Answers to your questions about diabetes mellitus

This internal medicine specialist helps readers with their tough diabetic regulation cases
Nov 01, 2010

Editor's note: We asked Dr. Cook to address a few questions we've received from readers concerning diabetic regulation in their patients. Here are her responses.

Insulin resistance and infection

Q. What's the mechanism behind chronic infections causing insulin resistance?

Dr. Audrey Cook and Texas
A. This issue is complicated but is due, in part, to increased endogenous cortisol released by any physiologic stress, along with insulin antagonism due to inflammatory mediators such as the cytokines. Studies in people have shown that numerous chemicals released in response to infection or inflammation, such as tumor necrosis factor, C-reactive protein, and interleukin-6, impact the peripheral response to insulin.

How high is too high?

Q. I have a patient named Sandy who is a 10-year-old spayed female terrier mix. She was diagnosed with diabetes mellitus in November 2009. At the time, she was a slightly obese dog (BCS 6.5/9), but she is now 25 lb (BCS 5/9) and receiving 8 U NPH twice a day.

I have been monitoring her glucose concentrations (every seven to 10 days the first two times and then every three to four weeks), usually five to six hours after the morning insulin dose. According to the owner, Sandy does not have polyuria, polydipsia or polyphagia; does not have an urgency to urinate during the night; and is doing well in general. The last glucose concentration was 333 mg/dl, which, again, was measured five to six hours after the last insulin dose. Unfortunately, she is a very aggressive patient.

A glucose concentration of 333 mg/dl is still high, but I am hesitant to change the dose because of the owner's good subjective opinion about signs of glucose control and the dog's stable physical examination findings. Should I increase the insulin dose until the glucose concentration decreases, regardless of the clinical signs? Measuring a fructosamine concentration is not an option because of financial limitations. And I think performing a glucose curve in the clinic is not an option either. If I do not increase the insulin dose, will the dog have significant complications from having a glucose concentration higher than ideal?

A. I would not feel comfortable increasing an insulin dose based on a single glucose measurement. The reason for this is that you do not know what the true nadir (true lowest value) was, and there is a real risk of an overdose. In addition, it is always important to look at the whole patient for signs of good regulation or poor regulation. If the owner reports minimal clinical signs, and body weight is holding on target, then I would certainly not increase the insulin dose based on this one reading. This dog may be a good candidate for at-home monitoring, and it would be an inexpensive way to get a lot more information. Your client can review several great web resources.

Q. I have a feline patient with a glucose concentration of 409 mg/dl (measurement obtained four to six hours after the morning insulin dose) that is doing well according to the owner. Since this is a high concentration, should I increase the insulin dose?

A. With feline patients, glucose concentrations measured in the hospital are often a poor representation of glucose concentrations in the home. Stress can trigger massive sustained hyperglycemia in cats, so it is always important to look at the whole picture. Again, checking glucose concentrations at home is often a great option. Otherwise, I would look at clinical signs (including weight) and consider measuring a fructosamine concentration. If this is on target, you have good evidence of acceptable glycemic control.