Transient neurologic symptoms (TNS) following spinal anaesthesia with lidocaine versus other local anaesthetics

Spinal anaesthesia has been in use since the turn of the late 19th century. The most serious complication of this technique is damage to the spinal cord or nerve roots resulting in lasting neurologic sequelae. Such serious adverse effects seldom happen. There has been an increase in the number of reports during the last nine years implicating lidocaine as a possible cause of temporary and permanent neurologic complications after spinal anaesthesia. Follow-up of patients who received uncomplicated spinal anaesthesia revealed that some of them developed pain in the lower extremities after an initial full recovery. This painful condition that occurs in the immediate post-operative period was named "transient neurologic symptoms" (TNS). The objectives of this review were to study the frequency of TNS and neurologic complications after spinal anaesthesia with lidocaine, compared to other local anaesthetics. Trials were identified by computerized searches of the Cochrane Controlled Trials Register (4th Quarter 2002), MEDLINE (1966 - January 2003), LILAC database, EMBASE (1980 - week 51, 2002), and by checking the reference lists of trials and review articles. All randomized and pseudo-randomized studies comparing the frequency of TNS and of neurologic complications after spinal anaesthesia with lidocaine as compared to other local anaesthetics. Two reviewers independently evaluated the quality of the relevant studies and extracted the data from the included studies. Fourteen trials, reporting 1,349 patients, 117 of whom developed transient neurologic symptoms, were included in the analysis. The use of lidocaine for spinal anaesthesia increased the risk of developing TNS. There was no evidence that this painful condition was associated with any neurologic pathology as it was clearly documented that no positive neurologic findings were present in any patient with TNS; the symptoms disappeared spontaneously by the fifth postoperative day. The relative risk for developing TNS after spinal anaesthesia with lidocaine as compared to other local anaesthetics (bupivacaine, prilocaine, procaine and mepivacaine) was 4.35 (95% Confidence Interval: 1.98, 9.54). The risk of developing TNS after spinal anaesthesia with lidocaine was significantly higher than when bupivacaine, prilocaine and procaine were used. The term "TNS", which implies a positive neurologic finding, should not be used for this painful condition, which is in fact comparable to another common adverse effect