Background and objectives: A commonly used test dose in parturients receiving continuous lumbar epidural analgesia for labor consists of 3 mL of dextrose-free 1.5% lidocaine with 1:200,000 epinephrine.
Methods: of 1,962 obstetric epidural anesthetics administered over a 17-month period, unintentional subarachnoid placement of the epidural catheter was detected by injection of the test dose in five laboring patients. The characteristics of the resulting subarachnoid blocks were studied.
Results: After negative aspiration for cerebrospinal fluid in each case, test dose injection resulted in the rapid onset of high sensory block with associated motor and sympathetic block, accompanied by significant hypotension requiring aggressive treatment.
Conclusions: While this test dose appears to be a sensitive indicator of an unexpected subarachnoid catheter, the resulting excessive spinal blocks in these laboring patients raise the question of its safety.