Can a patient with type 1 diabetes using a Tandem (insulin pump) Mobi continue to use it during an excisional breast biopsy?

Can a Type 1 Diabetes Patient Keep Using Tandem Mobi During Excisional Breast Biopsy?

Yes, the patient should continue using the Tandem Mobi insulin pump during an excisional breast biopsy, as this qualifies as minor elective surgery where maintaining the pump provides superior glycemic control and prevents the risk of rapid insulin deficiency. 1

Rationale for Pump Continuation

An excisional breast biopsy is a minor surgical procedure that typically requires only one missed meal and has a short operative duration, making it ideal for pump continuation rather than conversion to intravenous insulin. 1 The British Journal of Anaesthesia guidelines specifically recommend continuing insulin pumps throughout the perioperative period for minor elective surgeries like lumpectomy, which is comparable to excisional breast biopsy. 1

Maintaining pump therapy during this procedure preserves superior glycemic control compared to temporary conversion to alternative insulin regimens. 1

Critical Preoperative Requirements

Infusion Set Management

• Change the infusion set the morning or afternoon before surgery, allowing sufficient time to check two capillary blood glucose readings several hours apart to confirm proper function. 2
• Position the infusion site away from the breast/surgical field, ideally on the abdomen on the contralateral side or another accessible location. 2
• If metal cannulas are currently in use, switch to plastic infusion sets due to diathermy risks during surgery. 2

Coordination and Documentation

• Early communication with the diabetes pump team is essential to establish a definitive management plan and confirm the patient's competency with pump management. 2
• Document a concise management plan in the case notes detailing continued pump use during surgery, with signed patient consent. 2
• Ensure the patient brings adequate pump supplies for the entire hospital stay. 1

Intraoperative Management Protocol

Basal Rate Continuation

• Maintain the patient's usual basal infusion rate throughout the procedure. 1
• The patient should take responsibility for pump management except during periods of reduced consciousness, when a designated healthcare professional must assume this obligation. 2

Glucose Monitoring

• Monitor capillary blood glucose hourly during the procedure, targeting 6-10 mmol/L (108-180 mg/dL), with an acceptable range of 4-12 mmol/L (72-216 mg/dL). 1
• Do not rely on continuous glucose monitor (CGM) readings during surgery, as interstitial glucose measurements show lag time and may be inaccurate during hemodynamic changes—always confirm with capillary blood glucose. 2, 3

Equipment Safety Considerations

• The Tandem Mobi must be removed if CT imaging, MRI, or any ionizing radiation/electromagnetic field exposure is planned, as these will damage the device. 1
• For standard X-rays of the breast, cover the pump with a lead apron if it must remain on the patient. 1
• Ultrasound is safe but do not point the transducer directly at the pump. 1
• Ensure the pump is accessible to the anesthesiologist at all times during surgery. 2

Postoperative Management

Immediate Recovery Period

• Continue hourly capillary blood glucose monitoring until the patient is fully conscious and capable of managing their pump independently. 2, 1
• If blood glucose begins to increase postoperatively, use the pump's built-in bolus calculator to determine the correction dose required. 2

Return to Baseline

• Advise the patient to continue increased frequency of blood glucose monitoring for 1-2 days after surgery to re-establish baseline status. 2
• Bolus dosing of insulin can resume with the first postoperative carbohydrate ingestion. 2

Critical Safety Considerations

Risk of Pump Discontinuation

Disconnection, occlusion, or cessation of pump therapy will render the patient relatively insulin deficient within 1 hour and absolutely insulin deficient within 4 hours, with severe risk of hyperglycemia and ketosis. 2 This is because only short-acting insulin is infused in insulin pumps, making abrupt discontinuation particularly dangerous. 2

When to Convert to IV Insulin Instead

The pump should be discontinued and converted to intravenous insulin only if: 1

• The patient cannot self-manage and staff lack pump expertise
• Major surgery requiring prolonged operative time (>4 hours) is planned
• Abdominal operations are performed
• Prolonged NPO status is required

None of these conditions apply to an excisional breast biopsy, reinforcing that pump continuation is appropriate.

Common Pitfalls to Avoid

• Never abruptly discontinue the pump without IV insulin overlap, as type 1 diabetes patients develop rapid hyperglycemia and ketosis within hours. 1
• Do not assume CGM readings are accurate during surgery—always verify with capillary blood glucose. 2, 3
• Avoid placing the infusion site near the surgical field or in areas that will be inaccessible during the procedure. 2
• Do not forget to verify pump function after changing the infusion set preoperatively. 2