Blood Glucose Curves and the Fractious Diabetic Cat

My problem patient is a 12-year old, DSH, female spayed cat with a 2-year history of insulin-dependent diabetes mellitus. She has been treated with glargine insulin at a variable dose, but typically between 1-3 units, BID. This cat will not eat canned food so we are feeding higher protein, lower carb dry foods (Hill's MD and Purina DM).

Six months ago, the cat was diagnosed with immune-mediated hemolytic anemia (IMHA) and was treated successfully with prednisolone and cyclosporine (Atopica). This led to development of insulin resistance and loss of diabetic control, but the cat did relatively well after raising the insulin dose to 6 units while on prednisolone. After a long and slow taper, the cat is now off all glucocorticoids for the last month, and the insulin dose is back down to 2 U, twice daily. The cat remains on Atopica, probably for life.

We have periodically done in-house blood glucose curves to adjust her insulin dose, but she becomes extremely fractious when hospitalized, and we can't really handle her (she bites, scratches, cries, and screams louder than any other cat I've ever had!). The owner does not care to check blood glucose at home, and given the cat's nature, I doubt if they could even do it. Since weaning her off the prednisolone, we have seen a couple of hypoglycemic readings on spot blood glucose checks so we are now worried that the current insulin dose may be too high.

Therefore a week ago, we performed a serial glucose curve on 2 units glargine, BID. The results were as follows:

• 6 am = Insulin given
• 8 am = 317 mg/dl
• 10 am = 376 mg/dl
• 12 noon = 352 mg/dl
• 2 pm = 299 mg/dl
• 4 pm = 229 mg/dl

We were a bit surprised by the high glucose concentrations during the day on this curve, but we increased glargine from 2 to 3 units BID based on the severe and persistent hyperglycemia. However, when I checked a spot afternoon blood glucose value yesterday, it was low-normal at 69 mg/dl. I rechecked another blood glucose reading 30 minutes later, and it was even lower at 57 mg/dl. Right or wrong, I put her back down to 2 units glargine BID and pm spot check in 1 week.

My main question is this: could this cat's in-hospital curve be leading us astray because she is so fractious? I am aware that spot checks aren't ideal. However, this cat is relatively easy to handle during a quick exam and single spot check, but she become so angry when hospitalized throughout the day.

What would you do? How do I adjust the insulin dosage in this cat? We've been trying to get the cat into remission but it's not looking good!

My Response:

Well, first the bad news: I can almost guarantee that this cat's diabetes will not go into remission, given the fact that she has been diabetic for 2 years. A number of studies have reported that diabetic remission, when it does occur, will generally happen within the first 6 months of diagnosis (1,2). In addition, the fact that she has concurrent disease and has been treated with glucocorticoids certainly hasn't increased her chances for remission.

The good news is that once we decide that diabetic remission is no longer our goal, then we can be more lax with our glucose regulation. Our goal for diabetic cats should then be 3-fold:

1. Control clinical signs of diabetes (e.g., weight loss, polyuria, polydispsia)
2. Prevent diabetic ketoacidosis
3. Avoid hypoglycemia

To do this, it's not really necessary to do the tight glucose regulation and frequent blood glucose monitoring that we would ideally do if we are trying to increase the odds for diabetic remission (3-5).

In fractious diabetic cats, I would never recommend doing serial blood glucoses to determine the best insulin dose. The release of catecholamines during this excitable state can absolutely increase the glucose readings during the curve (commonly referred to as stress hyperglycemia) (6). Overall, this means that all of the serial blood glucose curves you have done in this cat are most likely next to meaningless and that such testing should be stopped.

Spot glucose checks can't hurt, but as you say, they can be hard to interpret and may be misleading. If the blood glucose reading is low, you might want to decrease the insulin dose, but if the blood glucose is in the ideal range or high, you could still be overdosing the insulin.

In cats like this, I'd recommend that you adjust the insulin dose based on the presence or absence of clinical signs, including body weight and water intake (7).  If the owners can measure water intake at home, that can be a very sensitive way to help determine if more insulin is needed. If there are no clinical signs of diabetes and the weight is stable, the cat is probably adequately controlled. Monitoring an occasional serum fructosamine level can also help (8,9), as well as home measurement of urine glucose, if the owner can do it (7,19,11). A weekly check for urinary ketones can also be used to monitor for pending ketoacidosis, and become extremely important if anorexia, vomiting, or any other signs of illness develop.

Bottom Line:
In fractious cats, I would not recommend in-hospital blood glucose curves for monitoring. Stress hyperglycemia will give you results that are meaningless, and one could easily be misled into giving higher doses of insulin than are actually needed. This is especially true in cats with long-term diabetes that are unlikely to ever develop remission.

In cats like this case, I use a combination of clinical signs and blood/urine values, looking at the overall trend in results rather than the specific or individual values. For example, I don't use serum fructosamine concentration as the sole means of judging control, but I still think it is helpful as one piece of the puzzle. If it is high, that suggests that the insulin dosage may have to be increased; if the fructosamine value is low to low-normal, this may indicate overdosage and hypoglycemia.

Believe me, both your hospital staff and the fractious diabetic cat will all be better off with this approach!

References:

1. Gottlieb S, Rand JS. Remission in cats: including predictors and risk factors. Vet Clinics North America 2013: 43: 245-249
2. Zini E, Hafner M, Osto M, et al. Predictors of clinical remission in cats with diabetes mellitus. J Vet Intern Med 2010;24:1314-1321.
3. Roomp K, Rand J. Intensive blood glucose control is safe and effective in diabetic cats using home monitoring and treatment with glargine. J Feline Med Surg 2009;11:668-682.
4. Roomp K, Rand J. Evaluation of detemir in diabetic cats managed with a protocol for intensive blood glucose control. J Feline Med Surg 2012;14:566-572.
5. Nack R, DeClue AE. In cats with newly diagnosed diabetes mellitus, use of a near-euglycemic management paradigm improves remission rate over a traditional paradigm. Vet Q 2014; 34:132-136.
6. Rand JS, Kinnaird E, Baglioni A, et al. Acute stress hyperglycemia in cats is associated with struggling and increased concentrations of lactate and norepinephrine. J Vet Intern Med 2002;16:123-132. 
7. Miller E. Long-term monitoring of the diabetic dog and cat. Clinical signs, serial blood glucose determinations, urine glucose, and glycated blood proteins. Vet Clin North Am Small Anim Pract 1995;25:571-584. 
8. Crenshaw KL, Peterson ME, Heeb LA, et al. Serum fructosamine concentration as an index of glycemia in cats with diabetes mellitus and stress hyperglycemia. J Vet Intern Med 1996;10:360-364. 
9. Thoresen SI, Bredal WP. Clinical usefulness of fructosamine measurements in diagnosing and monitoring feline diabetes mellitus. J Small Anim Pract 1996;37:64-68. 
10. Bennett N. Monitoring techniques for diabetes mellitus in the dog and the cat. Clin Tech Small Anim Pract 2002;17:65-69. 
11. Cook AK. Monitoring methods for dogs and cats with diabetes mellitus. J Diabetes Sci Technol 2012;6:491-495.