I'm pretty new to PICU here in the UK. I have never heard of this "rule of 3" that you are talking about. We have an injectable therapies guideline, which tells us how to make up and infuse any IV drug, eg paracetamol over 20 mins, certain antibiotics over 1 hour, others over 3-5 minutes etc, what to dilute different drugs with, their compatibilities etc. For things like sedation, it will tell you what concentration to make up, for example, 5mg/kg into 50mls. The prescribing Doctor can use this as a resource when prescribing a drug, and he tells us what amount of the drug he wants in the syrine, what he would like it making up to, and what dilutant he would like you to use. He also specifies a rate (or a range) at which he would like the infusion to run eg 2-5 mls/hour. It is then up to the nurse to double check all of those figures (using the injectable therapies guidelines) before making up and administering the infusion. We use infusion pumps which are set up with a "drugs and dosing" function. This allows you to label the infusion with the name of the drug being infused through that pump, and it has pre-set programs for the commony used drugs. It will ask you the drug you are using, the childs weight, and whether you are working to standard protocol. Once you have done this the pump will calculate the strength of the infusion, ask you to confirm that this is as you have made the infusion up, and then once running the display tells you name of the drug you are infusing, the rate at which it is running (eg 2.5ml/hr) and the dose being infused (eg 5mcg/kg/hr). It is not fool proof, and all infusions are checked by the nurse taking over the patients care at the start of the shift and yes, mistakes do happen. But it seems a good system, and is clear and fairly simple to use (its just my explanation which is long winded!).