Epidural anesthesia is widely used for pain control in surgeries, childbirth, and chronic pain management. Ensuring that the epidural is functioning effectively is essential prior to proceeding with any surgical or procedural intervention. Inadequate anesthesia can lead to patient discomfort, intraoperative complications, or conversion to general anesthesia. Therefore, clinicians rely on a combination of objective and subjective methods to verify the success of epidural anesthesia.
A main method of confirming the success of epidural anesthesia is the evaluation of sensory blockade. This involves determining whether the patient has lost sensation in the area targeted by the epidural. A common method of evaluation is cold sensation testing, where an alcohol swab or ice is applied to the skin along dermatomal lines. Patients are asked to report any difference in cold sensation compared to unaffected areas. A successful block will typically produce a diminished or absent cold feeling in the target dermatomes.
Another method is pinprick testing, which consists of using a blunt needle or similar pointed object to apply light pressure. In this test, a reduced or absent sharp sensation indicates effective sensory block. These tests help map the spread and level of anesthesia, ensuring it covers the appropriate surgical site 1–3.
Epidural anesthesia typically only needs to create sensory block, but in some cases, it can be beneficial for anesthesia providers to assess motor block as well. Assessing muscle weakness or an inability to move limbs can be a useful indicator of a dense epidural block. In general, monitoring motor function provides an additional layer of information, especially when paired with sensory testing 4–6.
Sympathetic blockade occurs alongside sensory and motor effects and can be assessed by observing physiological changes. A skin temperature increase in the anesthetized region is a common sign. Infrared thermometers or direct touch can be used to detect these changes 7,8. Epidural anesthesia may also impact heart rate and blood pessure. A drop in blood pressure can indicate sympathetic blockade, particularly in high blocks. Continuous monitoring of key vital signs helps detect the success of epidural anesthesia as well as any potential complications. 9-11.
Perhaps the most useful confirmation comes from the patient’s own feedback, when possible. The absence of pain or discomfort in the surgical or labor area is a strong indicator of successful anesthesia. Clearly communicating with the patient, such as by asking about sensations, numbness, or pain, provides immediate and relevant feedback 12-14.
References
1. de Souza Soares, E. C., Balki, M., Downey, K., Ye, X. Y. & Carvalho, J. C. A. Assessment of sensory block during labour epidural analgesia: a prospective cohort study to determine the influence of the direction of testing. Can J Anesth/J Can Anesth 69, 750–755 (2022). DOI: 10.1007/s12630-022-02228-x
2. Dyhre, H., Renck, H. & Andersson, C. Assessment of sensory block in epidural anaesthesia by electric stimulation. Acta Anaesthesiol Scand 38, 594–600 (1994). DOI: 10.1111/j.1399-6576.1994.tb03958.x
3. Sakura, S., Sumi, M., Yamada, Y., Saito, Y. & Kosaka, Y. Quantitative and selective assessment of sensory block during lumbar epidural anaesthesia with 1% or 2% lidocaine. British Journal of Anaesthesia 81, 718–722 (1998). DOI: 10.1093/bja/81.5.718
4. Russell, R. Assessment of motor blockade during epidural analgesia in labour. International Journal of Obstetric Anesthesia 1, 230–234 (1992). DOI: 10.1016/0959-289x(92)80011-g
5. Lanz, E., Theiss, D., Kellner, G., Zimmer, M. & Staudte, H. W. Assessment of motor blockade during epidural anesthesia. Anesth Analg 62, 889–893 (1983).
6. Zaric, D. et al. Sensory and motor blockade during epidural analgesia with 1%, 0.75%, and 0.5% ropivacaine–a double-blind study. Anesth Analg 72, 509–515 (1991). DOI: 10.1213/00000539-199104000-00016
7. Daos, F. G. & Virtue, R. W. Sympathetic-Block Persistence After Spinal or Epidural Analgesia. JAMA 183, 285–287 (1963). DOI: 10.1001/jama.1963.63700040039018b
8. Adolphs, J. et al. Evaluation of sympathetic blockade after intrathecal and epidural lidocaine in rats by laser Doppler perfusion imaging. Eur Surg Res 37, 50–59 (2005). DOI: 10.1159/000083148
9. Epidural and Spinal Anesthesia – Brigham and Women’s Hospital. https://www.brighamandwomens.org/anesthesiology-and-pain-medicine/pain-free-birthing/epidural-spinal-anesthesia.
10. Guidelines for Administering, Managing, and Monitoring Patients Receiving Epidural Infusions. https://nursing.ohio.gov/resources-for-practice-and-prescribing/interpretive-guidelines/04-guidelines-for-monitoring-and-management-of-epidural-infusions.
11. Crowhurst, J. A., Burgess, R. W. & Derham, R. J. Monitoring epidural analgesia in the parturient. Anaesth Intensive Care 18, 308–313 (1990). DOI: 10.1177/0310057X9001800305
12. Young Park, W., Thompson, J. S. & Lee, K. K. Effect of Epidural Anesthesia and Analgesia on Perioperative Outcome. Ann Surg 234, 560–571 (2001). DOI: 10.1097/00000658-200110000-00015
13. Operater. Epidural Anesthesia and Analgesia. NYSORA https://www.nysora.com/topics/abdomen/epidural-anesthesia-analgesia/ (2018).
14. Hewson, D. W., Tedore, T. R. & Hardman, J. G. Impact of spinal or epidural anaesthesia on perioperative outcomes in adult noncardiac surgery: a narrative review of recent evidence. Br J Anaesth 133, 380–399 (2024). DOI: 10.1016/j.bja.2024.04.044