How do you administer insulin via an insulin pump?

How to Administer Insulin via an Insulin Pump

Insulin pumps deliver rapid-acting insulin continuously through a subcutaneous cannula, with basal rates providing background insulin coverage (typically 50% of total daily dose divided over 24 hours) and patient-activated boluses covering meals and correcting hyperglycemia. 1

Device Components and Setup

The insulin pump system consists of three essential elements that work together for insulin delivery:

• The pump device itself is a small, programmable, battery-operated unit that holds a reservoir of rapid-acting insulin (such as insulin aspart, lispro, or glulisine) 1, 2
• A disposable subcutaneous cannula (either metal or plastic) is inserted into the skin and changed every 2-3 days, connected to the pump via flexible tubing 1
• "Patch pumps" are available as tubeless alternatives that adhere directly to the skin and are controlled manually 1

Types of Insulin Delivery

Basal Insulin Administration

Basal insulin is the continuous, programmed background infusion that maintains euglycemia during fasting periods and prevents ketosis:

• Calculate the initial basal rate as approximately 50% of the patient's total daily insulin dose (TDD), divided by 24 hours to determine the hourly infusion rate, though more recent evidence suggests 30-48% may be more appropriate to avoid overinsulinization 3
• The basal rate can be programmed to vary throughout the 24-hour period to address individual patterns such as the dawn phenomenon (early morning glucose rise from counter-regulatory hormones) 3
• Temporary basal rate modifications can be instituted for shorter periods to counteract exercise, illness, or menstrual cycle variations 3
• Patients may need alternate basal rate programs for different activity levels (weekday versus weekend schedules) 3

Bolus Insulin Administration

Bolus insulin is administered before or during meals to control glycemia during carbohydrate absorption:

• Boluses are calculated based on the amount of carbohydrates ingested and the patient's insulin-to-carbohydrate ratio 1
• Correction boluses are given to address elevated blood glucose levels, calculated using the patient's insulin sensitivity factor 1
• Modern pumps include integrated bolus calculators that are FDA-approved to ensure safety in dosing recommendations 4
• Healthcare professional input and education are helpful for setting initial dosing calculations with ongoing follow-up for adjustments 4

Critical Safety Considerations

Disconnection, occlusion, or interruption of the pump can cause insulin deficiency within 1 hour and absolute deficiency within 4 hours, risking hyperglycemia and ketosis:

• Only rapid-acting insulin is used in pumps, which has a short duration of action compared to long-acting basal insulins 1, 5
• If the pump is disconnected, IV insulin should be started at least 30 minutes before removing the pump, initially infused at the hourly basal rate and titrated to blood glucose 4, 6
• When transitioning back to the pump, connect it and maintain the basal rate for at least 2 hours before stopping IV infusion 4, 6

Blood Glucose Monitoring and Targets

Regular glucose monitoring is essential for safe pump therapy:

• Target fasting glucose should be 4.4-6.1 mmol/L (approximately 80-110 mg/dL) for optimal control 3
• Acceptable blood glucose levels are between 4 and 12 mmol/L, with a target range of 6-10 mmol/L 1
• If glucose levels fall below 4 mmol/L, treat according to hypoglycemia protocol with IV glucose if necessary 1
• If glucose levels exceed 14 mmol/L, check the pump and infusion set, and perform a ketone test 1

Advanced Pump Features

Modern insulin pumps offer sophisticated capabilities beyond basic insulin delivery:

• Sensor-augmented pumps can suspend insulin administration when glucose is low or predicted to drop within the next 30 minutes 4
• Automated insulin delivery (AID) systems adjust insulin delivery rates based on continuous glucose sensor values and are preferred over nonautomated pumps in people with type 1 diabetes 4
• Pump data can be uploaded to online registries allowing providers to review trends and usage patterns 7

Special Situations Requiring Pump Adjustment

During Surgery or Procedures

• For minor surgeries, insulin pump therapy can be continued with prior agreement and shared care between patient and healthcare professionals 4
• For major or emergency surgeries, pump therapy should be suspended and replaced with IV insulin according to local protocol 4
• The pump should be removed during radiological procedures like CT/MRI or body X-rays due to interference with imaging equipment 4, 1

During Hospitalization

If the patient requires IV insulin or is fasting:

• Start IV insulin at the basal rate per hour at least 30 minutes before pump removal 6
• When returning to pump therapy, overlap therapies by maintaining pump basal rate for at least 2 hours before discontinuing IV insulin 6

Common Pitfalls to Avoid

• Running supraphysiological basal rates (higher than physiologically required) in an attempt to lower average glucose, which increases hypoglycemia risk 3
• Failing to check for ketones when blood glucose exceeds 14 mmol/L, as pump failure can rapidly lead to diabetic ketoacidosis 1
• Not ensuring adequate overlap when transitioning between insulin delivery methods, creating gaps in insulin coverage 6
• Reusing cannulas beyond 2-3 days, which increases infection risk and may cause absorption problems 1