Osmol gaps in the pediatric population

Objective: To define the osmol gap (OG) range in pediatric ED (PED) patient s. Methods: This was a blinded, observational patient series involving an u rban FED with an annual census of 36,000. All patients presenting to the Ha sbro Children's Hospital Emergency Department who required electrolyte dete rmination during their evaluations were enrolled into the study. Exclusiona ry criteria included the presence of urinary ketones, alcohol ingestion wit hin the preceding 24 hours, or illnesses that are known to change serum osm olarity. Electrolytes, BUN, glucose, and freezing point depression osmolali ty were measured on a single serum specimen. Additional laboratory informat ion included ethanol and anion gap. The OG was determined using each of thr ee equations previously described in the literature (see Results). The best coefficients for sodium, BUN, and glucose were determined by multiple line ar regression. Results: 192 children (90 girls, 102 boys) with a median age of 6.6 years (mean: 7.3 years; range: 7 days to 17.9 years) made up the st udy population. The mean measured osmolality (+/- SD) for the entire sample was 284.2 +/- 6.9 mOsm/dL with a range of 265-311 mOsm/dl. Mean osmol gaps with standard deviations varied with the equation used for calculation. Co nclusion: Regardless of the equation used, the range of "normal" osmol gaps in the pediatric population is approximately 22 mOsm.