A 25 year old male who met with a roadside accident underwent debridement and reduction of fracture of both bones of right forearm under axillary block. Commonest cause of persistent numbness and paresthesia in the right forearm and hand on the second post operative day includes all of the following, EXCEPT:

Persistent paresthesia is due to injury to the peripheral nerve, which occur as a result of local complication of local anesthesia. It may be caused by alcohol contaminating the local anesthetic, sterilizing fluid contaminating the local anesthetic, nerve injury by the needle, hemorrhage in or around the neural sheath. Ref: Complications of Regional Anesthesia By Brendan T. Finucane, 2nd Edition, Page 143 ; Meyler's Side Effects of Drugs Used in Anesthesia By Jeffrey K. Aronson , 2009, Page 81