What is the recommended approach for managing glycemic control in critically ill patients with a history of diabetes in the Intensive Care Unit (ICU)?

Management of Glycemic Control in Critically Ill ICU Patients

For critically ill patients in the ICU, initiate insulin therapy when blood glucose persistently exceeds 180 mg/dL (10.0 mmol/L) confirmed on two occasions within 24 hours, then maintain glucose between 140-180 mg/dL (7.8-10.0 mmol/L) using continuous intravenous insulin infusion. 1, 2

Blood Glucose Thresholds and Target Ranges

Treatment initiation threshold:

• Start insulin therapy when blood glucose ≥180 mg/dL (≥10.0 mmol/L) persists on two measurements within 24 hours 1, 2
• This threshold applies to both diabetic and non-diabetic critically ill patients 1

Target glucose range:

• Maintain blood glucose between 140-180 mg/dL (7.8-10.0 mmol/L) for the general ICU population 1, 2, 3
• This moderate target reduces mortality and infection risk while minimizing hypoglycemia compared to tighter control 1, 4

More stringent targets (110-140 mg/dL) may be considered ONLY for:

• Cardiac surgery patients in the immediate postoperative period 1
• Select patients with acute ischemic cardiac or neurological events 2, 5
• These tighter targets are acceptable ONLY if achievable without significant hypoglycemia 1, 2

Never target glucose <110 mg/dL:

• The landmark NICE-SUGAR trial demonstrated increased mortality (27.5% vs 25%) with intensive control (80-110 mg/dL) compared to moderate control (140-180 mg/dL) 1, 4
• Intensive targets increase hypoglycemia risk 10-15 fold without improving outcomes 1, 2

Insulin Delivery Method

Continuous intravenous insulin infusion (CII) is mandatory:

• IV insulin is the exclusive method for glucose control in critically ill ICU patients 2, 5, 3
• The short half-life (<15 minutes) allows rapid dose adjustments in response to unpredictable changes in clinical status, nutrition, or hemodynamics 2, 5
• CII typically achieves target glucose within 4-8 hours 2

Never use subcutaneous insulin in the acute ICU phase:

• Subcutaneous insulin absorption is unreliable during hypotension, shock, or hemodynamic instability 2, 5
• This includes avoiding sliding-scale insulin, which causes undesirable glycemic fluctuations and worse outcomes 2, 3

Monitoring Requirements

Frequency of glucose monitoring:

• Check blood glucose every 1-2 hours during insulin infusion until stable 5
• Once stable, monitor every 4 hours 5
• Increase monitoring frequency with any change in clinical status, nutrition, or insulin dose 1

Blood sampling technique:

• Use arterial line samples for patients with invasive vascular monitoring 1
• Analyze samples using blood gas analyzers or central laboratory (blood gas preferred for rapid results) 1
• Capillary (fingerstick) samples are inaccurate in critically ill patients and should be avoided when arterial access is available 1, 5

Accuracy standards:

• Blood gas analyzers should perform to ±0.4 mmol/L (or ±8% above 5 mmol/L) 1
• Point-of-care glucose meters may be inaccurate in critically ill patients and should not be solely relied upon 5

Hypoglycemia Prevention and Management

Hypoglycemia definitions and risks:

• Level 1: 54-69 mg/dL (3.0-3.8 mmol/L) - requires prompt treatment 1
• Level 2: <54 mg/dL (<3.0 mmol/L) - requires immediate intervention 1
• Level 3: altered mental/physical status requiring assistance - medical emergency 1
• Even a single episode of mild hypoglycemia (<80 mg/dL) increases mortality risk 6
• Severe hypoglycemia (<40 mg/dL) independently increases mortality, with risk escalating with prolonged or frequent episodes 1, 7

Prevention strategies:

• Reassess insulin regimen if glucose falls below 100 mg/dL 3
• Modify insulin dose when glucose <70 mg/dL unless explained by missed meals 7
• Adjust insulin infusion for interrupted nutrition or NPO status for procedures 5
• Use validated computerized protocols or written algorithms to reduce hypoglycemia rates 2, 7

Special Population Considerations

Cardiac surgery patients:

• Implement moderate glucose control (BG <150 mg/dL) in the postoperative period to reduce deep sternal wound infection and mortality 1
• More stringent targets (110-140 mg/dL) acceptable only if hypoglycemia can be avoided 1

Traumatic brain injury and neurological patients:

• Maintain glucose 140-180 mg/dL as primary target 5
• Avoid tight glucose control (<110 mg/dL) as it may induce regional neuroglycopenia and worsen neurological outcomes 1, 5
• Both severe hypoglycemia and hyperglycemia can produce or exacerbate focal deficits, encephalopathy, seizures, and permanent cognitive dysfunction 1

Trauma patients (non-brain injury):

• Initiate insulin when BG ≥150 mg/dL, maintain <150 mg/dL, and absolutely <180 mg/dL 1
• This approach reduces infection rates and ICU length of stay 1

Patients with pre-existing diabetes:

• Use the same glucose targets (140-180 mg/dL) as non-diabetic ICU patients 8
• Diabetic patients do not benefit from tighter control to the same extent as metabolically healthy individuals 8
• They face clinically relevant hypoglycemia risk that outweighs potential benefits of intensive control 8

Elderly and frail patients:

• Follow general ICU recommendations (140-180 mg/dL target) with heightened emphasis on hypoglycemia prevention 2
• This population has elevated hypoglycemia risk due to renal failure, malnutrition, reduced counterregulatory responses, and impaired symptom recognition 2

Nutritional Support Integration

Diabetes-specific formulas for enteral nutrition:

• Use formulas with lower carbohydrate content and higher proportion of complex carbohydrates to reduce glucose spiking 1
• These contain modified maltodextrin, starch, fructose, isomaltulose, and sucromalt rather than standard maltodextrin and sucrose 1
• Fat content enriched in monounsaturated fatty acids and higher fiber content help limit glycemic variation 1

Coordination with insulin therapy:

• Adjust insulin infusion rates when nutrition is interrupted or modified 5
• Adequate nutrition protocol is essential for safe glucose targeting and optimal insulin dose titration 6

Transition from IV to Subcutaneous Insulin

Criteria for transition:

• Hemodynamic stability achieved 5
• Glucose measurements stable for 4-6 hours 5
• Acidosis resolved (if diabetic ketoacidosis was present) 2
• Stable nutrition plan established 5

Transition protocol:

• Start subcutaneous basal insulin 1-2 hours BEFORE stopping IV infusion 7
• Calculate basal insulin as 60-80% of total daily IV insulin dose 7
• Use basal-bolus regimens rather than sliding-scale insulin alone 5, 3
• Never stop IV insulin abruptly - ensure 1-2 hour overlap to prevent rebound hyperglycemia 7

Common Pitfalls to Avoid

Protocol errors:

• Never use sliding-scale insulin as the sole regimen - it increases glycemic variability and hospital complications 2, 5, 3
• Avoid setting overly stringent targets (<110 mg/dL) which increase hypoglycemia without improving outcomes 2, 4
• Do not continue insulin infusions without adjusting for NPO status or interrupted nutrition 5

Monitoring errors:

• Inadequate glucose monitoring frequency during insulin infusion is dangerous 5
• Relying solely on capillary glucose meters in critically ill patients leads to inaccurate readings 1, 5

Clinical management errors:

• Avoid subcutaneous insulin of any type during the acute ICU phase for critically ill patients 2, 5
• Do not pursue more liberal targets (>180 mg/dL) as hyperglycemia >180 mg/dL increases mortality, infection risk, and ICU length of stay 6, 9
• Never ignore glucose variability - high variability is independently associated with worse outcomes 4, 9