Vitamin D is a pleiotropic hormone important for the proper functioning of multiple organ systems. It has been hypothesized that vitamin D deficiency could contribute to or worsen outcomes in critical illness. The study objective was to determine the prevalence of vitamin D deficiency, risk factors for its presence, and potential association with clinically relevant outcomes in critically ill children.

A prospective cohort study, conducted from 2005 to 2008 in 6 tertiary-care PICUs in Canada. Data and biological samples from 326 critically ill children up to 17 years of age were available for analysis. Total serum 25 hydroxyvitamin D or 25(OH)D was measured by using liquid chromatography-mass spectrometry.

The prevalence of 25(OH)D <50 nmol/L was 69% (95% confidence interval, 64-74), and 23% (95% confidence interval, 19-28) for 25(OH)D between 50 to 75 nmol/L. Lower levels were associated with hypocalcemia, catecholamine utilization, and significant fluid bolus administration. Vitamin D deficiency was independently associated with a longer PICU length of stay (+1.92 days, P = .03) and increasing severity of illness as determined by the Pediatric Risk of Mortality score with every additional point increasing the likelihood of being vitamin D deficient by 8% (P = .005).

This study provides evidence that vitamin D deficiency is both common among critically ill children and associated with greater severity of critical illness. Further research will determine whether targeted vitamin D supplementation or rapid restoration will improve outcome.