Background: Recent case reports have suggested that subarachnoid or epidural administration of local anesthetics may cause peripheral neurologic deficits.
Methods: To describe the course and evaluate possible risk factors of such reactions, 21 reports in the Swedish adverse drug reactions register were reviewed.
Results: The reports concerned subarachnoid administration of hyperbaric lidocaine (n = 9), plain bupivacaine (n = 4), hyperbaric bupivacaine (n = 2), bupivacaine with epinephrine (n = 1) and mepivacaine (n = 1), and epidural administration of bupivacaine (n = 2) and mepivacaine (n = 2). Pain in the lower extremities was reported in 12 patients (57%) and paresthesias/hypesthesias were reported in 11 patients (52%). Seven reports (33%) concerned low back pain or abdominal pain from Th9-Th10 and downwards. Urinary incontinence was reported in 3 patients, fecal incontinence in 2 patients, and erectile dysfunction, loss of sensation of full bladder and quadriceps muscle paresis were each reported in one patient. Two clinically distinct subgroups of patients were identified, one group with reversible nerve root affection which disappeared within 2 weeks and one group with apparently irreversible nerve root affection, still persistent after 1 month to 4 years. In the group with reversible root symptoms, none had motor deficits, whereas 50% had motor deficits in the group with irreversible symptoms. Possible risk factors include concomitant peripheral neurologic disease and use of other drugs associated with neurotoxicity.
Conclusions: This database study does not contain complete information for the cases reported, and a causal relationship between subarachnoid or epidural administration of local anesthetics and neurologic deficits therefore remains uncertain. The increase in the number of reports on lidocaine after the introduction of very fine-bore spinal needles is consistent with the suspicion that lidocaine at the concentration 50 mg/ml is neurotoxic and that it may not be diluted rapidly enough in the cerebrospinal fluid when injected through such needles.