Basics
Description
Hypernatremia definition: Sodium >145 mEq/L:
- Mild hypernatremia: Serum sodium 146-155 mEq/L
- Severe hypernatremia: Serum sodium >155 mEq/L
Etiology
Divided into 3 categories
Hypovolemic Hypernatremia
- 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
Isovolemic Hypernatremia
- 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)
Hypervolemic Hypernatremia
- 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
- 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
Signs and Symptoms
- 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
Hypovolemic Hypernatremia
- Tachycardia
- Orthostasis
- Dry mucous membranes
- Oliguria
- Azotemia
Hypervolemic Hypernatremia
- Pulmonary edema
- Peripheral edema
Physical Exam
- 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
Essential Workup
Serum Na+ level
Diagnosis Tests & Interpretation
Lab
- Electrolytes, BUN/creatinine, glucose
- CBC
- Urinalysis:
- Specific gravity
- Urine/serum osmolality
- Urine Na+
Imaging
- CXR:
- For infection/aspiration
- Pulmonary edema with hypervolemic hypernatremia
- CT brain:
- For altered mental status
- Venous sinus thrombosis
- Subarachnoid hemorrhages
- Subdural hematoma
Diagnostic Procedures/Surgery
Consider Foley catheter to accurately monitor input and output
Differential Diagnosis
- Diabetic ketoacidosis
- Hyperosmolar coma
- Primary CNS lesions
Treatment
Pre-Hospital
Volume resuscitation if hypovolemic or evidence of hemodynamic compromise
Initial Stabilization/Therapy
- ABCs
- 0.9% NS IV bolus for severe hypotension
- Naloxone, thiamine, D50W (or Accu-Chek) for altered mental status
Ed Treatment/Procedures
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.
Hypovolemic Hypernatremia
- Replace volume contraction with 0.9% NS IV bolus.
- Change to D5W or hypotonic saline once volume replenished and hemodynamically stable.
Isovolemic Hypernatremia
- Calculate water deficit.
- Correct water deficit with D5W or hypotonic saline:
- Replace half of deficit in 1st 24 hr, then remainder over 1-2 days.
Hypervolemic Hypernatremia
- Remove excess water with diuretics or dialysis.
- When euvolemic, replace water deficit with D5W.
- Avoid hypertonic saline solutions because patient already has excess of total body sodium.
Diabetes Insipidus Hypernatremia
- 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.
Medication
- Chlorpropamide (Diabinese): 100-500 mg/d
- Vasopressin (DDAVP): 1-2 μg IV/SC q12h or 5-20 μg intranasally
First Line
Volume correction starting initially with NS
Second Line
Correct the underlying cause.
Follow-Up
Disposition
Admission Criteria
- Newly diagnosed sodium >150 mEq/L for monitoring and treatment
- Admit sodium >160 mEq/L or symptomatic patients to ICU.
Discharge Criteria
- 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
Followup Recommendations
Repeat serum sodium levels within a week.
Pearls and Pitfalls
- Up to 30% of acute hypernatremia patients will have permanent neurologic sequelae, a complete and well-documented neurologic exam is a must.
- Patients at extreme ages and with chronic conditions are most susceptible to neurologic complications:
- On going fluid losses may require recalculation of fluid needs
- Repeat lab work to confirm controlled correction of sodium
Additional Reading
- Ellison D. Disorders of sodium and water. Am J Kidney Dis. 2005;46(2):356-361.
- Fall P. Hyponatremia and hypernatremia. A systematic approach to causes and their correction. Postgrad Med. 2000;107(5):75-82.
- Lin M, Lu S, Lim I. Disorders of water imbalance. Emerg Med Clin North Am. 2005;23:749-770, ix.
- Pfennig CL, Slovis CM. Sodium disorders in the emergency department: A review of hyponatremia and hypernatremia. Emerg Med Pract. 2012;14(10):1-20.
- Ranadive SA, Rosenthal SM. Pediatric disorders of water balance. Endocrinol Metabol Clin North Am. 2009;38(4):663-672.
See Also (Topic, Algorithm, Electronic Media Element)
- Diabetic Ketoacidosis
- Hyperosmolar Coma
- Hyponatremia
Codes
ICD9
- 276.0 Hyperosmolality and/or hypernatremia
- 775.5 Other transitory neonatal electrolyte disturbances
ICD10
- E87.0 Hyperosmolality and hypernatremia
- P74.2 Disturbances of sodium balance of newborn
SNOMED
- 39355002 Hypernatremia (disorder)
- 7405009 Acute hypernatremia
- 12403008 Chronic hypernatremia (disorder)
- 206489003 Transitory neonatal hypernatremia (disorder)