What is the recommended management of severe hyperglycemia, likely due to diabetes mellitus, using insulin infusion in a patient with a history of kidney disease or heart disease?

Insulin Infusion for Severe Hyperglycemia Management

For severe hyperglycemia in hospitalized patients, particularly those with kidney or heart disease, continuous intravenous insulin infusion is the preferred treatment, targeting a glucose range of 140-180 mg/dL for most critically ill patients, with careful monitoring to prevent hypoglycemia and electrolyte disturbances. 1, 2

Critical Care Setting: IV Insulin Infusion Protocol

Continuous intravenous insulin infusion is the most effective method for achieving glycemic goals and avoiding hypoglycemia in critically ill patients. 1 This approach is mandatory for:

• Patients with diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS) 1
• ICU patients with hyperglycemia, including those without a prior diabetes diagnosis 1
• Patients with severe steroid-induced hyperglycemia 1
• Patients undergoing solid organ transplantation 1

Target Glucose Range

• Standard target: 140-180 mg/dL (7.8-10.0 mmol/L) for most critically ill patients 1, 3
• More stringent targets (110-140 mg/dL) may be appropriate for cardiac surgery patients using computerized algorithms that minimize hypoglycemia risk 1
• Higher ranges (up to 200 mg/dL) are acceptable when close nursing supervision is not feasible 1

Monitoring Requirements

Blood glucose must be monitored every 1-2 hours for most patients receiving insulin infusion. 1 Protocols using 4-hourly testing produce hypoglycemia rates above 10% and are not recommended unless demonstrated safe with the specific protocol in use 1. When using IV insulin, monitoring every 30 minutes to 2 hours is required 3.

Special Considerations for Kidney Disease

Patients with renal impairment require lower insulin doses and closer monitoring for hypoglycemia, as insulin clearance decreases with declining kidney function. 4 For patients with CKD Stage 5:

• Reduce total daily insulin dose by 50% for type 2 diabetes 5
• Reduce total daily insulin dose by 35-40% for type 1 diabetes 5

Electrolyte Management: Critical Pitfall

Hypokalaemia occurs in approximately 50% of patients during treatment of hyperglycemic crises, and severe hypokalaemia (<2.5 mEq/L) is associated with increased inpatient mortality. 1 Insulin stimulates potassium movement into cells, potentially causing life-threatening hypokalemia, respiratory paralysis, ventricular arrhythmia, and death 4. Potassium levels must be monitored closely and corrected before initiating insulin therapy. 2, 4

Transition to Subcutaneous Insulin

Patients can be transitioned from IV to subcutaneous insulin once they meet specific stability criteria: 1

• Stable glucose measurements for at least 4-6 hours consecutively 1
• Normal anion gap and resolution of acidosis (in DKA) 1
• Hemodynamic stability (not requiring vasopressors) 1
• Stable nutrition plan 1
• Stable IV insulin infusion rates 1

Transition Dosing Algorithm

Calculate the total daily subcutaneous insulin dose from the average insulin infused during the 12 hours before transition. 1 For example, if receiving an average of 1.5 units per hour, the estimated daily dose would be 36 units/24 hours 1.

Critical timing: Administer basal insulin 2-4 hours before discontinuing IV insulin to prevent rebound hyperglycemia. 2, 3 The most common pitfall is premature termination of IV insulin therapy and insufficient timing or dosing of subcutaneous insulin before discontinuation 6.

Initial Subcutaneous Insulin Dosing Post-Transition

For hospitalized patients transitioning from IV insulin:

• Insulin-naive or low-dose patients: 0.3-0.5 units/kg/day total daily dose, with 50% as basal insulin 5, 2
• Patients on high-dose home insulin (≥0.6 units/kg/day): Reduce total daily dose by 20% to prevent hypoglycemia 5
• High-risk patients (elderly >65 years, renal failure, poor oral intake): Use lower doses of 0.1-0.25 units/kg/day 5

Divide the total daily dose as 50% basal insulin (glargine or detemir once daily) and 50% prandial insulin (rapid-acting analog divided among three meals). 1, 5, 2

Heart Disease Considerations

For patients with ischemic events (myocardial infarction or ischemic stroke), rapid glucose control may be warranted given the known harms of hyperglycemia, but intensive lowering has not shown additional benefit and may increase hypoglycemia risk. 1 Targeting 140-180 mg/dL remains the standard approach 1.

Avoiding Sliding Scale Insulin Monotherapy

Sliding scale insulin as monotherapy is explicitly condemned by all major guidelines and should never be used alone. 1 It treats hyperglycemia reactively after it occurs rather than preventing it, leading to dangerous glucose fluctuations 5. Scheduled basal-bolus regimens with correction insulin as an adjunct are superior 1, 5.