Asthma

Notes

## Basic introduction

  • Asthma is defined as a chronic inflammatory disorder of the airways that is characterized by recurrent attacks of breathlessness and wheezing of varying severity and frequency.

## Pathogenesis of asthma

  • During the asthmatic attacks cells in the respiratory tract are infiltrated by neutrophils, eosinophils, and lymphocytes.
  • Mast cells are also activated to release vasoactive amines such as histamine and serotonin.
  • These factors are responsible for hyper-responsiveness of the respiratory system to environmental changes and infections, mostly by viruses.
  • These responses are generally genetically dependent and they result in restriction of airflow as well as other symptoms of asthma.
  • Pathogenesis of asthma is further complicated by such factors like sub-basement fibrosis, mucus hypersecretion, injury to epithelial cells, smooth muscle hypertrophy, and angiogenesis.
  • Atopic individuals have the high genetic likelihood to be hyper-responsiveness to allergens in IgE-mediated immune action.

## Statistics

  • Globally, 235 million people suffer from asthma, most of whom are from low- and lower-middle income countries (It is the commonest chronic lung disease in the world)
  • Globally, 250 000 deaths occur from asthma annually
  • In Kenya, the prevalence of asthma is thought to be 10% (or 4 million) of the general population.
  • In Kenya, asthma constitutes 0.24% of total annual deaths (2014)
  • The disease is apparently more common in urban areas compared to rural areas

## Risk factors for Asthma

  • Family history
  • Viral respiratory infections
  • Helminthic infections
  • Allergies
  • Occupational exposures
  • Smoking
  • Air Pollution
  • Obesity
  • Early exposure to the broad spectrum antibiotics
  • Premature and low birth weight
  • Past history of atropy
  • HIV infection
  • Gender: early M>F; Later F>M
  • Menses
  • Drugs such as beta blockers and NSAIDS
  • Emotional reactions

## Classification of asthma

  • Mild:

_Wheezing

_BP normal

_Pulse rate (< 100 / min)

_RR (< 20 / min)

  • Moderate:

_Wheezing with a cough

_BP normal

_Pulse rate (100 - 120/min)

_RR (20-30/ min)

  • Severe

_Wheezing with a cough

_Pulse rate (120/min)

_RR (30/ min)

_Cyanosis

_Pulsus paradoxus

_Respiratory distress in the upright position

  • Chronic

_Mild attack continuously

  • Status asthmaticus

_Moderate to chronic attacks that fail to respond to treatment or the attacks that last >12hrs

Symptoms
  • Wheezing
  • Breathlessness
  • Cough with tenacious sputum
  • Bronchospasm
  • Excessive production of secretions
Diagnosis
  • Chest X-rays
  • Forced expiratory volume (FEV1)
  • Maximal mid- expiratory flow rate (MMEFR)
  • Peak expiratory flow rate (PEFR)
Differential
  • COPD
  • Bronchiectasis
  • Aspergillosis
  • Chronic Sinusitis
  • Pneumonia
  • Pulmonary edema
  • Pulmonary embolism
  • Pneumothorax
  • Congestive Heart Failure (CHF)
  • Gastroesophageal Reflux Disease
  • Alpha1-Antitrypsin Deficiency
  • Chronic bronchitis
  • TB
  • Upper airway obstruction e.g. foreign body
Prevention
  • Cessation of smoking
  • Breast feeding
Reference

a. Abramson MJ, Perret JL, Dharmage SC, et al; Distinguishing adult-onset asthma from COPD: a review and a new approach. Int J Chron Obstruct Pulmon Dis. 2014 Sep 9;9:945-962. E Collection 2014.

b. Kenyan Ministry of Health. Clinical guidelines for management and referral of common conditions at levels 4-6. Hospitals. 2009; 3:259-261.http://apps.who.int/medicinedocs/documents/s21000en/s21000en.pdf

c. Ministry of Health, Kenya. Kenya Essential Medicine List (2016). http://publications.universalhealth2030.org/uploads/KEML-2016Final-1.pdf

d. Mohamed N, Ng’ang’a L, Odhiambo J, Nyamwaya J, Menzies R. Home environment and asthma in Kenyan schoolchildren: a case-control study. Thorax. 1995 Jan;50(1):74-8.

e. WHO. Asthma. Fact sheet N°307. http://www.who.int/mediacentre/factsheets/fs307/en/

Management
  • An under-treated asthma leads to chronic inflammation that modifies the airways leading to the development of fixed airways disease that does not respond to bronchodilator therapy.
  • Mild:

_SC Adrenaline 1:1000 STAT, repeat the dose after 20-30 minutes if the response is unsatisfactory (up to 3 doses) then discharge with:

_Tabs Salbutamol 4mg TID x 1/52 or Tabs Theophylline 200-250mg BD or TID x 1/52 then maintain with:

_Salbutamol or albuterol or terbutaline inhalers

  • Moderate:

_Rx SC Adrenaline 1:1000 STAT, repeat the dose after 20-30 minutes if the response is unsatisfactory (up to 3 doses) OR

_Salbutamol and Ipratropium bromide nebulization every 20 minutes (max dosage is determined by appearance of tremors) If the response is not satisfactory add:

_IV Aminophylline 6mg/kg slowly over 15 minutes, and then 0.9mg/kg/hr. then discharge with:

_Tabs Salbutamol 4mg TID x 1/52 or Tabs Theophylline 200-250mg BD or TID x 1/52

_If the response is not satisfactory treat as severe asthma below:

  • Severe

_Oxygen 3-5L/minutes in case the patient is cyanosed then:

_IV Aminophylline 6mg/kg slowly over 15 minutes (DO NOT GIVE THIS LOADING DOSE IF ALREADY GIVEN), and then 0.9mg/kg/hr then:

_IV Hydrocortisone 200mg STAT OR Methyl prednisolone 1gm STAT OR IV/IM Dexamethasone 2-4mg STAT then:

_Tabs Prednisolone 10-15mg TID on day 1, then tail off in 7-10 days then maintain with:

_Corticosteroid or long-acting beta-agonist inhalers OR theophylline tablet OR anti-leukotriene

_Antibiotic cover e.g. Amoxicillin.

  • Chronic

_Tabs Salbutamol 4mg TID OR Salbutamol inhaler or steroid inhaler

  • Status asthmaticus

_Treat as severe

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