Use of the Continuous Glucose Monitoring System in 5 Dogs Having Diabetes Mellitus
K. Bluwol; L. Lavans; R.N. Chaves; F.S. Fragata; M. Marcondes Santos
The blood glucose concentration monitoring in series is an usual diagnostic procedure greatly significant in veterinary medicine. Serial blood glucose concentration curves in cats and dogs having Diabetes Mellitus (DM) are performed to determine proper insulin type, dosage, and the necessary frequency of administration to maintain appropriate blood glucose concentration (Davison et al. 2003, Wiedmeyer et al. 2003). In order to perform such procedure, it is essential to have many blood samples during a certain period of time. Usually, repeated venipuncture in short periods of time (every 1 or 2 hours) is done to collect the necessary samples. This results in stress and pain, requiring the animal to have constant handling or restrain. Besides, there is a great risk of losing the peak or nadir between two samples. Nowadays, the clinician can count on many other laboratory exams to help monitoring the glycemia control of the animal. In a persistent hyperglycemic state, serum fructosamine and glycosylated hemoglobin increase and by measuring these two substances the clinician can adjust the previous treatment. Although they are excellent assays to determine the glycemic state of the animal, they have not been validated for use in all species, and false-positive and false-negative results have been reported. Also, these assays do not provide information regarding glucose nadirs nor changes in glucose concentration in response to insulin administration (Wiedmeyer et al. 2003). An alternative to glucose continuous measurement is through the interstitial space within the subcutaneous tissue. This new method of measuring the glycemic curve is better than the usual because it reduces the necessity of repeated venipuncture and the animal constant handling and restrain, in order to minimize its stress. The continuous glucose monitoring system (CGMS) is a new equipment using interstitial glucose going through a semipermeable membrane and reacts with the glucose oxidase enzyme, changing it into gluconic acid and hydrogen peroxidase. An electrical sign in proportion to the glucose concentration is obtained as well as registered by the system and converted into interstitial glucose concentration in units of milligrams per deciliters (mg/dl) (Wiedmeyer et al. 2003). By measuring the interstitial fluid glucose every ten seconds, an average value is checked every five minutes for 72 hours. Therefore, it can inform whether the glucose is quickly increasing or decreasing enabling the clinician to adjust the therapy. The system operates at intervals of 40 and 400 mg/dl. The CGMS sensor within the subcutaneous tissue causes no inflammation or irritation in addition to use a wireless system. There is no need to keep the equipment attached to the animal but it should be maintained close to it. The use of CGMS in human beings with unstable DM has had a significant improvement in glycemic control and, as a result, a decrease in the glycosylated hemoglobin (Davison et al. 2003). It has been demonstrated, not only in humans but also in dogs, that the interstitial fluid glucose concentration is similar to the blood glucose concentration (Wiedmeyer et al. 2005), although the difference between the changes in the blood and the interstitial fluid compartments takes less than 10 minutes in dogs (Davison et al. 2003). This system needs calibration along with the glycemia measurement using the portable blood glucose meters (being approximately 4 times on the first day) including information regarding the time of feeding and insulin injection. Later on these data will be available to perform the charts supplied by the program in order to help the clinician to check the therapeutic behavior.
Materials and Methods
Five dogs having diabetic ketoacidosis or unstable DM were admitted at Sena Madureira Veterinary Hospital from June 2007 to May 2008. These animals were submitted to CGMS. Their owners provided the clinicians a full daily report about the time of insulin injections, time feeding and kind of food, amount of carbohydrate as well as walking time. In case of non-satisfactory glycemia control, both insulin and food were severely administered according to the routine of each animal. To obtain the correct usage of the system, at least 4 calibrations glucose measurement by the portable blood glucose meters included in the program are needed, being the first one performed 60 minutes after starting. The feeding and insulin procedures are recorded in the system at the period of monitoring so as to analyze them. For the sensor placement, a small patch of hair was shaved on the lateral thoracic region and wiped with an alcohol swab. The sensor is inserted into the skin and once placed the needle is removed. The system is placed at the door of the kennel and the value is transmitted by wireless system. The equipment is kept for 48 to 72 hours.
Discussion and Conclusions
The CGMS in human medicine is used to show future interventions in patients as an answer to the possibility of high glycemia given by the monitoring (Bode 2000). The best advantage of CGMS is the amount of information automatically given. Furthermore, there might be some failure in obtaining the glycemia nadirs or peaks in the traditional blood glucose curves besides being stressful and painful. No inflammation or irritation was remarked on the skin of the animal according to the previous studies (Davison et al. 2003, Wiedmeyer et al. 2003, Wiedmeyer et al. 2005). The main difference between the glycemia measurement by portable blood glucose meters and by CGMS occurs with higher values while CGMS presents lower glucose values. However, these values are within the acceptable range so no different clinical intervention is needed. In spite of these occasional discrepancies, both methods show good correlation (Davison et al. 2003, Wiedmeyer et al. 2003, Wiedmeyer et al. 2005). The blood glucose measurement should be performed at least 3 times so as to get a correct calibration of the equipment which records the glucose range from 40 to 400 mg/dl. Values above 400 mg/dl are not correctly presented. As a matter of fact, a persistent glucose range over 400 mg/dl means an ill-controlled diabetes; in this case a suitable intervention is needed. The new CGMS is a reliable option for animals presenting an unstable DM, diabetic ketoacidosis and prompt post-operative diabetic patients. This method makes all the glycemia curves stress factors decrease as well as hyperglycemia risks induced by stress, which may change all the results of exams in some animals.
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