What to do for a patient with hypernatremia (elevated sodium level of 147) on a Comprehensive Metabolic Panel (CMP)?

Management of Mild Hypernatremia (Sodium 147 mEq/L)

For a sodium level of 147 mEq/L, you should first assess the patient's volume status and identify the underlying cause, then provide free water replacement with hypotonic fluids if hypovolemic, or implement fluid restriction if hypervolemic, while correcting at a maximum rate of 10-15 mmol/L per 24 hours. 1, 2

Initial Assessment

Determine volume status immediately by examining for:

• Hypovolemic signs: orthostatic hypotension, dry mucous membranes, decreased skin turgor, tachycardia 3, 2
• Hypervolemic signs: peripheral edema, ascites, jugular venous distention, pulmonary congestion 3, 2
• Euvolemic: normal vital signs, no edema, normal mucous membranes 2, 4

Check urine osmolality and sodium to differentiate causes:

• Urine osmolality >600-800 mOsm/kg suggests extrarenal water loss (dehydration, insensible losses) 4, 5
• Urine osmolality <300 mOsm/kg with hypernatremia indicates diabetes insipidus 4, 5
• Urine sodium <20 mmol/L suggests extrarenal losses; >20 mmol/L suggests renal losses 2, 4

Treatment Based on Volume Status

Hypovolemic Hypernatremia (Most Common)

Administer hypotonic fluids to replace free water deficit 1, 2:

• Use 0.45% NaCl (half-normal saline) for moderate hypernatremia 1, 2
• Use 0.18% NaCl or D5W for more aggressive free water replacement if needed 1, 2
• Never use isotonic saline (0.9% NaCl) as initial therapy - this will worsen hypernatremia 1, 2

Calculate free water deficit using: Water deficit = 0.5 × body weight (kg) × [(current Na/140) - 1] 1, 2

Euvolemic Hypernatremia

Evaluate for diabetes insipidus if urine osmolality is inappropriately low (<300 mOsm/kg) 4, 5:

• Central diabetes insipidus: trial of desmopressin (DDAVP) 4, 6
• Nephrogenic diabetes insipidus: ongoing hypotonic fluid administration required 1, 4

Provide free water orally if patient can tolerate (preferred route) or via nasogastric tube 1, 2

Hypervolemic Hypernatremia (Rare)

Implement fluid restriction to 1.5-2 L/day 1, 2:

• Focus on achieving negative water balance rather than aggressive fluid administration 1
• In heart failure patients, limit fluid intake to around 2 L/day 1
• In cirrhosis, discontinue IV fluids and restrict free water 1

Critical Correction Rate Guidelines

For chronic hypernatremia (>48 hours duration):

• Maximum correction rate: 10-15 mmol/L per 24 hours 1, 4, 6
• Do not exceed 0.4 mmol/L per hour 4, 6
• Correcting too rapidly causes cerebral edema, seizures, and permanent neurological injury 1, 4, 6

For acute hypernatremia (<24-48 hours):

• Can correct more rapidly, up to 1 mmol/L/hour if severely symptomatic 1, 4
• Still monitor closely to avoid overcorrection 4, 6

Monitoring Protocol

Check serum sodium every 2-4 hours initially during active correction, then every 6-12 hours 1, 2:

• Monitor daily weight, vital signs, and fluid balance 1, 2
• Track urine output, specific gravity, and urine osmolality 1, 2
• Assess neurological status frequently for confusion, altered mental status, or seizures 2, 4

Common Causes to Address

Identify and treat the underlying etiology 2, 4:

• Inadequate water intake (impaired thirst, lack of access to water) 2, 4, 5
• Excessive water loss (diarrhea, vomiting, burns, fever) 2, 4
• Medications causing nephrogenic diabetes insipidus (lithium, demeclocycline) 4, 5
• Osmotic diuresis (hyperglycemia, mannitol) 4, 5
• Excessive sodium intake (rare but can be fatal) 7

Common Pitfalls to Avoid

Never correct chronic hypernatremia faster than 10-15 mmol/L per 24 hours - this causes cerebral edema and seizures 1, 4, 6

Never use isotonic saline in patients with renal concentrating defects - this exacerbates hypernatremia 1, 2

Do not delay treatment while pursuing extensive diagnostic workup - begin correction based on volume status assessment 2

Avoid inadequate monitoring during correction - check sodium levels every 2-4 hours initially to prevent overcorrection or undercorrection 1, 2

Special Populations

Older adults require extra caution due to reduced renal function, cognitive impairment affecting thirst recognition, and higher risk of complications 1

Heart failure patients need careful fluid management - avoid excessive fluid administration and consider combining IV hypotonic fluids with free water via nasogastric tube 1

Cirrhotic patients with hypervolemic hypernatremia should focus on negative water balance rather than aggressive fluid replacement 1