## Postoperative Hypocalcemia in Thyroid Surgery ### Clinical Presentation The patient's perioral paresthesias and positive Chvostek's sign are classic signs of acute hypocalcemia. These symptoms typically appear within 24–48 hours of thyroidectomy. ### Most Common Cause: Parathyroid Injury **Key Point:** Hypoparathyroidism is the most common metabolic complication of thyroidectomy, occurring in 1–5% of cases (transient) and 0.3–1% (permanent). It results from inadvertent injury, devascularization, or removal of parathyroid glands during thyroid dissection. ### Mechanism of Injury 1. **Devascularization** — parathyroids lose blood supply during thyroid mobilization 2. **Direct trauma** — gland crushed or divided during dissection 3. **Inadvertent removal** — small parathyroid tissue mistaken for lymph node 4. **Edema** — transient ischemia from surgical manipulation ### Why Parathyroid Injury Is Most Common - Parathyroid glands lie in close anatomical proximity to the thyroid - Their small size (3–5 mm) makes identification challenging - Ectopic parathyroids increase risk if not identified preoperatively - Even experienced surgeons cannot prevent all cases ### Biochemical Confirmation - **Serum calcium:** < 8.5 mg/dL (normal 8.5–10.5) - **Serum phosphate:** elevated (> 4.5 mg/dL) - **PTH level:** low or inappropriately normal (< 15 pg/mL) ### Management - **Acute symptomatic:** IV calcium gluconate 10% (10–20 mL in 50 mL normal saline over 10 min) - **Chronic:** Oral calcium + calcitriol (active vitamin D) - Most cases resolve within 3–6 months (transient hypoparathyroidism) **High-Yield:** Transient hypoparathyroidism is more common than permanent; monitor calcium levels postoperatively and supplement as needed. [cite:Sabiston Textbook of Surgery Ch 38]
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