Diabetes Mellitus in Dogs and Cats

Diabetes mellitus is a common endocrine disorder in dogs and cats, characterized by persistent hyperglycemia due to inadequate insulin production, insulin resistance, or both. It is a significant disease requiring lifelong management, including insulin therapy, dietary modifications, and regular monitoring.

Pathophysiology #

Diabetes mellitus results from insufficient insulin production by the pancreatic beta cells (Type 1 diabetes) or impaired insulin utilization (Type 2 diabetes). In dogs, Type 1 diabetes is the predominant form, characterized by immune-mediated destruction of beta cells. In cats, Type 2 diabetes is more common and is often associated with obesity and insulin resistance. Chronic hyperglycemia leads to glucotoxicity, lipid metabolism abnormalities, and oxidative stress, which contribute to disease progression.

Medical Management #

The primary treatment for diabetes mellitus in both dogs and cats is exogenous insulin administration. Management also includes dietary control, exercise regulation, and glucose monitoring. In dogs, a consistent feeding schedule with high-fiber diets helps regulate glucose absorption. In cats, high-protein, low-carbohydrate diets improve insulin sensitivity and may lead to diabetic remission.

Types of Insulin Specific to Dogs and Cats #

Different insulin formulations are used based on species-specific pharmacokinetics:

• Dogs: Commonly used insulins include NPH (Neutral Protamine Hagedorn), Vetsulin (porcine lente insulin), and Detemir. Dogs generally require twice-daily insulin administration.
• Cats: Cats often respond better to longer-acting insulins such as PZI (Protamine Zinc Insulin), Glargine, or Detemir. Glargine has been associated with a higher likelihood of diabetic remission in cats when used early in the disease course.

Principles of How Glucometers Work #

Glucometers measure blood glucose levels through electrochemical biosensors. When a drop of blood is applied to the test strip, glucose reacts with an enzyme (glucose oxidase or glucose dehydrogenase) to generate an electrical current proportional to the glucose concentration. Veterinary-specific glucometers are calibrated for animal blood, which differs from human blood in hematocrit and glucose distribution.

Comorbidities Associated with Diabetes in Dogs and Cats #

Diabetic animals are prone to several comorbid conditions that can complicate management:

• Diabetic ketoacidosis (DKA): A life-threatening complication resulting from prolonged hyperglycemia and insulin deficiency, leading to ketone production, metabolic acidosis, dehydration, and electrolyte imbalances.
• Urinary tract infections (UTIs): Chronic hyperglycemia promotes bacterial growth in the urinary tract, leading to frequent infections.
• Diabetic neuropathy: More common in cats, it presents as plantigrade stance due to peripheral nerve damage.
• Cataracts: A common complication in diabetic dogs, resulting from sorbitol accumulation in the lens, leading to osmotic damage and lens opacification.
• Hypertension: Chronic hyperglycemia contributes to vascular dysfunction and increased blood pressure.
• Pancreatitis: Dogs and cats with diabetes are at increased risk for pancreatitis, which can further impair insulin secretion.
• Dehydration: Glucosuria causes obligate water loss (diuretic) so animals maybe clinically dehydrated prior to presentation

Anesthetic Considerations #

Diabetic animals require special considerations during anesthesia to prevent complications such as hypoglycemia, hyperglycemia, and electrolyte imbalances:

• Preoperative fasting: Shortened fasting times or administration of a half-dose of insulin with a small meal is recommended to prevent hypoglycemia.
• Blood glucose monitoring: Frequent intraoperative glucose measurements help maintain glucose stability.
• Fluid therapy: Balanced crystalloid solutions help manage dehydration and electrolyte imbalances.
• Anesthetic agent selection: Drugs with minimal metabolic effects, such as propofol and isoflurane, are preferred.

Complications of Diabetes Mellitus #

Hyperkalemia #

Hyperkalemia can occur in diabetic ketoacidosis due to shifting of potassium out of cells in response to acidosis and especially hyperosmalility during rapid or extreme hyperglycemia. However, insulin therapy may cause rapid intracellular potassium uptake, leading to hypokalemia. Management includes fluid therapy and careful potassium supplementation.

Hypoglycemia #

Hypoglycemia is a manageable complication that may result from excessive insulin administration or prolonged fasting. Clinical signs include weakness, ataxia, seizures, and coma. Emergency management involves administration of dextrose IV or oral glucose solutions.

Hyperglycemia #

Persistently high blood glucose levels due to inadequate insulin therapy, stress, or infection can exacerbate diabetes complications. Monitoring and insulin dose adjustments are necessary to maintain stable glucose levels. Regular insulin supplementation during anesthesia may be required since very high blood glucose can trigger life threatening hyperkalemia. A reasonable dose of REGULAR insulin (Humulin-R) is about 20% of the dose (given IV) of historical NPH or Vetsulin dose. This may be approximately 0.1 to 0.2 U/kg of REGULAR insulin. Expect a rapid (30-60 min decrease of blood glucose which lasts approximately 1-2 hours.

General anesthesia often induces a mild/moderate hyperglycemia due to the stress response. This will complicate intraoperative glucose management. Drugs such as alpha-2 agonsist can further complicate things.

Ketoacidosis #

Diabetic ketoacidosis (DKA) occurs when insulin deficiency leads to unchecked lipolysis and ketone body formation, resulting in acidosis, dehydration, and electrolyte disturbances. Treatment includes aggressive fluid resuscitation, electrolyte correction, and continuous insulin infusion.

Even if patients are not eating, some insulin will likely be required postop. The dog digests food which produces glucose in the blood. To feed the cells, insulin is needed to move glucose intracellular. Without glucose getting into the cells, animals will become ketoacidotic in a matter of hours to days. Owners should be carefully counseled on how to match insulin administration to food intake during the post anesthesia period until normal feeding resumes.

Dehydration #

Since obligate water loss occurs with glycosuria, owners should be counseled to observe water intake postoperatively. Dehydration can occur rapidly if food and water intake does not resume normally.

Communication Topics For Owners About Diabetic Pets After Anesthesia and Surgery #

Proper postoperative care is crucial for diabetic pets to ensure a smooth recovery while maintaining stable glucose levels. Follow these guidelines:

• Monitoring: Observe pet closely for signs of hypoglycemia (weakness, tremors, disorientation) or hyperglycemia (excessive thirst, urination, lethargy). If any concerning signs occur, contact a veterinarian immediately.
• Insulin Administration: Follow the veterinarian’s instructions regarding insulin dosing postoperatively. Insulin requirements may change due to stress or altered food intake.
• Feeding Schedule: Resume normal feeding as soon as reasonable. Offer a small meal at first. If the pet is not eating, the owner should consult the veterinarian.
• Hydration: Ensure your pet has access to fresh water at all times to prevent dehydration.
• Emergency Situations: Seek immediate veterinary care if the pet exhibits severe lethargy, vomiting, seizures, or signs of diabetic ketoacidosis (labored breathing, fruity odor on breath, extreme weakness).

References #

1. Nelson RW, Reusch CE. “Animal models of disease: diabetes mellitus in dogs and cats.” J Endocrinol 2014; 222(3):T41–T53.
2. Behrend EN, Holford A, Lathan P, et al. “Update on insulin therapy for managing diabetes mellitus in dogs and cats.” Vet Clin Small Anim 2018; 48(6):1133-1146.
3. Rucinsky R, Cook A, Haley S, et al. “AAFP guidelines for the management of feline diabetes mellitus.” J Feline Med Surg 2015; 17(3):235-250.
4. Hess RS, Kass PH, Shofer FS, et al. “Evaluation of risk factors for diabetic ketoacidosis in dogs with diabetes mellitus.” J Am Vet Med Assoc 2000; 216(4):554-559.
5. Feldman EC, Nelson RW. Canine and Feline Endocrinology and Reproduction. 4th ed. Elsevier; 2014.