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Discussion

Rule of three

Hello!

I've just started a new job in a PICU . I LOVE it!!!! I'm still on orientation and just thought I'd try to figure out the "Rule of Three" for drug concentrations/calculations. Any tips or web links would be greatly appreciated.

THANKS!

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  • Experts

It's actually pretty simple. It applies to standard concentrations for infusions that run as mcg/kg/min. Multiply the desired mcg/kg/min by the patient's weight then multiply that by 3 and it gives you the number of mg you need to mix in 50 ml (total volume) of diluent to obtain an infusion that will give you a concentration of 1 ml/hr = X mcg/kg/min. For example, dobutamine at 5 mcg/kg/min for a 6 kg patient = 5X6X3 = 90 mg in total volume 50 ml. The infusion running at 1 ml/hr will then give you 5 mcg/kg/min. Try it the long way if you want... 5 mcgX6kgX50mlX60 min/1000 to make it mcgs... 5X6X50X60 = 90000/1000 = 90. Another one... epinephrine at 0.1 mcg/kg/min would be 0.1X6X3 = 1.8 mg. Check it out!

Places still do this? I though JCHAO said it was a :nono:

  • Experts

You're probably right about that, dawngloves. In Canada JCHAO has nothing to do with us, and in our unit it isn't taught as the rule of threes or the rule of sixes or any other permutation. We're taught the long way to calculate our drips... which works out to fit perfectly with the rule of threes...

  • Author

Thanks for the replies. Yup...places still do this. I'm just learning. It seems doable. My preceptor is going to go over it with me this week.

Thanks Again:thankya:

Don't get too comfortable with it. JCAHO is requiring standardized concentrations of drugs (National Patient Safty Goal 3b) by December 31st, 2008.

We stopped doing this last year when they made the announcement.I thought it was already "law".

  • Author

Great advice...thanks. You're right about them phasing the Rule of three out. Some of the nurses are not comfortable with the standardized or computer calculated doses and prefer to "Do their own math" My preceptor is just showing me how to do it so I have a way to check the computer or how to do it if the computer is down. Always a good thing to know!

Thanks Again!

Rule of 3 is helpful for a drip that will be staying at the same dose for quite a while. In reality, most mcg/kg/min drips need to be titrated up or down several times throughout the shift, so it really is worth it to know how to do the calculations to change the rate, rather than hanging a new drip with each change in dose

  • Experts

We mix our drips so that 1 mL/hour gives us a standard concentration for that patient. For example, we mix epinephrine and norepinephrine so that 1 mL/hour = 0.1 mcg/kg/min, dopamine is 5, milrinone is 0.5, midazolam is 2, morphine is 50 (per hour), and so on. Scenario: baby weighs 4.7 kg and needs an epi drip. 4.7 kg x 0.1 mcgs desired concentration x 3 (50 mL x 60 min / 1000 mcg to get mg)= 1.4 mg in 50 mL diluent. We run all our titratable drugs on syringe pumps that can deliver as little as 0.1 mL/hr. So baby starts off at 0.05 mcg/kg/min, which is our usual order. The pump runs at 0.5 mL/hr. We can titrate up or down by 0.01 mcgs/kg/min by adjusting the pump by 0.1 mL/hr. And we can tell at a glance what dose the kid is getting just by checking the rate. It's easy as pie. If the milrinone is running at 1.5 mL/hr, the kid's getting 0.75 mcg/kg/min. If the dopamine is running at 2.5 mL/hr the kid's getting 12.5 mcg/kg/min. If the morphine is running at 1.8 mL/hr, the kid's getting 90 mcg/kg/hr. Does that make sense?

The rule of 6 never made any sense to me when I started 17 years ago, but I memorized the formula and did the math and made the drips. Finally about 4 years ago i had an epiphany and i discovered where the 6 came from and it was alright after that.

In reality though it works better to avoid the 6s or the 3s and go with the standard formula

1mcq/k/min = 1ml/hr or

1mcq/k/hr = 1ml/hr

You can make up anything with these two formulas and it is easy to increase the concentration to provide you with whole numbers making it easy to calculate the increases and decreases.

JAHCO doesn't like the formula, but fortunately we in canada are not governed by them

I know that when I was at U. Maryland and U. Mississippi the "rules" systems was a major issue before the JCAHO visit. A lot of nurses and doctors lived by it. Now that standardization is about to become manditory in 2008 you might want to look at your system and see what the plans are to convert. You also may want to get involved in the conversion. ICUdrips.Org shows our issues. Just my $0.02. LeAnthony

I am pretty certain JCAHO does not approve of that any longer. Personally i was never fond of the whole rule of 3 or 6.

Hi

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!).

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