A patient presents with new‑onset gait shuffling, tremor, and muscle weakness and a serum sodium of 129 mmol/L measured five days ago; how should the hyponatraemia be managed?

Management of Hyponatremia with Neurological Symptoms

This patient requires immediate workup to determine if this is chronic hyponatremia (>48 hours) and should NOT be rapidly corrected given the 5-day timeline, as the neurological symptoms (gait shuffling, tremor, muscle weakness) likely represent chronic hyponatremia complications rather than acute cerebral edema.

Critical First Steps

Immediate Assessment Required

Before any treatment, you must:

• Recheck serum sodium NOW - the 5-day-old value of 129 mmol/L may have changed
• Assess volume status (skin turgor, mucous membranes, orthostatic vitals, jugular venous pressure)
• Obtain urine osmolality, urine sodium, and serum osmolality 1
• Evaluate for severe symptoms indicating cerebral edema: altered mental status, seizures, or coma 1

Symptom Severity Classification

The presenting symptoms (gait shuffling, tremor, muscle weakness) represent mild to moderate chronic symptoms, NOT severe acute symptoms. These are consistent with chronic hyponatremia's effects on gait and cognition 2. This distinction is critical because:

• Severe symptoms = mental status changes, seizures, coma → require hypertonic saline 1
• Mild symptoms = nausea, vomiting, headache, weakness → require conservative management 1

Treatment Approach Based on Chronicity

Since Sodium Was 129 Five Days Ago (Chronic Hyponatremia)

Chronic hyponatremia should NOT be rapidly corrected 1. The brain has adapted over days, and rapid correction risks osmotic demyelination syndrome (ODS), which can cause permanent parkinsonism, quadriparesis, or death 2.

Conservative Management Protocol:

1. Fluid restriction to 1 L/day as first-line therapy 1
2. Increase solute intake (salt tablets 100 mEq PO TID, high-protein diet) 1, 3
3. Monitor sodium every 4-6 hours initially 1
4. Target correction rate:
   • Maximum 8 mmol/L in first 24 hours 1
   • Maximum 18 mmol/L in 48 hours 4
   • Ideal target: 6-8 mmol/L per 24 hours 4

If Severe Symptoms Develop (Seizures, Coma, Altered Mental Status)

Only then use 3% hypertonic saline 1:

• Give 100-150 mL bolus 3
• Target: increase sodium by 4-6 mmol/L over 1-2 hours to reverse cerebral edema 2, 5
• STOP at 6 mmol/L increase and reassess 1
• Do NOT exceed 8-10 mmol/L total correction in 24 hours 1, 5

Determining the Underlying Cause

Based on volume status and urine studies 1:

Hypovolemic (likely if dehydrated):

• Cerebral salt wasting (CSW) or diuretic use
• Treatment: Normal saline + fludrocortisone 0.1 mg TID 1

Euvolemic (likely if normal volume status):

• SIADH (most common)
• Treatment: Fluid restriction 1 L/day, consider urea or vaptans if refractory 1, 2, 3

Hypervolemic (unlikely but check):

• Heart failure, cirrhosis, renal failure
• Treatment: Treat underlying condition, fluid restriction 1

Critical Pitfalls to Avoid

1. Do NOT use hypertonic saline for mild symptoms in chronic hyponatremia - this is the most common error and risks ODS 1, 2

2. Monitor for spontaneous overcorrection - if urine output increases dramatically, the patient may develop water diuresis and overcorrect spontaneously 4, 6. Check sodium every 2-4 hours and be ready to give:

   • Desmopressin (DDAVP) 2-4 mcg IV/SC to stop water diuresis 4, 5
   • 5% dextrose in water to re-lower sodium if overcorrection occurs 6, 5

3. The neurological symptoms may worsen before improving - gait disturbances and tremor from chronic hyponatremia can take weeks to resolve even with appropriate correction 2

4. Nearly half of SIADH patients fail fluid restriction alone 3 - have second-line therapy ready (urea 30-60g/day or tolvaptan) 2, 3

Monitoring Protocol

• First 24 hours: Check sodium every 2-4 hours 1
• Monitor urine output closely - sudden polyuria signals risk of overcorrection 4, 6
• Daily weights and strict intake/output 1
• If correction exceeds 8 mmol/L in 24 hours: Give desmopressin and D5W immediately 4, 5