Diabetes Mellitus Part 3 - Monitoring Response to Therapy
Well, we will finally come back to diabetes mellitus and try to wrap it up over the next week. If you need a refresher, you can go to previous blogs where we talked about diabetes in general and insulins. Today, we need to talk about monitoring response to therapy.
With long-term management of diabetics, we will periodically perform complete lab work (CBC, serum chemistry profile, urinalysis, and urine culture) to make sure that no new problems have developed in these pets. Fructosamine concentrations can be measured to assess an average glucose over the previous two weeks, and if you need more information about this test, please look back at the first blog on diabetes mellitus. We will also perform a blood glucose curve. This test is one of the most important tools to assess response to therapy. Typically, we will have owners give insulin and feed breakfast normally when performing a curve. Then, glucose levels are checked every two hours throughout the day. This tells us two very important things: peak insulin effect when the glucose reaches its lowest point (nadir) and duration of blood glucose control (when the glucose level rises above 250).
When we are looking at our glucose nadir, we would like to see a glucose of 100 – 250. If glucoses stay below 250, the pets will not be spilling glucose in their urine, and their water consumption should be normal. I generally do not like to see glucoses get much below 100 to decrease the risk of hypoglycemia if a pet vomits or doesn’t eat well.
Ideally, we would like insulin to last as close to 12 hours as possible. So, if insulin only lasts 4-6 hours, glucoses will be way too high for way too long every day. This will cause the pets to drink excessively, urinate excessively, and lose weight – all of the clinical abnormalities that we are trying to control with our insulin therapy.
Although these blood glucose curves are traditionally performed in the office, some pets become so stressed with hospitalization that their curves are not reflective of glycemic control at home. In those pets, we talk about home glucose monitoring where owners check glucose concentrations every two hours.
When considering home glucose monitoring, I generally recommend that owners purchase an AlphaTRAK® 2 glucometer. This one has been designed for dog and cat blood, and it is generally more accurate than human glucometers. Human glucometers are designed to intentionally be inaccurate at the low of the detection range and at the high end of the range. So, if low glucose concentrations read lower than they really are, people will be frightened and go eat, and if their glucoses are higher than they really are, they will go give themselves an injection of a short-acting insulin to quickly lower their blood sugar. We don’t need that feature in our patients since we are more concerned with accuracy.
Typically, we will use the lancet provided with the AlphaTRAK® to obtain a glucose sample, and with cats, we get the blood from the inside of their ear pinnas near the outer edges. Sometimes, we will apply Vaseline before pricking the ear to help the blood droplet wick up, making it easier to get on the test strip. You can use the ears on dogs as well, although other sites used on dogs include the callouses on elbows and foot pads (I don’t like to use pads because they can get sore feet) and the inside of their lip. You never want to squeeze the site to “milk” out the blood as this will cause your blood glucose reading to be inaccurate. The AlphaTRAK® website has videos that you can watch to learn these techniques.
We recently had a client who told me about a lancing device that was developed for kids. It is called a Genteel® lancing device. It uses suction to obtain the sample, and it is supposedly painless. We have one now at the clinic, and I will tell you there is a learning curve with it because you have to find which tip works best for each animal, as the different tips prick at different levels and apply different amounts of suction. However, this can really be helpful to get a blood sample if you are a little squeamish about using the lancing device. The Genteel® website also has videos to demonstrate use of the device. You can see a video below on how to use the device, and if you want to see the device in use on a dog, you can go to the video here.
Another way to monitor glucose concentrations at home is a continuous glucose monitoring system (CGMS). A small sensor is inserted under the skin, and a recording device is glued to the skin. The device reads glucose levels every 5 minutes for up to 3 days. A docking station and a computer with appropriate software are required to read out the data. Unfortunately, these devices only read glucose concentrations between 40-400, and if you have a pet with significant hyperglycemia, they may be unable to read the values accurately. If the sensor becomes detached, no glucose levels will be obtained, and occasionally, a sensor will fail to read glucoses even when attached appropriately. The biggest problem with CGMS is the initial cost of the equipment is high, and few facilities have them.
To wrap glucose monitoring up, our goals with managing diabetic patients are to have a pet with a stable weight who is not drinking excessively or urinating excessively. To achieve these goals, veterinarians and owners must work closely together, and we will need to employ office visits with physical examinations, laboratory testing, and glucose monitoring which can occur at the office or at home, depending upon the pet. We will have one more blog about diabetes to discuss the role of diet in this disease.