Diabetic crises: Recognition and management (Proceedings)
Diabetes mellitus occurs in both dogs and cats and is the most common endocrine disorder in the emergency setting. Three types of diabetic emergencies may occur: (1) Insulin overdose, (2) Diabetic ketoacidosis, and (3) Non-ketotic hyperosmolar diabetes. Historical findings may be similar in all 3 cases, and may include polyuria, polydypsea, weight loss, anorexia, weakness, ataxia, severe depression, stupor, coma, or seizures. Diabetes most commonly occurs in middle-aged female dogs and in older male cats.
The initial approach to an animal with suspected diabetic crisis is aimed toward differentiating between the 3 types of diabetic emergencies and determining how "sick" the patient is. An intravenous catheter is placed and 4 capillary tubes of blood are collected to run the hematocrit and total protein, blood glucose (using a Dextrometer, Ames Laboratories, Ames IA), blood urea nitrogen (using a reagent stick), and serum electrolytes. Blood for serum electrolytes must be collected in a lithium heparin capillary tube rather than in a sodium heparin tube. Evaluation of the laboratory work will reveal whether the animal is hypoglycemic or hyperglycemic, and whether or not ketones and glucose are present in the urine, and whether the animal is dehydrated, anemic, azotemic, or has a serious electrolyte imbalance. Other tests which can be run rapidly in an emergency setting include serum osmolality and venous or arterial blood gases. Within a few minutes after the animal is presented to the hospital, the clinician should be able to determine which type of diabetic crisis is occurring and to manage it accordingly.
I. Insulin OverdoseInsulin overdose can occur through owner error (for example, switching from low dose insulin syringes to tuberculin syringes) or through change in the animal's insulin requirements. Insulin requirements will decrease following treatment for hyperadrenocorticism or after estrus is completed, and the insulin dosage must be lowered accordingly.
Problems in insulin regulation can also result in hypoglycemia, especially if insulin dosage is based on morning glucose readings. The "Somogyi overswing" occurs when an overdose of insulin is given resulting in hypoglycemia. Working owners often miss the signs of hypoglycemia which occur in the afternoon following the morning insulin dose. Release of stress hormones causes a rebound hyperglycemia to occur with accompanying signs of polyuria, polydypsea, and glucosuria. If the owner continues to increase the insulin dose based on morning urine glucose readings, clinically significant hypoglycemia will result. A similar problem can occur with rapid insulin metabolism. Animals with this problem should receive insulin injections twice daily, instead of increasing the insulin dosage based on morning glucosuria.
Clinical signs of hypoglycemia include lethargy, depression, ataxia, weakness, stupor, coma, or seizures. If an owner recognizes these signs at home, he or she should be instructed to give Karo syrup orally (rub it on the gums if the animal is comatose or seizuring) and bring it directly to the veterinary hospital. If significant hypoglycemia is present, the animal should be given a slow intravenous bolus of 50% Dextrose (0.5 g/kg diluted 1:4). Then, to prevent recurrent hypoglycemia, 5% dextrose can be administered by continuous IV infusion. Mild or subclinical hypoglycemia may be treated by simply feeding the animal.
Blood glucose must be monitored closely and insulin can be re-administered when hyperglycemia occurs. Sometimes, following an extreme insulin overdose, insulin therapy is not required again for several days. If poor insulin regulation is the cause of the hypoglycemia, the animal should be hospitalized for a glucose curve.
II. Diabetic Ketoacidosis (DKA)
Diabetic ketoacidosis is a medical emergency involving extreme alterations of metabolic parameters. The syndrome is characterized by hyperglycemia, metabolic acidosis, ketonemia, dehydration, and loss of electrolytes. Treatment goals include: (1) Restoration of electrolyte and acid-base balances, (2) Replacement of body fluids, (3) Reduction of blood glucose and (4) Identification of underlying or precipitating factors in the disease process.
DKA commonly occurs when there is a relative excess of stress hormones in an insulin deficient animal. Therefore, every effort should be made to detect underlying disease factors contributing to stress. The work-up should include bloodwork (CBC, chemistry panel, blood gases, electrolytes, osmolality); chest radiographs if dyspneic (rule out congestive heart failure, neoplasia, dirofilariasis, pneumonia); abdominal radiographs (rule out pancreatitis, pyometra, urolithiasis, etc.); urinalysis (including culture and sensitivity); and amylase and lipase in vomiting dogs.