Diabetic management is doctor/client responsibility
Canines and felines with diabetes mellitus require a considerable investment in time for both the client and clinician.
Veterinary endocrinologists point out that the changing status of pancreatic function and factors such as the development of antibodies toward insulin will result in changing exogenously administered insulin requirements in almost all patients as time passes.
All parties involved in the care of these patients should also be aware that concurrent disease entities (e.g. urinary tract or other infections, hyperadrenocorticism, hypothyroidism, hyperthyroidism) and/or physiologic factors such as changing exercise patterns or food intake also alter insulin requirements. Until pancreatic islet cell implants or totally self-contained integrated glucose monitor/insulin pumps are perfected, the best option is to set up a program where both the client and doctor follow the results of diabetic management. This article will discuss some relevant recent publications on this subject.
The first requirement of such a program is the observation of the patient at home by the clients/caretakers. The successfully managed diabetic will probably be eating well, maintaining body weight, feeling bright and alert, and hopefully will not be showing signs of neuromuscular (posterior paresis in the cat) or ophthalmic (cataracts) complications. A key positive observation is client perception that there is control of polyuria/polydipsia. Roughly speaking, this means less than 90 ml/kg/day of water consumption in the canine or <45 ml/kg/day in the feline. The caretaker should report no suspected episodes of hypoglycemia if all is going well.
In a recent article (pages 311-312, JAAHA, July/August 2001, Vol 37), Dr. Michael Schaer reminds us that there are important reasons to monitor urine glucose on a regular basis at home in these patients.
This is one practical method of monitoring day-to-day variations in glycemic control. It is especially important in identifying patients that may be experiencing a reduction in their insulin needs (i.e. the transient feline diabetic or the Cushing's/diabetic canine that is producing less cortisol due to effective therapy for hyperadrenocorticism). This method has received scant attention in recent literature, but it has no peer or replacement in its ability to reveal ketonuria when Keto-Diastix (Bayer Corp.) are used to test the urine. It brings the client in touch with the concept that close monitoring is vital to their pet's welfare, and demonstrates to them that, in fact, urine glucose, and thus blood glucose levels, are always in flux. In certain selected patient/client combinations, urine glucose determinations can be used to modify daily insulin dosages based on predetermined limitations specified by the attending clinician. Schaer has a detailed and eloquent discussion of this method in his article.
These tests may also signal changing insulin needs by identifying progressively higher urine glucose levels, leading the clinician to perform the next test we will discuss.
Blood glucose curve
The "blood glucose curve" is the method most commonly discussed in relation to insulin dosage determination and modification.
It can be used to document if hypoglycemia or "Somogyi" phenomenon are occurring. It can be used to re-evaluate insulin type selection or dosage in cases where clinical signs are flaring up or concurrent diseases appear. Blood glucose curves may also be used in the initial selection of insulin dosages and/or on a regular basis to follow up glycemic control. It is important to realize that these curves may be affected by changes in stress, exercise and food consumption, especially if they are performed in a hospital setting. In addition, the clinician should consider ruling out secondary factors contributing to poor diabetic regulation (e.g. urinary tract infection, hypothyroidism, Cushing's, etc.) before using this method to change an existing dosage regimen.
In the 2001 ACVIM Forum Proceedings abstract #101, Drs. Fleeman and Rand report results from 12 hour blood glucose curves performed on 10 canines with spontaneous diabetes mellitus. Results were recorded over two consecutive days on three different occasions for each patient.
Based on the curve results, a theoretical recommendation to increase, decrease or maintain the current insulin dosage was developed. The results were so varied that 27 percent of the time the results on day 1 resulted in an opposite recommendation from the results on day 2. Thus, especially in patients with control of clinical signs, the clinician may not wish to proceed solely on the results of this method.
Some clinicians and extremely cooperative patient/client combinations are beginning to sample drops of blood with the contemporary lance and "at home" glucose measurement devices.
In the 2001 ACVIM Forum abstract #149, Drs. Cohn et al compare results from several of these devices to those of a standard dry chemistry unit. They note that the accuracy of each device was lower at values less than 100 mg/dl, with median differences between dry chemistry and the devices ranging from 26 mg/dl to (+) 40 mg/dl. All devices tested had occasional readings markedly different than the dry chemistry determination "which could have led to clinically inappropriate treatment choices. "The doctor and client should probably double check low, low normal or unexpected values obtained from these devices before adjusting insulin dosages based on these tests.
Finally, information on glycemic control over the preceding weeks can be obtained by the use of fructosamine or glycosylated hemoglobin tests.
Schaer points out that these tests "will not assist in identifying any particular patient's day-to-day changing needs for more timely insulin dosage adjustments, especially in overdose situations,"and suggests that diabetic control be based "on the combined utilization of clinical signs, blood glucose curves, glycosylated blood tests and urine glucose monitoring."