For many parents, the most troubling aspect of diabetes is the possibility of low blood sugars during the night. We have recently tested two new products that are providing solutions to this problem.
It took over two decades to get to the level we are at today with meter reading, and it is exciting to see the coming of continuous glucose monitoring.
The MiniMed Continuous Glucose Monitoring System
Most diabetes-care providers have pushed families to attain the best sugar control and lowest HbA1c level that the family is able to achieve. Some families have tried to prevent the severe lows by doing eight or more blood-sugar tests per day. Unfortunately, this still does not help at night when children are sleeping. This is the time when continuous glucose monitoring is most important.
The MiniMed monitor has three parts:
- The monitor unit, which stores the values and is brought to the doctor’s office for downloading (it is just slightly larger than a pager),
- A sensor, which is placed under the skin much like the plastic cannula (tube) of an insulin pump, and
- A wire connecting the sensor to the monitor.
We have found that there is no difficulty in inserting the cannula, particularly if we apply EMLA cream to the skin as an anesthetic an hour beforehand.
Research Supports Sensors’ Advantages in Kids
The information that can be gained using the MiniMed monitor in kids is enormous. Our center reported the first research study on children using the device in Pediatrics (vol. 107, pages 222-226, 2001). The study was done in a home setting so that the children had their normal activity during the day.
The children had a total of 90 nights of monitoring. We found 20 nights—almost one in four—when glucose levels fell to less than 40 mg/dl. In only three of the 20 nights did the children awaken and complain of the symptoms of low blood sugar. Thus, for 17 of the nights (85 percent), the values went low, but the childrens’ bodies gradually brought their own glucose levels back up without the children waking.
It is our current hypothesis that if a person’s body has adequate stores of glucagon and epinephrine (hormones that raise blood sugars) and of stored sugar (glycogen), their body’s BGs can restore without the person waking up.
Chart one on page 47 shows one eight-year-old boy’s glucose levels at 40 mg/dl during the night, but a value of 105 mg/dl prior to breakfast. The boy’s mother thought he had had a great night until we showed her the numbers from his chart. Seeing the large spike to 325 mg/dl helped the mother realize that her son was missing boluses of insulin at both breakfast and lunch.
Another example of how useful the MiniMed monitor can be is shown in the two tracings of a six-year-old girl who had diabetes for 20 months (see chart two on page 49). The girl came to our center from another state after having 10 episodes of seizures or unconsciousness—mostly occurring during the night. She was receiving NPH insulin at dinner, and the dose had been increased to make it last through the night to lower morning values.
Chart two illustrates how the girl became quite low during the night. On day two, she was changed to Ultralente insulin at dinner, which is flatter in activity (see DIABETES HEALTH; September 2000). She no longer became low during the night (see chart three on page 49).
We thus proved by using the MiniMed monitor that the peak from the NPH at night was causing the lows, and that our change in therapy was correct. Indeed, some six months later, the girl has not had another seizure.
Currently, the MiniMed monitor is only used through the doctor’s office. It costs about $2,800 for the monitor (see page 48), and each three-day sensor costs $40. Insurance will often pay the office for the use of the monitor and sensor and for interpreting the results.
A consumer-oriented model is expected to be on the market sometime in the next couple of years.
The Cygnus GlucoWatch Biographer
Though currently not available for sale to adults or children, our center is now doing a home study of the GlucoWatch Biographer in children ages seven to 17. Twenty children are wearing at least two daytime and two nighttime Biographers each week.
During the first eight days of the study, there were eight episodes of the Biographer’s low-sugar alarm going off during the night, which was confirmed with a meter. The blood-sugar values were below 60 mg/dl.
For a 16-year-old boy with difficult-to-control diabetes (see chart four on page 49), the Biographer alarm alerted him to a low sugar level in the evening, which was confirmed with his meter (46 and 53 mg/dl). His blood sugar was 95 mg/dl at bedtime, but he became low most of the night. He did not wake up until 6:30 a.m. when his blood sugar was 32 mg/dl. The GlucoWatch Biographer showed that he had been low most of the night, although the alarm did not wake him. His insulin dosages were adjusted after these findings.
Although some children seem to have more difficulty with false alarms than others, part of this may be technical. One girl’s BG readings were better when her father installed the GlucoWatch than when she did.
Glitches and Side Effects
If a person sweats, the GlucoWatch will “skip” the reading. If there are six skips in a row, the GlucoWatch will shut off with no further values from that sensor.
Some people get redness either in the small central area of extraction or from the adhesion material around the outer edge. This has been minor in most children, and strangely, children seem to have less reaction than adults. A bit of tea tree oil (Fingers skin cream, distributed by Can-Am Care Corp. Chazy, NY 12921-0098; (800) 461-7448) seems to help the redness.
Which is Better?
We are often asked, “Which is better?” The answer is simple—both have their purposes and are ideal for different situations:
- For the seven-year-old girl discussed earlier who had 10 seizures in 22 months of diabetes, we wanted three days of continuous glucose monitoring, and the MiniMed system was ideal. For a family wanting to know if a child is getting low on a specific night after a heavy exercise day, a 12-hour GlucoWatch study might be ideal.
- The MiniMed sensor is inserted under the skin for a three-day period while the GlucoWatch is worn on the arm for a 15-hour period.
- The GlucoWatch is approved with the ability to automatically read the glucose levels, whereas the MiniMed system must currently have the glucose levels downloaded at the physician’s office after wearing for three days.
- Also, the FDA approved the GlucoWatch Biographer with alarms for low and high glucose levels, while the MiniMed system was not approved with alarms.
An important note to make is that the MiniMed monitor is the only one that is currently available. It is anticipated that MiniMed soon will be returning to the FDA to have their second-generation device approved. This will certainly have the ability to show BG levels and to have alarms for high and low glucose values.
The Future of Continuous Glucose Monitoring Devices
Although the FDA has approved only these two devices, there will probably be more in the future. As approval from the FDA generally takes one to two years and no other companies (to our knowledge) have even applied, it is unlikely that other products will be on the scene very soon.
The National Institutes of Health is planning a study using continuous glucose monitoring in children to try to safely attain better glucose control. This should help to familiarize physicians and families with the two devices, and teach all of us how to best use these innovations in providing new and improved care to children and adults with diabetes.