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?
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.
Dr. Audrey Cook and Texas
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
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
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
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