Introduction

The primary goal of management of feline diabetes is to achieve diabetic remission. Secondary goals are to control clinical signs and avoid clinical hypoglycaemia. If exemplary control of blood glucose concentrations is instituted early after diagnosis of diabetes, approximately 90% of cats achieve remission. To do this requires the use of long-acting insulin, feeding a low carbohydrate diet and frequent monitoring of blood glucose concentration and appropriate dose adjustments. Maximising the quantity and quality of information on which to base insulin dose changes is important, and home monitoring provides a number of advantages.

Advantages of Home Monitoring

Home monitoring has many advantages for both the pet and its owner. Spuriously high blood glucose concentrations caused by stress hyperglycaemia are likely to be reduced if a cat is tested in its home environment rather than in a veterinary hospital. Eating affects blood glucose concentrations, and in the home environment, cats are likely to be eating and behaving normally, therefore giving more accurate readings than those obtained in a veterinary clinic. Home monitoring also allows blood glucose concentrations to be assessed immediately by the owner, should the cat begin to behave abnormally. This is helpful for identifying and managing clinical hypoglycaemia. Early optimisation of blood glucose concentration is facilitated with home monitoring, because home monitoring provides more data on which to make more frequent insulin dose adjustments. This increases the likelihood of remission in the diabetic cat. Home monitoring reduces the need for expensive and inconvenient hospitalisation of a pet for the client, and decreases stress for the cat. Clients still should have frequent veterinary visits, particularly in the initial stabilisation phase, so that their home-log of glucose concentrations and insulin dose can be reviewed, along with their blood collection and blood glucose measurement techniques. In addition, visits provide the opportunity to examine and weigh the pet, and check accuracy of the glucose meter.

Blood Glucose Meters

It is critical owners are made aware of differences in blood glucose meters. All the reputable companies such as Abbott, Bayer and Roche make precise meters that produce results that are very similar to the feline blood glucose concentration measured by a serum chemistry analyser. This means the results they provide are very repeatable. However, the accuracy of human-use meters decreases substantially when used for feline (or canine) blood.

It is critical that the client be made aware that the target glucose concentration is dependent on the meter used. If they are using a meter calibrated for feline blood, they should not change to a meter calibrated for human blood without also changing the target blood glucose concentrations in the dosing protocol. A greater danger is the change from a meter calibrated for human use to one calibrated for feline use when using a protocol aimed at tight glycaemic control and with target blood glucose values designed for a whole blood human-use meter because there is an increased risk of unintentional hypoglycaemia.

The meters should be regularly checked for accuracy. Control solutions are available for glucometers from the individual manufacturers and allow owners to test for proper functioning of their glucometer. Blood glucose concentration can be measured both on the owner's meter and with a serum chemistry analyser for further validation.

Important features in appropriate blood glucose meters are a small sample size (≤ 0.6 µl), ease of use and reliability. Additionally, the cost of test strips should be reasonable. Test strips should also be easily available.

Practical Methods for Obtaining Blood in Cats

Typically, blood samples are taken from the capillaries in a cat's ear using a lancing device for human diabetics. There are many types of lancing devices available, including devices which create a vacuum to facilitate collection of sufficient blood volume. The depth of penetration is often adjustable for lancet devices and the lancet needles are disposable. The author has found that the lancet provided with the Abbott AlphaTRAK works very well in most cats, and we use it predominantly at the deepest depth setting. Some owners prefer not to use a lancing device, but draw blood using only a lancet needle or syringe needle. However, it is not recommended that this method be taught because the needle insertion time is longer than with an automatic device and can be problematic. Some lancets work better in some cats and with some owners. Often a successful approach is to test sites and lancets with the pet in the consulting room, to determine the best device and site to maximise the likelihood of obtaining a sample of adequate volume. It is vital that when introducing home monitoring, the owner is shown how to set up the meter and gets practice using it under guidance of a veterinarian or technician before going home.

Warming the ear sufficiently prior to taking blood is a crucial factor in being able to easily draw blood. Warm and rub the ear for several minutes prior to drawing blood. Once a cat has been home monitored for a period of time, extensive warming is often no longer necessary.

Some owners prefer to draw blood on the inner surface of the pinna. Alternatively, the outer surface of the pinna can also be used. Obtaining an adequate sample can be facilitated if the hair is clipped and/or a thin layer of petroleum jelly is first applied to the surface to encourage beading of the blood. When the ear has been well warmed, the marginal ear vein often produces too much blood, and sites near the vein will become preferable as they produce sufficient amounts of blood. With repeated use of an area for obtaining blood, samples are more readily obtained, probably because of increased vascularisation.

Capillary blood can also be obtained from the carpal or pisiform pad at the back of the leg and may be more reliable for obtaining blood than the relatively thick paw pad. This can be useful in some fractious cats or cats with ear problems.

Adjusting Insulin Doses

Until blood glucose concentration is well controlled, frequent monitoring of blood glucose concentration should be encouraged. It is recommended that, as a minimum, owners measure blood glucose just before the morning and evening insulin injection and again before they go to bed for 6 days out of 7, and on one day in the week they measure blood glucose every 3–4 hours throughout the day until they go to bed. If they are able to measure blood glucose more frequently than three times a day on more than 1 day a week, that is preferable. Even three blood glucose measurements per day and one full blood glucose curve a week provide more information to make insulin dose changes than blood glucose measurements obtained at the veterinary clinic once every 7–14 days.

Ketosis

Prior to treatment with insulin, or before regulation is achieved, hyperglycaemic cats may develop ketosis. Monitoring for ketones can be achieved using urine test strips, or in the blood using a handheld meter (e.g., Precision Xtra, Abbott Health). The new models of these handheld meters require only 1.5 µl of blood; however, test strips are relatively expensive.

The type of ketone (ketone body) detected by commonly used testing devices in urine and blood differs. While urine test strips measure the concentration of acetoacetate, handheld meters such as the Precision Xtra measure beta-hydroxybutyrate (BHBA) in whole blood. Blood ketones also appear days earlier than urine ketones, and low yet significantly elevated blood ketone levels can be detectable while urine ketones remain negative, i.e., undetectable. Well regulated cats have blood ketone concentrations from 0.0–0.2 mmol/l. Therefore, cats with a tendency to develop ketones or which previously had diabetic ketoacidosis may benefit from blood ketone testing.

Cats Requiring High Doses of Insulin

Cats with blood glucose concentrations that do not seem to respond to typical doses of glargine or detemir, e.g., > 1.5 IU/kg, should be tested for acromegaly.

Avoiding and Dealing with Relapse in Remission Cats

Once remission is achieved, medications such as corticosteroids and megestrol acetate should be avoided and the cats should continue receiving a strict low carbohydrate diet with energy intake controlled to achieve ideal body condition. Continued once-weekly home testing is recommended as it detects early increases in blood glucose concentration. Six-monthly veterinary examinations including comprehensive blood panels and, when necessary, dental prophylaxis are also recommended.

Approximately 25–40% of cats in remission will relapse and require insulin again. Cats which relapse should have insulin reinstituted as soon as fasting glucose concentrations are persistently 10 mmol/l or higher. If insulin is reinstituted early, better glycaemic control with smaller insulin doses is achievable and a second remission is more likely.

With thanks to Kirsten Roomp BSC, MSc.

References

Selected articles are available on our website: www.uq.edu.au/ccah