What are the implications of hyponatremia (low sodium levels) in an elderly person following orthopedic (orthopaedic) surgery?

From the Guidelines

Low sodium levels (hyponatremia) in elderly patients after orthopedic surgery should be promptly evaluated and treated as it can lead to serious complications, with a focus on fluid restriction, investigating underlying causes, and correcting sodium levels gradually to avoid osmotic demyelination syndrome, as recommended by recent guidelines 1.

Initial Management

The initial management of hyponatremia in elderly patients after orthopedic surgery includes fluid restriction to 800-1000 mL/day while investigating the underlying cause. Common causes include medication side effects (particularly thiazide diuretics, SSRIs, or certain pain medications), syndrome of inappropriate antidiuretic hormone secretion (SIADH), excessive IV fluids during surgery, or adrenal insufficiency.

Laboratory Tests and Assessment

Laboratory tests should include serum and urine osmolality, urine sodium, and assessment of volume status. For mild hyponatremia (sodium 130-135 mmol/L), fluid restriction may be sufficient.

Treatment of Moderate to Severe Hyponatremia

For moderate to severe cases (sodium <130 mmol/L) with symptoms like confusion, weakness, or seizures, more aggressive treatment is needed. Hypertonic saline (3% NaCl) may be administered at 1-2 mL/kg/hour with close monitoring to raise sodium levels gradually, aiming for correction of no more than 8 mmol/L in 24 hours to avoid osmotic demyelination syndrome.

Importance of Nutritional Support

Nutritional interventions in geriatric patients after hip fracture and orthopedic surgery shall be part of an individually tailored, multidimensional and multidisciplinary team intervention in order to ensure adequate dietary intake, improve clinical outcomes and maintain quality of life, as emphasized by recent guidelines 1.

Key Considerations

• Elderly patients are particularly vulnerable to hyponatremia due to age-related changes in renal function, multiple medications, and comorbidities, requiring careful monitoring during the postoperative period with regular electrolyte checks until sodium levels normalize.
• Underlying causes should be addressed by discontinuing contributing medications when possible and treating conditions like SIADH.
• The use of oral nutritional supplements (ONS) can lead to a significant increase in energy and nutrient intake, and may reduce the risk of postoperative complications, as supported by recent studies 1.

From the Research

Causes and Risks of Low Sodium Levels

• Low sodium levels, also known as hyponatremia, can occur in elderly patients after orthopaedic surgery, with a calculated incidence of 2.8% 2.
• The condition can be caused by infusion of dextrose containing fluids in the peri-operative period, and orthopaedic units need to be aware of this easily avoidable condition 2.
• Hyponatremia can have many causes, including medications used to treat chronic disease, particularly thiazide or thiazide-like drugs, or drugs acting on the central nervous system 3.
• Chronic hyponatremia can often be the result of medications used to treat chronic disease, and where a reversible trigger can be identified, hyponatremia may be treated relatively simply 3.

Diagnosis and Management

• Hyponatremia is defined by a serum sodium level of less than 135 mEq/L, and most commonly results from water retention 4.
• The approach to managing hyponatremia should consist of treating the underlying cause, and clinicians should categorize patients according to their fluid volume status (hypovolemic hyponatremia, euvolemic hyponatremia, or hypervolemic hyponatremia) 4.
• Fluid restriction can be an effective therapy in dilutional hyponatraemia, although poor compliance and the burdensome nature of the restrictions are important considerations 3.
• Tolvaptan is an oral vasopressin receptor antagonist that can increase serum sodium concentrations by increasing electrolyte-free water excretion, and its use is supported by clinical trial evidence in patients with hypervolaemic or euvolaemic hyponatraemia 3.
• Vaptans, such as tolvaptan, have been introduced as specific and direct therapy of SIADH, and appear advantageous to patients because there is no need for fluid restriction and the correction of hyponatremia can be achieved comfortably and within a short time 5.

Treatment and Monitoring

• For most patients, the approach to managing hyponatremia should consist of treating the underlying cause, and urea and vaptans can be effective treatments for the syndrome of inappropriate antidiuresis and hyponatremia in patients with heart failure 4.
• Severely symptomatic hyponatremia is a medical emergency, and US and European guidelines recommend treating severely symptomatic hyponatremia with bolus hypertonic saline to reverse hyponatremic encephalopathy 4.
• The speed of correction with 3% sodium chloride as a 100- to 150-ml intravenous bolus or continuous infusion depends on the severity and persistence of the symptoms and needs frequent biochemical monitoring 6.
• Close monitoring and readiness for administration of either hypotonic fluids or desmopressin may be crucial in the decision-making process for specific treatment and eventual overcorrection consequences 6.