Spinal anesthesia, also known as spinal block, is a common anesthetic technique used in various surgeries, particularly those involving the lower body, such as orthopedic, urological, and gynecological procedures. By injecting anesthetic medication into the cerebrospinal fluid surrounding the spinal cord, spinal anesthesia blocks the transmission of pain signals by part of the spinal cord, resulting in temporary numbness and loss of sensation for sensory areas below the injection site. There are several common medications for spinal anesthesia, and using an appropriate drug is crucial for ensuring effective, safe, and comfortable anesthesia for the patient 1–3.
Bupivacaine is one of the most common medications used in spinal anesthesia. It provides a long duration of anesthesia, making it suitable for surgeries that are expected to last several hours. Bupivacaine works by blocking sodium channels in nerve cells, preventing them from transmitting pain signals. In addition to sensory blockade, it can also cause motor blockade, which requires consideration when selecting it. For spinal use, bupivacaine is typically administered as a hyperbaric solution. Due to its potency, careful dosing is required to avoid side effects, such as cardiac or neurological complications, which are rare but possible with higher doses 4,5.
Lidocaine is another local anesthetic frequently used in spinal anesthesia, although it is generally used for shorter procedures, as it has a shorter duration of action compared to bupivacaine. Lidocaine works similarly by blocking sodium channels, creating an effective and quick onset of anesthesia. However, due to its shorter duration, lidocaine is generally used for procedures lasting less than an hour, such as some urological and outpatient surgeries. While effective, lidocaine has historically been associated with an increased risk of transient neurological symptoms (TNS), such as pain in the lower back, buttocks, or legs. Due to this potential, its use has decreased in favor of other agents with lower risk profiles, although it remains a valuable option for specific shorter procedures 6–8.
Ropivacaine is chemically similar to bupivacaine but has a lower potential for cardiac and central nervous system toxicity, making it a safer choice for some patients, especially those with cardiovascular concerns. It provides a longer duration of sensory block than motor block, making it suitable for surgeries where post-operative pain management is important. While ropivacaine may not last as long as bupivacaine, it still provides a sufficient duration of anesthesia for many types of surgeries and allows for a quicker recovery of motor function 9–11.
Mepivacaine is a short-acting local anesthetic that is sometimes used for spinal anesthesia in outpatient or short procedures. It has a similar onset time to lidocaine and provides effective pain relief for surgeries lasting 1-2 hours. Its advantage lies in its relatively low incidence of post-operative neurological symptoms and rapid postoperative recovery, making it a preferred choice for some shorter procedures 12–14.
There are several common medications used for spinal anesthesia, all belonging to the category of local anesthetic. In addition, anesthesiologists may choose to use an adjuvant as well, in which case the list of medications to consider expands greatly. Choosing the appropriate medication for spinal anesthesia is essential for ensuring safe, effective, and long-lasting anesthesia.
References
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8. Spinal Lidocaine: A Continuing Enigma – Anesthesia Patient Safety Foundation. https://www.apsf.org/article/spinal-lidocaine-a-continuing-enigma/.
9. Mohta, M. Ropivacaine: Is it a good choice for spinal anesthesia? J. Anaesthesiol. Clin. Pharmacol. 31, 457 (2015). DOI: 10.4103/0970-9185.169050
10. McNamee, D. A. et al. Spinal anaesthesia: comparison of plain ropivacaine 5 mg ml–1 with bupivacaine 5 mg ml–1 for major orthopaedic surgery. BJA Br. J. Anaesth. 89, 702–706 (2002).doi: 10.1093/bja/89.5.702
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12. Schwenk, E. S. et al. Mepivacaine versus Bupivacaine Spinal Anesthesia for Early Postoperative Ambulation. Anesthesiology 133, 801–811 (2020). DOI: 10.1097/ALN.0000000000003480
13. Siddiqi, A. et al. Mepivacaine Versus Bupivacaine Spinal Anesthesia for Primary Total Joint Arthroplasty: A Systematic Review and Meta-Analysis. J. Arthroplasty 37, 1396-1404.e5 (2022). DOI: 10.1016/j.arth.2022.03.031
14. Stock, L. A. et al. Postoperative outcomes of mepivacaine vs. bupivacaine in patients undergoing total joint arthroplasty with spinal anesthesia. Arthroplasty 4, 1–8 (2022).