These calls are inherently tricky and I've done a few myself. What works on one patient won't necassarily apply to the next. My experience with dehydrated paeds has been to scoop and shoot and try establish IV/IO access en route to definitive care. At least you're intervening whilst at the same time making haste to definitive care. If you don't mind my asking, does the LAS have access to the right kind of fluids for these patients? In South Africa, we usually only carry NaCl or Ringers Lactate, when these patients need fluids like Neonatalyte, etc., to avoid the risks of exacerbating the dehydration. After my first bad experience where the child arrested after three months of negligible care at a rural state facility, I made a point of practicing my IV/IO cannulation by volunteering at a paed ICU. It's given me a little more confidence and experience when the need has arisen to perform the skill in make-or-break situations. Once you have a rapport with the staff at the unit, I think you'll be inundated with requests to cannulate the kids.