Long-acting basal insulin is usually taken as normal the day before. For operations requiring bowel preparation, any reduction in insulin is agreed upon in advance.
Blood sugar is measured in the morning before surgery and then every 1–2 hours.
There are two different practices for managing insulin therapy on the day of surgery:
On the morning of the surgery day, the long-acting insulin injection is omitted entirely, and an intravenous drip of insulin and sugar (glucose) is started. Blood sugar is monitored hourly, and the insulin drip rate is adjusted based on blood sugar levels.
The other practice is to inject the normal dose of long-acting insulin on the morning of the surgery day. In addition, an intravenous glucose drip is started, blood sugar is monitored hourly, and if necessary, rapid-acting insulin is administered during surgery every two hours.
After the surgery, blood sugar is monitored every 1–2 hours. Later, when the person can eat normally again, the usual subcutaneous insulin dosing is resumed. Blood sugar is measured every 2–4 hours, and if necessary, rapid-acting insulin is taken in corrective doses in addition to what is required for eating.
The use of an insulin pump during surgery is agreed upon individually. Those using an insulin pump change the cannula and catheter the day before surgery. The use of the pump can be continued during and after the surgery if it is safe and feasible regarding the surgical area and position. Additional doses according to the rise in blood sugar are given as pump boluses or injections. If necessary, a backup system is used.
A glucose sensor can also be utilized during surgery alongside blood sugar measurements. Changes in fluid content and circulation can, however, affect the reliability of sensor values, so treatment-guiding measurements are made with single measurements from the fingertip or a possible arterial cannula.