptoms and signs that are very similarto life-threatening asthma– this is commonest in children.A low blood pressure (or normal in children) with a petechial or purpuric rashcan be a sign ofseptic shock.Seek help early if there are any doubts about the diagnosis and treatment.Following an ABCDE approach will help with treating the differentialdiagnoses.
Non life-threatening conditions (these usually respond to simple measures)Faint (vasovagal episode).Panic attack.Breath-holding episode in child.Idiopathic (non-allergic) urticaria or angioedema.There can be confusion between an anaphylactic reaction and a panic attack.Victims of previous anaphylaxis may be particularly prone to panic attacks if theythink they have been re-exposed to the allergen that caused a previous problem.The sense of impending doom and breathlessness leading to hyperventilation aresymptoms that resemble anaphylaxis in some ways.While there is no hypotension, pallor, wheeze, orurticarialrash or swelling, there may sometimes be flushing or blotchy skin associated with anxiety adding to the diagnostic difficulty.Vasovagal attacks after immunisation procedures-absence of rash, breathing difficulties, and swelling are useful distinguishing features, as is the slow pulse of a vasovagal attack compared with the rapid pulse of a severe anaphylactic episode. Fainting will usually respond to lying the patient down and raising the legs.
Adrenaline (Epinephrine)Adrenaline is the most important drug for the treatment of an anaphylactic Reaction.Consistent anecdotal evidence supporting its use to ease breathing difficulty and restore adequate cardiac output.As an alpha-receptor agonist, it reverses peripheral vasodilation and reduces oedema.Its beta-receptor activity dilates the bronchial airways, increases the force of myocardial contraction, and suppresses histamine and leukotriene release.There are also beta-2 adrenergic receptors on mast cells that inhibit activation, and so early adrenaline attenuates the severity of IgE-mediated allergic reactions.Adrenaline seems to work best when given early after the onset of the reaction but it is not without risk, particularly when given intravenously.Adverse effects are extremely rare with correct doses injected intramuscularly (IM). Sometimes there has been uncertainty about whether complications (e.g., myocardial ischaemia) have been caused by the allergen itself or by the adrenaline given to treat it.
Intramuscular(IM) AdrenalineTheintramuscular (IM) route is best for most who have to give adrenaline to treat ananaphylacticreaction. Monitor the patient as soon as possible (pulse, blood pressure, ECG,pulseoximetry) -To monitor the response to adrenaline.Benefits of IM route :There is a greater margin of safety.It does not require intravenous access.The IM route is easier to learn.Best site for IM injection - anterolateral aspect of the middle third of the thigh.The subcutaneous or inhaled routes for adrenaline are not recommended becausethey are less effectiveAdrenaline IM dose – adults0.5 mg IM (= 500 micrograms = 0.5 mL of 1:1000) adrenalineAdrenaline IM dose – children-scientific basis forrecommended doses is weak.> 12 years: 500 micrograms IM (0.5 mL) i.e. same as adult dose300 micrograms (0.3 mL) if child is small or prepubertal> 6 – 12 years: 300 micrograms IM (0.3 mL)> 6 months – 6 years: 150 micrograms IM (0.15 mL)< 6 months: 150 micrograms IM (0.15 mL)Repeat the IM adrenaline dose if there is no improvement .Further doses can be givenat about 5-minute intervals according to the patient’s response.