What is the initial management for a patient presenting with hyperglycemic hyperosmolar syndrome (HHS)?

Initial Management of Hyperglycemic Hyperosmolar Syndrome (HHS)

Begin immediate aggressive fluid resuscitation with isotonic saline (0.9% NaCl) at 15-20 ml/kg/h (1-1.5 L in the first hour for average adults) to restore intravascular volume and renal perfusion, and delay insulin administration until the blood glucose stops falling with fluids alone unless significant ketonemia is present. 1, 2

Immediate Diagnostic Workup

Upon presentation, obtain the following laboratory studies immediately 3, 1:

• Arterial blood gases
• Complete blood count with differential
• Urinalysis with ketones
• Plasma glucose, blood urea nitrogen, electrolytes, chemistry profile, and creatinine
• Electrocardiogram
• Chest X-ray and cultures if infection suspected

Calculate effective serum osmolality using the formula: 2[measured Na (mEq/l)] + glucose (mg/dl)/18 to confirm diagnosis (should be >320 mOsm/kg H₂O) and guide treatment 3, 1.

Correct serum sodium for hyperglycemia by adding 1.6 mEq to the measured sodium value for each 100 mg/dl glucose above 100 mg/dl 3.

Fluid Resuscitation Strategy

First Hour (0-60 minutes)

• Administer 0.9% NaCl at 15-20 ml/kg/h (typically 1-1.5 L for average adult) 1, 2
• This initial bolus expands intravascular volume and restores renal perfusion 3

After Initial Hour

• Continue 0.9% NaCl if corrected serum sodium is low 3
• Switch to 0.45% NaCl if corrected serum sodium is normal or elevated 3
• Target osmolality reduction of 3-8 mOsm/kg/h to minimize risk of cerebral edema and central pontine myelinolysis 1, 4, 2
• Aim to correct estimated fluid deficits (typically 100-220 ml/kg) within the first 24 hours 3, 1, 2

Critical Monitoring Point

Monitor serum osmolality regularly (every 2-4 hours initially) to ensure the rate of decline does not exceed 3-8 mOsm/kg/h, as rapid changes may precipitate central pontine myelinolysis 1, 4, 2.

Insulin Therapy

A key distinction from DKA management: withhold insulin until blood glucose stops falling with IV fluids alone, unless significant ketonemia (>3.0 mmol/L) is present 4, 2. This approach differs fundamentally from DKA treatment and prevents potentially detrimental early insulin use 4.

When to Start Insulin

• Once glucose plateaus despite ongoing fluid resuscitation 4, 2
• OR immediately if significant ketonemia is present (≥3.0 mmol/L) 2

Insulin Dosing

• Do NOT give an initial bolus in HHS (unlike DKA protocols) 3
• Start continuous IV infusion at 0.1 U/kg/h (typically 5-10 units/hour) 3, 1
• Target glucose decline of 50-75 mg/dl/h 3
• If glucose does not fall by 50 mg/dl in the first hour, verify adequate hydration, then double insulin infusion hourly until steady decline achieved 3

Glucose Target Adjustment

• When plasma glucose reaches 300 mg/dl, decrease insulin to 0.05-0.1 U/kg/h (3-6 U/h) 3, 1
• Add 5-10% dextrose to IV fluids at this point 3, 1
• Maintain glucose between 250-300 mg/dl until hyperosmolarity and mental status resolve 3, 1

Electrolyte Management

Potassium Replacement

Critical safety point: Do NOT start insulin if potassium <3.3 mEq/l 3. Replete potassium first to prevent life-threatening hypokalemia.

Once renal function is confirmed and potassium known 3, 1:

• Add 20-30 mEq/L potassium to IV fluids (2/3 KCl and 1/3 KPO₄) 3, 1
• Continue potassium supplementation until patient is stable and tolerating oral intake 3

Monitoring Schedule

• Check electrolytes (sodium, potassium, chloride, bicarbonate, phosphate, magnesium) every 2-4 hours initially 3, 1
• Monitor blood glucose every 1-2 hours until stable 1
• Calculate effective serum osmolality regularly 1, 2

Hemodynamic Monitoring

Monitor continuously 3, 1:

• Vital signs (blood pressure, heart rate)
• Mental status changes
• Fluid input and output (target urine output ≥0.5 ml/kg/h) 2
• Cardiac and renal function, especially in elderly patients or those with cardiac/renal compromise 3

Treatment of Underlying Precipitants

Identify and treat precipitating causes simultaneously 3, 1, 5:

• Infection (most common trigger) 5
• Myocardial infarction 3, 5
• Stroke 3, 5
• Medications (diuretics, corticosteroids, beta-blockers) 6
• Other acute illnesses 1

Transition to Subcutaneous Insulin

When HHS resolves (osmolality <300 mOsm/kg, mental status normalized, glucose <15 mmol/L) 2:

• Administer basal insulin subcutaneously 2-4 hours BEFORE stopping IV insulin 3, 1
• This prevents rebound hyperglycemia and recurrence 3

Critical Pitfalls to Avoid

Do not use bicarbonate therapy - it has not been shown to improve outcomes in HHS 3.

Avoid rapid osmolality correction - changes exceeding 3-8 mOsm/kg/h increase risk of central pontine myelinolysis 1, 4, 2.

Do not start insulin before adequate fluid resuscitation unless ketonemia is present - early insulin may be detrimental 4, 2.

Exercise extreme caution in elderly patients and those with cardiac/renal compromise - use slower fluid rates with closer monitoring to avoid iatrogenic fluid overload 3, 1.

Monitor for complications: cerebral edema, myocardial infarction, stroke, seizures, vascular thrombosis, and osmotic demyelination 1, 4.

Level of Care

Patients with HHS require intensive care unit admission due to the need for continuous monitoring, frequent laboratory assessments, and high mortality risk 3, 1, 7. Involve the diabetes specialist team as soon as possible 4, 2.