Highlights from the lectures of Deborah Greco DVM PhD ACVIM
Maryland Veterinary Medicine Association Conference

Telluride Colorado March 2005

Compiled by Rebecca A. Price MD

In no particular order, here are some of the thoughts and statements from Dr. Greco that I highlighted while attending this conference.

Most vets and owners use the worst site to inject insulin – the scruff of the neck.  This site has a poor blood supply and is prone to forming granulomas.  Because of these characteristics, insulin is absorbed very irregularly from the scruff.   The lateral thorax (chest) and abdomen (stomach) are much better sites.  Injection sites should be rotated to decrease the chance of granuloma formation.

If your cat is receiving regular subcutaneous fluid injections, do not inject insulin near the area where fluids are administered. 

You may have to gradually move the injection site from the scruff down lower to the optimal sites.  There is a new BD syringe available with a needle size of 31.  This is so small, cats don’t even seem to notice injections in the lateral thorax and abdomen. BD also has a new lancet that is 33 gauge.

Lack of regulation can be judged by clinical signs, namely PU/PD, abnormal weight, and presence of neuropathy.  You don’t need to perform serial blood glucose curves to know that your cat is unregulated.

Some studies show that 50% of diabetic cats have pancreatitis.  Current therapy is leaning toward continuing to feed cats with pancreatitis and to treat with Medrol, a steroid.

If a cat develops diabetes after receiving steroids, the steroids did not cause the diabetes but simply “unmasked” it.  These cats were already having glucose metabolism problems and would have eventually developed diabetes even without steroids.

An adult, obese male cat should be considered a pre-diabetic cat.

Regulation is not having all glucose readings between 80 and 350.  In this state of pseudo-regulation, the cat can still have complications such as neuropathy, low body weight, etc.  The villain here is FLUCTUATIONS in the blood glucose.  In a blood glucose curve for the cat, the difference between the highest and lowest blood glucose levels should be <150.  For example, a cat who stays around a steady 200 for blood glucose has fewer complications than a cat whose blood glucose ranges from 80 to 280.

Blood glucometers are most accurate in the 100-150 range.  Glucometers generally read about 20 mg/dl too LOW for readings below 100.  If your cat has a reading of 60, the actual BG is most likely 80.  You can't make any assumptions about your meter, though. Look at your cat.  If there are no clinical signs of hypoglycemia, do not aggressivelytreat.

Cat physiology is different from other animals, especially in glucose metabolism.  Most info about feline diabetes has previously come from human and dog studies and are NOT relevant to cats.

If you can’t regulate your cat or your cat has been stable on one insulin dose and then changes, the first thing you need to check is owner management errors.  A vet should check a “punch list” (see below) at every appointment.

Punch List for Owner Compliance

· Are injection sites being rotated?

· Is injection being done in the proper place?

· Is the insulin being stored properly (some new insulins should NOT be refrigerated – check your vial)

· Is the insulin too old or has it been damaged by improper handling?

· Does the owner have good injection technique?

· Is the client compliant with diet? (All canned, low-carb food; no free-feeding)

· If all the above are ok, change the type of insulin being used.

Everyone should home test.  Dr. Greco feels that urine testing is the first choice and that blood glucose curves are often not helpful in judging regulation and may be stressful to the cat.  (Notice that this is her statement about CURVES, not spot testing, and she admits that many veterinarian endocrinologists disagree with this statement. Also, she is referring to judging regulation, not to determining insulin doses with blood glucose curves.)

“There is no rationale at all for using NPH (N insulin) at all in a cat.  Period.”  (Dr. Greco says this is because onset of action and peak of action times are totally variable in cats with N, even in the same cat.)

Never put a cat on more than 3 units of insulin BID without doing an endocrine workup.  Chances are, a cat needing this much insulin has some other problem.  And before doing an endocrine workup, go through the punch list for owner compliance (above) first .

Be patient when changing insulin doses.  Allow 10 days for adjustment to a new insulin dose.

Studies show that on beef PZI, 50% of all cats can be regulated on a single shot per day.

Beef PZI should be the first choice when instituting insulin therapy.

If a cat is male and weighs more than 6 kg (13.2 pounds), they are prone to hypoglycemia when being treated with insulin.  These cats should be tried on oral medications first.  About 50% can be controlled on oral medications.

Dr. Greco once conducted a study that showed vanadium might be of benefit to diabetic cats.  Dr. Elizabeth Hodgkins pointed out that all cats were fed a canned diet in this study.  When the study was repeated using canned food and no vanadium, the same results were obtained!

Chromium is essential for cats.  It is lost in the urine, so if your cat has PU/PD, it needs chromium supplements of 200-600 mcg/day.  Even the best commercial diets provide only 24 mcg of chromium/1000 kcal.

Bacon and pork rinds are a great source of chromium.  These are good treats for your cat.

She emphasized that one of the big mistakes that vets make is assuming that cats metabolize glucose just like humans and dogs. It is very different and if we treat feline diabetes just like human diabetes, a lot of cats are going to be in trouble.

This interpretation of Dr. Greco's lectures has not been reviewed by her. Any errors present are purely my own fault.
Last updated 3/24/05.