What is the management for an older adult patient with type 2 diabetes and acute kidney injury due to Hyperosmolar Hyperglycemic State (HHS)?

Management of Acute Kidney Injury Due to Hyperosmolar Hyperglycemic State (HHS)

Aggressive fluid resuscitation with isotonic saline is the absolute priority and cornerstone of management for acute kidney injury in HHS, as restoration of intravascular volume and renal perfusion directly reverses the prerenal azotemia that characterizes this condition. 1, 2

Initial Fluid Resuscitation Protocol

Begin with isotonic saline (0.9% NaCl) at 15-20 mL/kg/h (1-1.5 liters in the first hour for average adults) to restore intravascular volume and renal perfusion. 1, 2 This aggressive initial approach is critical because:

• HHS patients present with profound total body water deficits of approximately 9 liters (100-220 mL/kg body weight), with the acute kidney injury being primarily prerenal in nature from severe volume depletion 2
• Fluid resuscitation alone causes blood glucose to fall significantly without insulin administration, and restoration of renal perfusion is essential before any other interventions 2
• The initial isotonic saline matches plasma tonicity, preventing rapid osmotic shifts that could worsen cerebral complications during resuscitation 3

Critical Monitoring During Fluid Resuscitation

Monitor serum osmolality every 2-4 hours and ensure the rate of osmolality correction does not exceed 3 mOsm/kg/h to prevent osmotic demyelination syndrome (central pontine myelinolysis). 2 This is particularly crucial in older adults with pre-existing renal compromise.

In elderly patients or those with cardiac/renal compromise, use more cautious fluid rates with continuous hemodynamic monitoring to avoid iatrogenic fluid overload. 1, 2 Track:

• Hourly vital signs and mental status 1
• Fluid input/output measurements 1, 2
• Blood pressure improvement as a marker of adequate resuscitation 2
• Serial osmolality calculations 2

Subsequent Fluid Management (Hours 1-24)

After initial resuscitation and once vital signs stabilize:

• Continue 0.9% NaCl at 4-14 mL/kg/h if corrected sodium is low 2
• Switch to 0.45% NaCl at 4-14 mL/kg/h if corrected sodium is normal or elevated 2
• Calculate corrected sodium by adding 1.6 mEq/L to measured sodium for each 100 mg/dL glucose above 100 mg/dL 3

Electrolyte Replacement and Renal Protection

Once urine output is established (confirming renal function recovery), add 20-30 mEq/L potassium to IV fluids (2/3 KCl and 1/3 KPO4) regardless of initial potassium level. 1 This is essential because:

• Insulin therapy will drive potassium intracellularly, potentially causing life-threatening hypokalemia 1
• Total body potassium deficits in HHS are 5-15 mEq/kg despite potentially normal or elevated initial serum levels 2

Insulin Therapy Timing

Withhold insulin until blood glucose stops falling with IV fluids alone and serum potassium is confirmed >3.3 mEq/L. 1, 2 This approach is critical because:

• Starting insulin before adequate fluid resuscitation worsens intravascular depletion and can precipitate cardiovascular collapse 2
• Insulin administration when potassium <3.3 mEq/L can cause fatal cardiac arrhythmias 1

When appropriate to start insulin:

• Administer IV bolus of 0.15 units/kg regular insulin followed by continuous infusion of 0.1 units/kg/h 2
• Alternatively, start continuous IV regular insulin infusion at 0.1 units/kg/h (typically 5-10 units/hour) 1

Special Considerations for Acute Kidney Injury

Avoid all nephrotoxic agents during the acute phase. 4 In cases where acute kidney injury does not resolve with fluid resuscitation alone:

• Consider continuous hemodiafiltration if hemodynamic instability persists or renal function continues to worsen despite adequate fluid resuscitation 5
• This may be necessary in severe cases complicated by rhabdomyolysis, which can occur in HHS and further compromise renal function 5, 6

Monitor for complications including rhabdomyolysis (check creatine kinase) and ischemic colitis (monitor for bloody stools), as these can complicate HHS and worsen renal outcomes. 5

Common Pitfalls to Avoid

• Never use hypotonic fluids initially in severely dehydrated patients—this risks cerebral edema from rapid osmotic shifts 3
• Never start insulin before confirming potassium >3.3 mEq/L 1
• Never correct osmolality faster than 3 mOsm/kg/h 2
• Never delay fluid resuscitation to obtain complete laboratory results—begin isotonic saline immediately upon clinical diagnosis 2

Long-Term Renal Management

For older adults with diabetes and chronic kidney disease who survive HHS:

• Initiate ACE inhibitors or angiotensin receptor blockers once acute phase resolves, especially if estimated GFR <60 mL/min/1.73m² or albuminuria is present 4
• Maintain blood pressure <140/85-90 mmHg 4
• Target HbA1c <7% to slow progression of diabetic kidney disease 4