General Medical Information

Endocrine Abnormalities

David M. Barrs

Diabetes Mellitus
A fasting blood glucose is obtained as a routine test because the frequency of diabetes is approximately 1% and rises to 5% of the population aged over 40 years. Surgery and anesthesia increase production of stress hormones and worsen hyperglycemia. The aim of perioperative care in the known diabetic is reasonable control of glucose levels in the range of 120 to 250 mg/dL. Patients scheduled for minor surgery under local anesthesia need no special adjustments. All other patients may require insulin coverage. Adjustments to the patient’s usual treatment are guided by blood (not urine) glucose monitoring every 1 to 2 hours at the start of surgery. It is important that diabetics receive 3 g/kg of body weight each day of carbohydrates to prevent protein catabolism and lipolysis. Intravenous administration of 5% dextrose in water at 100 mL/h provides 5 g glucose/h.

Management of poorly controlled patients must be obtained before surgery. The goal is to lower the glucose level below 250 g/dL. Regular insulin is given at a dose of 4 to 10 U subcutaneously every 4 to 6 hours. Alternatively, a constant regular insulin infusion can be administered with a loading dose of 0.1 to 0.2 U/kg, followed by an infusion rate of 0.1 U/kg per hour in a 0.9% sodium chloride solution. Blood glucose levels are measured every 1 to 2 hours. The patient then may be monitored during surgery in the same way as the well-controlled diabetic.

In ketoacidosis, an i.v. bolus of 12 to 20 U of regular insulin is followed by constant infusion of 5 to 10 U/h. Hyperosmolar nonketotic hyperglycemia requires lower doses of insulin (0.05 to 0.10 U/kg hourly). In both conditions, fluid deficit is present, and replacement with normal saline at 1 L/h is started with potassium replacement always required and guided by serum potassium measurement.

In the immediate postoperative period, subcutaneous regular insulin is given every 2 to 4 hours, depending on serum glucose. A typical regular insulin sliding scale for hyperglycemia control is 4 U of regular insulin for glucose levels of 200 to 250 g/dL or 6 to 8 U for glucose levels from 251 to 300 g/dL. Intravenous glucose is continued to provide nourishment. In the later postoperative period, the patient must be continued on a modified insulin dose and i.v. glucose until regular diet and activity is resumed. One half to two thirds of the patient’s usual daily dose of intermediate-acting insulin is given each morning, and blood sugar is measured every 6 hours. Discharge insulin or oral hypoglycemic agent dose depend on glucose control at the end of the patient’s hospitalization.