How should hyponatremia be managed in patients undergoing anesthesia?

From the Guidelines

Patients undergoing anesthesia with hyponatremia should have their condition corrected to reach a state as close to euvolaemia as possible before anesthesia, taking into account pre-existing comorbidities and avoiding prolonged preoperative fasting. This approach is supported by the Enhanced Recovery After Surgery (ERAS) society recommendations 1, which emphasize the importance of correcting preoperative fluid and electrolyte excesses or deficits to improve outcomes.

Key Considerations

• Preoperative assessment and management of hyponatremia are crucial to prevent complications during anesthesia.
• Correction of hyponatremia should be done carefully, considering the severity, chronicity, and symptoms of the condition.
• The use of isotonic fluids such as normal saline or lactated Ringer's is recommended during anesthesia to avoid exacerbating hyponatremia.
• Frequent monitoring of serum sodium levels is essential throughout the perioperative period.
• Anesthetic agents should be chosen with consideration of their effects on antidiuretic hormone secretion.

Management Strategies

• For mild asymptomatic hyponatremia, close monitoring may be sufficient without delaying surgery.
• For moderate to severe hyponatremia, especially if symptomatic, correction should be initiated before elective procedures.
• Correction rates should not exceed 8-10 mEq/L in 24 hours to avoid osmotic demyelination syndrome.
• For acute symptomatic hyponatremia, 3% hypertonic saline can be administered at 1-2 mL/kg/hr with frequent electrolyte monitoring.
• For chronic hyponatremia, slower correction with isotonic saline or fluid restriction is appropriate.

Underlying Cause Management

• The underlying cause of hyponatremia (SIADH, heart failure, cirrhosis, medications) should be addressed simultaneously for comprehensive management, as recommended by the guidelines 1.

From the FDA Drug Label

Patients should be in a hospital for initiation and re-initiation of therapy to evaluate the therapeutic response and because too rapid correction of hyponatremia can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, affective changes, spastic quadriparesis, seizures, coma and death In controlled clinical trials in which tolvaptan was administered in titrated doses starting at 15 mg once daily, 7% of tolvaptan-treated subjects with a serum sodium <130 mEq/L had an increase in serum sodium greater than 8 mEq/L at approximately 8 hours and 2% had an increase greater than 12 mEq/L at 24 hours Osmotic demyelination syndrome has been reported in association with SAMSCA therapy Patients treated with SAMSCA should be monitored to assess serum sodium concentrations and neurologic status, especially during initiation and after titration.

Management of Hyponatremia in Patients Undergoing Anesthesia:

• Patients with hyponatremia should be managed in a hospital where serum sodium can be closely monitored.
• Tolvaptan can be used to treat hyponatremia, but it should be initiated and re-initiated in a hospital setting.
• The dose of tolvaptan should be titrated carefully to avoid too rapid correction of serum sodium.
• Patients should be monitored for changes in serum electrolytes and volume, and for signs of osmotic demyelination syndrome.
• Fluid restriction should be avoided during the first 24 hours of therapy, and patients should be advised to drink fluids in response to thirst. 2

From the Research

Management of Hyponatremia in Patients Undergoing Anesthesia

• Hyponatremia is a common electrolyte abnormality that can have serious complications if not properly managed, especially in patients undergoing anesthesia 3.
• The management of hyponatremia in patients undergoing anesthesia involves identifying and addressing the underlying cause of the condition, as well as correcting the sodium imbalance 4.
• Conventional management techniques include water restriction, demeclocycline, lithium, and urea, but these methods have variable efficacy and toxicity 4.
• Vasopressin receptor antagonists, such as conivaptan and tolvaptan, are promising new therapeutic options for the treatment of hyponatremia, especially in patients with euvolemic and hypervolemic hyponatremia 4, 5.
• Tolvaptan has been used successfully in children with chronic hyponatremia due to inappropriate antidiuretic hormone secretion, and may be a viable option for patients undergoing anesthesia 6.

Risk Factors for Hyponatremia

• Preoperative hyponatremia, female sex, older age, lower body weight, knee surgery, and bilateral knee arthroplasty are risk factors for developing hyponatremia after elective orthopedic surgery 3.
• Thiazides and angiotensin-converting enzyme inhibitors are medications that can contribute to low postoperative sodium values 3.

Treatment of Hyponatremia

• Rapid correction of hyponatremia can lead to major neuropathological sequelae, and treatment should aim to correct the sodium imbalance gradually 7.
• Hypotonic fluids may be safely administered to decrease the natremia after excessive correction of hyponatremia, and can help prevent myelinolysis 7.
• Conivaptan has been shown to be effective in increasing serum sodium concentrations in neurosurgical patients, and may be a useful agent in the management of hyponatremia in patients undergoing anesthesia 5.