What is the best management approach for an older adult patient with type 2 diabetes (T2D) and acute kidney injury (AKI) due to Hyperosmolar Hyperglycemic State (HHS) presenting with severe oliguria, producing only a minimal amount of urine?

Management of Severe Oliguria in HHS with Acute Kidney Injury

Aggressive intravenous fluid resuscitation with isotonic saline (0.9% NaCl) at 15-20 ml/kg/h is the absolute priority and must be initiated immediately, as fluid replacement alone will cause blood glucose to fall significantly and restore renal perfusion without requiring insulin initially. 1

Immediate Fluid Resuscitation Protocol (First Hour)

• Administer 0.9% NaCl at 15-20 ml/kg/h (1-1.5 liters in average adults) to restore intravascular volume and renal perfusion immediately. 1
• The profound oliguria (300 ml/24h) indicates severe intravascular depletion from the approximately 9-liter total water deficit typical in HHS (100-220 ml/kg body weight). 1
• Withhold insulin until blood glucose stops falling with IV fluids alone, unless significant ketonaemia is present, as early insulin use before adequate fluid resuscitation can worsen intravascular depletion and is detrimental. 1, 2

Critical Monitoring Parameters

• Measure serum osmolality every 2-4 hours and ensure the rate of decline does not exceed 3 mOsm/kg/h to prevent osmotic demyelination syndrome (central pontine myelinolysis). 1, 3, 4
• Calculate effective serum osmolality using: 2[measured Na (mEq/L)] + glucose (mg/dL)/18. 3
• Monitor urine output hourly, targeting ≥0.5 ml/kg/h as a marker of adequate renal perfusion restoration. 4
• In older adults with cardiac or renal compromise, perform continuous hemodynamic monitoring (blood pressure, heart rate) and frequent assessment of cardiac, renal, and mental status to avoid iatrogenic fluid overload. 1

Subsequent Fluid Management (Hours 1-24)

• Continue 0.9% NaCl at 4-14 ml/kg/h if corrected sodium is low (calculate corrected Na by adding 1.6 mEq for each 100 mg/dL glucose >100 mg/dL). 1, 3
• Switch to 0.45% NaCl at 4-14 ml/kg/h if corrected sodium is normal or elevated. 1, 3
• Target fluid replacement to correct estimated deficits within 24-48 hours, with more cautious rates in elderly patients. 3

Insulin Therapy Timing

• Start insulin only when blood glucose stops falling with IV fluids alone: IV bolus of 0.15 units/kg regular insulin followed by continuous infusion of 0.1 units/kg/h. 1
• When plasma glucose reaches 300 mg/dL, decrease insulin infusion to 0.05-0.1 U/kg/h and add 5-10% dextrose to IV fluids to prevent hypoglycemia while continuing to treat hyperosmolarity. 3
• Target glucose 250-300 mg/dL in first 24 hours, not aggressive normalization. 3

Addressing the Acute Kidney Injury

• The AKI in HHS is typically prerenal from severe volume depletion and may be complicated by rhabdomyolysis (check creatine kinase levels). 5, 6, 7
• Aggressive fluid resuscitation is the definitive treatment for both the oliguria and AKI, with urine output expected to improve as intravascular volume is restored. 5, 7
• If oliguria persists despite adequate fluid resuscitation (assessed by hemodynamic stability and corrected sodium trends), consider continuous renal replacement therapy (CRRT) or hemodialysis. 5
• Monitor BUN, creatinine, and potassium every 2-4 hours during initial resuscitation. 3

Potassium Management

• Despite total body potassium deficits of 5-15 mEq/kg, serum potassium may initially appear normal or elevated due to hyperosmolarity. 1
• Add potassium supplementation (20-30 mEq/L) to IV fluids once urine output is established and serum potassium is confirmed, as insulin therapy will drive potassium intracellularly. 3

Common Pitfalls to Avoid

• Never start insulin before adequate fluid resuscitation unless significant ketonaemia is present, as this precipitates worsening intravascular depletion and cardiovascular collapse. 1, 2
• Never correct osmolality faster than 3 mOsm/kg/h, as rapid correction causes central pontine myelinolysis with devastating neurological consequences. 1, 4, 2
• Do not use hypotonic saline initially despite hypernatremia—an initial rise in measured sodium is expected and appropriate as glucose falls. 2
• In older adults with organ failure, preventing hypoglycemia takes priority over aggressive glucose lowering, and dehydration must be prevented and treated aggressively. 8