How to manage hyponatremia (low sodium levels) in a patient with fever?

Hyponatremia During Fever: Management Approach

Initial Assessment and Diagnostic Workup

Fever-associated hyponatremia requires immediate evaluation of volume status, symptom severity, and underlying etiology before initiating treatment. 1

The diagnostic workup should include:

• Serum and urine osmolality to confirm hypotonic hyponatremia and assess water excretion capacity 1
• Urine sodium concentration - values <30 mmol/L suggest hypovolemia (71-100% positive predictive value for saline responsiveness), while >20-40 mmol/L with high urine osmolality suggests SIADH 1
• Serum uric acid - levels <4 mg/dL have 73-100% positive predictive value for SIADH 1
• Assessment of extracellular fluid volume status through physical examination: look for orthostatic hypotension, dry mucous membranes, decreased skin turgor (hypovolemia) versus peripheral edema, ascites, jugular venous distention (hypervolemia) 1

Fever as a Nonosmotic Stimulus for Hyponatremia

Fever, like other acute illness states, represents a nonosmotic stimulus for arginine vasopressin (AVP) release, leading to impaired free water excretion and hyponatremia. 2 Pain, nausea, and stress associated with febrile illness trigger AVP excess, placing patients at risk when electrolyte-free water is supplied 1. This creates a SIADH-like state where water retention occurs followed by physiologic natriuresis 1.

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Seizures, Coma, Altered Mental Status)

For severe symptoms, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until symptoms resolve. 1, 3

• Give 100 mL boluses of 3% saline over 10 minutes, repeating up to three times at 10-minute intervals until symptoms improve 1
• Total correction must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 3
• Monitor serum sodium every 2 hours during initial correction 1
• ICU admission is required for close monitoring 1

Mild to Moderate Symptomatic Hyponatremia

Treatment depends on volume status determination:

For Hypovolemic Hyponatremia (most common with fever-induced dehydration):

• Discontinue any diuretics immediately 1
• Administer isotonic saline (0.9% NaCl) for volume repletion at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on response 1
• Avoid hypotonic fluids (lactated Ringer's, 0.45% saline, D5W) which worsen hyponatremia 1
• Once euvolemic, switch to maintenance isotonic fluids at 30 mL/kg/day 1

For Euvolemic Hyponatremia (SIADH from fever/infection):

• Fluid restriction to 1 L/day is the cornerstone of treatment 1, 3
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• Consider vasopressin receptor antagonists (tolvaptan 15 mg once daily) for resistant cases 1

For Hypervolemic Hyponatremia (if concurrent heart failure/cirrhosis):

• Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
• Temporarily discontinue diuretics if sodium <125 mmol/L 1
• Consider albumin infusion in cirrhotic patients 1
• Avoid hypertonic saline unless life-threatening symptoms present 1

Critical Correction Rate Guidelines

The maximum correction rate is 8 mmol/L in 24 hours for all patients. 1, 3 This is the single most important safety principle to prevent osmotic demyelination syndrome 1.

High-risk patients require even slower correction (4-6 mmol/L per day): 1

• Advanced liver disease
• Alcoholism
• Malnutrition
• Prior encephalopathy
• Severe hyponatremia (<120 mmol/L)

Monitoring During Treatment

• Severe symptoms: Check sodium every 2 hours initially 1
• Mild symptoms: Check sodium every 4 hours after symptom resolution 1
• Asymptomatic/chronic: Check sodium every 24-48 hours 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours: 1

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water)
• Consider administering desmopressin to slow or reverse the rapid rise
• Target relowering to bring total 24-hour correction to ≤8 mmol/L from starting point

Common Pitfalls to Avoid

• Never use fluid restriction as initial treatment for symptomatic hyponatremia - this is a medical emergency requiring hypertonic saline 1
• Never exceed 8 mmol/L correction in 24 hours - overcorrection risks osmotic demyelination syndrome 1, 3
• Never use hypotonic fluids (lactated Ringer's, 0.45% saline) in hyponatremia - these worsen the condition 1
• Never ignore mild hyponatremia (130-135 mmol/L) - even mild hyponatremia increases fall risk (21% vs 5%) and mortality (60-fold increase with sodium <130 mmol/L) 1, 3
• Inadequate monitoring during active correction leads to complications 1
• Failing to recognize and treat the underlying cause (infection, fever) perpetuates the problem 1