What are the guidelines for permissible hyperglycemia in critically ill patients or those with diabetes, considering their individual health status, age, and comorbidities?

Permissible Hyperglycemia in Hospitalized Patients

For most critically ill and noncritically ill hospitalized patients, insulin therapy should be initiated when blood glucose persistently exceeds 180 mg/dL (checked on two occasions), with a target range of 140-180 mg/dL (7.8-10.0 mmol/L). 1

Initiation Threshold

• Start insulin therapy at ≥180 mg/dL (10.0 mmol/L) confirmed on two separate measurements for both ICU and non-ICU patients 1, 2
• Blood glucose between 140-180 mg/dL warrants observation and monitoring without active insulin treatment in most non-critically ill patients 2
• The 180 mg/dL threshold represents the consensus from multiple major societies (American Diabetes Association, Society of Critical Care Medicine) after the NICE-SUGAR trial demonstrated that intensive glucose control (80-110 mg/dL) increased mortality by 2.5% and hypoglycemia risk 10-15 fold 1

Target Ranges by Clinical Setting

Critically Ill Patients (ICU)

• Standard target: 140-180 mg/dL (7.8-10.0 mmol/L) for the majority of ICU patients 1
• More stringent target of 110-140 mg/dL (6.1-7.8 mmol/L) may be appropriate for select patients including cardiac surgery patients and those at centers with extensive nursing support, only if achievable without significant hypoglycemia 1
• Continuous intravenous insulin infusion is the preferred method in the ICU setting 1

Noncritically Ill Patients (General Medicine/Surgery)

• Target range: 100-180 mg/dL (5.6-10.0 mmol/L) for most noncritically ill patients 1
• Premeal glucose targets should be <140 mg/dL (7.8 mmol/L) 1
• Random blood glucose <180 mg/dL (10.0 mmol/L) 1
• Fasting glucose <100 mg/dL predicts hypoglycemia within 24 hours and should trigger insulin regimen reassessment 1

Special Populations Requiring Higher Targets

Terminally Ill and Severe Comorbidities

• Glucose levels up to 200-250 mg/dL (11.1-13.9 mmol/L) may be acceptable in terminally ill patients with short life expectancy 1
• Less aggressive insulin regimens should focus on minimizing glucosuria, dehydration, and electrolyte disturbances rather than tight control 1

Elderly Patients

• Follow general adult guidelines but with heightened emphasis on hypoglycemia prevention 1
• Target 140-180 mg/dL (7.8-10.0 mmol/L) for most elderly ICU patients 1
• Elderly patients have blunted neuroglycopenic and autonomic hypoglycemic symptoms, delaying recognition and treatment of low blood glucose 1
• Renal failure, sepsis, and low albumin are predictive markers of hypoglycemia risk in elderly hospitalized patients 1

Critical Safety Thresholds

Hypoglycemia Prevention

• Reassess insulin regimen when blood glucose falls below 100 mg/dL (5.6 mmol/L) unless easily explained by missed meals 1
• Modify insulin regimen when glucose <70 mg/dL (3.9 mmol/L) 1, 3
• Level 2 hypoglycemia (<54 mg/dL or 3.0 mmol/L) represents the threshold for neuroglycopenic symptoms and requires immediate treatment 1, 3

Avoid Targets Below 110 mg/dL

• Targets <110 mg/dL (6.1 mmol/L) are not recommended due to unacceptable hypoglycemia risk without mortality benefit 1
• The landmark NICE-SUGAR trial definitively showed that intensive control targeting 80-110 mg/dL increased mortality compared to 140-180 mg/dL 1

Clinical Decision Algorithm

Step 1: Confirm Persistent Hyperglycemia

• Check blood glucose on two separate occasions 1, 2
• If ≥180 mg/dL on both checks, initiate insulin therapy 1

Step 2: Determine Clinical Setting

• ICU patients: Use continuous IV insulin infusion targeting 140-180 mg/dL 1
• Non-ICU patients: Use scheduled subcutaneous basal-bolus insulin targeting 100-180 mg/dL 1

Step 3: Assess for Special Circumstances

• Cardiac surgery or acute ischemic events: Consider tighter control (110-140 mg/dL) only with robust hypoglycemia prevention protocols 1
• Terminal illness or severe comorbidities: Accept higher targets (up to 200-250 mg/dL) 1
• Elderly or renal failure: Prioritize hypoglycemia avoidance with standard 140-180 mg/dL target 1

Step 4: Monitor and Adjust

• Check glucose every 4-6 hours in non-eating patients, before meals in eating patients 1
• If glucose <100 mg/dL, reassess insulin regimen 1
• If glucose <70 mg/dL, modify insulin doses and implement hypoglycemia protocol 1, 3

Common Pitfalls to Avoid

• Never use sliding-scale insulin alone as monotherapy—it is associated with poor outcomes and inadequate glycemic control 2
• Avoid aggressive targets <140 mg/dL in acute settings, as intensive control increases hypoglycemia risk 10-15 fold without mortality benefit 1, 2
• Do not ignore glucose values between 140-180 mg/dL in non-critically ill patients—these warrant monitoring but not immediate insulin initiation 2
• Ensure potassium ≥4.0 mEq/L before starting insulin, as hypoglycemia occurs in 50% during treatment and severe hypokalemia (<2.5 mEq/L) increases mortality 2
• Never administer insulin when glucose <70 mg/dL—treat hypoglycemia first with 15-20 g fast-acting carbohydrate 3