ACHIEVING AND MAINTAINING LONG-TERM STABILITY IN A DIABETIC is every vet’s goal when managing these
sometimes difficult cases.
The importance of this is highlighted by data stating that 15% of diabetics go on to develop ketoacidosis and, of these, only 30% actually go on to survive a DKA crisis. These data were cited by Susanna Spence from Glasgow University who led a recent webinar on Recent advances in diabetes, organised by The Webinar Vet.
Susanna focused her webinar towards short- and long-term monitoring of diabetics, which included the more familiar monitoring techniques commonly used in practice, and the more advanced techniques already utilised by our medical colleagues which are now trickling their way into the field of veterinary medicine.
Assessing clinical signs
The resolution or recurrence of clinical signs in diabetic patients can be a very useful indicator of stability in a patient. Relevant clinical signs include PU/PD, weight loss, muscle wastage and polyphagia,
all of which should improve significantly when stability is achieved.
Checking for glucosuria on a daily basis can be useful for detecting trends in the diabetic patient. It is a simple and cheap method which can be easily achieved by owners in their own homes.
In order to interpret any changing trends, it is very helpful for owners to keep a record of their pet’s daily routine, feeding habits, insulin doses, timings and urine glucose measurements. The use of urine dipsticks, however, gives no indication of very low blood glucose levels and dipstick measurements can be subject to interpretational errors.
It is also important to remember when measuring ketones that human dipsticks only measure acetoacetate and not beta hydroxybutyrate, the ketone most commonly formed in dogs.
Susanna also warned us that, although seemingly obvious, it is always worth checking that the operator reading the dipsticks is not colour blind!
Blood glucose curves
Blood glucose curves certainly play an important role in determining the type of insulin, the dose of insulin and the frequency of insulin administration in the newly diagnosed patient. This can be achieved by ascertaining the insulin’s onset of action, its duration of action and the blood glucose nadir.
Susanna explained that blood glucose curves can also be particularly useful in cases where the efficacy of insulin is being questioned, if you suspect a Somogyi over-swing, in ketoacidotics, and in the unwell, unstable patients. Glucose curves are, however, useless in patients which don’t eat within the hospital, or in-patients that get very stressed. The speaker also emphasised that glucose curves are most definitely not a measure of ongoing stability in a diabetic patient and are of no value in the clinically stable patient.
At-home glucose curves, although still not a measure of long-term stability in diabetics, can be more reliable than hospital curves due to decreased stress levels in the patient and can be particularly useful if trying to assess for hypoglycaemia. However, studies have shown there is a high rate of owner failure in performing at-home glucose curves and there is no evidence to demonstrate a decrease in vet visits or an improvement in quality of life or duration of life of the affected animal.
When hyperglycaemia is present for four days or more, glucose attaches to the plasma protein albumin and forms the measurable fructosamine. As the half-life of albumin is between 15 to 20 days, fructosamine offers a good measure of blood glucose levels in the preceding two to three weeks.
This is useful in cases where persistent hyperglycaemia requires confirmation but is a poor measure of long-term stability as levels over a two-to three-week period offer little value when monitoring for stability over a three-month period.
It is also important to remember that fructosamine levels are dependent on the amount and half-life of protein present in the blood and its value will alter when these fluctuate.
Continuous glucose monitoring systems (CGMS) are used regularly in humans and involve the placement of an intradermal sensor which measures the levels of glucose within interstitial fluid.
Previously, these systems have been too bulky and expensive to consider for use in veterinary patients; however, a system called Dexcom G4 Platinum has now become available and is used regularly by Susanna in her veterinary patients.
This is a wireless device which is placed into the skin on the neck of the patient and bandaged in place for a seven-day period. It measures interstitial glucose anywhere between 2-22mmol/l over this seven-day period and sends its measurements to a monitor which has to be kept within seven metres of the patient. These measurements can then be uploaded onto a computer via a USB stick.
Susanna advises that to produce reliable and accurate measurements, the Dexcom G4 Platinum needs to be calibrated against blood glucose measurements made by the Alphatrak-2 glucometer at least two to three times a day.
She explained that the use of the CGMS helps to reduce the stress and discomfort in patients usually associated with performing glucose curves using glucometer measurements. The CMGS also stops peak and trough levels being missed and allows for a much more thorough evaluation of the glucose curve.
The cost of the Dexcom G4 Platinum is surprisingly affordable, totalling around £1,460 (£800 for the monitor, £600 for the transmitter and £60 for the sensor) and Susanna advises that it can be particularly useful for a variety of patients in practice, including diabetic ketoacidotics, sick diabetics which are hospitalised, unstable diabetics where other problems have been excluded and the perioperative management of insulinomas.
Susanna added that although the CGMS is an excellent tool for the short-term monitoring of diabetics, it is not useful for monitoring long-term stability in the diabetic patient.
HbA1c is a form of glycosylated haemoglobin and is the primary measure of long-term stability (over two to three months) in humans. Recent developments in assay technology for human HbA1c have enabled these assays to be transferred to dogs.
A few human HbA1c assays were effective in dogs but they are no longer available and the rest were either ineffective or too expensive to use in dogs. The good news is that an affordable and time-efficient option is now available in the form of the Siemens DCA Vantage Analyzer.
Susanna explained that HbA1c levels measured in the DCA Vantage may also be an excellent indicator of long-term stability in dogs and advises measuring levels in clinically stable patients every three months. HbA1c measurements do of course have limitations and will not pick up changes in blood glucose levels which have taken place in the last two to three weeks rather than the last two to three months. Anaemia, bilirubin and triglyceride levels also have the potential to interfere with results.
Unfortunately, as of yet, there is no effective method of measuring HbA1c levels in cats as their protein sequences which make up HbA1c are very different to those which make up HbA1c in humans and dogs, both of which are very similar.
CGMS and HbA1c levels are recent monitoring techniques delivered to us by our medical colleagues and are most definitely a step forward in helping vets reach their goal of achieving and maintaining stable diabetics.
Susanna advised, however, that we must always look at the whole clinical picture and decisions should never be made based only on a set of laboratory results.
If the lab results indicate a patient is not stable and yet clinically a patient is doing well, there may be no good reason to alter a patient’s insulin dose. Also, if a patient is difficult to stabilise, always check the basics are right. Is the insulin being stored correctly? Is it being administered correctly? Has the patient’s routine and/or diet been altered? It is also always worth checking there are no other diseases which could be interfering with a patient’s stabilisation.
Susanna delivered an excellent webinar on recent advances in monitoring veterinary diabetics and offered valuable insights into how these advances could be and are being used in veterinary practice today. To find out more, log into “The Webinar Vet” and spend a very useful hour of your time learning more about managing diabetics in veterinary medicine both now and in the future.