Type I

As all forms of general anaesthesia involve a period of starvation, careful control of blood glucose is required. On the day of surgery the patient should be starved to the local protocol and their morning dose of insulin withheld.

The risk to the patient is of hyperglycaemia. Insulin must be administered to maintain to stable blood glucose levels.

There are two approaches to the management of the insulin-dependent diabetic.

A variable rate intravenous infusion of insulin plus concomitant intravenous dextrose and potassium containing fluid
An Alberti regimen, which involves the addition of insulin directly into the intravenous dextrose and potassium containing fluid

Variable rate intravenous infusion of insulin

This approach requires two elements:

A syringe containing 50 units of human actrapid in 50 ml of 0.9% saline.
Intravenous dextrose-containing fluids must also have potassium added to run at 100 ml/h.

Both elements are essential. An intravenous infusion of insulin should never be run alone.

In most hospitals, 5% dextrose plus 1 g of potassium in 500 ml is the standard fluid to prescribe. This should run at 100 ml/h.

While a patient is managed with intravenous insulin, they should have their blood sugar monitored hourly. The rate at which the infusion runs is determined by a sliding scale; you must be aware of your local protocol for prescribing a sliding scale for insulin.

An Alberti regimen

The Alberti regimen is based upon the addition of actrapid insulin to intravenous dextrose-containing fluids. The amount of insulin added can be varied. The standard intravenous fluid used is 10% dextrose with ten units of actrapid and 1 g of potassium in 500 ml.

Blood sugar and potassium is measured every two hours and if blood sugars are high, the amount of insulin added is increased. Conversely, if the blood sugar is low, insulin should be omitted from the next bag of fluid. You should be familiar with your local protocol.