Predictors of laterality of motor block during epidural analgesia in a mixed surgical population

Abstract

Predictors of laterality of motor block during epidural analgesia are currently unknown, as studies so far have yielded conflicting results. We aimed to evaluate predictors of post-operative asymmetric lower extremity motor blockade in a mixed surgical population. This is a retrospective analysis of 578 consecutive patients with post-operative epidural analgesia for a variety of surgical procedures. A priori determined potential predictors of unilateral motor block were age, gender, body mass index, type of surgical procedure, vertebral level of puncture, catheter insertion depth into the epidural space and concentration of local anaesthetic. Logistic regression analysis was employed for evaluating predictors of laterality. Unilateral motor block occurred in 29.2% of the patients. Univariate logistic regression analysis showed that young age, female gender, gynaecologic procedures, a low puncture level, an increased depth of catheter insertion and a high ropivacaine concentration (2 mg/ml vs. less than 2 mg/ml) were significantly associated with increased incidence of laterality. Multivariate analysis revealed that age (OR = 0.73 per decade increase, P = 0.00001), the vertebral level of epidural puncture (OR = 1.37 per lowering vertebral level, P < 0.000001) and the depth of catheter insertion (OR = 1.46 per centimetre deeper, P = 0.001) were independent predictors of unilateral motor block. These results suggest that young patients with lumbar epidural analgesia or deep catheter insertion should be frequently monitored for the occurrence of laterality of motor block. Also, these results provide support for a prospective study to determine the optimal catheter insertion depth to decrease the risk of unilateral motor block.