Definition – serum calcium < 8.9 OR ionized calcium < 4.6

Correction needed before surgery – Preoperative SYMPTOMATIC hypocalcemia must be corrected before surgery

Intraoperative causes – the patient may develop hypocalcemia as a result of PRBC infusion (citrate from PRBCs binds calcium), hypothermia, and alkalosis (bicarbonate administration and hyperventilation).

Bronchospasm risk – There is a higher risk for bronchospasm in these patients.

Thyroid or parathyroid resection – the patient can develop acute hypocalcemia postoperatively.  This can precipitate a laryngospasm.  Symptoms will typically occur within 24 or 48 hours postoperatively.  Anxiety, circumoral numbness, tingling in the fingertips, cramping, and positive Chvostek or Trousseau signs are all indicative of hypocalcemia.

Acute treatment – manifestations of this acute hypocalcemia (tetany, seizures, etc) should be treated immediately with IV calcium:
10-20 ml of 10% calcium gluconate OR 3-5 ml of 10% calcium chloride.  This should be followed by an infusion of 1-2 mg/kg/hr of elemental calcium. Keep in mind that calcium gluconate contains less elemental calcium, but a lower risk of ischemia/necrosis of surrounding tissues if your IV infiltrates.

Treat hypomagnesemia – If hypomagnesemia is also present magnesium must be supplemented as well or treatment may not be effective.

Treat alkalosis – Treatment would also include correcting metabolic or respiratory alkalosis if present

If the patient has metabolic or respiratory acidosis – correct the calcium problem FIRST.  Interventions for acidosis such as bicarbonate administration or hyperventilation will make problems worse.

Massive transfusions – the implications of hypocalcemia should always be considered when administering PRBCs in a massive transfusion.

NMB sensitivity – Hypocalcemia may prolong neuromuscular blockade

Careful positioning – patients with chronic hypocalcemia may have brittle bones

Hypocalcemia symptom severity is directly related to how fast ionized calcium is reduced.  Acute loss will typically produce the most acute symptoms.

Non-surgical reasons for this condition include: decreased parathyroid hormone (PTH) secretion, end-organ resistance to PTH, Vitamin D metabolism disorders, liver disease, renal failure, pancreatic disease, nutritional deficiencies and TPN administration.

Most of the signs and symptoms are cardiovascular and neuromuscular:
paresthesias, tetany, irritability, seizures, hypotension, myocardial depression, prolonged QT interval (greater than 440ms).

Asymptomatic/Chronic hypocalcemia is treated with calcium and vitamin D supplementation