What are the symptoms and treatment of hyponatremia?

Symptoms of Hyponatremia

Symptoms of hyponatremia range from mild nonspecific complaints to severe life-threatening neurological manifestations, with severity depending on the degree of hyponatremia and its rate of development. 1, 2

Symptom Presentation by Severity

Mild Hyponatremia (126-135 mEq/L)

• Often asymptomatic or subtle symptoms
• Nonspecific symptoms may include:
  • Weakness
  • Fatigue
  • Headache
  • Nausea
  • Mild cognitive impairment
  • Difficulty concentrating

Moderate Hyponatremia (120-125 mEq/L)

• More pronounced symptoms:
  • Muscle cramps
  • Gait instability
  • Lethargy
  • Headache
  • Dizziness
  • Nausea and vomiting
  • Forgetfulness
  • Apathy
  • Loss of balance 1, 3

Severe Hyponatremia (<120 mEq/L)

• Serious neurological manifestations:
  • Confusion
  • Delirium
  • Seizures
  • Obtundation
  • Coma
  • Brain edema (in acute cases)
  • Cardiorespiratory distress (in severe cases) 1, 2, 4

Factors Affecting Symptom Severity

1. Rate of development:

   • Acute hyponatremia (developing within 48 hours) typically causes more severe symptoms at the same sodium level compared to chronic hyponatremia
   • Chronic hyponatremia allows the brain to adapt through volume regulatory mechanisms

2. Duration of hyponatremia:

   • Chronic hyponatremia (>48 hours) may present with milder symptoms despite low sodium levels due to cerebral adaptation
   • However, chronic mild hyponatremia is associated with:
     • Cognitive impairment
     • Gait disturbances
     • Increased risk of falls and fractures 2

3. Underlying cause:

   • Symptoms may be influenced by the underlying condition causing hyponatremia (cirrhosis, heart failure, SIADH)

Treatment Considerations

Treatment depends on symptom severity, chronicity, and volume status:

For Symptomatic Severe Hyponatremia

• Emergent treatment with hypertonic 3% saline is indicated for life-threatening symptoms (seizures, coma)
• Target initial correction of 4-6 mEq/L within 1-2 hours to reverse severe symptoms
• Limit correction to no more than 10 mEq/L in first 24 hours to prevent osmotic demyelination syndrome (ODS) 1, 2

For Moderate Hyponatremia

• Fluid restriction to 1,000 mL/day is recommended
• For patients with cirrhosis, albumin infusion may be beneficial 1

For Mild Hyponatremia

• Often requires only monitoring and mild fluid restriction
• Address underlying cause 1

Important Caveats

1. Risk of Osmotic Demyelination Syndrome (ODS):

   • Occurs with overly rapid correction of chronic hyponatremia
   • Presents 2-7 days after correction with dysarthria, dysphagia, oculomotor dysfunction, and quadriparesis
   • Higher risk in patients with alcoholism, malnutrition, or advanced liver disease 1, 2

2. Hyponatremia in Cirrhosis:

   • Associated with increased risk of hepatic encephalopathy, hepatorenal syndrome, and spontaneous bacterial peritonitis
   • Even modest hyponatremia (131-135 mEq/L) increases risk of complications 1

3. Chronic Hyponatremia Complications:

   • Associated with cognitive impairment, gait disturbances, falls, and fractures
   • Can be a secondary cause of osteoporosis 2

Treatment should always be tailored based on the underlying cause (hypovolemic, euvolemic, or hypervolemic hyponatremia) and the chronicity of the condition to optimize outcomes and minimize risks.