What is the mechanism of sliding scale insulin therapy for managing hyperglycemia?

Sliding Scale Insulin Therapy: Mechanism and Efficacy

Sliding scale insulin (SSI) therapy is an ineffective approach to managing hyperglycemia that works by administering short-acting insulin doses based on pre-meal blood glucose readings without addressing basal insulin needs, and should not be used as monotherapy for diabetes management. 1

Mechanism of Sliding Scale Insulin

Sliding scale insulin therapy operates on the following principles:

• It uses short or rapid-acting insulin (like regular insulin or insulin aspart)
• Insulin doses are determined by current blood glucose readings
• Higher doses are given for higher blood glucose values
• No insulin is given when blood glucose is below a certain threshold
• It is reactive rather than preventative, addressing hyperglycemia after it occurs

For example, a typical sliding scale might look like:

Blood Glucose (mg/dL)	Insulin Dose
<90	No insulin
90-250	No correction dose needed
>250	2 units
>350	4 units

Limitations and Efficacy Issues

The American Diabetes Association strongly discourages the use of sliding scale insulin alone for managing diabetes due to several significant problems:

• It fails to provide basal insulin coverage
• It reacts to hyperglycemia rather than preventing it
• It leads to wide fluctuations in blood glucose levels
• It results in poor overall glycemic control 1

Research confirms these limitations:

• Only 12% of sliding scale insulin injections successfully bring glucose levels into target range 2
• 84% of sliding scale insulin injections result in subtherapeutic effects with persistently elevated glucose levels 2
• Patients on sliding scale insulin regimens are more likely to be poorly controlled than relatively well controlled 2
• Meta-analysis shows sliding scale insulin provides no benefits in blood glucose control and increases hyperglycemic events 3

Recommended Alternative Approaches

Instead of sliding scale insulin monotherapy, the American Diabetes Association recommends:

1. Basal-bolus insulin regimen with:

   • Basal insulin (0.3-0.5 units/kg/day) using long-acting insulin (glargine or detemir)
   • Mealtime bolus insulin doses
   • Correction doses for hyperglycemia based on individualized sensitivity factors 1

2. For patients with type 2 diabetes and severe/acute hyperglycemia:

   • Basal-bolus regimens achieve lower fasting blood glucose (10.8 ± 2.3 vs 11.6 ± 3.5 mmol/L) and better mean glucose levels (12.3 ± 1.9 vs 12.8 ± 2.2 mmol/L) compared to sliding scale insulin 4

Dose Adjustment Protocol

For proper insulin management, the American Diabetes Association recommends:

• Calculate total daily insulin dose at 0.3-0.5 units/kg/day for insulin-naive patients
• Divide total daily dose into 50% basal insulin and 50% prandial insulin
• Adjust basal insulin by 2 units when blood glucose values are consistently above target
• If 50% of fasting glucose readings remain above 8.3 mmol/L (150 mg/dL) after one week, increase dose by another 2 units
• If any fasting glucose readings fall below 4.4 mmol/L (80 mg/dL), decrease dose by 2 units 1

Risk Factors for Poor Glycemic Control

When managing hyperglycemia, be aware of factors that increase risk of:

Hypoglycemia:

• African American race
• Low serum albumin levels 5

Hyperglycemia:

• Female gender
• Higher illness severity
• Severe diabetic complications
• High admission glucose level
• Infectious disease
• Corticosteroid use 5

Common Pitfalls to Avoid

1. Using sliding scale insulin as monotherapy - This approach is ineffective and leads to poor glycemic control 1, 3

2. Failing to adjust insulin regimens - Studies show sliding scale regimens are never adjusted in 81% of patients despite persistent hyperglycemia 2

3. Inadequate monitoring - Approximately 30% of sliding scale insulin administration points have missing or uncertain information related to execution, timing, blood glucose levels, or insulin dose 2

4. Overlooking the need for basal insulin - Sliding scale insulin alone is associated with a 3-fold higher risk of hyperglycemic episodes compared to no pharmacological regimen 5

5. Continuing ineffective regimens - Despite evidence showing poor outcomes, sliding scale insulin continues to be widely used 3, 4