Authors' contributions
MH, DM, NB, MLL
DM conceived of the study. DM, KM, DF, LM, and KA led the steering committee in the trial design and coordination of the study, as well as drafted the manuscript. Subspecialty expertise and valuable insight during trial design and during the conduct of the trial are as follows: critical care (DM, KM, KA, LM, SRedpath, SRoedl), pediatric nephrology (PG), pediatric endocrinology (MLL), laboratory methodology (MH, AK, GJ, HW, MK), vitamin D (AK, HW), and clinical trial methodology (DF). KO drafted the manuscript, figures, and supporting documentation. AT and NB performed the statistical analysis and contributed to the manuscript draft. AG, RB, RC and VC were responsible for data collection at their participating institutions. All authors read, provided input, and approved the final manuscript, and will be involved in the communication and publication of trial results.