Post operative glycaemic control

Glycaemic control, across patients with and without diabetes, is an extremely important part of reducing rates of complications.

In colorectal patients in particular, hyperglycaemia is very common (around a third of all patients), and this is associated with higher rates of surgical site infections. Surgical site infections are result in increased length of stay and with increased mortality. In patients with diabetes, interruptions to routine diet and medications can cause hyperglycaemia, but stress-induced hyperglycaemia is observed in patients having surgical interventions and in those with critical illness.

While hyperglycaemia is associated with complications, studies in patients requiring intensive care have found that attempts to maintain normoglycaemia is associated with poorer outcomes, and so – for most patients – glucose targets of 6.0 to 10.0 mmol/l are acceptable. This is to mitigate the risks of hypoglycaemia – which while a patient is sedated or under general anaesthesia may be harder to identify in-between blood glucose testing.

For patients with diabetes, in the past almost all would have received a variable-rate intravenous insulin infusion (VRIII – or what used to be known as a ‘sliding scale’). The use of these infusions has now reduced greatly to only those patients who:

• Are missing more than one meal;
• Are clinically unwell; or
• Have not responded to other strategies for correcting hyperglycaemia.

During an operation, patients with diabetes should have their blood glucose measured once an hour, and documented, with readings treated as appropriate. This might also include the giving of intravenous glucose if blood glucose readings drop below 4.0mmol/l.

Post-operatively, blood glucose will be measured closely in recovery and on the ward. If an insulin infusion is started, this is usually continued until the patient is eating and drinking normally, and is re-established on their usual diabetes medications. Dexamethasone is commonly used intraoperatively as prophylaxis against post-operative nausea and vomiting – this can cause a transient rise in blood glucose. The most important part of post-operative glycaemic control is for patients to eat and drink as normally as possibly with their normal medications.