what is the pathophysiology of asthma, its cardinal features

What is Asthma?

It is a chronic inflammatory disease in which the patient suffers from airway obstruction due to bronchial hyper-responsiveness.

In the acute phase besides bronchoconstriction, there is excessive secretion of mucus that may block bronchi and bronchioles.

In the chronic phase, inflammation is followed by edema, necrosis, and fibrosis of bronchial epithelial
cells.

what is the Pathophysiology of Asthma:-

Antigens sensitize individuals by forming IgE antibodies, which remain either circulating in the blood or become attached to mast cells of the trachea-bronchial tree. On re-exposure to the same antigens, an antigen-antibody reaction takes place on the surface of lung mast cells, causing their degranulation which releases spasmogens like Histamine, Serotonin, Leucotriens, Prostaglandins, Interleukins, etc. leads to bronchoconstriction and later on inflammation and epithelial damage.

What are Cardinal features of asthma are:-

a. Breathlessness

b. Wheezing and cough

c. Chest tightness with worsening of symptoms at night.

Hospitalization:-

A high concentration of 40-60% Humidified oxygen should be given by face mask.

Salbutamol 5 mg and Ipratropium bromide 0.5 mg should be given by nebulizer till the patient is able to take my inhaler.

Injection Hydrocortisone hemisuccinate 100 mg IV stat followed by 100 mg injection 8 hourly by infusion till patients improve then it is shifted to oral prednisolone.

Injection Azithromycin 500 mg is once daily for 7 days.

Rehydrate the patients with 5% glucose saline with the appropriate quantity of potassium.

Drugs used in Bronchial Asthma:-

1. Salbutamol – It is a B, agonist. It has a bronchodilator effect.

Mechanism of Action:-

 i. It relaxes bronchial smooth muscles especially smaller airways are affected.

ii. It inhibits the release of bronchoconstriction chemical mediators from the mast cells.

So, it causes symptomatic relief. But it does not control the disease process, so this group of drugs is a reliever.

In acute severe asthma, salbutamol is given by nebulizer wherein synchronization with breathing is not required.

Nebulizer:-

It is a medical device that converts liquid medicine into vapor or aerosol. So that it can be inhaled directly into the lungs. It is very valuable for children and old people who can’t coordinate inhalers. It is also very useful in acute severe asthma or status asthmaticus.

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WHO-recommended oral rehydration salts

Whitfield ointment uses

pathophysiology of asthma

Dose & Route of administration:-

1. Inhalational preferred via Rotacap & MDI:-100-200mcg

Via Nebulizer:-2.5-5mg

2. Oral:-2 to 4mg

Side effects:-

1. Muscle tremor

2. Nervousness

β2 agonist may cause hypokalemia which can be aggravated by concurrent use of other drugs like theophylline, diuretics, glucocartic coids, and by hypoxia. So, potassium supplement must be given with i.v. fluids.

Other β2 agonists:-

Short acting:-Terbutaline

Long acting:-Salmeterol, Bambuterol

Terbutaline is the only drug safe in pregnancy.

2. Ipratropium bromide:- It is a muscarinic (M3) receptor antagonist/anti-cholinergic.

Mechanism of action:-

It binds with M3, a receptor on airway smooth muscle and thereby preventing the action of Acetylcholine released from parasympathetic neurons. So it causes bronchodilation. But these bronchodilators are less effective than, agonists. They act primarily in larger airways.

A combination of ipratropium bromide and p, agonist works better in severe asthma and has a longer duration of action than either drug alone.

3. Corticosteroid:- These are called controllers because they provide long term
   stabilization of symptoms due to their anti-inflammatory effects. In acute severe asthma, it is given i.v. So that dose can be adjusted according to clinical need.

Once the patient shows improvement it should be switched to oral glucocorticoids. The dose should be reduced by 5 mg every 3-4 days.

Mechanism of Action:-

1. They enhance β2, a response by upregulating the receptors in lung cells and leucocytes.

2. They inhibit the release of prostaglandins and leukotrienes and thus prevent smooth muscle contraction and airway secretion.

3. They inhibit release of cytokines and chemical mediators from mast cells and
   eosinophils.

Parenterally used corticosteroids:- Hydrocortisone hemisuccinate, methylprednisolone, etc.

Inhalers are:- Beclomethasone, fluticasone, budesonide, etc.

Azithromycin:- It is given to present any kind of chest infection. Macrolide antibiotics are preferred because they also increase the half-life of glucocorticoids.

Rehydration:- Rehydration not only corrects dehydration but also makes the bronchial secretions less tenacious.

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