Synopsis
Protect patients from perioperative hypoglycaemia, insulin deficiency and adrenal crisis through an individual medication plan that accounts for fasting, surgical stress and postoperative recovery.
- Type 1 diabetes requires continuing insulin provision during fasting; stopping every insulin dose can cause ketoacidosis.
- Link insulin adjustments and monitoring to the expected missed meals, usual regimen and ability to self-manage.
- For perioperative patients with diabetes using SGLT2 inhibitors, measure capillary blood ketones daily until normal eating and drinking resume, even with normal glucose; assess immediately for ketones and acidosis if unwell.
Key red flags
A fasting patient with type 1 diabetes needs an immediate review if no basal or intravenous insulin provision exists. A glucose value currently in range does not demonstrate that insulin deficiency is safe. Establish the last dose, glucose, ketones and clinical state and seek the appropriate diabetes or anaesthetic plan.
A patient exposed to an SGLT2 inhibitor may develop nausea, abdominal pain, tachypnoea or malaise with glucose that is not strikingly high. Check blood ketones and acid–base status promptly and assess for ketoacidosis. Do not attribute the symptoms solely to surgery or exclude the diagnosis from glucose alone.
Hypotension, vomiting, weakness or hypoglycaemia in a person with adrenal insufficiency can signal crisis, particularly after missed medication or surgical stress. Escalate, resuscitate and administer emergency hydrocortisone promptly. Diagnostic sampling may be helpful if it causes no delay, but treatment must not wait for cortisol results.
Reasoning priorities
Identify the diabetes type, usual regimen, technology and expected period without normal meals.
Record the last insulin and oral or injectable medicine doses. Ask about hypoglycaemia awareness, self-management skills and the availability of pumps or sensors. A patient’s usual successful routine is useful information, but anaesthesia may temporarily remove their ability to manage it.
Worked reasoning
At 07:30, a stable 39-year-old with type 1 diabetes awaits a first-list elective operation. Their usual Lantus insulin glargine is 40 units subcutaneously at 08:00; the last dose was yesterday at 08:00. They use rapid insulin with meals. Glucose is 8.4 mmol/L, ketones 0.2 mmol/L and eGFR 90 mL/min/1.73 m². Only breakfast is expected to be missed, lunch intake is expected, and there is no acute illness. A fasting order has incorrectly omitted the morning basal dose.
- Confirm the named insulin, usual dose, last actual administration and absence of another morning dose. Glucose is currently within the insulin-treated perioperative target, but fasting does not remove the basal requirement in type 1 diabetes.
- The anaesthetic and diabetes team agree adjusted subcutaneous treatment for this stable patient and single missed meal. Apply the CPOC/UKCPA once-daily morning glargine adjustment: 80% × 40 units = 32 units. Correct the prescription and administer 32 units subcutaneously at the usual 08:00 time after the appropriate checks.
- Omit the breakfast meal-related dose while that meal is omitted. Prescribe access to hypoglycaemia treatment and an agreed correction pathway; do not give an arbitrary rapid-insulin replacement for basal insulin. Check glucose on admission and at least hourly intraoperatively, recording results and actions.
- If delay means more than one meal will be missed, intake fails or metabolic instability develops, obtain urgent team review for the variable-rate intravenous insulin pathway with appropriate substrate and electrolytes. Preserve basal coverage; suspected DKA requires its separate emergency regimen.
- At recovery, verify actual insulin delivery, glucose and ability to eat before resuming the usual meal-related plan. Reassess the next basal dose against intake and recovery; if an infusion became necessary, document safe overlap and basal coverage before stopping it.
- Handover the exact 32-unit dose and time, latest glucose, next check and escalation contact. Reconcile the electronic chart with the patient and administering clinician so the corrected order cannot be duplicated.