Anaphylaxis
Anaphylaxis is a potentially life threatening systemic reaction mediated by IgE or possibly IgG4. It occurs within few minutes of exposure to susceptible antigen in previously sensitized individuals.
Signs and symptoms of Anaphylaxis
Flushing pruritus, diaphoresis, urticaria in chest, shock, arrhythmia, hypotension, G.I. symptoms and angiodema. Anaphylactoid reactions are non immunologically medicated reactions with similar end organ responses.
The mast cell deregulation that produces histamines, kinins, prostaglandin D2 and leukotrienes are responsible for these symptoms. Histamine cause endothelial and bronchial smooth muscle contraction (H-1 receptor) or dilatation of vascular smoothy muscle (H2 receptors).
Management of Anaphylaxis
1. IM / SC adrenaline at the first sign of anaphylaxis can prevent the more serious reactions. The dose is 0.01 ml / kg up to a maximum of 0.5 ml of 1:1000 sol. 0.1 ml of injection to injection or sting site may also be help. IM/SC dose can be repeated every 15 minutes till response is obtained or complications like adrenaline 0.5 ml in adults and upto 0.3 ml in children, diluted in 20 ml of saline injected very slowly.
2. Oxygen inhalation. 4.5 litres / min.
3. Elevation of foot end of bed by 1 foot to augment circulation to brain.
4. IV diphenudramine or chlopheniramine, promethazine 25 mg.
5. I.V. aminophyline 4-7 mg / kg if there is bronchopasam.
6. In severe shock rapid saline infusion at first followed by dopamine infusion to maintain systolic BP above 100mm Hg.
7. Methyl prednisolone 2 mg / kg every 4 hours or dexamethason 2 mg every 4 hours.
8. Tourniquest to be applied proximal to the injection / sting site to obstruct lymphatic flow.
9. Monitoring of vital signs every 15 minutes till recovery.
Causative agents of Anaphylaxis
|
ANAPHYLAXIS |
ANAPHYLACTOID |
| Antibiotics : pencillin, tetracycline SM, cephalosorins | Aspirin |
| Antisera | Food and drug additives (Terazine, benzoate, sulphite) |
| Insulin, ACTHChymopapin (meat tenderizer,Contact lens cleaning agent) | Captopril |
| Insect sting | Dextran, Iron dextran |
| Food : Milk, egg white, shellfish, prawn, nuts | Muscle relaxant |
| Radiographic contrast media Vit B12, thiamine | Opitates |
| Procaine |
Precautions/Preventions of Anaphylaxis
Avoidance of drugs to which patient is sensitive. When pencillin or any aent known to cause anaphylaxis is being proposed to be injected, askin test is mandatory. Desensitization technique should be employed with gradually increasing doses while injecting antisera to sensitive patients.
A patient receiving injection should remain in hospital for 30 minutes.
Predisposed patients should avoid beta blockers.
Exercise induced asthma needs salbutamol or sodium chromoglycate inhalation 30 minutes before exercise.
All injections likely to produce anaphylaxis when are to be injected for more than a week are to be retested with skin after 5-7 injections
Antihistamines (H1 Blockers)
|
Compound |
Dose |
Frequency |
| Diphenhydramine |
25-50 mg |
4-6 hours |
| Clemastine |
0.34-2.68 |
12 hours |
| Triplenamine |
25-50mg |
4-6 hours |
| Chlorpheniramine |
4mg |
4-6 hours |
| Bropheniramine |
4mg |
4-6 hours |
| Tripolidine |
2.5mg |
4-6 hours |
| Promethazine |
10-25mg |
8-12 hours |
| Hydroxyzine |
25mg |
6-8 hours |
| Cetirizine |
10mg |
24 hours |
| Azatadine |
1-2mg |
12 hours |
| Loratadine |
10mg |
24 hours |
| Terfenadrine |
60mg |
12 hours |
| Fexofenadine |
120-180mg |
24 hours |