Endocrinology · USMLE Step 1 and Step 2

Hyperosmolar Hyperglycemic State song

Hyperosmolar Hyperglycemic State - HHS vs DKA, as a song. Hear the short teaser here. The full song is on YouTube and Spotify.

Hyperosmolar Hyperglycemic State

Full song on YouTube ↗Spotify ↗

Key points in this song10

HHS occurs almost exclusively in type 2 diabetics and is characterized by plasma glucose >600 mg/dL, serum osmolality >320 mOsm/kg, and minimal to no ketoacidosis (pH >7.3, bicarbonate >18 mEq/L).
The key pathophysiology is relative insulin deficiency — enough insulin remains to suppress lipolysis and ketogenesis, but not enough to prevent severe hyperglycemia and osmotic diuresis.
Corrected sodium must be calculated: add 1.6 mEq/L to measured sodium for every 100 mg/dL glucose above 100; this guides true fluid deficit estimation.
Fluid resuscitation with isotonic saline (0.9% NaCl) is the first and most critical step, often requiring 4–6 liters in the first few hours to restore hemodynamic stability.
Insulin is NOT started until fluid resuscitation is underway and serum potassium is ≥3.5 mEq/L, as insulin drives potassium intracellularly and can precipitate life-threatening hypokalemia.
The most common precipitating factor is infection (especially pneumonia and UTI), followed by medication noncompliance, myocardial infarction, and certain drugs (steroids, thiazides, atypical antipsychotics).
Neurological manifestations — including focal deficits, seizures, and coma — are hallmarks of HHS and correlate with the degree of hyperosmolality, distinguishing it clinically from DKA.
Goal of glucose management is to reduce plasma glucose by 50–75 mg/dL per hour; when glucose reaches 300 mg/dL, switch IV fluids to dextrose-containing solution to prevent cerebral edema from overly rapid correction.
Resolution criteria for HHS include plasma osmolality <315 mOsm/kg, mental status normalization, and glucose <300 mg/dL — unlike DKA, anion gap closure is not a primary endpoint.
Mortality in HHS is significantly higher than DKA (up to 20% vs. <1%), largely due to older patient age, underlying comorbidities, and delayed presentation.