side by side comparison

Sodium Imbalance: Hyponatremia vs Hypernatremia — Causes, Neuro Signs, Correction

Both sodium imbalances present with altered mental status, but the fluid shift direction is opposite — and so is the neurological picture. Picking the wrong IV fluid or correcting too fast can cause osmotic demyelination or cerebral edema, turning a fixable lab value into permanent brain damage.

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Comparison

Side-by-side2 compared
Dimension
Hyponatremia (< 135 mEq/L)
Hypernatremia (> 145 mEq/L)
Pathophysiology & risk
  • Hypotonic serum
  • water shifts INTO cells
  • SIADH, water intoxication
  • Thiazides
  • HF dilution
  • polydipsia
  • Hypertonic serum
  • water shifts OUT of cells
  • Diabetes insipidus
  • dehydration
  • Hypertonic IV fluids
  • impaired thirst
Signs & symptoms
  • Confusion, lethargy, headache (cells swell then coma)
  • Muscle weakness, cramps, hyporeflexia
  • ★Twitching, hyperreflexia, spasticity
  • Restlessness, irritability (cells shrink then coma)
Diagnostics & labs
  • Serum Na⁺ < 135 mEq/L
  • May appear euvolemic / hypervolemic
  • Serum Na⁺ > 145 mEq/L
  • ↑ urine specific gravity (except DI)
Nursing priorities
  • Seizure precautions
  • neuro checks q1h
  • Serum Na⁺ q2–4h during correction
  • strict I&O
  • Monitor fluid status
  • offer water
  • Serum Na⁺ q2–4h
  • neuro checks, daily weight
Treatment / meds
  • ★Severe/seizures: 3% saline via pump
  • Mild: fluid restriction
  • treat cause
  • Replace free water: D5W or 0.45% NS
  • ★Desmopressin for diabetes insipidus
Patient teaching
  • Follow fluid restriction
  • avoid excess water
  • Report headache, confusion, nausea
  • Drink adequate water
  • don't ignore thirst
  • Report restlessness, dry mouth
Red flags — escalate
  • ★Seizures from cerebral edema
  • Obtundation, falling level of consciousness
  • Seizures if Na⁺ > 160 (acute severe)
  • Rapid level of consciousness decline then coma
Complications
  • Over-fast correction then ODS / CPM
  • Limit: raise Na⁺ ≤ 8 mEq/L per 24 hr
  • Over-fast correction then cerebral edema
  • Limit: lower Na⁺ ≤ 10–12 mEq/L/24 hr
Pathophysiology & risk

Hyponatremia (< 135 mEq/L)

  • Hypotonic serum
  • water shifts INTO cells
  • SIADH, water intoxication
  • Thiazides
  • HF dilution
  • polydipsia

Hypernatremia (> 145 mEq/L)

  • Hypertonic serum
  • water shifts OUT of cells
  • Diabetes insipidus
  • dehydration
  • Hypertonic IV fluids
  • impaired thirst
Signs & symptoms

Hyponatremia (< 135 mEq/L)

  • Confusion, lethargy, headache (cells swell then coma)
  • Muscle weakness, cramps, hyporeflexia

Hypernatremia (> 145 mEq/L)

  • ★Twitching, hyperreflexia, spasticity
  • Restlessness, irritability (cells shrink then coma)
Diagnostics & labs

Hyponatremia (< 135 mEq/L)

  • Serum Na⁺ < 135 mEq/L
  • May appear euvolemic / hypervolemic

Hypernatremia (> 145 mEq/L)

  • Serum Na⁺ > 145 mEq/L
  • ↑ urine specific gravity (except DI)
Nursing priorities

Hyponatremia (< 135 mEq/L)

  • Seizure precautions
  • neuro checks q1h
  • Serum Na⁺ q2–4h during correction
  • strict I&O

Hypernatremia (> 145 mEq/L)

  • Monitor fluid status
  • offer water
  • Serum Na⁺ q2–4h
  • neuro checks, daily weight
Treatment / meds

Hyponatremia (< 135 mEq/L)

  • ★Severe/seizures: 3% saline via pump
  • Mild: fluid restriction
  • treat cause

Hypernatremia (> 145 mEq/L)

  • Replace free water: D5W or 0.45% NS
  • ★Desmopressin for diabetes insipidus
Patient teaching

Hyponatremia (< 135 mEq/L)

  • Follow fluid restriction
  • avoid excess water
  • Report headache, confusion, nausea

Hypernatremia (> 145 mEq/L)

  • Drink adequate water
  • don't ignore thirst
  • Report restlessness, dry mouth
Red flags — escalate

Hyponatremia (< 135 mEq/L)

  • ★Seizures from cerebral edema
  • Obtundation, falling level of consciousness

Hypernatremia (> 145 mEq/L)

  • Seizures if Na⁺ > 160 (acute severe)
  • Rapid level of consciousness decline then coma
Complications

Hyponatremia (< 135 mEq/L)

  • Over-fast correction then ODS / CPM
  • Limit: raise Na⁺ ≤ 8 mEq/L per 24 hr

Hypernatremia (> 145 mEq/L)

  • Over-fast correction then cerebral edema
  • Limit: lower Na⁺ ≤ 10–12 mEq/L/24 hr

★ marks the fact that sets a column apart.

Clinical Pearl

Low sodium, swollen brain, seizures; high sodium, shrunken brain, agitation — correct either one slowly.

Component Topics

HypernatremiaHyponatremia

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