Monitoring diabetes mellitus in diabetic cats (Sponsored by Intervet Schering-Plough Animal Health)

Monitoring diabetes mellitus in diabetic cats (Sponsored by Intervet Schering-Plough Animal Health)

Jun 01, 2008

Protocols for monitoring diabetic cats have evolved over the years. Random spot-checking a blood glucose concentration, although easy to perform, is unacceptable as the sole means of monitoring because it cannot accurately represent the cat's response to insulin. Therefore other methods of monitoring diabetic cats need to be employed.

The goals of diabetic regulation include the following:

1. Maintain the blood glucose level between 100 to 300 mg/dl over 24 hours. 1

2. Ameliorate the clinical signs of diabetes mellitus; polydipsia, polyuria, and polyphagia.1

3. Attain and maintain a healthy body weight.2

Before or during the initiation of insulin therapy, you must identify and resolve or control any other medical problems. I routinely evaluate retroviral status, serum biochemical and electrolyte panels, total T4 concentrations, complete blood count with differential, complete urinalysis, and urine culture. In addition, thoracic and abdominal radiographs are useful to determine any additional abnormalities that need to be addressed. I also find it useful to assess the pancreas via abdominal ultrasound and feline pancreatic lipase immunoreactivity (fPLI) testing. Establishing the baseline serum fructosamine concentration is also helpful for long-term monitoring.

Blood glucose curves

In my opinion the blood glucose curve remains the gold standard for determining effective diabetic regulation.1 Veterinarians have learned the importance of performing a blood glucose curve to establish the nadir, the duration of insulin response, and the variation of blood glucose concentration. In addition, the blood glucose curve is the best way to detect the Somogyi effect.3,4 The advent of glucometers requiring an extremely small blood sample, along with the ease of using the lateral ear vein for sample collection, have facilitated performing blood glucose curves in cats.

Traditionally, the curve begins at the time of insulin administration (time 0), and additional blood samples are taken every two hours for the next 10 to 12 hours. The ideal blood glucose curve starts and ends with blood glucose concentrations of 250 mg/dl with the nadir at 100 mg/dl and occurring five to six hours after insulin administration, based on a 12-hour dosing interval.4 In reality, all of these values can vary widely, underscoring the importance of performing a blood glucose curve—rather than spot-checking. Optimally, the difference between the nadir and the starting and ending blood glucose values should be as small as possible.4,5 If the difference remains large, this may indicate the need for a different type of insulin.

Hospitalized blood glucose curves

Figure 1. How to take a sample for a blood glucose curve.
When I perform curves with a hospitalized cat, I prefer to have the client feed the cat at home and to administer the insulin at the hospital (after the time 0 glucose concentration is determined). Offer the cat additional food throughout the day, and obtain blood glucose samples two, four, six, eight, 10, and 12 hours later, if time permits. Alternatively, the client feeds and administers the insulin at home following the routine schedule, then drops off both the cat and its food for the day. Then take blood glucose samples two, four, six, eight, 10, and 12 hours after insulin administration. The latter scenario is occasionally what happens in my hospital if the client routinely administers the insulin one to two hours prior to the hospital opening. To keep things simple, I strive for minimal disruption of the client's and cat's routine. Figures 1a to 1d explain how to take a sample for a blood glucose curve.

Utilizing the lateral ear vein has dramatically reduced the stress my in-clinic patients undergo. My staff and I can obtain a sample in the cage, while the cat is eating or sleeping, or while it is held on a lap. I use a 25-ga needle and find that warming and shaving the ear first are usually not necessary. I do not use an alcohol swab because the cats seem to dislike the odor and it adds additional time to the sampling.

The advantages of hospitalized blood glucose curves include:

1. You can conduct a physical exam, including determining the cat's weight.

2. You can observe the owner administering the insulin (this is of paramount importance early in the course of treatment).

3. Trained personnel obtain the samples with minimal disturbance to the cat.

4. You can observe the cat during its stay, administering glucose intravenously or Karo syrup orally, if necessary.

In some cases, accuracy can be the major drawback of the hospitalized blood glucose curve. The blood glucose values in some cats will always be falsely elevated because of excitement and stress. During other curves, blood glucose concentrations may be deceivingly low, presumably because the cat would not eat while hospitalized. These cats need glucose or dextrose supplementation and leave us questioning the reason for the low blood glucose concentrations—is it because they did not eat, or is the insulin dose too high?

In-home blood glucose curves

In-home blood glucose curves have become more popular in recent years because of the premise that they are less stressful to cats. The validity of these blood glucose curves is solely dependent on the client's ability to accurately and gently obtain the blood sample. In one study, the blood glucose concentrations for the same group of cats were actually higher at home than in the hospital, possibly because of client-induced stress or the cats' improved appetite at home.3

Careful client selection and training are crucial to the success of in-home monitoring.3 You must ensure that the client understands the optimal blood glucose range and how to respond when values are outside the range (they will know how to respond after consulting with a veterinarian). I believe that in-home monitoring offers the best opportunity to determine the true status of a diabetic cat, especially if you make it fun and educational for the client. However, remember that this process can become overwhelming, even for carefully chosen clients, and you must be sensitive to their needs and the cats' needs.