A 63-year-old woman has undergone a surgery for a large multinodular euthyroid goiter. Subtotal resection of the both lobes of the thyroid gland had to be performed, which was done with technical difficulties. On the 4th day after the surgery, the woman developed abdominal pain and muscle spasms in her face and arms. The Chvostek and Trousseau signs were positive. What is the most likely the cause of the patient’s condition?