What is the best approach to managing a diabetic patient's blood glucose levels using the insulin sliding scale method?

Sliding Scale Insulin Should Be Avoided as Monotherapy in Hospitalized Patients

The sole use of sliding-scale insulin (SSI) in the inpatient hospital setting is strongly discouraged and should be replaced with scheduled basal-bolus insulin regimens for most patients. 1

Why Sliding Scale Insulin Fails

Sliding scale insulin treats hyperglycemia reactively rather than preventing it, leading to dangerous blood glucose fluctuations that worsen both hyperglycemia and hypoglycemia. 2 This approach addresses elevated glucose only after it has already occurred, creating a pattern of persistent poor control. 2

Key problems with SSI monotherapy:

• Only 12% of SSI injections successfully reduced elevated glucose to target range (90-130 mg/dL) in hospitalized patients 3
• 84% of SSI injections resulted in persistently elevated glucose levels that remained subtherapeutic 3
• SSI regimens were never adjusted in 81% of patients despite persistent hyperglycemia 3
• Only 6% of patients achieved good glycemic control over 5 days of SSI therapy 3
• Documentation and monitoring deficiencies occurred in approximately 30% of anticipated care points 3

The Preferred Alternative: Basal-Bolus Insulin

For hospitalized patients with good nutritional intake, a basal-bolus insulin regimen is the preferred treatment. 1 This approach provides scheduled subcutaneous insulin with basal, nutritional, and correction components. 1

Initial Dosing Algorithm

For insulin-naive patients or those on low insulin doses:

• Start with total daily dose of 0.3-0.5 units/kg 2
• Allocate 50% as basal insulin (once daily) 2
• Allocate 50% as rapid-acting prandial insulin (divided before meals) 2

For patients at higher risk of hypoglycemia (elderly >65 years, renal failure, poor oral intake):

• Use lower doses of 0.1-0.25 units/kg/day 2, 4

For patients already on high insulin doses at home (≥0.6 units/kg/day):

• Reduce total daily dose by 20% during hospitalization to prevent hypoglycemia 2, 4

Glycemic Targets

Target glucose range of 140-180 mg/dL for most hospitalized patients. 1, 2 More stringent targets of 110-140 mg/dL may be appropriate for cardiac surgery patients and those with acute ischemic cardiac or neurologic events, if achievable without significant hypoglycemia. 1

When SSI Alone May Be Acceptable (Very Limited Circumstances)

SSI as monotherapy is appropriate only for:

• Patients without pre-existing diabetes who have mild stress hyperglycemia 5
• Patients with well-controlled diabetes (HbA1c <7%) on minimal home therapy who develop mild hyperglycemia during hospitalization 2, 5
• Patients who are NPO with no nutritional replacement and only mild hyperglycemia 2
• Patients who are new to steroids or tapering steroids 2

For Patients with Poor Oral Intake or NPO Status

A basal-plus-correction insulin regimen is the preferred treatment for patients with poor oral intake or those receiving nothing by mouth. 1 This consists of:

• Basal insulin at 0.1-0.25 units/kg/day 2, 5
• Correction doses of rapid-acting insulin before meals or every 6 hours if NPO 5

Critical Care Setting

In the critical care setting, continuous intravenous insulin infusion is the best method for achieving glycemic targets. 1 IV insulin should be administered using validated written or computerized protocols that allow for predefined adjustments. 1

Evidence Supporting Basal-Bolus Over SSI

Randomized trials consistently demonstrate superior outcomes with basal-bolus approaches:

• 68% of patients receiving basal-bolus insulin achieved mean blood glucose <140 mg/dL versus only 38% with SSI alone 2
• Basal-bolus approach is associated with reduced complications, including postoperative wound infection and acute renal failure 2
• Better glycemic control with basal-bolus therapy compared to SSI in patients with type 2 diabetes 2

Important Safety Consideration

Basal-bolus regimens carry a 4-6 times higher risk of hypoglycemia compared to SSI alone (relative risk 5.75 for blood glucose ≤70 mg/dL). 5 This necessitates careful monitoring and appropriate dose adjustments, but the improved glycemic control and reduced complications justify this approach when properly implemented. 2

Common Pitfalls to Avoid

• Never rely on SSI monotherapy for patients with known diabetes requiring insulin 1, 2
• Do not continue SSI regimens without modification when control remains poor 2
• Avoid premixed insulin therapy in hospitals due to unacceptably high rates of hypoglycemia 2
• Ensure a standardized hospital-wide hypoglycemia treatment protocol is in place to immediately address hypoglycemia 1

Transition Planning

When transitioning from IV insulin to subcutaneous insulin, give subcutaneous insulin 1-2 hours before discontinuing IV therapy. 1 Converting to basal insulin at 60-80% of the daily infusion dose has been shown to be effective. 1