Relation of measures of asthma severity and response to treatment to outcome in acute severe asthma.

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Abstract
BACKGROUND: It would be helpful if patients with asthma who require admission to hospital for an acute attack could be identified. METHODS: The relation between the severity of an attack of asthma as determined by admission assessment and the eventual outcome was studied in 52 asthmatic patients aged 14 to 44 years and admitted to an asthma emergency room. The patient's history, including medication and previous admissions to hospital, was recorded and a clinical assessment, including a full inspiratory and expiratory flow-volume loop, was performed on four occasions: on admission, at two hours and at 12-18 hours after the start of a standardised treatment, and two weeks later on an outpatient basis. Patients who were discharged and who had an uneventful follow up at the two week assessment were defined as good responders. Patients who had to be admitted to hospital after 12 to 18 hours or were readmitted during the two weeks, or both, were defined as poor responders. RESULTS: Thirty eight patients were good responders and 14 were poor responders (seven admitted at 12 to 18 hours, seven returned to hospital). All four patients with a raised arterial carbon dioxide tension (PaCO2) (> or = 6 kPa) and the three with cyanosis were in the poor responder group, and this group had lower peak expiratory flow (PEF) values (21% v 30% predicted) on admission. There was, however, considerable overlap in PEF between the two groups and no clinical measure was able to distinguish between the good and the poor responders reliably. Poor responders had a history of more chronic systemic steroid administration, regular use of inhaled beta agonists, and asthma related hospital admissions. Nearly all the subjects showing a good response to standardised treatment had a PEF > 75% predicted and an FEV1 > 65% predicted 12 to 18 hours after the start of treatment. CONCLUSION: Prediction of outcome at admission was not possible in individual patients. A history of poor long term control of asthma, a PEF < 30% of predicted, a PaCO2 > or = 6 kPa, the presence of cyanosis, and lack of early response to treatment indicated a group of asthmatic patients who are less likely to respond to conventional emergency treatment over a short period.