Reply 1

Sir, Harbers et al. (1) compared recently the effects of lidocaine 2% with or without glucose for spinal anesthesia. As the use of hyperbaric 5% lidocaine solution is subject to discussion regarding the cauda equina syndrome, they stated that the 2% lidocaine solution with or without glucose has advantages. These considerations lead to some comments. Local anesthetics neurotoxicity may include less severe but far more common neurologic complications than cauda equina syndrome. Cases were reported in which symptoms consistent with transient radicular irritation (TRI) were observed following an uneventful single spinal injection of 5% hyperbaric lidocaine solution (2-4). Data from a subsequent study suggest that hyperosmolarity of the 5% lidocaine solution does not contribute to TRI following single spinal administration (5). However, it appears that reduction in lidocaine concentration up to 2% does not reduce the risk of TRI (6). This finding is consistent with previous data suggesting that the incidence of TRI after spinal administration does not differ between 5% with dextrose or 2% plain lidocaine, and may be as high as 19% (7). Finally, difference in solution concentration and/or baricity does not explain TRI following a single spinal injection of lidocaine. On the other hand, results in a previous study suggest that the incidence of TRI after a single dose of subarachnoid injection differs between lidocaine and bupivacaine: TRI occurred in 37% of patients receiving 5% lidocaine, but not in those receiving hyperbaric 0.5% bupivacaine (8). These results are consistent with those from another recent study (9). Until further studies elucidate the factors that affect the occurence of TRI, we think that it would be wiser to avoid using lidocaine for spinal anesthesia, even if it may have advantages for patients in day-case settings, and to prefer bupivacaine.