From the Research
Low sodium levels (hyponatremia) after parathyroid surgery can occur due to several reasons, with the most common cause being syndrome of inappropriate antidiuretic hormone secretion (SIADH), as supported by the recent review on hyponatremia diagnosis and management 1.
Causes of Hyponatremia
- Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common cause, where the body temporarily releases too much antidiuretic hormone following surgical stress, causing water retention and sodium dilution.
- Excessive intravenous fluid administration during and after surgery, particularly hypotonic fluids, can also contribute to hyponatremia.
- Medications used during the perioperative period, such as certain pain medications, anesthetics, and diuretics, can also contribute to hyponatremia.
- Some patients may experience hungry bone syndrome, where calcium and other electrolytes rapidly move into bone tissue after removal of a hyperactive parathyroid gland, disrupting overall electrolyte balance including sodium levels.
- Postoperative nausea and vomiting can lead to dehydration and electrolyte imbalances.
Management of Hyponatremia
- Management typically involves fluid restriction, sodium supplementation, and close monitoring of electrolyte levels.
- The approach to managing hyponatremia should consist of treating the underlying cause, as recommended by recent guidelines 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.
- Severely symptomatic hyponatremia is a medical emergency and should be treated with bolus hypertonic saline to reverse hyponatremic encephalopathy.
Monitoring and Prevention
- Close monitoring of electrolyte levels is crucial in the postoperative period to detect hyponatremia early.
- Measuring parathyroid hormone (PTH) levels after surgery can help predict the development of hypocalcemia and hypoparathyroidism, as shown in a recent meta-analysis 3.
- Patients with normal PTH levels can still experience hypocalcemia, and therefore, close monitoring of calcium levels is also necessary 4.
- A single early postoperative intact PTH measurement may be the most cost-effective screening tool for hypocalcemia, but even greater specificity can be achieved by combining those findings with a serum calcium measurement taken 6 hours postoperatively 5.