From the Guidelines
The workup for hypernatremia should prioritize identifying the underlying cause and assessing the patient's volume status, with a focus on calculating the free water deficit and evaluating for potential causes such as inadequate water intake, excessive water loss, or iatrogenic sodium administration. A systematic approach is crucial, starting with a thorough history and physical examination, including measurements of serum sodium, osmolality, urine sodium, and urine osmolality 1. The calculation of the free water deficit is essential to determine replacement needs, and assessing volume status involves examining vital signs, skin turgor, mucous membranes, and orthostatic changes.
Additional laboratory tests, such as serum glucose, potassium, calcium, blood urea nitrogen, creatinine, and urine specific gravity, can help identify potential causes of hypernatremia. In cases of euvolemic hypernatremia, consideration of diabetes insipidus and performance of water deprivation testing if appropriate is necessary, as outlined in the international expert consensus statement on the diagnosis and management of congenital nephrogenic diabetes insipidus 1. For hypervolemic hypernatremia, evaluation for conditions like hyperaldosteronism or Cushing's syndrome is required.
Key aspects of the workup include:
- Calculating the free water deficit to guide replacement therapy
- Evaluating volume status to determine if the patient is hypovolemic, euvolemic, or hypervolemic
- Assessing for potential causes of hypernatremia, including inadequate water intake, excessive water loss, or iatrogenic sodium administration
- Performing additional laboratory tests to identify underlying conditions
- Considering diabetes insipidus in cases of euvolemic hypernatremia and performing water deprivation testing if necessary
Treatment should address the underlying cause while carefully correcting sodium levels at a rate not exceeding 0.5 mEq/L/hour to prevent cerebral edema, particularly in chronic cases, as recommended in the management of hypernatremia 1. The importance of a thorough workup cannot be overstated, given the significant neurological consequences of hypernatremia due to cellular dehydration, with mortality rates of 40-60% in hospitalized patients.
From the Research
Workup for Hypernatremia
The workup for hypernatremia involves several steps to determine the underlying cause and guide treatment.
- Exclude pseudohypernatremia
- Confirm glucose-corrected sodium concentrations
- Determine the extracellular volume status
- Measure urine sodium levels
- Measure urine volume and osmolality
- Check ongoing urinary electrolyte free water clearance
- Determine arginine vasopressin/copeptin levels
- Assess other electrolyte disorders 2
Diagnostic Approach
A systematic approach to the diagnosis of hypernatremia includes:
- Thorough history taking and physical examination
- Laboratory evaluation, including serum osmolality, urine osmolality, and urine sodium concentration 3
- Measurement of serum and urine osmolality and urine sodium concentration to establish the primary underlying causes 4
Management
Management of hypernatremia involves:
- Replacing water deficits, ongoing water losses, and insensible water losses
- Identifying underlying causes
- Distinguishing between acute and chronic hypernatremia
- Determining the amount and rate of water administration
- Selecting the type of replacement solution
- Adjusting the treatment schedule
- Considering additional therapy for diabetes insipidus 2