This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
A patient undergoing caesarean section following prolonged labour under subarachnoid block developed carpopedal spasm. Lignocaine was' used as anaesthetic agent. The most likely' diagnosis is: 
Select and explain. 
A. Amniotic fluid embolism, B. Lignocaine toxicity, C. Hypocalcemia, D. Hypokalemia
C: Hypocalcemia
Answer: C: Hypocalcemia 
Explanation: Hypocalcemia. Patient developing carpopedal spasm is indicative of hypocalcemia. Lignocaine in subarachnoid block can not cause hypocalcemia rather can cause hypercalcemia by releasing calcium from sarcoplasmic retinaculum (that is why amide local anaesthetics may trigger malignant hypehermia).