Diabetes management: Can we do a better job?
Continuous glucose monitoring devices provide a complete picture of the glucose trends in patients with diabetes.
Canine and feline diabetes is an endocrinopathy most often caused by an insulin-dependent etiology similar to type 1 diabetes in humans. Treatment for diabetes relies on exogenous insulin therapy, in most cases, to reverse existing glucose toxicity and attempt to achieve near normoglycemia.1 Following an initial diagnosis and institution of insulin and dietary therapy, patient monitoring is key to finding optimal insulin.
Until recently, it has been advisable to perform a blood glucose curve to determine whether adjustments in the initial dose were needed. Typically, attaining a blood glucose curve means collecting a blood sample every 1 to 2 hours, either with a hospitalized patient using conventional venipuncture or using a monitor such as AlphaTRAK.2 It is well documented that blood glucose curves vary from day to day in the same patient.3 In-hospital sampling rarely collects more than 12 data points during a 12-hour workday. Home sampling results using an AlphaTRAKglucometer are owner-dependent and often lead to stress in both owner and patient, which for certain patients can have clinical significance.4 These problems reveal the most obvious benefit of continuous glucose monitoring (CGM): Providing the clinician with an accurate picture of the blood glucose patterns in the patient 24 hours a day for up to 14 days. However, in this author’s experience, it was the unexpected benefits to the owner and patient that made the difference.
CGM in veterinary medicine has been described as early as 1993,5 with research papers and reference articles becoming more prominent within the last 5 years.6-10 Use of CGMs is still largely limited to veterinary teaching hospitals, specialty clinics, and the occasional private practice. However, the general veterinary population can also use this affordable and simple treatment option.
Use of a monitor that can be linked to a smartphone provides real-time accessibility to glucose levels in dogs and cats without the purchase of the reader. A reader must be purchased if the owner does not own a smartphone. Once insulin is started, a prescription to any pharmacy will allow the client to purchase the FreeStyle Libre monitor, and its package insert includes a link to the software on the Abbott website. Within minutes after monitor placement, the Abbott software begins to generate curves that collect a data point every minute for up to 14 days.
This system allows remote access by the veterinarian to manage the case. The response to adjustments in dosage be tracked, and any problems with regulation can be identified and addressed in real-time. The pet owner has access to real-time data as well. Client concerns over the well-being of their pets are common for patients with diabetes, yet the reassurance that clients derive from knowing the numbers often gives them confidence and relief. This author has managed cases beginning with the purchase of a monitor and ending with resolution of a dysregulated diabetic patient without any hands-on contact at all—strictly email and telephone conversations. This is an advantage when practicing during a pandemic.
Concerns regarding reliability have been addressed.11 Continuous glucose monitors measure the interstitial glucose levels, which closely mimic blood glucose levels.12-18 Abbott states that reliability is highest between 40 and 500 mg/dl (CGM package insert). Outside these limits, the sensor will read “Lo” or continue to report 500 mg/dl, even though values may exceed that amount. Severe persistent hyperglycemia (>300 mg/dl) will be detected by CGM. Should an absolute value be required that is beyond the monitor’s high level of confidence (>500 mg/dl), the clinician can get that through conventional means. In the event of hypoglycemia, timely therapy with an exogenous oral source of calories can prevent an emergency situation. This one attribute of CGM—the capability of the owner to recognize that low blood sugar is imminent, become adept in realizing trends, and have the confidence to self-manage a stressful event—is one of the most important of the unexpected benefits.
Feline patients present a specific challenge when using CGM.19,20 In this author’s experience, finding a patient that will tolerate a monitor placed between the shoulder blades is a 50:50 proposition: About half of the cats get “tired” of the monitor and figure out ways to dislodge the sensor at some point during the 14-day period. Although frustration may play a role in a client’s decision to continue with CGM, placing another sensor is easy and any data collected have value.
The most challenging cases are those that do not respond to typical insulin types and protocols.21 It is beyond the scope of this article to describe the various causes of diabetic dysregulation in dogs and cats.1 The management of a dysregulated diabetic patient is also problematic for several reasons. There is a dearth of comparative information on the subject, including clinical trials at university research centers and specialty clinics. Use of combination insulin products is complex and individualized.22 Therefore, few references and virtually no algorithm exists that can assist the clinician in the process. Fortunately, documenting quality of life (QOL) and maintaining a diabetic clinical score together with CGM provide adequate confidence to both the clinician and the pet owner.23 Euglycemia is not an absolute requirement for a successfully managed case provided the QOL is high and the clinical picture remains normal.
Using some form of CGM when managing diabetic cases has the potential to transform client satisfaction and adds new options for handling diabetic dysregulation in dogs and cats.
- Nelson RW, Reusch CE. Animal models of disease: classification and etiology of diabetes in dogs and cats. J Endocrinol. 2014;222(3):T1-T9. doi:10.1530/JOE-14-0202
- Stein JE, Greco DS. Portable blood glucose meters as a means of monitoring blood glucose concentrations in dogs and cats with diabetes mellitus. Clin Tech Small Anim Pract. 2002;17(2):70-72. doi:10.1053/svms.2002.33041
- Fleeman LM, Rand JS. Evaluation of day-to-day variability of serial blood glucose concentration curves in diabetic dogs. J Am Vet Med Assoc. 2003;222(3):317-321. doi:10.2460/javma.2003.222.317
- Nelson R. Stress hyperglycemia and diabetes mellitus in cats. J Vet Intern Med. 2002;16(2):121-122. doi:10.1892/0891-6640(2002)16<121:shadmi>2.0.co;2
- Moussy F, Harrison DJ, O’Brien DW, Rajotte RV. Performance of subcutaneously implanted needle-type glucose sensors employing a novel trilayer coating. Anal Chem. 1993;65(15):2072-2077. doi:10.1021/ac00063a023
- Bennett N. Monitoring techniques for diabetes mellitus in the dog and the cat. Clin Tech Small Anim Pract. 2002;17(2):65-69. doi:10.1053/svms.2002.33044
- Wiedmeyer CE, Johnson PJ, Cohn LA, et al. Evaluation of a continuous glucose monitoring system for use in veterinary medicine. Diabetes Technol Ther. 2005;7(6):885-895. doi:10.1089/dia.2005.7.885
- Cook AK. Monitoring methods for dogs and cats with diabetes mellitus. J Diabetes Sci Technol. 2012;6(3):491-495. doi:10.1177/193229681200600302
- Fleeman L. Flash glucose monitoring of diabetic dogs and cats. Presented at: 2019 American College of Veterinary Internal Medicine Forum; June 5-8, 2019; Phoenix, AZ.
- Deiting V, Mischke R. Use of the “FreeStyle Libre” glucose monitoring system in diabetic cats. Res Vet Sci. 2021;135:253-259. doi:10.1016/j.rvsc.2020.09.015
- Gerritsen M, Jansen JA, Kros A, et al. Influence of inflammatory cells and serum on the performance of implantable glucose sensors. J Biomed Mater Res. 2001;54(1):69-75. doi:10.1002/1097-4636(200101)54:1<69::aid-jbm8>3.0.co;2-q
- Dietiker-Moretti S, Müller C, Sieber-Ruckstuhl N, et al. Comparison of a continuous glucose monitoring system with a portable blood glucose meter to determine insulin dose in cats with diabetes mellitus. J Vet Intern Med. 2011;25(5):1084-1088. doi:10.1111/j.1939-1676.2011.00778.x
- Brunner R, Kitzberger R, Miehsler W, Herkner H, Madl C, Holzinger U. Accuracy and reliability of a subcutaneous continuous glucose-monitoring system in critically ill patients. Crit Care Med. 2011;39(4):659-664. doi:10.1097/CCM.0b013e318206bf2e
- Surman S, Fleeman L. Continuous glucose monitoring in small animals. Vet Clin North Am Small Anim Pract. 2013;43(2):381-406. doi:10.1016/j.cvsm.2013.01.002
- Corradini S, Pilosio B, Dondi F, et al. Accuracy of a flash glucose monitoring system in diabetic dogs. J Vet Intern Med. 2016;30(4):983-988. doi:10.1111/jvim.14355
- Kim W, Kim H, Kang S, et al. Comparison of continuous and intermittent glucose monitoring systems in a dog with diabetic ketoacidosis: a case report. Vet Med (Praha). 2017:285-291.
- Del Baldo F, Canton C, Testa S, et al. Comparison between a flash glucose monitoring system and a portable blood glucose meter for monitoring dogs with diabetes mellitus. J Vet Intern Med. 2020;34(6):2296-2305. doi:10.1111/jvim.15930
- Del Baldo, F, Fracassi, F, Pires, J, et al. Accuracy of a flash glucose monitoring system in cats and determination of the time lag between blood glucose and interstitial glucose concentrations. J Vet InternMed.2021;35(3):1279-1287. doi:10.1111/jvim.16122
- Gilor, Chen. Continuous glucose monitoring in practice. Presented at: 2019 American College of Veterinary Internal Medicine Forum; June 5-8, 2019; Phoenix, AZ.
- Shoelson AM, Mahony OM, Pavlick M. Complications associated with a flash glucose monitoring system in diabetic cats. J Feline Med Surg. 2021;23(6):557-562. doi:10.1177/1098612X20965012
- Gilor C. Challenging canine diabetics: case studies. Presented at: British Small Animal Veterinary Association Congress; April 6-9, 2017; Birmingham, England.
- Zerrenner D, Peterson, M, Crawford MA. The evolution of insulin therapy. Internal Medicine Compendium. 2007;29(9):522-536.
- Ackerman N, Benchekroun G, Bourne D, et al. Diabetes mellitus: guidance for managing diabetes in practice Companion Anim. 2018;23(3): 143-151. doi:10.12968/coan.2018.23.3.143