From the Guidelines
Postoperative hyponatremia should be managed with isotonic fluids to prevent its development, and treatment should be based on severity, onset rate, and symptoms, with careful monitoring and addressing underlying causes being crucial. The management of postoperative hyponatremia involves identifying and addressing the underlying causes, such as excessive hypotonic fluid administration, medications (e.g., diuretics, opioids), or stress-induced SIADH 1.
Causes of Postoperative Hyponatremia
- Excessive hypotonic fluid administration
- Medications (e.g., diuretics, opioids)
- Stress-induced SIADH
- Other medical conditions (e.g., heart failure, liver disease)
Management of Postoperative Hyponatremia
- For mild asymptomatic hyponatremia (sodium >130 mEq/L), careful monitoring and addressing underlying causes may be sufficient.
- For moderate to severe hyponatremia (<130 mEq/L) or symptomatic cases, more aggressive intervention is needed, including:
- Fluid restriction (800-1000 mL/day) for SIADH-related cases
- Isotonic fluid administration for hypovolemic hyponatremia
- Administration of 3% hypertonic saline at 1-2 mL/kg/hr initially for severe symptomatic hyponatremia, aiming for sodium correction of 4-6 mEq/L in the first 24 hours to relieve symptoms while avoiding overcorrection 1
- Regular monitoring of serum sodium (every 2-4 hours initially) is essential to prevent osmotic demyelination syndrome, which can occur with correction rates exceeding 8 mEq/L/day.
Prevention of Postoperative Hyponatremia
- The use of isotonic fluids for maintenance hydration in hospitalized children and adults can help prevent hyponatremia 1.
- Avoiding excessive hypotonic fluid administration and monitoring volume status can also help prevent hyponatremia 1.
In summary, the management of postoperative hyponatremia requires a careful approach, taking into account the severity, onset rate, and symptoms of the condition, as well as the underlying causes, and isotonic fluids should be used to prevent its development 1.
From the Research
Causes of Postoperative Hyponatremia
- Hyponatremia is the most common electrolyte disorder, affecting approximately 5% of adults and 35% of hospitalized patients 2
- It can result from water retention and is often associated with increased hospital stay and mortality 2
- In the orthopedic patient, hyponatremia can mimic common postoperative sequelae, making diagnosis difficult 3
- Risk factors for postoperative hyponatremia include preoperative hyponatremia, female sex, older age, lower body weight, knee more than hip surgery, and bilateral knee arthroplasty 3
- Thiazides and angiotensin-converting enzyme inhibitors are medications associated with low postoperative sodium values 3
Management of Postoperative Hyponatremia
- The approach to managing hyponatremia should consist of treating the underlying cause 2
- Urea and vaptans can be effective treatments for the syndrome of inappropriate antidiuresis and hyponatremia in patients with heart failure, but have adverse effects 2
- Severely symptomatic hyponatremia is a medical emergency and should be treated with bolus hypertonic saline to reverse hyponatremic encephalopathy 2, 4, 5
- Algorithm 1 addresses acute correction of hyponatremia posing as a medical emergency, and is applicable to both severe euvolemic and hypovolemic hyponatremia, using iv 3% hypertonic saline solution 4, 5
- Algorithm 2 is directed to the therapy of SIADH-induced mild or moderate, non-acute hyponatremia, using fluid restriction, solute, furosemide, and tolvaptan to achieve eunatremia in patients with SIADH 4, 5
- Careful preoperative evaluation of the hyponatremic patient enables assessment of surgical risk and individualization of the management of hyponatremia 6
- A practical guide to the assessment of the cause of hyponatremia is necessary to dictate the correct management of hyponatremia and the correct selection of perioperative fluids 6