From the Guidelines
After a parathyroidectomy, phosphorus levels rise and calcium levels fall because the parathyroid glands have been removed, eliminating the source of parathyroid hormone (PTH). PTH normally maintains calcium homeostasis by increasing calcium reabsorption in the kidneys, promoting calcium absorption from the intestines via vitamin D activation, and stimulating bone resorption to release calcium. Simultaneously, PTH decreases phosphorus levels by promoting its excretion through the kidneys. Without PTH, these regulatory mechanisms are lost, resulting in decreased calcium absorption and increased phosphorus retention. This imbalance typically manifests as hypocalcemia and hyperphosphatemia, as noted in the guidelines for parathyroidectomy in patients with chronic kidney disease 1.
According to the guidelines, patients who undergo parathyroidectomy should have their blood level of ionized calcium measured every 4 to 6 hours for the first 48 to 72 hours after surgery, and then twice daily until stable 1. If the blood levels of ionized or corrected total calcium fall below normal, a calcium gluconate infusion should be initiated at a rate of 1 to 2 mg elemental calcium per kilogram body weight per hour and adjusted to maintain an ionized calcium in the normal range 1. Patients may require calcium supplementation and active vitamin D analogs to manage these electrolyte abnormalities. Symptoms of hypocalcemia include numbness, tingling, muscle cramps, and in severe cases, tetany or seizures, requiring prompt treatment.
Key points to consider after parathyroidectomy include:
- Monitoring ionized calcium levels closely after surgery
- Initiating calcium gluconate infusion if calcium levels fall below normal
- Providing calcium supplementation and active vitamin D analogs as needed
- Managing symptoms of hypocalcemia promptly.
From the Research
Phosphorus and Calcium Levels after Parathyroidectomy
- Phosphorus levels are often high and calcium levels are low after parathyroidectomy due to the sudden drop in parathyroid hormone (PTH) levels 2, 3.
- PTH plays a crucial role in regulating calcium and phosphorus levels in the body, and its removal can lead to an imbalance in these minerals 4, 5.
- The high phosphorus levels can be attributed to the decreased excretion of phosphorus in the urine, which is normally regulated by PTH 3.
- The low calcium levels, on the other hand, can be caused by the sudden decrease in PTH, which normally stimulates the release of calcium from bones and increases its absorption in the gut 2, 5.
Risk Factors for Hypocalcemia after Parathyroidectomy
- Patients with renal hyperparathyroidism are more likely to develop hypocalcemia after parathyroidectomy compared to those with primary hyperparathyroidism 2.
- The extent of surgery, including subtotal parathyroidectomy, can also increase the risk of hypocalcemia 2.
- Vitamin D deficiency has been shown to be common in patients with hyperparathyroidism, but its impact on postoperative calcium requirements is unclear 6, 5.
Management of Postoperative Hypocalcemia
- Intravenous calcium supplements are often required to manage hypocalcemia after parathyroidectomy, especially in patients with renal hyperparathyroidism 4, 2.
- Oral calcium supplements and active vitamin D metabolites, such as calcitriol, can also be used to prevent and treat hypocalcemia 4, 3.
- Daily monitoring of serum calcium and phosphorus levels is essential to prevent and manage postoperative hypocalcemia 4.