Vibration sensation as an indicator of surgical anesthesia following brachial plexus block

Local anesthetic instillation in close vicinity to nerves anywhere in body blocks sensations in the same order as in central neuraxial blockade. The main purpose of this study was to evaluate the efficacy of vibration sense as criteria to determine the onset of surgical anesthesia following brachial plexus block and its correlation with loss of sensory and motor power.

This prospective study included fifty patients of American Society of Anaesthesiologist physical status I and II, aged between 18 and 45 years, undergoing elective upper limb surgery under brachial plexus block by supraclavicular approach. The baseline values of vibration sense perception using 128 Hz Rydel-Seiffer tuning fork, motor power using formal motor power of wrist flexion and wrist extension, and sensory score by pinprick method were recorded preoperatively and every 5 min after giving block till the onset of complete surgical anesthesia.

The mean ± standard deviation of time (in minutes) for sensory, motor, and vibration block was 13.33 ± 3.26, 21.10 ± 3.26, and 25.50 ± 2.02, respectively (P < 0.05). Although all the patients achieved complete sensory and motor block after 25 min, 14% of the patients still had vibration sensations intact and 100% of the patients achieved complete sensory, motor, and vibration block after 30 min.

Vibration sense serves as a reliable indicator for the onset of surgical anesthesia following brachial plexus block. Vibration sense testing with 128 Hz Rydel-Seiffer tuning fork along with motor power assessment should be used as an objective tool to assess the onset of surgical anesthesia following brachial plexus block.