Hyperglycemic Crisis in an Older Adult on a Sulfonylurea
A 68-year-old woman with type 2 diabetes treated with glimepiride is brought in by her daughter after 5 days of vomiting and poor oral intake during a respiratory illness. She is drowsy but arousable and answers questions slowly. Temperature is 38.1°C, pulse 112/min, blood pressure 98/58 mmHg supine, respirations 24/min. Mucous membranes are dry and skin turgor is poor. Point-of-care glucose reads "HI" (>600 mg/dL). Serum sodium 131 mEq/L, potassium 4.9 mEq/L, bicarbonate 22 mEq/L, chloride 98 mEq/L, BUN 48 mg/dL, creatinine 1.8 mg/dL (baseline 0.9). Serum ketones are negative at a 1:2 dilution; beta-hydroxybutyrate 0.4 mmol/L; measured serum osmolality 318 mOsm/kg.
1. Which hyperglycemic syndrome is this, and which findings carry the discriminating weight?
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Hyperosmolar hyperglycemic state (HHS).
Supporting features:
- Glucose >600 mg/dL and measured osmolality 318 mOsm/kg; effective (tonic) osmolality ≈ 2×Na⁺ + glucose/18 ≈ 262 + ~50 = ~312 mOsm/kg, well above the ~320 threshold used in some criteria and high enough to explain the altered sensorium.
- Absent ketosis: beta-hydroxybutyrate 0.4 mmol/L with negative nitroprusside ketones.
- Bicarbonate 22 mEq/L with no anion gap acidosis - ketoacidosis would typically show bicarbonate <18 and a widened gap.
- Profound volume depletion (BUN 48, creatinine 1.8 from 0.9, supine hypotension, dry mucosae) and a several-day prodrome.
DKA and HHS exist on a spectrum and can coexist; what separates them here is the degree of insulin deficiency (enough to permit lipolysis and ketogenesis in DKA, not here) versus the degree of volume depletion. Precipitants to look for include infection (this patient's respiratory illness) and medications such as the sulfonylurea.
2. The resident wants to begin an insulin infusion immediately. Explain why that is the wrong first move and outline the first 6 hours of management.
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Insulin before volume repletion is dangerous in HHS.
- Insulin shifts glucose (and water) into cells, pulling intravascular volume with it. In a patient already hypotensive from a 8–10 L free-water deficit, this can precipitate vascular collapse and shock.
- Rapid osmolality shifts in a hyperosmolar brain predispose to cerebral edema, especially in older adults and children. The osmolality should fall smoothly.
- Insulin also drives potassium intracellularly; starting it before knowing the potassium risks arrhythmia.
A reasonable sequence:
- Volume first: isotonic crystalloid bolus(es), then continuous replacement. Choose tonicity based on the corrected sodium - if the corrected Na⁺ is high, free water is the deficit and 0.45% saline may be appropriate after initial resuscitation.
- Potassium: today it is 4.9 mEq/L - adequate urine output permitting, add ~20–30 mEq/L of potassium to the fluids and recheck hourly initially. Hold insulin if K⁺ <3.3 mEq/L.
- Insulin: start a low-dose infusion only after volume resuscitation and potassium repletion, and target a gradual decline in glucose (roughly 50–75 mg/dL/h). Add dextrose once glucose approaches ~250–300 mg/dL so the infusion can continue without hypoglycemia.
- Treat the precipitant: evaluate for pneumonia and other infection; this is not a diagnosis of exclusion.
- Monitor osmolality, sodium, potassium, phosphate, and mental status; watch for rhabdomyolysis and thrombosis.
3. At discharge the daughter asks whether the glimepiride should be restarted. What is the concern, and how does it interact with this admission?
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Glimepiride is a long-acting sulfonylurea and a poor choice after a hyperosmolar crisis in an older adult.
- It lowers glucose by closing beta-cell K-ATP channels independently of glucose level, so once the stress resolves and intake returns, the patient is at risk for prolonged, recurrent hypoglycemia - particularly with a creatinine now of 1.8 mg/dL, since reduced renal clearance of the drug and its active metabolites extends the effect.
- Hypoglycemia in an older adult carries high morbidity (falls, arrhythmia, cognitive injury), and the risk persists for days after a dose.
- A sulfonylurea was also a plausible contributor to the severity of this presentation in a patient who stopped eating.
Practical answer: do not restart it unchanged. Reassess the regimen - consider a DPP-4 inhibitor or other agent with low hypoglycemia risk and appropriate dosing for her kidney function - and provide sick-day rules (hold the agent and call if unable to eat or vomiting). She also needs education on glucose monitoring and hydration during illness, since the precipitating sequence (vomiting → poor intake → hyperosmolality) is likely to recur.