History
Patients developing hypernatremia outside of the hospital setting are generally elderly and debilitated, and often present with an intercurrent acute (febrile) illness. Hospital-acquired hypernatremia affects patients of all ages.
The history should be used to discover why the patient was unable to prevent hypernatremia with adequate oral fluid intake. For example, the clinician should determine whether the patient is suffering from an altered mental status or whether there are any factors causing increased fluid excretion (eg, diuretic therapy; diabetes mellitus; or fever, diarrhea, and vomiting). The history should also cover the symptoms and causes of possible diabetes insipidus (eg, the presence of preexisting polydipsia or polyuria, a history of cerebral pathology, or medication use [lithium]).
It is important to find out if the hypernatremia developed acutely or over time, because this will guide treatment decisions.
Risk factors for hypernatremia include the following:
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Advanced age
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Mental or physical impairment
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Uncontrolled diabetes (solute diuresis)
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Underlying polyuria disorders
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Diuretic therapy
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Residency in nursing home, inadequate nursing care
Hospitalized patients may develop hypernatremia because of any of the following:
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Decreased baseline levels of consciousness
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Tube feeding
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Hypertonic infusions
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Osmotic diuresis
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Lactulose
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Mechanical ventilation
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Medication (eg, diuretics, sedatives)
Physical Examination
The examination should include an accurate assessment of volume status and cognitive function. Symptoms can be related to volume deficit and/or hypertonicity and shrinkage of brain cells, which can tear cerebral blood vessels in severe cases, leading to cerebral hemorrhage.
The worsening symptoms associated with hypernatremia may go unnoticed in elderly patients who have a preexisting impairment of their mental status and decreased access to water.
Table 1. Characteristics and symptoms of hypernatremia (Open Table in a new window)
Characteristics of hypernatremia |
Symptoms related to the characteristics of hypernatremia |
Cognitive dysfunction and symptoms associated with neuronal cell shrinkage |
Lethargy, obtundation, confusion, abnormal speech, irritability, seizures, nystagmus, myoclonic jerks |
Dehydration or clinical signs of volume depletion |
Orthostatic blood pressure changes, tachycardia, oliguria, dry oral mucosa, abnormal skin turgor, dry axillae, |
Other clinical findings |
Weight loss, generalized weakness |
In a prospective, case-control, multicenter study, Chassagne and colleagues looked at the symptoms associated with hypernatremia in 150 geriatric patients. [38] The likelihood that patients with hypernatremia would have low blood pressure, tachycardia, dry oral mucosa, abnormal skin turgor, and a recent change in consciousness was significantly greater than that of the controls. The only clinical findings to occur in at least 60% of patients with hypernatremia were orthostatic blood pressure and abnormal subclavicular and forearm skin turgor (poor specificity and sensitivity for all physical findings).
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Figure A: Normal cell. Figure B: Cell initially responds to extracellular hypertonicity through passive osmosis of water extracellularly, resulting in cell shrinkage. Figure C: Cell actively responds to extracellular hypertonicity and cell shrinkage in order to limit water loss through transport of organic osmolytes across the cell membrane, as well as through intracellular production of these osmolytes. Figure D: Rapid correction of extracellular hypertonicity results in passive movement of water molecules into the relatively hypertonic intracellular space, causing cellular swelling, damage, and ultimately death.
Tables
Characteristics of hypernatremia |
Symptoms related to the characteristics of hypernatremia |
Cognitive dysfunction and symptoms associated with neuronal cell shrinkage |
Lethargy, obtundation, confusion, abnormal speech, irritability, seizures, nystagmus, myoclonic jerks |
Dehydration or clinical signs of volume depletion |
Orthostatic blood pressure changes, tachycardia, oliguria, dry oral mucosa, abnormal skin turgor, dry axillae, |
Other clinical findings |
Weight loss, generalized weakness |
