21st May 2025

Preoperative care

During the preoperative assessment, it is important to identify the underlying type of diabetes, as this will influence the patient’s management plan. The most common types are bullet-pointed below:

• Type 1 DM 
• Type 2 DM and insulin-dependent (+/- non-insulin glucose-lowering medication) 
• Type 2 DM and on non-insulin glucose-lowering medication 
• Type 2 DM diet-controlled

Optimising diabetic control is known to improve surgical outcomes. Several investigations should be considered to assess an individual’s baseline diabetic control.

Investigations

• HbA1c – The patient should ideally have their HbA1c checked three months prior to surgery, allowing for prompt referral to the Diabetes specialist team for optimisation, especially if the HbA1c is >69mmol/mol (8.5%).  
• Blood Glucose Levels – The degree of metabolic derangement on presentation should be noted. This includes if the patient is known to have recurrent or severe hypoglycaemia, or persistent hyperglycaemia (defined as two or more consecutive BG values >13mmol/l or hyperglycaemia with ketone levels >1.5mmol/l).
• Blood Osmolarity, Ketones and Electrolytes – These should be checked to assess for evidence of Diabetic Ketoacidosis (DKA) and Hyperosmolar Hyperglycaemic State (HHS).

Clinical Management

Identify other comorbidities that often coexist with diabetes and refer to the relevant teams for optimisation where necessary e.g. hypertension, cardiac disease, renal disease etc.

Medication Management

A pharmacist should be consulted to ensure medication reconciliation before admission. Instructions regarding necessary changes to medication before admission should be discussed and given to the patient. The anticipated period of total fasting (from the last meal to the next meal) should be assessed, as this will alter whether variable rate insulin (VRIII) is required and for how long. Also, a pre-prescribe rescue treatment for hypoglycaemia should be prescribed as a precaution. 

• Insulin Therapies (Type 1 and Type 2 DM) – Insulin should not be omitted for patients with T1DM. However, if only one meal is likely to be missed, it may be possible to give a reduced dose of their usual insulin. If a prolonged operation and a significant starvation period is anticipated, a VRIII regime can be prescribed. A VRIII can also be considered for patients who have T2DM. The indications for VRIII are:
  1. Patients with insulin-dependent Diabetes, in which the anticipated/actual fasting period is greater than one missed meal.
  2. Patients with Diabetes and recurrent hyperglycaemia (CBG > 12mmol/l).
• Non-Insulin Therapies – The table below has been adapted from Diabetes UK and outlines the guidance for the common non-insulin therapies. It should be noted that each patient should be assessed on an individual basis.

Table 1: Guidance for non-insulin therapies

Other Considerations

Where possible, the urgency of the procedure and the possibility of postponement should be discussed, with a view to optimising the patient’s weight, diabetic control, and other comorbidities during the preoperative period. The patient should also be listed for a morning operation to reduce starvation time and the likelihood of delays.