Experiences with Blood Glucose Home Monitoring by Owners of Diabetic Dogs and Cats
Claudia E. Reusch, Dipl ECVIM-CA
Clinic for Small Animal Internal Medicine, University of Zurich
Long-term management of diabetic dogs relies on the owner's observation of clinical signs and on periodic evaluation by a veterinarian. The latter includes evaluation of the owner's observations, measurement of body weight and determination of concentrations of blood glucose and glycated proteins, which include serum fructosamine and glycated hemoglobin. Strongly increased concentrations of serum fructosamine or glycated hemoglobin suggest poor glycemic control and a need for insulin adjustment. However, these parameters do not identify the underlying problem.
Serial blood glucose curves (BGCs) are necessary to assess insulin efficacy, the glucose nadir, the time of peak insulin effect, the duration of the effect of insulin and the degree of fluctuation in blood glucose concentration. Blood glucose curves are also needed to recognize the Somogyi phenomenon. Until recently, BGCs were performed in a hospital, because most owners cannot perform venipuncture at home. However, there are several problems associated with determining BGCs in hospitalised patients. It is time consuming and expensive and therefore, it is often not performed as frequently as required. Many patients would benefit from more frequent blood glucose determinations. For example, short-notice adjustments of the insulin dosage are necessary in diabetic patients with infections (increased dose) or at times of increased physical activity (mostly decreased dose). Close monitoring of blood glucose concentration is also indicated in diabetic patients that are diagnosed with and treated for a concomitant disease, such as hyperadrenocorticism or hypothyroidism. Similarly, bitches may require adjustment of the insulin dosage at the transition from one estrus cycle stage to another. Due to the abolition of the resistance to insulin associated with these conditions, the required insulin dosage may have to be reduced drastically in order to prevent life-threatening hypoglycemia. It is difficult to manage these cases without frequent blood glucose determinations. In hospitalized patients, the concentration of blood glucose can be markedly influenced by stress or refusal to eat.
In human medicine, the problems described above have been largely eradicated with the introduction, in the late 70s, of self-monitoring of blood glucose concentrations (SMBG). For SMBG, human patients obtain a drop of capillary blood by pricking a fingertip with a lancing device. The drop is then placed on a test strip, and the glucose concentration is measured using a portable glucose meter. The availability of automated, spring-operated devices makes the finger-pricking process simple and virtually painless.
Until recently, a method analogue to self-monitoring of blood glucose concentrations in diabetic dogs and cats was not thought possible. The majority of pet owners are not able to collect blood via venipuncture and pricking of a fingertip, of course, is not feasible. However, methods have recently been developed for obtaining capillary blood from the ear of dogs and cats. Blood glucose concentration can then be determined using a portable glucose meter. Those methods are inexpensive, fast and easy to perform and can be used by owners of diabetic dogs and cats to determine blood glucose concentrations and to generate BGCs at home.
For pet owners, home monitoring of an animal can constitute a challenge and therefore it is important to minimize any technical difficulties as much as possible. Owners should choose a portable blood glucose meter that is simple to operate. In our experience, of all meters on the market, the Glucometer Elite® (Bayer Diagnostics) is the easiest to operate: it has no buttons to press, turns on automatically when the test strip is inserted and requires a very small amount of blood (2 µl), which is automatically aspirated into the reaction chamber after contacting the test strip. This meter employs an amperometric detection method and is remarkably small and easy to handle with a measurement range of 20 to 600 mg/dl. The result is displayed after 30 seconds and the last 20 measurements are stored. However, as with all portable blood glucose meters, problems may occur. It is important that the test strip chamber be filled to the mark. When too small a volume of blood (< 2 µl) is used, the acoustic signal, that normally marks the end of the aspiration of blood, erroneously sounds, and measurement follows, producing an inaccurate low reading. Blood glucose concentrations that are measured by portable blood glucose meters almost always vary slightly from those measured by a reference method; values obtained by the Glucometer Elite® consistently underestimate true concentrations.
For approximately two years, we have been involved in home monitoring of blood glucose concentrations of diabetic dogs and cats by owners. The results have been extremely positive. The majority of owners are very interested in performing blood glucose determinations in their pets, and more than 70% have been capable and willing to do this on a short- to long-term basis.
There are a number of steps that should precede the introduction of home monitoring. The first step is a definitive diagnosis of diabetes mellitus. Additional tests may be indicated at this point; determination of serum fructosamine concentration is routinely performed. The owner then receives detailed information on various aspects of diabetes mellitus and careful instruction on injection technique, and the concept of home monitoring is introduced for the first time. This consultation takes approximately 45 minutes. The second step consists of re-evaluation of the patient after one week. Observations made by the owner are discussed, a clinical examination is performed and fructosamine concentration and an in-clinic BGC over 12 hours are determined. Treatment is adjusted if necessary. At the time of discharge, the importance of the BGC in the control of the disease is emphasized. In addition, the advantages of home monitoring for owner and pet are discussed and she/he is informed that this procedure can be started after the next checkup.
The third step follows approximately three weeks after a diagnosis has been made. Once again, owner observations are assessed and a physical examination, a BGC and fructosamine concentration are determined. The owner is now provided the opportunity to learn the technique of home monitoring. This requires a minimum of 30 minutes and consists of repeated demonstrations of the use of the lancing device and the portable blood glucose meter. The owner then performs the technique several times using her/his pet. The owner is also taught how to calibrate the blood glucose meter, check its accuracy using the control strips and record the blood glucose values on forms prepared by us. Home monitoring is not started before the third week after a diagnosis of diabetes mellitus. This allows the owner to become familiar with the disease and to gain experience with the injection of insulin. However, introduction of home monitoring is delayed to a later date if the owner does not seem ready for it.
Once the owner is comfortable with the procedure, we request that fasting blood glucose concentration be determined twice weekly and a BGC once monthly. The former serves to detect morning hypoglycemia, in which case the owner is instructed to call us. For determination of a BGC, the blood glucose concentration is measured before the insulin injection (fasting) and every two hours. Since all our diabetic animals receive insulin BID the BGC is performed for 12 hours. The owner sends the results of the BGC, and appropriate changes in treatment are discussed, if necessary, on the telephone. Over time, the owners gain experience in the collection of blood and operation of the blood glucose meter. During the first few weeks of home-monitoring, periodic re-evaluations of the entire procedure are performed at the clinic. Regular veterinary re-evaluation of a diabetic patient is recommended, even when the owner is experienced with home monitoring.
It is important that owners have ready access to veterinary support, if required. The majority of our clients call for advice one or more times, especially after the start of home monitoring. Some have specific questions regarding the procedure, while others want reassurance that they are performing the procedure correctly. Sometimes support via telephone is not sufficient and additional explanation or demonstration of the technique must be provided. By watching an owner perform the procedure, a veterinarian can immediately identify and correct errors. The prerequisite for good owner instruction is a knowledgeable veterinarian, who is able to perform the procedure correctly and is aware of all potential sources of error. According to a recently performed study, the most frequently encountered technical problems included, inadequate formation of a blood drop due to excessive pressure of the finger behind the ear while lancing the ear, repeated depression of the plunger instead of allowing the negative pressure to slowly build up, and failure to fill the test strip to the mark. These procedural steps require explicit explanation and demonstration. Handling the glucose meter usually is not a problem for owners, and most report that their pet tolerates blood collection well. Usually, owners feel that their technique improves quickly, which leads to increased confidence in the test results. The skin puncture does not seem to be painful, and the puncture sites are barely visible, even after numerous blood collections.
We recently performed 2 long-term studies in diabetic dogs and cats where the results of in hospital glucose curves were compared with those generated by the owner at home. In about 40% of cases, treatment based on hospital curves would have been different if based on home curves. Home monitoring is a new and very important tool in the management of diabetes mellitus in pet animals. The greatest advantage is that blood glucose concentration can be measured at any time. In questionable cases, a number of curves can be generated.
1. Reusch CE, Wess G, Casella M: Home monitoring of blood glucose concentration in the management of diabetes mellitus. Comp Cont Educ 23(6), 544-557, 2001
Claudia E. Reusch, Dipl ECVIM-CA