Types of Sensations that a Nerve Block Affects
Commonly used in surgeries, chronic pain treatment, and diagnostic procedures, nerve blocks manage pain or provide anesthesia by interrupting the transmission of signals in specific nerves. By targeting specific nerves, these blocks can suppress pain from the area of interest without having systemic effects. In addition to blocking the sensation of pain, a nerve block also affects other sensations, including temperature and touch.
Nociception
The primary goal of most nerve blocks is to block pain. Nociceptive signals travel through sensory nerves to the brain, where they are interpreted as pain. A local anesthetic, such as lidocaine or bupivacaine, disrupts the transmission of these signals by inhibiting sodium channels on the nerve fibers. This leads to a loss of pain sensation in the targeted area. For example, during orthopedic surgeries or dental procedures, a nerve block can provide effective pain relief by halting the transmission of painful stimuli 1,2.
Temperature Sensation
A nerve blocks also affects temperature-related sensations, particularly cold. This is because temperature sensation is carried by small, lightly myelinated or unmyelinated fibers that are similar to pain fibers. Cold sensation tends to be lost before heat, but both are often impaired. Patients receiving a nerve block may report that they cannot feel hot or cold objects on the affected area, which can be beneficial for comfort but also requires caution to avoid harm 3,4.
Tactile Sensation
Touch sensation, including light touch and pressure, is transmitted through larger, more heavily myelinated fibers than those for pain and temperature. Though some studies show no effect of nerve blocks on tactile sensation thresholds, these fibers are usually the last to be affected and the first to return after a nerve block 5,6.
Vibration and Proprioception
Vibration and proprioceptive sensations are transmitted by the largest and most heavily myelinated fibers. In most routine blocks, these sensations are only minimally affected unless high concentrations of anesthetic are used or the nerve is completely blocked. In deeper or more comprehensive blocks, such as those used in major limb surgeries, even proprioception may be temporarily lost 7–9.
Motor Function
Although not a sensation in the traditional sense, nerve blocks may also impair motor function by affecting motor nerves, especially in blocks intended for surgical anesthesia. Though some studies show no effect of nerve blocks on motor function, some patients may temporarily lose the ability to move muscles in the blocked region, which can add to the sensation of numbness and immobility 10,11.
A nerve block can affect a range of sensations including pain, temperature, touch, and proprioception, depending on the type, concentration, and location of the block. Understanding these effects ultimately helps ensure safe and effective use of nerve blocks in clinical practice.
References
1. Nerve block. Cleveland Clinic https://my.clevelandclinic.org/health/treatments/12090-nerve-blocks.
2. Vijay. Nerve Blocks for Pain Relief: Types, Side Effects, and Uses. Physician Partners of America https://www.physicianpartnersofamerica.com/health-news/health-wellness/nerve-blocks-for-pain-relief-types-side-effects-and-uses/ (2024).
3. Borum, A. D., Voogd, K. L., Smith, M. A., Gerlif, C. & Jensen, H. I. Relationship between Temperature and Pain Sensation Following a Peripheral Ulnar Block: An Exploratory Pilot Study. DOI:10.2174/0125896458335716241002075140.
4. Fruhstorfer, H. Thermal sensibility changes during ischemic nerve block. Pain 20, 355–361 (1984). DOI: 10.1016/0304-3959(84)90112-X
5. Sakamoto, A., Tanaka, S., Ishida, T. & Kawamata, M. Differences in sensory nerve block between levobupivacaine and bupivacaine at low concentrations in humans and animals. DOI: 10.1101/2024.06.23.24309364 (2024).
6. Ekblom, A., Hansson, P., Lindblom, U. & Olofsson, Ch. Does a regional nerve block change cutaneous perception thresholds outside the anaesthetic area? Implications for the interpretation of diagnostic blocks. Pain 50, 163–167 (1992). DOI: 10.1016/0304-3959(92)90157-7
7. Jindal, S., Sidhu, G. K., Sood, D. & Grewal, A. Vibration sensation as an indicator of surgical anesthesia following brachial plexus block. Saudi J Anaesth 10, 432–435 (2016). DOI: 10.4103/1658-354X.179114
8. Ferrell, W. R. & Smith, A. The effect of digital nerve block on position sense at the proximal interphalangeal joint of the human index finger. Brain Research 425, 369–371 (1987). DOI: 10.1016/0006-8993(87)90522-1
9. Ilfeld, B. M., Duke, K. B. & Donohue, M. C. The Association Between Lower Extremity Continuous Peripheral Nerve Blocks and Patient Falls After Knee and Hip Arthroplasty. Anesth Analg 111, 1552–1554 (2010). DOI: 10.1213/ANE.0b013e3181fb9507
10. Carteron, A. et al. Temporary Nerve Block at Selected Digits Revealed Hand Motor Deficits in Grasping Tasks. Front. Hum. Neurosci. 10, (2016). DOI: 10.3389/fnhum.2016.00596
11. Liu, Q., Chelly, J. E., Williams, J. & Gold, M. S. Impact of Peripheral Nerve Block With Low Dose Local Anesthetics on Analgesia and Functional Outcomes Following Total Knee Arthroplasty: A Retrospective Study. Pain Med 16, 998–1006 (2015). DOI: 10.1111/pme.12652