What is anaphylaxis symptoms ?
Anaphylaxis is a systemic hypersensitivity reaction which is life threatening and cause by reaction to allergen mediated by IgE antibodies.
Following an antigen exposure to sensitized patient it may leads to an IgE mediated acute systemic reaction.
Besides IgE mediated anaphylactic reaction , a non IgE mediated idiopathic anaphylactoid reaction are also common.
Anaphylaxis and anaphylactoid reaction are indistinguishable and both are treated in the same manner.
Cardiovascular, respiratory, gastrointestinal, metabolic, endocrine, hematology and lymphatic as well as skin/exocrine systems are affected.
What are the etiology of anaphylaxis reaction ?
The etiology may includes :
Iodinated radiological contrast.
administration of blood product in patient with IgA deficiency ( formation of anti IgA- antibodies )
antimicrobial ( penicillin )
fish , peanuts, eggs and insect stings
ethylene oxide gas ( dialysis tubing )
macromolecules( insulin, protamine, glucocorticoid and chymopapain)
What are the associated risk factor for anaphylaxis ?
Anaphylaxis is associated with other condition such as allergic hypersensitivity reaction ( allergic rhinitis and atopy asthma )
How common is anaphylaxis reaction ?
Anaphylaxis is common affect all ages and male and female equally.
1 in 5000 patients may develop anaphylaxis reaction due to exposure to parenteral cephalosporin and penicillins antibiotics.
0-5% - !% may develop peanut allergy common in children.
1%-2% may develop anaphylaxis reaction as a result from iodinated radiological contrast media ( hypersensitivity reaction) .
1 in 700 patient is presented with selective IgA deficiency .
Idiopathic anaphylaxis account up to 40 000 cases per year where the causes remain unknown, 0.3 - 0.7 per 100 000 per year anaphylactic death.
How does the anaphylactic patient present ?
In acute case of anaphylactic reaction , the patient may present with :
wheeze, sensation of choking,
rash and pruritus as well as shortness of breath,
swelling of the lips and faces.
Generally, the patient may present with flushing, urticaria , angioedema , develop rhonchi, bronchorrhea, rhinorrhea, swallowing difficulty, cramping bloating, nausea, vomiting, diarrhea, tachycardia, shock hypotension, syncope, mydriasis, shivering and malaise.
While examining the patient, the patient may present with :
Signs of airway edema, such as rhinitis, swelling of upper airways and eyes as well as conjunctival injection.
Signs of shock such as hypotension and tachycardia.
Signs of bronchospasm such as tachypnoea , wheeze and cyanosis.
Signs on the skin such as wheal/urticarial rash and angioedema.
How to detect anaphylaxis reaction ?
Arterial blood gases may reveals hypercarbia ( increase in carbon dioxide level ) , hypoxemia ( reduction in oxygen level ) and acidosis.
Urea and electrolytes
Raised in potassium level ( K+) hyperkalemia, as acidosis may cause the movement of potassium extracellularly. In certain cases the potassium level is reduced due to the effect of certain drugs such as albuterol and epinephrine ( adrenaline ).
Elevation of serum tryptase which is an enzyme from a mast cell that are released from anaphylactic and allergic reaction.
IgE level may be raised
Allergen skin identifying test :
To identify allergen,potentially dangerous as it may precipitate anaphylactic reaction.
RAST test to identify specific IgE.
Differential diagnosis of anaphylaxis reaction:
Foreign body aspiration, pulmonary embolism and arrhythmias.
Hereditary angioedema- due to deficiency of the C1q esterase deficiency may present with painless, non pruritic angioedema , no evidence of wheezing, flushing or urticaria.
Pharyngeal edema ( globus hystericus )
Pheochromocytoma - Patient presented with tachycardia and hypotension due to beta 2 stimulation.
Pseudoanaphylactic reaction due to exposure to procaine penicillin .Drug effect of procaine is the cause of anaphylactic reaction rather than penicillin allergy.
Scromboid poisoning - after ingestion of dark meat fish such as mackarel and tune. The mast cell mediator may leads to headache, nausea, vomiting, sweating, flushing, diarrhea, dizziness, palpitations, swelling of the face and tongue, rash and respiratory distress.
Benign overgrowth as well as malignant overgrowth of mast cell.Benign overgrowth may present with urticaria pigmentosa and reddish - brownish macular - papular cutaneous lesion ( Darier ‘s sign ) .Develop after trauma.
Serum sickness - several days develop.
Vasovagal syncope- present with hypotension and bradycardia.
What is the pathology behind anaphylaxis ?
Anaphylaxis reaction is a Type 1 hypersensitivity reaction . It develop probably due to exposure of the allergen to the previously sensitized individuals.The allergen will bind to the IgE . The IgE is binding to the mast cell and basophil which leads to cross link.
IgE will mediated mast cell degranulation . This will leads to the activation of and the release of vasoactive compound such as histamine, leukotriene and prostaglandin, It will also leads to the activation of the complement . ( C3a. C4a and C5a ).
This condition will leads to increase in membrane permeability, bronchospasm, reduced vascular tone and tissue edema as a result of increase in fluid loss onto the extravascular space.
Non IgE mediated anaphylactoid reaction is clinically similar to anaphylaxis without any antibodies involvement and involve non - immunological release of histamine and complement activation. It is also modulated by arachnoid acid metabolism.
What is the treatment of anaphylaxis ?
Generally the treatment depends on how severe the anaphylaxis reaction is .
The main aim of the treatment is to maintain a patent airway which can be achieved with endotracheal intubation and assisted ventilation.
In children less than 12 years old, tracheostomy and possible needle cricothyrotomy is performed.
This is follow later by oxygen and iv normal saline solution or lactated ringers fluid.
Patient is advised for bed rest until the patient is hemodynamically stable and clear from anaphylactic reaction.
In emergency setting
Removes any precipitant/contributing factor such as drugs or food.
Resuscitation following the principle of airway, breathing and circulation , Gives 100% of oxygen, secure the airway intubation and consider transfer to ITU for anesthetic evaluation .
Adrenaline ( epinephrine) is given IM ( 0.5 ml or 1: 1000) repeatedly every 10 minutes based on blood pressure and pulses.
This is follow by antihistamine given IV ( 10 mg chlorpheniramine)
Later by steroid IV ( 100mg hydrocortisone ).
To maintain the blood pressure , patient required IV colloid or crystalloid solution .
If patient is hypotensive , patient needs to lie flat and head tilt down .
If the patient suffer from bronchospasm , IV salbutamol and ipratropium bromide are needed and IV aminophylline may also be required.
What is the complication of anaphylaxis reaction ?
The complication of anaphylaxis reaction may includes shock , respiratory failure, cardiac arrest, death and hypoxemia .
What is the prognosis of anaphylaxis reaction ?
In moderate and severe cases of anaphylaxis may required admission for further evaluation.
Patient is discharged if he suffer from cutaneous angioedema, with minimal bronchospasm, and urticaria where signs and symptoms are cleared.
Patient is rede to a specialist if the causes of anaphylaxis remain unknown. Desensitization immunotherapy is helpful for patient that develop anaphylaxis reaction with insect stings.
Prognosis is good if prompt treatment is given.
Delay in admission of adrenaline ( epinephrine ) - > 30 minutes will carry worse outcome.
Any case of idiopathic anaphylaxis may present with > 60% of individual free of anaphylaxis episodes at 2- 5 years
In elderly patient, adrenaline ( epinephrine ) may leads to myocardial ischemia and other cardiac disease, Adrenaline ( epinephrine) may also reduce the placental blood flow and increase risk of congenital malformation.
1st line of drugs may include- adrenaline ( epinephrine), H2 blocker/diphenhydramine , corticosteroids, bronchidilator ( beta agonist ) and dopamine - in case of persistent hypotension.
2nd line of drugs may include aminophylline, tranexamic acid, anti IgE monoclonal antibody and venom immunotherapy ( for insect stings).
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