What is the appropriate sliding scale for short-acting insulin for a patient with HbA1c 6.8% and RBS 347 mg/dl on hydrocortisone 100mg BD?

Sliding Scale Insulin for Glucocorticoid-Induced Hyperglycemia

Direct Recommendation

Do not use sliding scale insulin (SSI) alone for this patient; instead, initiate a basal-bolus insulin regimen with NPH insulin given twice daily (morning and early evening) to match the glucocorticoid-induced hyperglycemia pattern, combined with correctional doses of short-acting insulin. 1

Rationale for Avoiding SSI Alone

• Sliding scale insulin alone is strongly discouraged and ineffective for managing hyperglycemia in hospitalized patients, as it provides no benefit and is associated with a 3-fold higher risk of hyperglycemic episodes compared to structured insulin regimens 2, 3
• SSI creates a "reactive" approach that leads to glucose variability rather than stable control, with studies showing only 6% of patients achieve good glycemic control through 5 days of SSI therapy 4, 2
• The American Diabetes Association explicitly recommends basal-bolus insulin regimens over SSI alone 2

Specific Insulin Regimen for Glucocorticoid Use

Initial Dosing Strategy

• Start NPH insulin at 0.3 units/kg per day total dose, divided as 2/3 in the morning and 1/3 in the early evening to match the afternoon and evening hyperglycemia pattern caused by hydrocortisone 1
• For a patient on high-dose glucocorticoids (hydrocortisone 100mg BD), this dosing accounts for the significant insulin resistance induced by steroids 1

Correctional Insulin Component

• Add short-acting insulin for correctional doses using a more resistant sliding scale due to glucocorticoid-induced insulin resistance 1:
  • For premeal glucose >250 mg/dL (>13.9 mmol/L): give 2 units of short-acting insulin 1
  • For premeal glucose >350 mg/dL (>19.4 mmol/L): give 4 units of short-acting insulin 1
• Given the current RBS of 347 mg/dL, an immediate correctional dose of 4 units short-acting insulin is appropriate 1

Clinical Context Considerations

HbA1c vs. Current Glucose

• The HbA1c of 6.8% indicates reasonable long-term control, but the current RBS of 347 mg/dL reflects acute glucocorticoid-induced hyperglycemia requiring immediate intervention 1
• This discrepancy confirms the hyperglycemia is primarily steroid-induced rather than reflecting baseline poor control 1

Monitoring and Titration

• Check blood glucose before meals and at bedtime to titrate both NPH and correctional insulin doses 1
• Target blood glucose: 90-150 mg/dL (5.0-8.3 mmol/L) before meals, though this may be relaxed to <180 mg/dL given the acute glucocorticoid use 1, 5
• If 50% of premeal values over 2 weeks remain above goal, increase NPH dose by 2 units 1

Critical Safety Warnings

Rapid Insulin Requirement Changes

• Insulin requirements can decline rapidly after dexamethasone/hydrocortisone is stopped, and doses must be adjusted accordingly to prevent severe hypoglycemia 1
• Monitor closely during glucocorticoid taper and reduce insulin doses proportionally 1

Avoid Common Pitfalls

• Do not continue sulfonylureas during glucocorticoid therapy, as they are not recommended in this clinical scenario and increase hypoglycemia risk 1
• Do not use premixed insulin (70/30), as it has unacceptably high rates of hypoglycemia in hospitalized patients 2
• Do not rely solely on the simplified sliding scale provided above; it should only supplement the basal NPH regimen, not replace it 1

Alternative Approach if NPH Not Available

• If NPH insulin is unavailable, use basal insulin analog (glargine, detemir, or degludec) at 0.1-0.3 units/kg per day in the morning, combined with the correctional short-acting insulin doses outlined above 1
• However, NPH twice daily provides better matching to the glucocorticoid hyperglycemia pattern 1