Severe Exacerbations in Children with Mild Asthma: Characterizing a Pediatric Phenotype

Background: NHLBI guidelines classify asthma in children as intermittent, mild persistent, moderate persistent, and severe persistent asthma based on baseline symptoms and pulmonary function. However, this may not capture the spectrum of asthma in children, since even mild baseline disease can have significant effects on quality of life. Our objective was to describe a population of children with mild asthma admitted to the ICU with severe exacerbations. Methods: We examined data from all children with asthma who were admitted to the ICU with an acute exacerbation between April 1997, and December 2006. Children were defined as having mild asthma if their disease was classified as intermittent or mild persistent according to NHLBI criteria. Results: Of the 298 children admitted to the ICU with asthma, 164 (55%) were classified as having mild baseline asthma. Compared with children with more severe baseline asthma, mild asthmatic children were younger and less likely to have been previously admitted to the hospital for asthma. Other demographics, including admission severity of illness, gender, and prevalence of overweight, were similar in the two groups. There were no differences between the groups in ICU length of stay, hospital length of stay or types of therapies received. Thirteen children with mild asthma were intubated, although less frequently than those with more severe disease. Conclusions: Children with mild asthma have severe exacerbations. This suggests that chronic asthma severity does not necessarily predict asthma phenotypes during acute exacerbations.