We read with interest the article by Simpao et al. regarding the association between clear fluid fasting duration and postinduction low blood pressure in anesthetized children. In this retrospective analysis, the authors reported that, among children (0 to 18 yr) who underwent inhalational induction of anesthesia for elective surgical procedures, longer duration of clear fluid fasting was associated with increased risk of postinduction low blood pressure during the surgical preparation. Despite the clinical relevance of the topic and the elegant study design, certain methodologic issues require clarification.

First, although the exposure (fasting duration) was collected as a continuous variable, the authors transformed this continuous variable into categorical groups using some clinically useful, though arbitrary, cutpoints. The statistical limitations of this approach must be highlighted. As elegantly assessed by the authors, the association between clear fasting time...

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