Asthma is a chronic inflammatory disorder of the airways. Inflammation causes recurrent episodes of wheezing, breathlessness, chest tightness, and coughing particularly at night and early morning.
Asthma can be classified by severity depending on how well the symptoms respond to treatment. Severe asthma refers to asthma that does not respond well to regular asthma treatments, such as inhaled corticosteroids and inhaled bronchodilator medications.
Hospital treatment of acute severe asthma relies on pressurized metered dose inhalers (MDIs) and/or nebulizers for delivery of bronchodilators and anti-inflammatory agents.
Disappearance of nebulized clouds during inspiration and cloud increase on expiration are signs of improvement. Commencement of coughing and expelling of mucous plugs, return of audible wheeze or its reduction, less use of accessory muscles, improvement of consciousness, return of speech, and arterial blood CO2 reduction are also signs of improvement.
Salbutamol is the preferred short-acting beta2-agonist because it has an excellent safety profile and the most data related to safety during human pregnancy are available for this medication.
Nebulized magnesium sulphate, ipratropium bromide, adrenaline, frusemide are additional therapies.
Nebulized MgSO4, either alone or combined with salbutamol, has a significant bronchodilator effect in acute bronchial asthma. Bronchodilator effect of nebulized MgSO4 alone is similar to that of nebulized salbutamol but significantly less than that of nebulized combination.
Furthermore, MgSO4 has a stabilizing effect on the atria which may attenuate tachycardia occurring after inhaled and i.v. salbutamol.
Adding furosemide to salbutamol in patients suffering from acute reactive airway disease considerably improve peak expiratory flow rate (a person’s maximum speed of expiration), but there is not sufficient proof to confirm it as a routine standard treatment of acute reactive airway diseases like asthma.
Nebulized adrenaline is an efficacious, well tolerated, less expensive and safe drug of choice in cases of croup, angioedema, bronchiolitis and post-extubation stridor. However in some conditions such as hypertension, diabetes mellitus, coronary artery disease, and cerebrovascular disease, it should be used with caution because it has alpha adrenergic effects (vasoconstiction).
If an asthmatic is unable to speak, coughing excessively, or unable to breathe in adequate volumes, inhalation therapy is unlikely to reverse bronchospasm. Instead, i.v. drugs (magnesium sulphate, salbutamol, terbutaline, adrenaline, montelukast and aminophylline) are recommended in such cases. However, there is currently no consensus on the use of systemic (i.v. epinephrine, terbutaline, and salbutamol) over aerosol therapy in asthma. Some authorities like the Canadian Medical Association advocates for Iv route only if the response to nebulization is poor.
Leukotrienes antagonists such as i.v. montelukast given to moderate to severe asthmatics demonstrated a significant improvement in pulmonary function within 10 min of administration.
Methyl xanthines are not recommended in USA guidelines, but British Thoracic Society guidelines state that i.v. aminophylline can be used in acute severe asthma if there is little response to other treatment (which does not include i.v. salbutamol in adults).
MgSO4 i.v. has anti-convulsant and anti-arrhythmic actions and may be used to minimize some of the side-effects of aminophylline.
Anaesthetic inhalation agents (e.g. halothane, sevoflurane, norflurane) have smooth muscle relaxing properties and can be delivered to spontaneous breathing asthmatic patients using tight-fitting anaesthetic face masks and continuous positive airway pressure devices.
Although the intravenous anaesthetic propofol and ketamine have been shown to produce less wheezing and thus safe induction agents for tracheal intubation than thiopental and methohexital, ketamine is considered to be the bronchodilator of choice in rescue therapy for refractory bronchospasm and refractory status asthmaticus in the intensive care unit (ICU).