Hypocalcaemia may present immediately following total parathyroidectomy due to the development of hypoparathyroidism. This is due to the sudden drop in parathyroid hormone (PTH) levels, further exacerbated by “hungry bones” (skeletal demineralisation) prior to surgery. Hypocalcaemia following parathyroidectomy will eventually correct itself when the bone has been re-mineralised, although calcium supplements may be needed for 6 to 12 months post-surgery. Symptoms caused by hypocalcaemia may constitute a medical emergency that may require immediate treatment with intravenous calcium. If the symptoms below are present then an urgent calcium level must be taken and reported to medical staff.
Signs and symptoms of hypocalcaemia include:
• numbness and tingling of hands
• irritability, anxiety
• carpopedal spasm
• muscle cramps and tetany
• laryngeal spasm
• prolonged QT interval, leading to VF or heart block.
In order to ensure that serum calcium levels are maintained in the acceptable range the patient must be given oral calcium supplementation before and after surgery as described under 'Post-operative management'. They may have a dramatic drop in their serum calcium level soon after surgery which is likely to persist. Initial calcium supplementation may therefore need to be given intravenously [IV] as described in the table below.
|Adjusted calcium level
|Less than 2·0mmol/L
||IV 50mL (11·25mmol) calcium gluconate 10% in 500mL sodium chloride 0·9% or glucose 5% infusion over 4 hours
||Recheck adjusted calcium 60 minutes after end of infusion.
||10mL (2·25mmol) calcium gluconate 10% injection given as an IV bolus over 5 minutes
||Recheck adjusted calcium and magnesium levels 60 minutes after end of infusion.
All infusions must be administered via an infusion pump. ECG monitoring generally not required unless hypocalcaemic tetany is evident or patient is taking digoxin, due to interaction with calcium.