What is a common cause of stridor following a parathyroidectomy when the drain is empty?

Laryngospasm is a reflexive contraction of the vocal cords that can lead to stridor, a high-pitched wheezing sound resulting from turbulent airflow in the upper airway. Following a parathyroidectomy, hypocalcemia can occur due to damage or removal of parathyroid glands, which regulate calcium levels in the body. Low calcium levels can induce neuromuscular irritability, leading to laryngospasm.

When the drain is empty, the most pertinent consideration in a post-operative setting involves the patient's calcium levels. If hypocalcemia develops, it can trigger laryngospasm, thus causing stridor. This makes laryngospasm due to hypocalcemia a likely explanation for stridor in this context.

The other options do not fit as common causes in this scenario. Excessive bleeding might lead to other complications but is less likely to cause stridor alone, particularly when there’s no associated hematoma or direct airway compression. Airway obstruction may be a concern but would usually be more evident in cases of hematoma or postoperative edema rather than directly following a parathyroidectomy with an empty drain. Vocal cord paralysis can occur, but it is typically a result of surgical trauma rather than a direct consequence in the immediate postoperative