Acute Severe Asthma (Status Asthmaticus)

Acute severe asthma (status asthmaticus) is a life-threatening emergency. Patients are severely dyspneic, cyanosed, and often moribund. At this stage, many of them are unresponsive to the ordinary bonchiodilators. Dehydration may be evident.

Laboratory findings
These are often non-specific and they help in identifying the coexisting disease. Some cases show moderate esosinophilia (10-15%). Examination of feces may reveal helminthes which may also contribute to the allergic reaction and increase in eosinophils. Sputum may reveal numerous eosinophils, mucus plugs and Curschmann's spirals (casts of distal airways). Purulent sputum is indicative of respiratory infection. Culture revels the infecting organisms.

Identification of the allergen
Several tests have been introduced to identify the precipitating allergen. Intradermal tests are performed using a battery of antigens prepared from the common allergens prevalent in the area. In many instances the causative agent can be detected by the positive skin tests. Respiratory function tests reveal marked airway obstruction, which is relieved by the administration of bronchodilators.

Skiagram taken during the acute attack may show hypertranslucency due to emphysema but there may be an abnormality in between the attacks. It should be remembered that the radiological appearances and clinical severity show wide disparity in bronchial asthma.

Complications
Mortality is uncommon in asthma but severe attack may result in respiratory failure and death. This is more so in status asthmaticus. Other complications include frequent respiratory infections, pulmonary collapse due to obstruction by viscid secretions, penumothorax, mediastinal emphyseama and cough fractures (fractures of ribs due to violent coughing). Children with asthma may show retardation of growth, especially if treated with corticosteroids on a long-term basis. Long standing bronchial asthma, punctuated with frequent respiratory infections may lead on to emphysema and chronic cor pulmonale.

Diagnosis
Diagnosis of bronchial asthma is clinical. The history of sudden attack of paroxysmal dyspnea, cough, and the auscultatory hallmark of expiratory wheeze heard all over the chest are diagnostic. Long duration of complaints, history of allergy, and positive family history are other helpful clinical points.

Differential diagnosis
Bronchial asthma has to be differentiated from other causes of paroxysmal dyspnea. These include chronic bronchitis emphysema syndrome (CBES), acute left-sided heart failure, acute bronchitis, tropical pulmonary eosinophilia, metabolic acidosis, and tracheal obstruction by foreign bodies. It is important to distinguish left-sided heart failure (cardiac asthma) from bronchial asthma. Left-sided heart failure complicates valvular heart disease, systemic hypertension or ischemic heart disease. It causes paroxysmal dyspnea in the first half of the night whereas bronchial asthma is more common in the early hours of the morning. In bronchial asthma, there is generalized wheeze all over the chest, whereas in cardiac failure, basal crepitations are more prominent, though generalized bronchospams may also be evident at times. In heart failure, gallop rhythm may be evident. Careful search for the underlying disease may reveal the etiology.