Acute Management of Hyperosmolar Hyperglycemic Syndrome in Older Adults
Begin immediate aggressive fluid resuscitation with 0.9% NaCl at 15-20 mL/kg/hour for the first hour, withhold insulin until glucose stops falling with fluids alone (unless ketonemia is present), and aim to correct the estimated 9-liter fluid deficit within 24 hours while limiting osmolality reduction to 3-8 mOsm/kg/hour to prevent catastrophic cerebral edema and central pontine myelinolysis. 1, 2, 3
Initial Assessment and Diagnostic Confirmation
Upon suspicion of HHS, immediately obtain plasma glucose, serum electrolytes with calculated anion gap, effective serum osmolality (calculated as 2[measured Na] + glucose/18), blood urea nitrogen, creatinine, arterial blood gases, complete blood count, urinalysis with urine ketones, electrocardiogram, and HbA1c 1. Bacterial cultures (blood, urine, throat) and chest X-ray should be obtained if infection is suspected, as infection is the most common precipitating factor 1.
Calculate corrected serum sodium by adding 1.6 mEq/L to measured sodium for each 100 mg/dL glucose elevation above 100 mg/dL 1. This corrected value guides subsequent fluid selection and prevents dangerous sodium overcorrection 1.
HHS is confirmed when all five metabolic criteria are met: glucose ≥600 mg/dL, effective osmolality ≥320 mOsm/kg, arterial pH ≥7.30, serum bicarbonate ≥15 mEq/L, and small or absent ketones 1. The absence of altered mental status does not exclude HHS when metabolic criteria are met 1.
Fluid Resuscitation Protocol
First Hour
Start with 0.9% NaCl at 15-20 mL/kg/hour to restore intravascular volume and ensure vital organ perfusion 1, 2. This aggressive initial resuscitation is critical because HHS patients have profound dehydration with average total water deficits of approximately 9 liters 1, 2.
Subsequent Hours
After hemodynamic stabilization, transition to 0.45% NaCl at 4-14 mL/kg/hour if corrected serum sodium is normal or elevated 2. If corrected sodium is low, continue 0.9% NaCl 2. The critical safety parameter is limiting osmolality reduction to 3-8 mOsm/kg/hour—exceeding this rate precipitates central pontine myelinolysis, which carries 70% mortality once clinical symptoms beyond lethargy develop 4, 1, 2.
In older adults with cardiac or renal compromise, careful monitoring of volume status is essential to prevent fluid overload 2. However, the mortality risk from inadequate resuscitation exceeds that of cautious fluid administration 1.
Insulin Management: A Critical Departure from DKA
Withhold insulin until blood glucose stops falling with intravenous fluids alone, unless ketonemia is present 1, 3. This recommendation distinguishes HHS management from DKA and reflects the fact that fluid replacement alone will cause substantial glucose decline in HHS 3. Early insulin administration before adequate fluid resuscitation may be detrimental 3.
Once glucose plateaus despite ongoing fluid resuscitation (or if ketonemia is present), initiate insulin with an IV bolus of 0.1-0.15 units/kg, followed by continuous infusion at 0.1 units/kg/hour 1, 5, 6. Target a glucose decline of 50-75 mg/dL/hour 1. If glucose does not fall by 50 mg/dL in the first hour, reassess hydration status; if acceptable, double the insulin infusion rate hourly until steady decline is achieved 1.
When plasma glucose reaches 250-300 mg/dL, add 5% dextrose to 0.45% saline and reduce insulin infusion to 0.05-0.1 units/kg/hour 1, 2. Maintain glucose at 250-300 mg/dL until hyperosmolarity and mental status improve and the patient becomes clinically stable 4, 1. This prevents overly rapid osmolality correction, which is the primary mechanism of cerebral edema 4.
Potassium Management
If serum potassium is <3.3 mEq/L, hold insulin and aggressively replete potassium until the level reaches ≥3.3 mEq/L 1, 2. This is a Class A recommendation based on high-quality evidence 7. Insulin drives potassium intracellularly, and initiating insulin with hypokalemia precipitates life-threatening cardiac arrhythmias 2.
Once renal function is assured (urine output established) and potassium is ≥3.3 mEq/L, add 20-30 mEq/L potassium to IV fluids using 2/3 KCl and 1/3 KPO₄ 1, 2. Total body potassium deficit in HHS is 5-15 mEq/kg and requires close monitoring 1. Check potassium every 2-4 hours initially 2.
Monitoring Protocol
Draw blood every 2-4 hours to measure glucose, sodium, potassium, bicarbonate, anion gap, BUN, creatinine, and calculated effective osmolality 1, 2. Monitor calculated osmolality, not just individual components—this is the critical parameter guiding therapy 1. Continuous cardiac monitoring is indicated if hyperkalemia is present 2.
Special Considerations for Older Adults
Older adults face substantially higher risk of both hypoglycemia and mortality in HHS 4, 2. Elderly patients with renal insufficiency have decreased renal gluconeogenesis, impaired insulin clearance, and reduced release of glucagon and epinephrine in response to hypoglycemia 4, 2. Critically, elderly patients fail to perceive neuroglycopenic and autonomic hypoglycemic symptoms, which delays recognition and treatment 4, 2.
In elderly patients with renal impairment, consider reduced-dose insulin therapy to prevent dangerous hypoglycemia 2. The presence of renal failure, sepsis, and low albumin are predictive markers of hypoglycemia in elderly hospitalized patients 4.
Older adults in nursing homes or with cognitive impairment may be unable to recognize or communicate evolving dehydration 4. Adequate supervision and caregiver education regarding signs of dehydration and hyperglycemia could prevent many HHS admissions 4.
Transition to Subcutaneous Insulin
HHS is considered resolved when osmolality <300 mOsm/kg, hypovolemia is corrected, cognitive status returns to baseline, and blood glucose <270 mg/dL 1. At this point, administer long-acting basal insulin (glargine or detemir) subcutaneously 2-4 hours before stopping the IV insulin infusion 1, 2, 7. Continue IV insulin for 1-2 hours after the basal dose to ensure adequate absorption and prevent rebound hyperglycemia 7.
Critical Pitfalls to Avoid
Never correct osmolality faster than 3-8 mOsm/kg/hour—rapid correction causes osmotic demyelination syndrome with 70% mortality 4, 1, 2. This is the single most important safety parameter in HHS management.
Never add dextrose too early—this delays correction of hyperosmolarity and prolongs altered mental status 1. Wait until glucose reaches 250-300 mg/dL 1.
Never initiate insulin when potassium is <3.3 mEq/L—this precipitates fatal arrhythmias 1, 2, 7. This is a Class A recommendation 7.
Never stop IV insulin without prior basal insulin administration 2-4 hours earlier—this is the most common error leading to recurrent hyperglycemic crisis 2, 7.
In older adults with congestive heart failure or cerebral stroke, aggressive fluid replacement becomes more challenging but remains necessary 8. These precipitating factors are frequent causes of death, requiring careful balance between correcting dehydration and avoiding fluid overload 8.
Prognosis and Complications
Mortality rates in HHS reach up to 15%, higher than in DKA 1, 3. Potential complications include myocardial infarction, stroke, seizures, cerebral edema, central pontine myelinolysis, vascular occlusions, and rhabdomyolysis 1, 3, 6. The age of the patient is the best known prognostic indicator 8. Identification and treatment of the underlying precipitating illness is essential to limit mortality 5, 8, 6.