Differential sensory block: spinal vs epidural with lidocaine

In this study we sought to determine if and when a difference exists with regards to differential sensory blockade between spinal and epidural anaesthesia using lidocaine.

Ten healthy volunteers were randomly assigned to receive both spinal and epidural anaesthesia. Non-epinephrine containing solutions of lidocaine, 100 mg lidocaine 5% with 7.5% dextrose (spinal) and 600 mg lidocaine 2% (epidural), were used to establish sensory blockade. At five minute intervals, 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 dermatome), cold sensation (complete loss of cold temperature discrimination).

At all times, except at time = 0 during spinal anaesthesia, the levels of analgesia and cold sensation were more cephalad than the level of anaesthesia for both spinal and epidural anaesthesia. Multiple comparison testing among the three dermatomal response levels showed that, during epidural 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 min. In contrast, the level of analgesia was not different from the level of cold sensation during spinal anaesthesia.

Spinal and epidural anaesthesia with lidocaine produce a similar 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 study.