HHS is a life-threatening diabetic emergency characterized by glucose >600 mg/dL, serum osmolality >320 mOsm/kg, minimal/absent ketosis, and neurologic impairment — most commonly affecting older adults with type 2 diabetes. [1-2] In-hospital mortality for pure HHS ranges from 10–20%, approximately 10 times higher than DKA. [3-4] Approximately 32% of patients presenting with HHS have no prior diabetes diagnosis. [4]
1. History
- Key HPI: Duration of polyuria, polydipsia, weight loss; oral intake and hydration status; medication adherence; recent illness/fever/infection
- Symptom characterization: Insidious onset over days to weeks (unlike DKA which develops over hours) [5-6]
- Timing/triggers: Recent infection (most common — pneumonia, UTI, sepsis), stroke, MI, surgery, medication changes [2][5]
- Associated symptoms: Progressive weakness, fatigue, visual changes, nausea/vomiting, altered mental status ranging from lethargy to coma [5-6]
- Important negatives: Absence of Kussmaul respirations and fruity breath odor (these suggest DKA rather than pure HHS); absence of abdominal pain (more common in DKA) [3]
2. Alarm Features
- Altered mental status / coma — correlates with osmolality >330 mOsm/kg [7]
- Hemodynamic instability — hypotension, tachycardia from profound dehydration (average fluid deficit 8–12 L) [5]
- Seizures — focal or generalized, may occur with severe hyperosmolality
- Signs of precipitating illness: fever/sepsis, chest pain (ACS), focal neurologic deficits (stroke) [2]
- Mixed DKA-HHS — carries higher mortality than either condition alone [1][8]
3. Medications
Precipitating medications: [9-11]
- Glucocorticoids — most common drug class
- Atypical antipsychotics (olanzapine, clozapine, quetiapine)
- Thiazide diuretics and loop diuretics (dehydration + hyperglycemia)
- Phenytoin — impairs insulin secretion
- Beta-blockers — mask symptoms, impair insulin release
- Immune checkpoint inhibitors
- Benzodiazepines — associated with HHS precipitation in elderly [12]
Treatment medications
- Regular insulin IV infusion: 0.1 units/kg/h (ADA) or 0.05 units/kg/h (JBDS) — start only after initial fluid resuscitation [5][13]
- Potassium replacement: 20–40 mEq/L in IV fluids when K⁺ <5.2 mEq/L and urine output established
- VTE prophylaxis: Consider LMWH — prophylactic heparin was associated with reduced mortality in one study (OR 0.033) [14]
Contraindicated: Do not give insulin if K⁺ <3.3 mEq/L — replace potassium first [5]
4. Diet
- NPO initially — patients are often obtunded; aspiration risk is high due to gastroparesis from hypertonicity
- Hydration is paramount — average 9 L of IV fluids over 48 hours in adults [5]
- Post-recovery: Structured diabetes dietary education, carbohydrate-controlled diet
- Long-term: Adequate daily fluid intake, especially in elderly or cognitively impaired patients who may not self-hydrate
5. Review of Systems
- Neuro: Mental status changes, focal deficits, seizures, vision changes
- Infectious: Fever, cough, dysuria, skin/wound infections (most common precipitant)
- Cardiovascular: Chest pain, dyspnea (rule out ACS as trigger)
- GI: Nausea, vomiting, abdominal pain (less prominent than DKA)
- Musculoskeletal: Muscle pain/weakness (rhabdomyolysis) [15-16]
- Vascular: Limb pain, swelling (thromboembolism) [17]
6. Collateral History and Family History
- Collateral: Medication compliance, baseline functional/cognitive status, recent sick contacts, access to fluids (nursing home residents, cognitively impaired patients at highest risk)
- Family history: Type 2 diabetes, cardiovascular disease
- Social context: Living situation (isolated elderly), substance use, access to medications and healthcare [5]
7. Risk Factors
- Age >65 years — median age at presentation is 69 years [4]
- Type 2 diabetes (most common), though incidence per capita is actually higher in type 1 diabetes [4]
- Undiagnosed diabetes — 32% of HHS cases are the initial presentation of diabetes [4]
- Nursing home/institutional residence — limited access to free water
- Cognitive impairment/dementia — impaired thirst mechanism and self-care
- Renal insufficiency
- Comorbidity burden — higher Charlson Comorbidity Index independently predicts mortality [14]
- Medication nonadherence [5]
- Infection — present in ~40% of cases as the precipitant [18]
8. Differential Diagnosis
- DKA — acidosis (pH <7.3), elevated ketones, lower glucose threshold (>250 mg/dL); Kussmaul breathing present [19]
- Mixed DKA-HHS — ~27–38% of hyperglycemic crises have overlapping features; carries the highest mortality [1][8]
- Stroke — can both mimic and precipitate HHS; focal deficits may be from hyperosmolality alone
- Sepsis — may coexist; lactic acidosis may confound the picture
- Acute coronary syndrome — can trigger HHS; troponin should be checked
- Drug intoxication / toxic ingestion — check osmol gap
- Central diabetes insipidus — hypernatremia and dehydration but normal glucose
9. Past Medical History
- Prior episodes of HHS or DKA
- Type 2 diabetes — duration, HbA1c, current regimen
- Cardiovascular disease, CKD, cerebrovascular disease
- Psychiatric illness (antipsychotic use)
- Prior infections, immunocompromised state
- Surgical history (recent procedures can precipitate)
10. Physical Exam
- Vitals: Tachycardia, hypotension (orthostatic or frank), tachypnea (but NOT Kussmaul pattern in pure HHS), hypothermia or fever
- Dehydration: Dry mucous membranes, poor skin turgor, sunken eyes, delayed capillary refill
- Neuro: GCS assessment — lethargy, obtundation, coma; focal deficits may be present (hemiparesis, aphasia from hyperosmolality); seizures [5-6]
- Absent Kussmaul breathing — distinguishes from DKA
- Absent fruity/acetone breath — distinguishes from DKA [3]
- Abdominal exam: Distension (gastroparesis), tenderness (evaluate for surgical abdomen as precipitant)
- Extremities: Check for signs of DVT, peripheral vascular compromise [17]
11. Lab Studies
12. Imaging
- Chest X-ray: First-line — evaluate for pneumonia (common precipitant), pulmonary edema from aggressive fluid resuscitation
- CT head: Indicated if focal neurologic deficits, seizures, or failure to improve with treatment — rule out stroke (both precipitant and mimic) [7]
- CT abdomen/pelvis: If abdominal pathology suspected as precipitant (pancreatitis, bowel ischemia)
- Imaging is unnecessary if the clinical picture is straightforward with a clear precipitant and expected neurologic findings for the degree of hyperosmolality
13. Special Tests
- Serum osmolality calculator[20]
- Corrected sodium: Add 1.6 mEq/L to measured Na⁺ for every 100 mg/dL glucose above 100 mg/dL — corrected Na⁺ is hypernatremic in 95% of HHS cases [20]
- Anion gap: Calculate to assess for concurrent metabolic acidosis / mixed DKA-HHS
- Point-of-care glucose: Immediate bedside confirmation
- Urine/blood ketones: Rule out significant ketosis
14. ECG
- Obtain on all patients — both to evaluate for ACS as a precipitant and to assess electrolyte-related changes
- Hypokalemia findings (common during treatment): Flattened/inverted T waves, U waves, ST depression, prolonged QT, widened QRS
- Hyperkalemia findings (may be present initially): Peaked T waves, widened QRS, sine wave pattern
- Ischemic changes: ST elevation/depression, new Q waves — ACS can precipitate HHS [2]
- Arrhythmias: Atrial fibrillation (dehydration), ventricular arrhythmias (electrolyte shifts)
- Continuous telemetry recommended during treatment given rapid electrolyte shifts
15. Assessment
- HHS is an endocrine emergency with mortality 10–20% historically, though recent data show improvement to ~0.77% inpatient mortality in some series while other cohorts report 17% for pure HHS [1][3-4]
- Severity correlates with osmolality: Mental status changes typically begin at >330 mOsm/kg; coma at >340–350 mOsm/kg [7]
- Atypical presentations: Younger patients (rising incidence in obese adolescents with new-onset T2DM); mixed DKA-HHS (~27–65% of cases depending on criteria used) [8][15][20]
- Key complications: Thromboembolism (arterial and venous — far greater risk than DKA), rhabdomyolysis, AKI, cerebral edema (especially pediatric), DIC, mesenteric ischemia [7][15-17][21]
- Mortality predictors: Elevated BUN, cystatin C, D-dimer, Charlson Comorbidity Index, age, infection as trigger [14][18]
16. Treatment Plan
Initial stabilization (ABCs)
- Airway protection if GCS severely depressed
- Two large-bore IVs, continuous monitoring, Foley catheter for strict I/Os
Fluid resuscitation (PRIORITY #1): [1][5][13]
- 0.9% NS at 15–20 mL/kg/h (or 1–1.5 L/h) for the first hour
- Reassess hemodynamics, then switch based on corrected Na⁺:
- Corrected Na⁺ high or normal → 0.45% NS at 250–500 mL/h
- Corrected Na⁺ low → continue 0.9% NS at 250–500 mL/h
- When glucose reaches ~300 mg/dL, add D5 to IV fluids and reduce insulin rate
- Target: ~50% of fluid deficit replaced in first 12 hours; remainder over next 12–24 hours
- Avoid overcorrection: Osmolality decline should be <3 mOsm/kg/h (ADA) [13]
Insulin therapy: [5][13]
- Do not start insulin until fluid resuscitation is underway and K⁺ ≥3.3 mEq/L
- ADA: IV bolus 0.1 units/kg, then continuous infusion 0.1 units/kg/h; OR no bolus with infusion at 0.14 units/kg/h
- JBDS: Lower initial rate of 0.05 units/kg/h, titrate up by 1 unit/h as needed
- Target glucose decline: 50–75 mg/dL per hour — if not achieved, double infusion rate
- When glucose <300 mg/dL: reduce insulin to 0.02–0.05 units/kg/h and add D5 to fluids
Potassium replacement: [5][22]
- K⁺ <3.3 mEq/L → Hold insulin, give 20–40 mEq/h IV KCl until K⁺ >3.3
- K⁺ 3.3–5.2 mEq/L → Add 20–40 mEq K⁺ per liter of IV fluids
- K⁺ >5.2 mEq/L → Hold K⁺, recheck in 2 hours
VTE prophylaxis: Consider LMWH given high thrombotic risk [7][14]
Treat the precipitant: Antibiotics for infection, cardiology for ACS, neurology for stroke [1-2]
17. Disposition
- ICU admission is generally required for all patients with HHS — these are critically ill patients requiring continuous monitoring, IV insulin infusion, and frequent lab reassessment [6]
- Step-down/telemetry: Consider once osmolality normalizing, mental status improving, hemodynamically stable, and transitioned to subcutaneous insulin
- Specialist consultation: Endocrinology (all cases), nephrology (if rhabdomyolysis or severe AKI), vascular surgery (if arterial thrombosis), neurology (if stroke suspected)
- Discharge criteria: Osmolality <315 mOsm/kg, glucose <250 mg/dL, mental status at baseline, tolerating oral intake, stable on subcutaneous insulin regimen, precipitant treated
Critical pitfall: Transition to subcutaneous insulin must include basal insulin given 2–4 hours before stopping IV insulin to prevent rebound hyperglycemia [1][23]
18. Follow Up / Return Precautions
- Follow-up: Endocrinology within 1–2 weeks of discharge; PCP within 1 week [1]
- Discharge education: [1][9]
- Sick day rules: Never stop insulin; increase glucose monitoring during illness; maintain hydration
- Signs/symptoms requiring immediate return: persistent vomiting, inability to keep fluids down, confusion, glucose >400 mg/dL, fever unresponsive to treatment
- Medication adherence counseling
- Ensure access to glucose monitoring supplies and insulin
- Expected recovery: Mental status typically improves within 24–48 hours with osmolality correction; full metabolic normalization over 48–72 hours
- Recurrence prevention: Many patients post-HHS can be managed long-term with oral agents ± insulin once the acute precipitant resolves; structured diabetes education reduces readmission [1][11]
- Long-term mortality risk: Patients discharged after hyperglycemic crises have a 1-year age-corrected mortality rate 13 times higher than the general population [1]
Images
References
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