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: Unknown
Which nerve is used for monitoring anesthesia during surgery? 
Select and explain. 
A. Radial, B. Ulnar, C. Facial, D. Median
B: Ulnar
Answer: B: Ulnar 
Explanation: Ref. Oxford textbook of anesthesia. Page. 449
 
Ulnar nerve is monitored because ulnar nerve supplies adductor pollicis muscle which is monitored for neuromuscular blockade during anaesthesia
 
Nerve Injuries in anesthesia
In the supine position the main nerves at risk are:

Brachial plexus (excessive abduction and extension of the shoulder, especially if the head is turned away from the abducted arm),
Ulnar nerve (direct compression in ulnar groove, especially if the hand is supinated, or stretching by acute elbow flexion)
Radial nerve (arm allowed to hang over the side of the operating table)
Supraorbital (compression by the facemask)