Sodium Imbalances

Sodium Imbalances – Nursing Notes

Key Points

Sodium is the major extracellular electrolyte that regulates fluid balance, nerve transmission, and muscle contraction.

Normal serum sodium range: 135–145 mEq/L.

Imbalances occur as Hyponatremia (<135) or Hypernatremia (>145).

Both conditions primarily affect the brain due to fluid shifts across cell membranes(Always prioritize neurological assessment)

Correction should be slow and controlled to prevent fatal complications.

SODIUM (135–145 mEq/L)

Key Functions:

Works with water to control fluid balance & plasma osmolality
Essential for nerve impulse transmission and muscle contraction.

Dietary sources: Table salt, Butter, cheese, Canned foods, mustard, Processed foods.

HYPONATREMIA (Na < 135 mEq/L)

Causes

A. Increased Sodium Excretion

Vomiting, Diarrhea
Diuretics
Kidney disease

B. Inadequate Sodium Intake - Low-salt diet, Fasting or NPO

C. Dilutional Hyponatremia (Water Excess)

Excess hypotonic fluids (oral/irrigation),
Freshwater drowning,
SIADH (↑ ADH), Hyperglycemia, Heart failure

Pathophysiology:

Low extracellular sodium causes osmotic water shift into cells causing cell swelling, especially in brain which leads to neurological and systemic symptoms.

Signs & Symptoms

Weakness, cramps, twitching ( Due to impaired muscle contraction)
Headache, confusion, lethargy (Due to Incr. ICP, Cerebral edema)
Seizures, coma (In severe hyponatremia)
Hypovolemic type: Hypotension, tachycardia, dry mucosa
Hypervolemic type: Edema, weight gain, hypertension
Hyponatremia - Increases Lithium toxicity risk

Interventions

Monitor cardio, respiratory, neuro, renal & GI status.
If hypovolemic: IV 0.9% NaCl.
If hypervolemic: Osmotic diuretics- Mannitol (remove water, retain sodium)
SIADH: ADH antagonists (demeclocycline, tolvaptan)
Increase dietary sodium if advised.

HYPERNATREMIA (Na > 145 mEq/L)

Causes

A. Sodium Gain

IV hypertonic saline / sodium bicarbonate
Sodium-containing drugs
Excess oral sodium (seawater ingestion)

B. Poor Sodium Excretion

Hyperaldosteronism (Aldosterone increases sodium retention)
Cushing’s syndrome (High cortisol acts like aldosterone)
Corticosteroids
Kidney disease

B. Water deficit

Diabetes insipidus (low ADH, leads to profuse dilute urine)
Diuretics and Osmotic diuresis (Hyperglycemia)
Fever, excessive sweating
Watery diarrhea
Inadequate Water Intake

Pathophysiology

"Hyperosmolality (High sodium) in ECF, pulls water out of cells, causing cellular dehydration"

Clinical Manifestations

Intense thirst, Dry, sticky mucous membranes,
Flushed skin
Agitation, restlessness,
Confusion, Seizures, coma
Orthostatic hypotension, tachycardia

Interventions

Monitor cardiac, respiratory, neuro, renal & integumentary status
If water deficit: Oral or IV hypotonic/isotonic fluids (D5W, 0.45% NaCl) slowly
If sodium excess: Use loop diuretics with sodium-free IV fluids(D5W) to promote sodium excretion.
Restrict sodium intake
Treat underlying cause:
- - Diabetes insipidus →Treat with Desmopressin to replace ADH.
  - Cushing’s syndrome / Hyperaldosteronism: Treat with surgery (adrenalectomy) or medications such as spironolactone (aldosterone antagonist).
  - Osmotic diuresis as in hyperglycemia → Control blood glucose with insulin.

Comparison Table - Hyponatremia vs. Hypernatremia

Feature	Hyponatremia (<135 mEq/L)	Hypernatremia (>145 mEq/L)
Main Cause	Sodium loss or water excess	Sodium gain or water loss
Neuro Signs	Confusion, seizures, coma	Restlessness, seizures, coma
Skin/Mucosa	Pale, dry if hypovolemic	Flushed, dry mucous membranes
Treatment	Normal saline, if deficit; osmotic diuretics, if water excess	Hypotonic fluids, if deficit; D5W + loop diuretics, if sodium excess
Key Risk	Brain swelling → respiratory arrest	Brain shrinkage → seizures, coma

Remember for Exams!

Hyponatremia (<135): Most critical complication is cerebral edema
Severe hyponatremia can progress to respiratory arrest due to cerebral edema and brainstem compression.
Hypernatremia (>145): Most critical complications – Seizures, coma, and potentially fatal brain herniation.
Earliest sign of hyponatremia: Change in level of consciousness (LOC) → Neurological checks are the first priority
Earliest protective sign of hypernatremia: Thirst (alert patients rarely get severe hypernatremia).
Correction of hyponatremia must be slow → rapid correction causes Osmotic Demyelination Syndrome (permanent brain damage)
Correction of hypernatremia must be gradual → rapid fall in sodium leads to cerebral edema.
Remember: “Hyponatremia swells the brain, Hypernatremia shrinks the brain.”