My 10 year old son recently started using an insulin pump, and yesterday, when he got out of bed, the tubing pulled loose from the cartridge on the pump. He got out a new set, rewound the pump, installed new tubing to the cartridge. When the pump screen asked him which concentration to use (U-100 or U-50), he mistakenly selected U-50. He did a manual prime, reconnected the tubing to his set, went to school, and had severe low blood glucoses all day, which he effectively countered with Lifesavers (one reading on his meter was simply LOW!). When he got home, I found the error and reprogrammed the pump.

I am looking for information that would tell me exactly how much insulin he was getting from the mis-programmed pump. His normal basal rate is 0.4 units/hr, and normally he takes 3 to 5 units for lunch. Would the “actual delivered” amount have been double that? I can’t find anything in the literature, nor does a search for U-50 on your website turn up anything. Have there been any discussion about blocking the U-50 option? This is especially important since mistakenly selecting that one apparently triggers extreme lows.

Your son’s insulin pump thought he was using diluted insulin at one half the usual strength. Normal insulin has 100 units/cc (U-100), and U-50 insulin contains 50 units/cc. To deliver the actual number of units programmed, the pump delivered twice the usual volume because the pump “thought” that each cc of insulin of insulin contained only half the usual number of units. Therefore your child was received twice the amount of insulin you thought he was receiving.

TGL
Additional comments from Dr. David Schwartz:

U-50 means that there are 50 units of insulin in every milliliter (mL) of the insulin solution. Standard insulin is 100 units of insulin in each mL. So I presume that when your son punched in “U-50” to the pump, it’s program indicated that the insulin in the reservoir was 1/2 as strong as standard. So given whatever rates were programmed into the pump, your child actually received twice as much insulin as he would have thought. I know you won’t allow that mistake again!

If you think that was confusing, there used to be U-80 insulins and U-40 insulins. Whew! What a chore all that mathematical gymnastics that was!

DS

[Editor’s comment: A few additional thoughts:

If you search our website for “diluted insulin,” you will find several references to it.
If your son’s pump manual does not explain what U-50 insulin is, I think you ought to call customer service and report what happened. It seems that this information should be included in the instructions for use.
Diluted insulin is typically used for people (such as small children and infants) who require very small doses. This allows for less clogging of the pump tubing along with the ability to deliver the correct amounts more precisely.
As you have learned, a 10 year old should never be allowed to change infusion sets, etc. without adult supervision. There are just too things that can go wrong!

Your son was very lucky that he did not have a severe insulin reaction. Please remember to oversee the pump and always recheck things.

SS]