the effect of needle type, duration of surgery and position of the patient on the risk of transient neurologic symptoms

background the incidence of transient neurologic symptoms (tns) after spinal anesthesia with lidocaine is reported as high as 40%. objectives this prospective clinical trial was designed to determine the incidence of tns in patients who underwent spinal anesthesia with two different needles, in two different surgical positions. patients and methods the present randomized clinical trial was conducted on 250 patients (asa i-ii), who were candidates for surgery in supine or lithotomy positions. according to the needle type (sprotte or quincke) and local anesthetics (lidocaine and bupivacaine) all patients were randomly divided into four groups. after performing spinal anesthesia in sitting position, the position was changed into supine or lithotomy, according to surgical procedure. the patients were observed for complications of spinal anesthesia during the first five post-operative days. the primary end-point for this trial was to recognize the incidence of tns among the four groups. our secondary objective was to evaluate the effect of patient's position, needle type, and duration of surgery on the development of tns following spinal anesthesia. results tns was most commonly observed when lidocaine was used as anesthetic drug (p = 0.003). the impact of needle type, was not significant (p = 0.7). according to multivariate analysis, the duration of surgery was significantly lower in cases suffering from tns (p = 0.04). also, the risk of tns increased following surgeries performed in lithotomy position (p = 0.00). conclusions according to the results of this clinical study, spinal anesthesia with lidocaine, and the lithotomy position in surgery increased the risk of tns.