Unintentional subdural placement of epidural catheters during attempted epidural anesthesia: an anatomic study of spinal subdural compartment.

Background: Although infrequent, subdural block is a complication of epidural anesthesia with obvious implications. Knowledge of the spinal subdural compartment (dura-arachnoid interface) may help elucidate controversies arising from evidence that subdural catheter placement is feasible and may be difficult to identify clinically.

Methods: Samples of arachnoid lamina obtained during in vivo lumbosacral surgery (n = 4) and from cadavers (n = 6) were obtained and prepared for transmission electron microscopy and scanning electron microscopy.

Accidental subdural injection during attempted lumbar epidural block may present as a failed or inadequate block: radiographic evidence.

Background And Objectives: Until now, case reports after accidental subdural injection during attempted epidural block have usually described extensive neuraxial blocks with a delayed onset, after low doses of local anesthetic, with a characteristic radiographic appearance on contrast injection. Our radiographic investigation of atypical "epidural" blocks has revealed that subdural injection may go unrecognized clinically and may be a cause of inadequate blocks. The mechanism is explored.