What is the approach to managing a patient in the Intensive Care Unit (ICU) with hypernatremia who is receiving enteral nutrition via tube feeds (nasogastric tube or orogastric tube)?

From the Guidelines

To work up a patient in the ICU on tube feeds with hypernatremia, the primary intervention should be increasing free water delivery, as enteral nutrition via tube feeding is the preferred way of feeding the critically ill patient, according to the ESPEN guidelines on enteral nutrition in intensive care 1. When managing hypernatremia in ICU patients on tube feeds, it is essential to assess the severity and acuity of the sodium elevation, as this will guide management.

• Obtain serum sodium, osmolality, urine sodium, urine osmolality, and volume status assessment to determine the underlying cause of hypernatremia.
• Calculate the free water deficit using the formula: Free water deficit = 0.6 × weight (kg) × [(current Na⁺/140) - 1].
• Administer free water via the feeding tube (typically 30-60 mL/hr of water flushes) or adjust to a more dilute formula, as commercial formulas often have inadequate free water relative to solute load 1.
• If using a 2 kcal/mL formula, consider switching to 1.5 or 1 kcal/mL to increase free water content.
• Correct sodium slowly at a rate of 8-10 mEq/L per day to avoid cerebral edema.
• Monitor electrolytes every 4-6 hours initially.
• Address any underlying causes such as diabetes insipidus (consider DDAVP 1-2 μg IV/SC every 12-24 hours if confirmed), excessive insensible losses, or osmotic diuresis.
• Ensure tube feed rates meet fluid requirements, typically 30-35 mL/kg/day total fluid, as recommended by the ESPEN guidelines 1. In severe cases (Na⁺ >160 mEq/L with symptoms), consider IV hypotonic solutions like 0.45% saline or D5W alongside tube feeds.
• It is crucial to note that enteral nutrition should be given to all ICU patients who are not expected to be taking a full oral diet within three days, and it should have begun during the first 24 hours using a standard, as stated in the ESPEN guidelines 1.

From the Research

Assessment and Diagnosis of Hypernatremia

• Hypernatremia is a common condition in intensive care units, defined as a plasma sodium concentration >145 mEq/L 2.
• It indicates a decrease in total body water relative to sodium and is associated with plasma hyperosmolality 2.
• The diagnosis of hypernatremia can be made by measuring plasma sodium levels and assessing the patient's clinical condition.

Mechanisms and Causes of Hypernatremia

• Hypernatremia can result from sodium gain and/or loss of free water, which can be discriminated by clinical assessment and urine electrolyte analysis 3.
• Critically ill patients are at high risk of hypernatremia due to their inability to control free water intake, excessive fluid losses, and treatment with sodium-containing fluids 2.

Management of Hypernatremia

• The management of hypernatremia focuses on judicious replacement of free water deficit to restore normal plasma osmolality and identification and correction of underlying causes 2.
• Electrolyte-free water replacement is the preferred therapy, although electrolyte (sodium) containing hypotonic fluids can also be used in some circumstances 2.
• The rate of correction depends on the rapidity of hypernatremia development, and frequent monitoring of plasma sodium levels is essential to ensure appropriate response and adjust the rate of fluid replacement 3, 2.

Treatment of Hypernatremia in ICU Patients on Tube Feeds

• For patients on tube feeds, the treatment of hypernatremia should involve careful assessment of their fluid and electrolyte balance 3, 2.
• The use of desmopressin acetate may be considered in some cases, particularly in patients with essential hypernatremia or central diabetes insipidus 4.
• However, the use of desmopressin acetate in the treatment of hypernatremia is not well established, and more research is needed to determine its efficacy and safety in this context.

Monitoring and Adjustment of Treatment

• Frequent monitoring of plasma sodium levels, urine output, and fluid balance is essential to ensure appropriate response to treatment and adjust the rate of fluid replacement as needed 3, 2.
• The goal of treatment is to correct hypernatremia gradually and safely, avoiding rapid changes in plasma sodium levels that can lead to cerebral edema or other complications 3, 2.