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Management of acute severe asthmaInitial assessment The features of acute asthma are listed in Box 19.25. An immediate assessment of patients (Fig. 19.25) should include their ability to speak, pulse rate, respiratory rate, BP and SaO2. Measurement of PEF is mandatory unless the patient is too ill to cooperate and is most easily interpreted when expressed as a percentage of the predicted normal or of the previous best value obtained on optimal treatment. Arterial blood gas analysis is essential to determine the PaCO2, a normal or elevated level being particularly dangerous. A chest X-ray is not immediately necessary unless pneumothorax is suspected.
Oxygen High concentrations of oxygen (humidified if possible) should be administered to maintain the oxygen saturation above 92% in adults. The presence of a high PaCO2 should not be taken as an indication to reduce oxygen concentration but is a warning sign of a severe or life-threatening attack. Failure to achieve appropriate oxygenation is an indication for assisted ventilation. High doses of inhaled bronchodilators Short-acting β2-agonists represent the agent of first choice. In hospital they are most conveniently administered via a nebuliser driven by oxygen but delivery of multiple doses of salbutamol via a metered dose inhaler through a spacer device provides equivalent bronchodilation and may be considered in primary care. Ipratropium bromide provides additional bronchodilator therapy and should be added to salbutamol in patients with acute severe or life-threatening attacks. Systemic corticosteroids Systemic corticosteroids reduce the inflammatory response and hasten the resolution of exacerbations. They should be administered to all patients with an acute severe attack. They can usually be administered orally (prednisolone 30-60 mg), but intravenous hydrocortisone 200 mg may be used in patients who are unable to swallow or vomiting. Intravenous fluids There are no controlled trials to support the use of intravenous fluids but many patients are dehydrated due to high insensible water loss and will probably benefit from hydration therapy. Potassium supplements may be necessary because repeated doses of salbutamol can lower serum potassium. Subsequent management If patients fail to improve, a number of further options may be considered. Intravenous magnesium may provide additional bronchodilation in patients whose presenting PEF is < 30% predicted. Some patients appear to benefit from the use of intravenous aminophylline but careful monitoring is required. Intravenous leukotriene receptor antagonists may soon become available. Monitoring of treatment PEF should be recorded every 15-30 minutes and then every 4-6 hours. Pulse oximetry should ensure that SaO2 remains > 92% but repeat arterial blood gases are necessary if the initial PaCO2 measurements were normal or raised, the PaO2 was < 8 kPa (60 mmHg), or the patient deteriorates.
The newest asthma medication is omalizumab (Xolair), a recombinant DNA-derived humanized immunoglobulin G monoclonal antibody that binds selectively to human immunoglobulin E on the surface of mast cells and basophils. The drug reduces mediator release, which promotes an allergic response. Indicated for moderate-to-severe persistent asthma in patients who react to perennial allergens, in whom symptoms are not controlled by inhaled corticosteroids. The dose (adults and children >12 y) is 150-375 mg subcutaneously every 2-4 weeks (precise dose and frequency is established by serum immunoglobulin E levels). The estimated annual cost is $12,000-15,000.
Date: 2016-06-13; view: 7
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