is designed to provide an early indication of intrathecal
catheter misplacement using a small local anesthetic dose,
while preserving the opportunity to recognize intravascular
misplacement and employing a commonly available
test dose solution standard to many epidural trays (5 mL of
1.5% lidocaine; 1:200,000 epinephrine). An initial 1-mL
injection delivers approximately 0.8 mL to the patient,
with a priming volume of 0.2 mL for the standard multiorifice
20-gauge epidural catheter. There is a 60-second waiting
period in the protocol (Figure 4) to follow for any
developing intrathecal block, signified by sensory and
motor symptoms, hypotension, and bradycardia. If the initial
dose is negative, the remaining 2 to 3 mL are administered
in a similar fashion to the traditional lumbar dose,
with vigilance for both intravascular and intrathecal injections.
After 2 to 3 minutes, the sequence is complete. The
goal of this modified strategy is to expose thoracic intrathecal
catheter misplacement early while reducing the
chance of profound spinal block and to preserve the ability
to identify the more common problem of intravascular
catheter misplacement.