Some argue against doing a “test dose” because it lacks specificity and sensitivity for picking up an IT/IV epidural catheter placement.
- ideal test: safe for mom and fetus
- test dose is important if large volumes of concentrated local anesthetics are given
- traditional test dose:
- lidocaine: 1.5% w/ epinephrine
- bupivacaine 0.25% w/ epi
- 2-chloroprocaine w/ epi
- double test dose:
- avoids pitfalls of giving epi
- give 2 doses of 2% lidocaine, plain IT, then give 5ml of lido IV, about 3 min after IT dose.
- May be useful in cases where it is imperative to have fxal catheter.
What is a positive test dose? Increase in HR by 10 beats is usually taken as an IV injection IT injection is usually evidenced by unusual sx by the pt: tinnitus, dysgeusia(odd taste in mouth), periororal numbness/tingling
One approach is performa “double test dose.” This avoids pitfalls of giving epinephrine by giving two 5ml boluses of plain 2% lidocaine through the epidural catheter 3-5 minutes apart: The patient should be evaluated for motor block after the first dose, which would test for intrathecal placement, and search for a sensory level after the second dose, which confirms epidural placement. If no sensory level found, consider replacing the epidural. The patient should be evaluated for neurological signs (perioral numbness, tinnitus) that will indicate IV placement, after each dose.