FCA1-0527

FCA1-0527

A 33-year old man was referred to you because of difficulty moving his limbs. History revealed that he was placed under anaesthesia for a major surgery 12 hours prior to the referral. Other symptoms were noted such as anxiousness, agitation, and fever of 38°C. Upon physical examination, he was tachycardic at 119 beats per minute. Moreover, his medical history showed that he was on Fluoxetine for clinical depression. The nurses reported that, because of his frequent complaints of axillary pain, he was given tramadol with paracetamol. Which of the following is responsible for his clinical features?