How to manage a patient with hypernatremia (elevated serum sodium)?

Management of Hypernatremia (Elevated Serum Sodium)

Immediate Assessment and Diagnosis

For hypernatremia, immediately assess volume status, measure urine osmolality and sodium, and determine chronicity (acute <24-48 hours vs. chronic >48 hours), as the rate of correction depends critically on these factors. 1, 2, 3

Key Diagnostic Steps

• Volume status determination: Look specifically for orthostatic hypotension, dry mucous membranes, decreased skin turgor (hypovolemic), versus peripheral edema, ascites, jugular venous distention (hypervolemic) 3
• Urine osmolality: <300 mOsm/kg suggests diabetes insipidus; >600 mOsm/kg indicates appropriate renal water conservation 3
• Urine sodium: Helps differentiate renal vs. extrarenal losses 3
• Exclude pseudohypernatremia from hyperglycemia or hyperlipidemia 3
• Measure ongoing urinary electrolyte-free water clearance to guide replacement 3

Treatment Algorithm

Step 1: Calculate Water Deficit

Water deficit (L) = 0.6 × body weight (kg) × [(current Na/140) - 1] 1, 3

This represents the baseline deficit that must be replaced, in addition to ongoing losses and insensible losses (typically 500-1000 mL/day) 3

Step 2: Determine Correction Rate Based on Chronicity

For chronic hypernatremia (>48 hours): Reduce sodium by no more than 8-10 mmol/L per 24 hours to prevent cerebral edema from osmotic demyelination. 4, 2, 3

• Chronic hypernatremia (>48 hours): Maximum 8-10 mmol/L per day reduction 2, 3
• Acute hypernatremia (<24 hours): Can correct more rapidly, but still monitor closely 2
• Severe symptoms (confusion, seizures, coma): May require faster initial correction but transition to slower rate once stabilized 1, 5

Step 3: Select Replacement Fluid

Use hypotonic fluids for hypernatremia correction:

• 0.45% NaCl (half-normal saline): Contains 77 mEq/L sodium; appropriate for moderate hypernatremia 6
• 0.18% NaCl (quarter-normal saline): Contains 31 mEq/L sodium; for more aggressive free water replacement 6
• D5W (5% dextrose in water): Provides pure free water; use for severe hypernatremia or when sodium >160 mmol/L 6, 1

Never use isotonic saline (0.9% NaCl) in patients with renal concentrating defects or diabetes insipidus, as this will worsen hypernatremia. 6

Step 4: Address Underlying Cause

• Diabetes insipidus: Administer desmopressin (Minirin) 1-4 mcg subcutaneously or intravenously 2
• Dehydration with impaired thirst: Ensure adequate water access and oral intake if possible 1, 5
• Excessive sodium intake: Discontinue hypertonic saline or sodium-containing medications 2
• Renal losses: Address diuretic use, osmotic diuresis from hyperglycemia 3

Step 5: Monitoring Protocol

Check serum sodium every 2-4 hours during active correction, then every 6-8 hours once stable. 2, 3

• Monitor for signs of cerebral edema: worsening confusion, seizures, increased intracranial pressure 5
• Track fluid balance meticulously, including insensible losses 3
• Adjust replacement rate if correction is too rapid or too slow 3

Special Populations

Critically Ill Patients

Hypernatremia is an independent risk factor for mortality in ICU patients and requires aggressive but controlled correction. 7

• Intensivists must actively manage water balance as patients cannot regulate via thirst 7
• Consider diuretics to promote renal sodium excretion if sodium overload is present 7
• Monitor for multiorgan dysfunction associated with severe hypernatremia 7

Pediatric Patients

Hypernatremic dehydration in children has the highest morbidity and mortality rate among electrolyte disorders, primarily from CNS dysfunction. 5

• Correct slowly even in acute cases to prevent cerebral edema 5
• Monitor neurological status continuously during correction 5
• CNS damage can occur from hypernatremia itself or from overly rapid correction 5

Patients with Liver Disease

In cirrhotic patients, sodium levels of 150 mmol/L indicate worsening hemodynamic status and require careful management. 6

• These patients are at higher risk for complications from both hypernatremia and rapid correction 6
• Consider albumin infusion alongside hypotonic fluid replacement 6

Critical Pitfalls to Avoid

• Overly rapid correction (>10 mmol/L per day in chronic hypernatremia) causes cerebral edema and seizures 2, 5, 3
• Using isotonic saline in patients with diabetes insipidus or renal concentrating defects worsens hypernatremia 6
• Inadequate monitoring during correction leads to overcorrection or undercorrection 2, 3
• Ignoring ongoing losses: Must replace insensible losses (500-1000 mL/day) plus any ongoing urinary or GI losses 3
• Starting renal replacement therapy without adjusting for chronic hypernatremia can cause precipitous sodium drops 2

Hemodialysis Consideration

For acute hypernatremia (<24 hours) with severe symptoms, hemodialysis is an effective option to rapidly normalize sodium levels. 2

However, in chronic hypernatremia, dialysis initiation must be carefully managed to avoid rapid sodium correction 2