| Learning Objective #1: The learner will be able to will understand that it would require <1mA to observe motor activity in the intrathecal space. | |||
| Learning Objective #2: The learner will be able to understand that it is vitally important to distinguish between the epidural and the intrathecal space. |
METHODS
A 18 or 20 gauge introducer was inserted at the L4-5 level followed by insulted 24 gauge Pajunck unipolar needle. The needle was then advance into the intrathecal space and confirmed by the presence of cerebrospinal fluid (CSF). At this point, an independent observer attached the insulated needle to a nerve stimulator and the current was increased until minimal threshold current for motor activity was observed.
RESULTS
Twenty pediatric oncology patients (ASA II or III) aged 7.9 +/-4.0 (1.6-16 yrs) were studied. The mean patient weight was 28.2 +/- 15.0 kg. There were 10 male and 10 female patients. The mean current to elicit motor activity in the intrathecal space was 0.6 +/-0.3 mA (range 0.1 –1 mA). Nineteen twitches were at the L3-5 myotomes and one patient had twitches at L2. 19 twitches at L2 were unilateral and 1 bilateral.
DISCUSSION
This study demonstrated that the mean threshold current necessary to elicit motor response in the intrathecal space of pediatric space of pediatric patients was 0.6 +/- 0.3mA and confirms the hypothesis that the minimal threshold current in the intrathecal space is < 1mA. As this differs from the threshold currents reported for electrical stimulation in the epidural space, one may potentially distinguish the epidural space from the intrathecal space.