From the Guidelines
Elevated glucose does not directly cause hypernatremia, but it can indirectly contribute to it through osmotic diuresis and excessive free water loss. Hypernatremia is defined as a serum sodium concentration above 145 mEq/L and occurs due to water loss exceeding sodium loss or from excess sodium intake. While elevated glucose (hyperglycemia) can affect sodium levels, it typically causes hyponatremia, not hypernatremia, as high blood glucose draws water from cells into the bloodstream, diluting sodium concentration [ 1 ]. For every 100 mg/dL increase in glucose above normal, serum sodium decreases by approximately 1.6 mEq/L [ 1 ]. However, hyperglycemia can lead to osmotic diuresis, causing excessive urination and significant free water loss without adequate replacement, which may eventually result in hypernatremia, particularly in patients who cannot maintain adequate fluid intake, such as elderly or debilitated individuals [ 1 ].
Key Considerations
- Hyperglycemia typically causes hyponatremia, not hypernatremia
- Osmotic diuresis from hyperglycemia can lead to excessive free water loss and potentially hypernatremia if not adequately replaced
- Treatment focuses on addressing the underlying hyperglycemia with insulin therapy while carefully managing fluid replacement to normalize both glucose and sodium levels
- Close monitoring of weight, fluid balance, and biochemistry is crucial to inform adjustments to the rate of administration and fluid composition [ 1 ].
Management
- Addressing the underlying hyperglycemia with insulin therapy is crucial
- Careful management of fluid replacement to normalize both glucose and sodium levels
- Monitoring of serum osmolality and frequent assessment of cardiac, renal, and mental status must be performed during fluid resuscitation to avoid iatrogenic fluid overload [ 1 ]. In patients who need to fast for prolonged periods, such as prior to anesthesia, intravenous water administration should be provided, and a reasonable initial approach is 5% dextrose (glucose) in water at the usual maintenance rate [ 1 ]. Regular control of blood glucose is recommended to avoid hyperglycemia with subsequent osmotic diuresis [ 1 ]. The infusion of glucose can lead to hyperglycemia, and close monitoring of weight, fluid balance, and biochemistry is crucial to inform adjustments to the rate of administration and fluid composition [ 1 ]. In summary, while elevated glucose does not directly cause hypernatremia, it can indirectly contribute to it, and careful management of fluid replacement and addressing the underlying hyperglycemia are crucial to prevent hypernatremia and other complications.
From the Research
Relationship Between Elevated Glucose and Hypernatremia
- Elevated glucose levels can lead to hypernatremia due to various factors, including fluid exit from the intracellular compartment, thirst, and osmotic diuresis 2.
- Osmotic diuresis can result in losses of both solute and water, leading to hypernatremia if the combined loss of sodium and potassium per liter of urine is lower than the concurrent serum sodium level 3.
- Hyperglycemic patients with hypernatremia often have large deficits of body water and hypovolemia, which can develop severe clinical manifestations and significant mortality 2.
Mechanisms of Hypernatremia in Hyperglycemia
- The serum sodium concentration can be influenced by the fluid exit from the intracellular compartment, thirst, and osmotic diuresis, which can cause decreases or increases in serum sodium concentration 2.
- The sum of the monovalent cation concentrations in the lost fluids should be considered when computing the volume and composition of the fluid replacement for hyperglycemic syndromes 2.
- Electrolyte-free water clearance can be a better index of the effect of osmotic diuresis on serum sodium concentration than the classic solute-free water clearance 3.
Clinical Implications and Management
- Identifying the correct composition of the fluids that need to be infused to restore volume losses is crucial to prevent complications in hyperglycemic patients with hypernatremia 4.
- A quantitative approach based on the comparison between the measured plasma sodium concentration and the expected plasma sodium concentration in the presence of an exclusive water shift can provide more thorough information about the true hydroelectrolytic status of the patient 4.
- Drinking ample amounts of water and fluids with appropriate electrolyte composition is important to prevent dehydration in diabetic patients 5.