High sodium levels

Disease Description (Causes and Symptoms)

• Definition summary: A condition in which the blood sodium concentration (serum Na+) rises to typically 145 mEq/L or higher, increasing plasma osmolality (hypernatremia).
• Pathophysiology: When total body water decreases relatively (water loss > sodium loss) or excess sodium accumulates, plasma osmolality increases and water moves from inside the cells to outside the cells (cellular contraction). The main concern is neurological symptoms, particularly those caused by a decrease in brain-cell volume.
• Main causes
  • Inadequate water intake (reduced central thirst mechanism, dysphagia, inadequate voluntary intake in older adults and infants)
  • Diabetes insipidus (central or nephrogenic DI)
  • Hyperglycemic osmotic diuresis (in severe hyperglycemia)
  • Water loss due to fever, vomiting, diarrhea, etc.
  • Excessive salt or hyperosmolar fluid (hyperosmolar intravenous fluid) administration
  • Impaired water retention due to kidney disease
• Main symptoms
  • Mild cases: thirst, nausea, loss of appetite, decreased skin turgor, lethargy
  • Severe/acute cases: headache, anxiety/agitation, ataxia, stupor, delirium, seizures, coma
  • Physical findings: signs of dehydration (dry mouth, hypotension, tachycardia), changes in urine volume (polyuria in diabetes insipidus)

Treatment Methods

• Diagnosis and classification
  • Measure serum sodium (criterion: 145 mEq/L or higher) and check plasma osmolality
  • Assess fluid status (hypovolemic, isovolemic, hypervolemic)
  • Check urine volume, urine osmolality, urine Na+, blood glucose, and kidney function
  • Determine whether it is acute (onset <48 hours) or chronic (>48 hours)
• Basic principles
  • In hemodynamically unstable cases: stabilize the circulation first (immediately administer isotonic fluid, e.g., 0.9% NaCl)—in hypovolemic states, first improve blood pressure and perfusion
  • After hemodynamic stabilization, gradually lower the sodium concentration (decrease osmolality) to prevent cerebral edema
• Rate of correction (important)
  • Even with acute, severe symptoms (e.g., seizures, coma), an excessively rapid decrease is dangerous; therefore, it generally should not decrease by more than 1 mEq/L per hour (careful adjustment is recommended even in acute cases).
  • For chronic or asymptomatic cases: 0.5 mEq/L or less per hour (approximately ≤10 mEq/L per day) is recommended.
• Choice of fluid therapy
  • Hypovolemic hypernatremia: stabilize hemodynamics with 0.9% normal saline for initial resuscitation, then gradually switch to a hypotonic fluid (5% dextrose in water (D5W) or 0.45% NaCl)
  • In isovolemic or hypervolemic cases: depending on the cause, use diuretics (in acute edema), or restrict salt and administer hypotonic fluid
  • In diabetic osmotic diuresis: control blood glucose + replace water
• Cause-specific treatment
  • Central diabetes insipidus: administer desmopressin (DDAVP)
  • Nephrogenic diabetes insipidus: ensure water intake, restrict salt, use thiazide diuretics, a low-protein and low-salt diet, etc., and correct the underlying cause
  • Excessive salt intake/administration: restrict salt intake and gradually correct with fluids
• Monitoring
  • Measure serum Na+ every 2–4 hours initially (more frequently during correction)
  • Monitor body weight, urine volume, vital signs, and neurological status
• Other
  • Patients with severe neurological symptoms (seizures/coma) or unstable patients should be managed in an intensive care unit
  • For patients with kidney disease, consider restricting sodium intake (e.g., 500–2,000 mg/day; individual needs vary)

Checklist Before an Outpatient Visit (Including Example Questions)

• What to prepare
  • A list of recently taken medications (diuretics, lithium, antipsychotics, etc.)
  • Recent test results (serum Na+, Cr, blood glucose, urinalysis, etc.)
  • A record of when symptoms began and how they have changed (when they started, suddenly or gradually)
  • Changes in daily water intake and urine volume (polyuria/oliguria·anuria)
  • Changes in body weight (within the past week)
  • Associated symptoms (vomiting, diarrhea, fever, degree of thirst, changes in consciousness)
• Examples of information to provide at the outpatient visit (preparation before referral)
  • Whether intravenous fluids were recently administered (at a hospital or long-term care facility)
  • Whether dysphagia or intake restrictions are present (need for meal assistance)
• Example questions that patients can record and bring with them (recommended)
  • How many times a day do you drink water, and how many ml each time?
  • How many times a day do you urinate, and has the amount increased or decreased?
  • Have you recently had a fever, diarrhea, or vomiting?

Examples of General Questions to Ask the Doctor

• "What is my blood sodium level, and is it acute or chronic?"
• "What is the target correction level, and what fluid do you plan to give and how quickly?"
• "What are the side effects of this medication (the prescribed medication), and how will they be monitored?"
• "What should I be careful about in my lifestyle to prevent recurrence?"

Examples of Disease-Specific Questions

• "If diabetes insipidus is the cause in my case, how will you distinguish between central and nephrogenic diabetes insipidus, and do I need desmopressin?"
• "How many mEq/L per day is it safe to lower my blood sodium? How often will blood tests be performed during correction?"

(Note: Treatment, correction rate, medications, and other factors vary depending on the patient's condition, so medical professionals must make decisions based on an individual examination and test results.)