Epidural Anesthesia

At what vertebral level is the epidural space most commonly accessed for lumbar epidural anesthesia?

Regarding epidural anesthesia and its physiological effects, all of the following statements are correct EXCEPT:

A 38-year-old woman undergoing cesarean section under epidural anesthesia develops sudden onset of severe headache, neck stiffness, and photophobia 6 hours postoperatively. She is afebrile and hemodynamically stable. CSF analysis shows pleocytosis (WBC 180/μL, predominantly lymphocytes) with normal glucose and protein. What is the most appropriate next step in management?

A 52-year-old man undergoing lower abdominal surgery receives epidural anesthesia. During the procedure, he develops sudden onset hypotension, bradycardia, and loss of consciousness. Which is the most common cause of this acute complication?

A 52-year-old man with severe osteoarthritis of the knee is scheduled for epidural anesthesia for total knee replacement. During needle insertion at L3-L4, the anesthesiologist encounters unexpected resistance and cannot identify the epidural space using the loss-of-resistance technique. Which investigation is most appropriate to confirm correct needle placement and guide further intervention?