Converting from Insulin Infusion to Mixtard
When transitioning from intravenous insulin infusion to subcutaneous Mixtard (premixed insulin), the recommended conversion is to calculate 60-80% of the total daily insulin requirement from the IV infusion and administer this as Mixtard in a split dose regimen, typically with 2/3 in the morning and 1/3 in the evening. 1
Conversion Process
Step 1: Calculate Total Daily Dose
- Calculate the total daily insulin requirement based on the average hourly rate during the final 6-12 hours of the IV insulin infusion 1
- Multiply the hourly rate by 24 to get the estimated total daily requirement 1
- Example: If average IV insulin rate is 1.5 units/hour, the estimated 24-hour requirement would be 36 units
Step 2: Determine Subcutaneous Dose
- Convert to 60-80% of the calculated total daily requirement 1
- Research suggests that using 80% of the total daily insulin requirements results in the highest percentage of blood glucose values within target range 2
- This reduction accounts for differences in bioavailability between IV and subcutaneous administration 1
Step 3: Split the Mixtard Dose
- Divide the total Mixtard dose into two daily injections 1
- Typically use a morning:evening ratio of approximately 2:1 (or 60:40 to 70:30) 1, 3
- For example: If total daily dose is 30 units, give 20 units in morning and 10 units in evening 1
Step 4: Timing of Transition
- Administer first dose of subcutaneous Mixtard 2-4 hours before discontinuing the IV insulin infusion 1
- This overlap ensures adequate insulin coverage during the transition period 1
Special Considerations
Monitoring and Adjustment
- Perform capillary blood glucose monitoring before meals and at bedtime 2
- Adjust doses based on pre-meal glucose patterns 1
- For hypoglycemia: determine cause; if no clear reason, lower corresponding dose by 10-20% 1
Caution with Premixed Insulin
- Be aware that premixed insulin formulations like Mixtard have been associated with higher rates of hypoglycemia in hospitalized patients compared to basal-bolus regimens 1
- Consider individual patient factors such as meal patterns, renal function, and risk of hypoglycemia 1
Alternative Approaches
- For patients at high risk of hypoglycemia (elderly, renal impairment), consider using a lower conversion percentage (closer to 60% rather than 80%) 1
- For patients with type 1 diabetes, ensure basal insulin requirements are adequately covered 1
Pitfalls to Avoid
- Avoid prolonged use of sliding scale insulin alone as the sole treatment strategy 1
- Do not use the same insulin dose calculation for all patients without considering individual factors 1
- Remember that Mixtard has different pharmacokinetics compared to IV insulin, with slower onset and longer duration 4
- Be cautious with evening doses as nocturnal hypoglycemia risk is higher 1