Rosen & Barkin's 5-Minute Emergency Medicine Consult (364 page)

BASICS

Hypernatremia definition: Sodium >145 mEq/L:

• Mild hypernatremia: Serum sodium 146–155 mEq/L
  
• Severe hypernatremia: Serum sodium >155 mEq/L
  

Divided into 3 categories

• Most common
  
• Loss or deficiency of water and sodium with water losses being greater than sodium losses
  
• Examples:
  
  • Renal failure
    
  • Medications (e.g., diuretics, lactulose)
    
  • Osmotic diuresis (mannitol, glucosuria, high protein feedings)
    
  • Insensible losses (burns, sweating)
    
  • Respiratory loss
    
  • Defective thirst mechanism
    
  • Lack of access to water
    
  • Diarrhea/vomiting
    
  • Intubated patients
    

• Water deficiency without sodium loss; free water loss
  
• Examples:
  
  • Fever
    
  • Hypothalamic diabetes insipidus (DI):
    
    • Head trauma
      
    • Tumor
      
    • Congenital
      
    • Infection (TB, syphilis, mycoses, toxoplasmosis, encephalitis)
      
    • Granulomatous disease (sarcoid, Wegner)
      
    • Cerebrovascular accident
      
    • Aneurysm
      
  • Nephrogenic DI:
    
    • Congenital
      
    • Drugs (lithium, amphotericin B, foscarnet, demeclocycline)
      
    • Obstructive uropathy
      
    • Chronic tubulointerstitial disease (sickle cell nephropathy, multiple myeloma, amyloidosis, sarcoidosis, systemic lupus erythematosus, polycystic kidney)
      
    • Electrolyte disorders (hypercalcemia, potassium depletion)
      

• Gain of water and sodium, with sodium gain greater than water gain.
  
• Examples:
  
  • Iatrogenic—most common cause:
    
    • Sodium bicarbonate administration
      
    • NaCl tablets
      
    • Hypertonic parenteral hyperaliment
      
    • Hypertonic IV fluid (IVF)
      
    • Hypertonic dialysis
      
  • Hypertonic medicine preparations such as ticarcillin and carbenicillin
    
  • Cushing disease
    
  • Adrenal hyperplasia
    
  • Primary aldosteronism
    
  • Sea water drownings
    

• More prone to iatrogenic causes
  
• More likely to die or to have permanent neurologic sequelae
  
• Morbidity ranges from 25% to 50%.
  
• May present with high-pitched cry, lethargy, irritability, muscle weakness
  
• Poor breast feeding and inappropriate formula preparations are a potential cause in neonates
  
• If hypernatremia is due to DKA, follow pediatric DKA protocols for fluid resuscitation
  
• DDAVP dose for 3 mo–12 yr is 5–30 μg/day intranasally
  
  • Consider NG hydration
    

• Most commonly affected group due to impaired renal concentrating ability and reduced thirst mechanism
  
• Consider neglect if underlying etiology is dehydration alone
  

• May encounter transient DI of pregnancy
  
• Vasopressin and desmopressin are category B drugs in pregnancy
  
• Hydration status much more difficult to evaluate accurately by exam
  

DIAGNOSIS

• Most symptoms attributed to underlying cause (e.g., dehydration)
  
• More marked with acute changes
  
• Death likely to occur with sodium of ≥185 mEq/L
  
• May see the following symptoms, usually at levels ≥160 mEq/L:
  
  • Neurologic:
    
    • Headache
      
    • Tremulousness
      
    • Irritability
      
    • Ataxia
      
    • Mental confusion
      
    • Delirium
      
    • Seizures
      
    • Coma
      
    • Hyperreflexia
      
    • Asterixis
      
    • Chorea
      
    • Subarachnoid, intracerebral, and subdural hemorrhages
      
    • Dural sinus thrombosis
      
  • Musculoskeletal:
    
    • Spasticity
      
    • Muscle weakness
      
    • Muscle twitching
      
  • Other:
    
    • Anorexia
      
    • Tachypnea
      
    • Poor skin turgor
      
    • Nausea/vomiting
      

• Tachycardia
  
• Orthostasis
  
• Dry mucous membranes
  
• Oliguria
  
• Azotemia
  

• Pulmonary edema
  
• Peripheral edema
  

• Evaluate for hydration status
  
• Look at mucous membranes, neck veins, and skin turgor
  
• Perform a complete neurologic exam and repeat throughout ED stay
  
• Obtain orthostatic vital signs
  

Serum Na
⁺
level

• Electrolytes, BUN/creatinine, glucose
  
• CBC
  
• Urinalysis:
  
  • Specific gravity
    
  • Urine/serum osmolality
    
  • Urine Na
    ⁺
    

• CXR:
  
  • For infection/aspiration
    
  • Pulmonary edema with hypervolemic hypernatremia
    
• CT brain:
  
  • For altered mental status
    
  • Venous sinus thrombosis
    
  • Subarachnoid hemorrhages
    
  • Subdural hematoma
    

Consider Foley catheter to accurately monitor input and output

• Diabetic ketoacidosis
  
• Hyperosmolar coma
  
• Primary CNS lesions
  

TREATMENT

Volume resuscitation if hypovolemic or evidence of hemodynamic compromise

• ABCs
  
• 0.9% NS IV bolus for severe hypotension
  
• Naloxone, thiamine, D
  ₅₀
  W (or Accu-Chek) for altered mental status
  

General:

• Calculate water deficit:
  
  • Water deficit = 0.6 (weight in kg) × (1 − desired sodium/actual sodium)
    
• Do not rapidly correct hypertonicity to normal serum osmolality:
  
  • Rapid correction may cause seizures.
    
  • Reduce serum sodium level by <0.5–0.7 mEq/L/hr.
    

• Replace volume contraction with 0.9% NS IV bolus.
  
• Change to D
  ₅
  W or hypotonic saline once volume replenished and hemodynamically stable.
  

• Calculate water deficit.
  
• Correct water deficit with D
  ₅
  W or hypotonic saline:
  
  • Replace half of deficit in 1st 24 hr, then remainder over 1–2 days.
    

• Remove excess water with diuretics or dialysis.
  
• When euvolemic, replace water deficit with D
  ₅
  W.
  
• Avoid hypertonic saline solutions because patient already has excess of total body sodium.
  

• Sodium restriction
  
• Desmopressin:
  
  • Aqueous vasopressin (DDAVP)
    
  • Best therapeutic agent
    
• Chlorpropamide (Diabinese) enhances effect of vasopressin at renal tubule.
  
• Carbamazepine causes release of vasopressin.
  
• Hydrochlorothiazide enhances sodium excretion.
  
• Discontinue DI-inducing drugs.
  

• Chlorpropamide (Diabinese): 100–500 mg/d
  
• Vasopressin (DDAVP): 1–2 μg IV/SC q12h or 5–20 μg intranasally
  

Volume correction starting initially with NS

Correct the underlying cause.

FOLLOW-UP

• Newly diagnosed sodium >150 mEq/L for monitoring and treatment
  
• Admit sodium >160 mEq/L or symptomatic patients to ICU.
  

• Sodium <150 mEq/L in asymptomatic patient
  
• Sodium >150 mEq/L in patients with history of chronically elevated sodium who are at their baseline and asymptomatic