Background: Transient neurologic symptoms (TNS) after spinal anesthesia (SPA) is defined as back pain with radiation or dysesthesia in the buttocks, thighs, hips and calves, occurring within 24 h after recovery from otherwise uneventful SPA. The symptoms last for about 1-3 days but neurophysiologic evaluation does not show pathologic findings. The type and the preparation of the local anesthetic drug (baricity, concentration, additives or preservatives) are most often discussed as the underlying cause of TNS.
Methods: Randomized controlled comparative studies reporting the incidence of TNS were systematically searched. Descriptive statistics are presented summarizing the identified trials and the pooled relative risk (RR), the number-needed-to-harm (NNH) with their 95% confidence intervals (95%-CI) were calculated using a random effects model.
Results: A total of 29 studies with a 2,813 patients fulfilled the inclusion criteria. Summarizing all patients in these trials without further adjustment, the incidence of TNS was 16.9% after lidocaine, 19.1% after mepivacaine, but only 1.1% after bupivacaine and 1.7% after prilocaine. For tetracaine, procaine, and ropivacaine there were too few studies to draw meaningful conclusions. Using meta-analysis techniques these data were confirmed: the pooled relative risk (RR) for suffering from TNS was 6.7-fold higher after lidocaine (95%-CI: 2.5-18) than after SPA with bupivacaine and 5.5-fold higher (95%-CI: 2-15) than after prilocaine. Furthermore, data show that baricity, concentration of the local anesthetic, and addition of vasoconstrictors have no significant influence on the occurrence of TNS.
Conclusion: Prilocaine and bupivacaine for SPA are associated with less TNS than lidocaine and mepivacaine. For the other local anesthetics there were not enough comparative trials to give conclusive recommendations.