From the Guidelines
Hypernatremia is characterized by an elevated sodium concentration in the blood, specifically above 145 mmol/L, resulting from an imbalance between sodium and water in the body, with either too much sodium or too little water. This condition is often iatrogenic, especially in very low birth weight infants (VLBWI), and mostly results from incorrect replacement of transepidermal water loss (TEWL), inadequate water intake, or excessive sodium intake during the transition phase 1. The imbalance between sodium and water can lead to various complications, including cerebral edema, seizures, and neurological injury if not managed properly.
Key Points to Consider
- Hypernatremia can occur due to water deficit rather than sodium excess, with common causes including insufficient fluid intake, excessive water loss through the kidneys, gastrointestinal losses, or increased insensible losses 1.
- The condition creates an osmotic gradient that pulls water out of cells, potentially leading to cellular dehydration, particularly affecting brain cells.
- Treatment should focus on carefully correcting the water deficit while monitoring sodium levels to prevent rapid changes that could cause cerebral edema, especially in chronic cases where the brain has adapted to the hyperosmolar state.
- A reduction rate of 10-15 mmol/L/24h is recommended to avoid rapid correction of hypernatremia, which can induce cerebral edema, seizures, and neurological injury 1.
Management Considerations
- Therapeutic measures should be based on the aetiology of hypernatremia, ascertained by assessment of the infant's intravascular volume and hydration status 1.
- In case of symptomatic hypovolaemia, plasma volume should be replaced to ensure adequate fluid intake and prevent further complications.
From the Research
Definition of Hypernatremia
- Hypernatremia is defined as a serum sodium level above 145 mmol/L 2
- It is a frequently encountered electrolyte disturbance in the hospital setting, with an unappreciated high mortality
Relationship between Sodium and Water
- Hypernatremia requires a comprehension of body fluid compartments, as well as concepts of the preservation of normal body water balance 2
- The human body maintains a normal osmolality between 280 and 295 mOsm/kg via Arginine Vasopressin (AVP), thirst, and the renal response to AVP; dysfunction of all three of these factors can cause hypernatremia 2