Patients with diabetes mellitus who are being considered for enteral feeding should be notified to the Diabetes Specialist Nurses. The Dietitian and Nutrition Nurse should already be involved.
If the patient is insulin-dependent then insulin will of course be required throughout the course of the tube feed. If the patient had tablet-controlled diabetes it is likely that poor glycaemic control will already have been recognised and the patient switched to subcutaneous insulin.
If however the patient's diabetes had previously been controlled by "diet alone" or oral agents, always assume that insulin will be necessary to cover enteral feeding.
The general principle is for the Dietitian and Nutrition Nurse to make decisions on the nutritional requirement of the patient and for the insulin to be fitted around the feeding regime. We should never be in the position of having to adjust the enteral feed because the patient is taking a particular insulin regime. Enteral feeding will usually begin with a slow infusion over 20 hours. Commence an intravenous insulin infusion, Humulin S 1 unit/ml in normal saline. Infuse at an initial rate of 1 unit/hr. For the first 48 hours of enteral feeding, two-hourly bedside capillary blood glucose measurements should be performed aiming for blood glucose levels of between 5 and 9 mmol/l. The insulin infusion rate can be adjusted in steps of ½ unit, 1 unit, 2 units, 3 units, 4 units, and 6 units/hr. If more than 6 units/hr are required obtain advice from the Diabetes Team. After 48 hours enteral feeding, consider switching to subcutaneous insulin. Use once daily glargine as background insulin. Use isophane insulin at the commencement of the cycle of feeding and halfway through the cycle. e.g. enteral feeding to run 09.00 to 05.00 the following day (20hours feeding). Give glargine insulin subcutaneously 10 units at 9.00 a.m. Give Humulin I insulin 8 units subcutaneously at 9.00 a.m. Give Humulin I insulin 8 units subcutaneously at 7.00 p.m. Continue to monitor blood glucose 2-hourly. Aim for blood glucose levels of between 5 and 9 mmol/l, be prepared to increase the insulin doses as necessary to achieve the target.
