Anesthesiologists have long observed that surgical anesthetic blocks tend to progress from smaller to larger diameter nerves. This onset of blockade results in a progressive loss of temperature (cold before hot), pain, light and deep touch, vibration and proprioception. Restoration of these sensations usually occurs in reverse order as patients recover from a block.
128 Hz tuning forks have been used as a simple method of assessing vibration perception in patients undergoing surgical anesthesia. Tuning forks have proven useful as vibration perception is often one of the last sensations to be lost and one of the first to be regained. Vibration recovery is especially useful as it is associated with a return of motor function. This was highlighted in a study by Schulz-Stubner et al. In their study, they were able to correlate a return to baseline vibration sense with recovery from motor blockade after epidural anesthesia. They concluded that a return of vibration perception to baseline was a valid method of documenting recovery prior to discharge after surgery.
In another more recent study by Jindal et al, the onset of sensory and motor blockade after brachial plexus block was assessed with a 128 Hz Rydel-Seiffer tuning fork and manual motor testing. The decision to use the Rydel-Seiffer instead of the traditional tuning fork was made based on its quantitative output. Jindal determined that vibration sense was a valid indicator for the onset of surgical anesthesia after brachial plexus block. They further advocated for the use of the Rydel-Seiffer tuning fork along with motor testing as objective tools for assessing onset of surgical anesthesia after brachial plexus block.
These studies may signal a new role for quantitative vibration testing in the assessment of surgical anesthesia patients. Instruments like the Rydel-Seiffer tuning fork and the ETF128 are well-suited to this task due to their quantitative output and reliability. Given the results presented by Schulz-Stubner and Jindal, tuning fork testing could become the new standard for evaluating onset and recovery from surgical anesthesia.