Differential sensory block: spinal vs epidural with lidocaine

Purpose: in this study we sought to determine if and when a difference exis ts with regards to differential sensory blockade between spinal and epidura l anaesthesia using lidocaine. Methods: Ten healthy volunteers were randomly assigned to receive both spin al and epidural anaesthesia. Non-epinephrine containing solutions of lidoca ine, 100 mg lidocaine 5% with 7.5% dextrose (spinal) and 600 mg lidocaine 2 % (epidural), were used to establish sensory blockade. At five minute inter vals, for a total of 65 min, the following sensory modalities were tested: anaesthesia (complete loss of sensation to pinprick), analgesia (loss of an equally sharp sensation to pinprick compared with that at an unblocked der matome), cold sensation (complete loss of cold temperature discrimination). Results: At atl limes, except at time = 0 during spinal anaesthesia, the le vels of analgesia and cold sensation were more cephalad than the level of a naesthesia for both spinal and epidural anaesthesia. Multiple comparison te sting among the three dermatomal response levels showed that, during epidur al anaesthesia, the level of analgesia was more cephalad than the level of cold sensation at the following times: 25 min. 30 min. and from 40 to 60 mi n. In contrast, the level of analgesia was not different from the level of cold sensation during spinal anaesthesia. Conclusions: Spinal and epidural anaesthesia with lidocaine produce a simil ar degree of differential sensory blockade. Epidural anaesthesia produces a detectable difference between the level of analgesia and cold sensation at various times. whereas spinal anaesthesia did not reliably do so in this s tudy.