Reusch, Claudia E

ZORA

University of ZurichZurich Open Repository and ArchiveWinterthurerstr. 190CH-8057 Zurichhttp://www.zora.uzh.chYear: 2008Diabetes mellitus - monitoring at home and in the hospitalReusch, C EReusch, C E. Diabetes mellitus - monitoring at home and in the hospital. In: Congress at the Royal VeterinaryCollege, University of London, Hertfordshire, UK, 12 November 2008 - 12 November 2008.Postprint available at:http://www.zora.uzh.chPosted at the Zurich Open Repository and Archive, University of Zurich.http://www.zora.uzh.chOriginally published at:Congress at the Royal Veterinary College, University of London, Hertfordshire, UK, 12 November 2008 - 12November 2008.Reusch, C E. Diabetes mellitus - monitoring at home and in the hospital. In: Congress at the Royal VeterinaryCollege, University of London, Hertfordshire, UK, 12 November 2008 - 12 November 2008.Postprint available at:http://www.zora.uzh.chPosted at the Zurich Open Repository and Archive, University of Zurich.http://www.zora.uzh.chOriginally published at:Congress at the Royal Veterinary College, University of London, Hertfordshire, UK, 12 November 2008 - 12November 2008.Diabetes mellitus – monitoring at home and in the hospital Claudia E. Reusch Dipl ECVIM-CA    The general aim of therapy is to provide a good quality of life by eliminating clinical signs of diabetes and preventing complications such as hypoglycemia and ketoacidosis. In cats immediate therapy may reverse the effects of glucose toxicity and the diabetes may go into remission.  The latter usually occurs during the first 3 months of therapy; however, it may take 1 year or longer and is one of the reasons why close supervision and regular measurement of blood glucose is of utmost importance. In dogs diabetic remission is a rare event and usually only happens after castration in some cases of diestrus-related diabetes. In case remission occurs unnoticed serious hypoglycemia may result.  In dogs and cats with permanent diabetes it is not necessary to establish normal or near normal blood glucose levels as it is the case in humans, where it is well known that good glycemic control significantly reduces the risk of life-threatening chronic complications (e.g. nephropathy, cardiovascular disease). Due to the fact that those complications require many years to develop they are rare in diabetic dogs and cats. Most diabetic pets are doing well if the blood glucose concentrations are kept between 15 and 5 mmol/l  throughout 24 hours.   Successful treatment requires that the owner be highly motivated and collaborate closely with the veterinarian.  Monitoring in the hospital After diagnosis of diabetes mellitus the owner should be informed that it usually takes 2 – 3 months until stable glycemic control is achieved and that life-long regular re-evaluations in the hospital are required. The exception to the latter are animals (usually cats) which experience diabetic remission. Initially, frequent re-evaluations should be scheduled, with time, intervals can be extended. In our hospital re-evaluations are suggested 1, 3, 8, 12 weeks after diagnosis and then approximately every 4 months.  Evaluations should include assessment of the owner`s observations, measurement of body weight, and determination of blood glucose and serum fructosamine concentrations. Clinical signs and body weight are the most important parameters to monitor and an animal which drinks, eats, urinates normally and has a stable body weight can be considered well controlled. Traditionally, blood glucose measurements and generation of serial blood glucose curves were almost always performed in veterinary hospitals because most owners are unable to collect venous blood samples. Recently, methods have been developed to collect capillary blood samples from the pet`s ear that allows owners to measure blood glucose concentrations at home. Home monitoring of blood glucose (HM) has displaced the measurement of urine glucose nearly completely in our clientele.    Monitoring in the hospital: fructosamine Fructosamine measurements are widely used as an indicator of glycemic control in diabetic dogs and cats. Measurement is done in serum using commercially available test kits adapted to autoanalysis. Storage at 25oC for 5 days does not cause a significant change in fructosamine concentrations, allowing shipping of serum samples. Fructosamine is the product of an irreversible reaction between glucose and the amino groups of various serum proteins, and its concentration reflects the mean blood glucose concentration of the preceding 1 – 2 weeks. Reference ranges differ slightly among laboratories but are usually around 200 – 360 µmol/l. In most cases with newly diagnosed diabetes, fructosamine levels are > 400 µmol/l and may be as high as 1500 µmol/l. Normal fructosamine levels may be seen with very recent onset of diabetes. Fructosamine may also be normal in animals suffering from certain concurrent diseases. It has been shown that in dogs hypoproteinemia, hyperlipidemia and azotemia, in cats hypoproteinemia and hyperthyroidism can decrease the fructosamine concentration.  Fructosamine concentrations increase when glycemic control worsens and decrease when glycemic control improves. Since even well-controlled pets may be slightly to moderately hyperglycemic throughout the day, fructosamine concentration will not usually decrease into the normal range. On the contrary, a normal fructosamine concentration (particularly a fructosamine value in the lower half of the reference range) should raise concern about prolonged periods of hypoglycemia (insulin overdose, diabetic remission). Metabolic control is considered good when fructosamine levels are between 350 and 450 µmol/l, moderate when values are between 450 and 550 µmol/l and poor when levels are > 550 – 600 µmol/l. In the latter case, fructosamine is not helpful in characterizing the problem because all the possible reasons for poor regulation (e.g. insulin underdose, too short a duration of insulin effect, diseases causing insulin resistance, insulin absorption problems, Somogyi effect) have the same impact on fructosamine. In some pets, fructosamine levels remain high, suggesting poor metabolic control, although clinical signs and blood glucose levels are well controlled. The reason for this discrepancy, in most cases, remains unknown.   Monitoring in the hospital: blood glucose measurements  Blood glucose curves (BGCs) are necessary to assess insulin efficacy, glucose nadir, duration of insulin effect, degree of fluctuation and the Somogyi effect. In general, single glucose measurements are considered insufficient to assess metabolic control.  We prefer that owners give insulin and food at home, and then bring the animal to the hospital as soon as possible (within 2 hours) for a BGC. This approach eliminates the effect of lack of food intake on blood glucose levels, at least in animals which are only fed at the time of insulin administration. Only when technical difficulties are suspected are owners asked to bring the animal to the hospital before insulin application and to carry out the entire administration procedure under supervision. Different approaches may be more appropriate depending on the circumstances, for instance when the distance between home and hospital is very long.   BGCs are generated by measuring the glucose concentration every 1 to 2 hours throughout the day until the next insulin administration is due. In our hospital, we avoid multiple venipunctures by collecting capillary blood from the ear using the same sampling technique and the same portable glucometer (PBGM) as owners at home.  However, there are several problems associated with serial blood glucose measurements in hospitalized animals. First of all, the procedure is time-consuming and expensive and therefore in many patients may not be carried out as often as indicated. Secondly, the concentration of blood glucose can be markedly influenced by stress or lack of food intake. Cats in particular are sensitive to stress caused by veterinary manipulation in an unfamiliar environment. Consequently, the BGC may show a continual increase in glucose concentration or it may be elevated from the beginning. In the latter, it is not possible to differentiate between stress-associated hyperglycemia, insulin underdose and the many causes of insulin resistance. In pets that are brought to the hospital to generate a BGC before feeding, or in pets (in particular cats) that are used to nibbling food throughout the day, refusal to eat has a serious impact on blood glucose concentration. It is then difficult to decide whether lack of food intake or insulin overdose is the cause of low glucose concentration.    Monitoring at home: clinical signs and blood glucose measurements The owner should assess his animal with regard to the clinical signs of diabetes mellitus on a daily basis. Body weight should be taken at least once a week. It is important that the owner is familiar with the clinical signs of the most important complications of diabetes mellitus, i.e. hypoglycemia and diabetic ketoacidosis. In the late 1970s, self-monitoring of blood glucose (SMBG) was introduced in human medicine. For SMBG, humans obtain a drop of capillary blood, usually by pricking a fingertip, with the aid of a lancing device. The drop is then placed on a test strip, and the glucose concentration is measured using a PBGM. Today, all human diabetes treatment guidelines include SMBG as an integral part of their recommendations. During the last years methods analogue to SMBG have been developed for dogs and cats. The method used in Zurich is performed by the use of a lancing device creating a negative pressure. Capillary blood is obtained from the inner aspect of the pinna and blood glucose concentration is determined with a PBGM. The method is relatively 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. Several companies are now marketing PBGMs for veterinary use and claim that they give more accurate results than those designed for humans. However, so far only very few independent investigations have been published. PBGM readings usually differ to some extent from values measured by a reference method. However, these differences should be as small as possible to avoid treatment errors. Each new type of PBGM should be validated before it is used in dogs and cats.  HM has been part of the routine protocol for long-term management of diabetic pets in our clinic since 1999. Owners are introduced to HM approximately 3 weeks after the initial presentation and only after they became familiar with the disease and the insulin injection technique.   Owners can certainly be taught to interpret a BGC; however, we prefer that decisions regarding changes in the insulin dose be made by the veterinarian and therefore, BGCs be sent to the hospital. Interpretation of BGCs generated at home follows the same rules as BGCs generated in the hospital. Ideally, the blood glucose concentration ranges from 12 – 15 mmol/l before the insulin injection and from 5 – 9 mmol/l at the time of maximal effect.  The most important variables to assess are insulin efficacy, glucose nadir and duration of effect. Insulin efficacy (= difference between the highest and the lowest glucose concentration) must be interpreted in light of the highest blood glucose concentration and the insulin dose. A small difference (e.g. 3 mmol/l) is acceptable when the highest blood glucose is less than approximately 12 mmol/l, but is not acceptable if the highest glucose level is > 15 mmol/l.  An identical difference (e.g. 5 mmol/l) may indicate insulin efficacy in an animal receiving small amounts of insulin, but may point to insulin resistance if the insulin dose is high (> 1.5 U/kg). In the latter situation, technical problems and the counter-regulatory phase of the Somogyi effect must also be considered.  The next variable to be assessed is the glucose nadir, a lower nadir may occur in insulin overdose (including sudden improvement of insulin-resistant states), excessive overlap of insulin actions and lack of food intake. If the nadir is > 9 mmol/l, insulin underdose, the counter-regulatory phase of the Somogyi effect and technical problems involving the injection of insulin by the owner must be considered. In diabetic pets that already receive high doses of insulin (> 1.5 U/kg/injection), concurrent diseases causing insulin resistance are also possible. On several occasions, we have seen nadirs that were somewhat lower (in the range of 3 – 4.5 mmol/l)  than the above mentioned 5 – 9 mmol/l during HM. The animals were well regulated and overdose of insulin was considered unlikely. We presume that blood glucose levels measured in a stress-free environment are generally lower than those measured in the hospital. The duration of effect is defined as the time from insulin injection through the glucose nadir until the blood glucose concentration exceeds 12 – 15 mmol/l. If the duration is less than 8 – 10 hours, the animal usually has signs of diabetes, and if the duration is longer than 14 hours and the insulin is given twice daily, the risk of hypoglycemia or the occurrence of the Somogyi effect increases. In humans, it is well known that blood glucose concentrations can vary markedly from day to day. There is also a high degree of variability among BGCs of diabetic pets. We recently compared BGCs generated at home with those generated in the hospital within the same week under the same conditions (i.e. same insulin dose, same blood sampling conditions) in diabetic cats. In about 60% of cases, treatment decisions would have been the same, regardless of which of the two corresponding BGCs was used for evaluation, whereas in about 40% of cases, the decisions would have differed. In a follow-up study, BGCs generated on two consecutive days at home and on one day in the hospital within the same week were compared. It turned out that the differences between consecutive home curves were also relatively high and often not smaller than between home and clinic curves. One can conclude from these studies that single BGCs may not be reliable for treatment decisions, regardless of whether they are generated in the hospital or at home. However, one of the major advantages of HM is that it enables frequent generation of BGCs, which may be of particular importance in animals that are difficult to regulate. In those cases, more than one BGC can be generated at home before a change in treatment is initiated.     Continuous Glucose Monitoring Continuous Glucose Monitoring Systems (CGMS) have recently been introduced into veterinary medicine. Studies using CGMS for home monitoring of blood glucose have not been reported. However, the latest generation of devices which provide glucose levels in real time (e.g. Guardian Real Time System) may have great potential. The system uses a small electrode, which is inserted and fixed under the skin, to measure glucose levels in the interstitial fluid. The sensor is connected to a transmitter that sends glucose readings in a wireless fashion every 5 min to a monitor, which displays up to 288 readings per day. Currently, the system still has some shortfalls: it requires calibration with a blood glucose measurement at least every 12 hours, the sensor can only be left in place for 72 hours, and it is expensive. However, with some further improvements, it is very likely that CGMS will also be used at home in the future.   

Diabetes mellitus - monitoring at home and in the hospital

http://www.zora.uzh.ch/9562/1/DiabetesmellitusMonitoringV.pdf

Diabetes mellitus - monitoring at home and in the hospital

Abstract

Similar works

Full text

Available Versions

ZORA