What is the recommended approach for in-patient insulin therapy in patients with diabetes, including those with type 1 (T1DM) and type 2 (T2DM) diabetes, and considerations for patients with impaired renal function or hepatic impairment?

In-Patient Insulin Therapy

For non-critically ill hospitalized patients with diabetes, a scheduled basal-bolus-correction insulin regimen is the preferred treatment for those with good oral intake, while basal insulin plus correction insulin only should be used for patients with poor or no oral intake. 1, 2

Critical Care vs. Non-Critical Care Settings

Critically Ill Patients

• Continuous intravenous insulin infusion is the preferred method, targeting blood glucose of 140-180 mg/dL 1, 2
• Avoid glucose targets <110 mg/dL, as they are not recommended due to increased hypoglycemia risk 1

Non-Critically Ill Patients

• Premeal glucose targets should generally be <140 mg/dL (7.8 mmol/L), with random blood glucose <180 mg/dL 1
• Scheduled subcutaneous insulin regimens are strongly preferred over sliding scale insulin (SSI) as monotherapy 1, 2

Insulin Regimen Selection by Clinical Scenario

Patients with Good Oral Intake

• Use basal-bolus-correction regimen: 1, 2
  • Basal insulin: Once daily (glargine, detemir, or degludec)
  • Prandial insulin: Rapid-acting analog (lispro, aspart, or glulisine) before each meal
  • Correction insulin: Additional rapid-acting insulin for elevated glucose levels

Patients with Poor/No Oral Intake (NPO)

• Use basal insulin plus correction insulin only 1, 2
• Lower starting dose of 0.1-0.25 units/kg/day for high-risk patients (elderly >65 years, renal failure, poor oral intake) 3, 2
• Avoid prandial insulin when patients are not eating 1

Type 1 Diabetes (T1DM) Patients

• Basal insulin must never be discontinued, even if NPO 2
• Require basal and correction components at minimum, with prandial insulin added if eating 1, 2
• Typical total daily dose: 0.4-1.0 units/kg/day, with approximately 50% as basal and 50% as prandial 3

Type 2 Diabetes (T2DM) Patients

Initial Dosing for Insulin-Naive Patients:

• Start with 0.3-0.5 units/kg/day as total daily dose, divided 50% basal and 50% bolus 3, 2
• For moderate hyperglycemia (201-300 mg/dL): 0.2-0.3 units/kg/day 3
• For severe hyperglycemia (>300 mg/dL): 0.3-0.5 units/kg/day 3

Patients on Home Insulin:

• If on high-dose home insulin (≥0.6 units/kg/day), reduce total daily dose by 20% upon admission to prevent hypoglycemia 3, 2

Transitioning from IV to Subcutaneous Insulin

Critical timing to prevent rebound hyperglycemia: 2

• Administer subcutaneous basal insulin 2-4 hours before discontinuing IV insulin infusion
• Calculate subcutaneous basal dose at 60-80% of the daily IV infusion dose, based on the last 6-8 hours when stable glycemic goals were achieved 2

Special Populations

Renal Impairment

• Patients with renal insufficiency should receive lower insulin doses 1, 2
• Type 2 diabetes patients with varying degrees of renal impairment show increased insulin sensitivity as renal function declines 4, 5
• For CKD Stage 5: reduce total daily insulin dose by 50% in T2DM and 35-40% in T1DM 3
• Monitor closely for hypoglycemia, as insulin clearance decreases and duration of action increases with impaired kidney function 3

Hepatic Impairment

• Type 2 diabetes patients with impaired hepatic function show no significant effect on insulin lispro pharmacokinetics 4
• However, some studies with human insulin show increased circulating insulin levels in liver failure 4
• Lower doses and closer monitoring are prudent 3

Critical Pitfalls to Avoid

Never Use Sliding Scale Insulin (SSI) as Monotherapy

• SSI as the sole regimen is strongly discouraged and leads to poorer glycemic control with increased risk of both hypoglycemia and hyperglycemia 1, 2, 6
• SSI treats hyperglycemia reactively after it occurs rather than preventing it 3
• In comparative trials, basal-bolus regimens resulted in 0% treatment failure vs. 19% with SSI 6

Avoid Premixed Insulin in Hospital Settings

• Premixed insulin formulations are not routinely recommended for in-hospital use 2
• A randomized trial was stopped early due to 64% of patients on premixed insulin experiencing hypoglycemia vs. 24% on basal-bolus regimen 7
• Fixed ratios cannot be adjusted for variable oral intake 2

Discontinue SGLT2 Inhibitors

• Stop SGLT2 inhibitors 3-4 days before surgery and avoid during hospitalization due to increased risk of ketonemia and ketonuria 2

Hypoglycemia Prevention and Management

Mandatory hospital-wide protocol: 1, 2

• Implement standardized hypoglycemia management protocol
• Review and adjust treatment regimens when blood glucose falls below 70 mg/dL 1, 2
• Document all hypoglycemic episodes in the medical record and track for quality improvement 1
• Critical warning: 84% of patients with severe hypoglycemia had a prior episode during the same admission 2

Treatment approach:

• Treat blood glucose <70 mg/dL immediately with 15 grams of fast-acting carbohydrate 1
• Reduce insulin dose by 10-20% if hypoglycemia occurs without clear cause 3

Insulin Administration Considerations

Insulin Pens vs. Vials

• Insulin pens may be safely used in hospitals and are associated with improved nurse satisfaction 1
• FDA warning: Pens must be strictly labeled "For single patient use only" to prevent blood-borne disease transmission 1, 2

Human Insulin vs. Analogs

• Human insulin and analog insulins provide similar glycemic control in the hospital setting 1, 2
• Rapid-acting analogs (lispro, aspart, glulisine) have faster onset and shorter duration than regular human insulin 4, 8

Timing of Rapid-Acting Insulin

• Administer rapid-acting insulin 0-15 minutes before meals for optimal postprandial control 3, 8
• Regular human insulin should be given 30-45 minutes before meals 3

Continuation of Home Medications

• In certain circumstances, it may be appropriate to continue home oral glucose-lowering medications 1
• If oral medications are held, implement a protocol for resuming them 1-2 days before discharge 1
• Consider discontinuing saxagliptin and alogliptin in patients who develop heart failure 1