Ketamine has emerged as a significant agent in the management of pain, both in acute and chronic settings, although its efficacy as an analgesic continues to be evaluated in various clinical scenarios. The analgesic properties of ketamine are attributed to its antagonism of the N-methyl-D-aspartate (NMDA) receptor, which plays a crucial role in pain modulation and is implicated in the processing of neuropathic pain (Niesters et al., 2014; Wiryana et al., 2017).
Numerous studies have demonstrated that low-dose ketamine can effectively enhance analgesia when used in conjunction with opioids and local anesthetics, thus contributing to multimodal analgesic strategies. Ellakany et al. found that perioperative administration of low-dose ketamine could significantly reduce postoperative pain and enhance the effects of bupivacaine in cholecystectomy (Ellakany et al., 2014). Furthermore, a study by Michelet et al. indicated that subanesthetic doses of ketamine administered alongside patient-controlled analgesia with morphine significantly decreased morphine consumption and improved pain scores following thoracic surgery, facilitating a more effective pain management approach (Michelet et al., 2007).
Research indicates that ketamine's analgesic effects extend beyond the immediate treatment period. For instance, Radford et al. reported substantial antinociceptive effects lasting beyond the infusion period in rodent models, suggesting that ketamine might also induce central nervous system adaptations contributing to extended pain relief (Radford et al., 2017). This phenomenon is corroborated by systematic reviews examining surgeries, demonstrating prolonged analgesia post-administration even after cessation of the infusion (Laskowski et al., 2011). This suggests a beneficial aspect of ketamine in preventing postoperative hyperalgesia, a common complication following surgical procedures (Ménigaux et al., 2001).
In pediatric populations, the analgesic efficacy of ketamine, whether administered intravenously or as an adjunct in regional anesthesia (e.g., caudal blocks), has been documented. Sahoo et al. reported that ketamine can enhance the duration and intensity of pain relief in children undergoing infra-umbilical surgeries, indicating its viability as an analgesic in younger patients (Sahoo et al., 2022; Parikh et al., 2011). Additionally, a systematic review suggested that intravenous ketamine is particularly effective in patients undergoing major orthopedic and thoracic surgeries, underscoring its role as a valuable adjunct to traditional analgesics (Laskowski et al., 2011).
Nevertheless, while the benefits of ketamine as an analgesic are substantial, caution is warranted regarding its administration. Under dosing of ketamine can result in early reemergence from sedation or analgesia. Rapid IV push administration can result in hypersalivation and hallucinations. Proper dosing requires right dose for the patient’s weight, in conscious patients the dose should be given over three minutes while asking the patient about “the best day they ever had” and should never be given rapid IV push.
In summary, the evidence demonstrates that ketamine can serve as an effective analgesic, particularly when used as part of a multimodal pain management approach. Its ability to enhance analgesia, reduce opioid consumption, and produce lingering postoperative pain relief underscores its therapeutic potential. However, errors in administration can produce unwanted effects, thus a careful approach to its administration in clinical practice is warrented.
References:
- Ellakany, M., Megahed, N., Elatter, A., & Teima, M. (2014). Comparison between analgesic effect of bupivacaine thoracic epidural and ketamine infusion plus wound infiltration with local anesthetics in open cholecystectomy. Anesthesia Essays and Researches, 8(2), 162.
https://doi.org/10.4103/0259-1162.134492
- Laskowski, K., Stirling, A., McKay, W., & Lim, H. (2011). A systematic review of intravenous ketamine for postoperative analgesia. Canadian Journal of Anesthesia/Journal Canadien D Anesthésie, 58(10), 911-923.
https://doi.org/10.1007/s12630-011-9560-0
- Michelet, P., Guervilly, C., Hélaine, A., Avaro, J., Blayac, D., Gaillat, F., … & Kerbaul, F. (2007). Adding ketamine to morphine for patient-controlled analgesia after thoracic surgery: influence on morphine consumption, respiratory function, and nocturnal desaturation. British Journal of Anaesthesia, 99(3), 396-403.
https://doi.org/10.1093/bja/aem168
- Ménigaux, C., Guignard, B., Fletcher, D., Sessler, D., Dupont, X., & Chauvin, M. (2001). Intraoperative small-dose ketamine enhances analgesia after outpatient knee arthroscopy. Anesthesia & Analgesia, 93(3), 606-612.
https://doi.org/10.1097/00000539-200109000-00016
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https://doi.org/10.1111/bcp.12094
- Parikh, B., Maliwad, J., & Shah, V. (2011). Preventive analgesia: effect of small dose of ketamine on morphine requirement after renal surgery. Journal of Anaesthesiology Clinical Pharmacology, 27(4), 485.
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- Radford, K., Park, T., Lee, B., Moran, S., Osborne, L., & Choi, K. (2017). Dose-response characteristics of intravenous ketamine on dissociative stereotypy, locomotion, sensorimotor gating, and nociception in male sprague-dawley rats. Pharmacology Biochemistry and Behavior, 153, 130-140.
https://doi.org/10.1016/j.pbb.2016.12.014
- Sahoo, A., Misra, S., Behera, B., Srinivasan, A., Jena, S., & Mohanty, M. (2022). Subanesthetic intravenous ketamine vs. caudal bupivacaine for postoperative analgesia in children undergoing infra-umbilical surgeries: a non-inferiority randomized, single-blind controlled trial. Korean Journal of Anesthesiology, 75(2), 178-184.
https://doi.org/10.4097/kja.21373
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- Zhang, M., Spencer, H., Berman, R., Radford, K., & Choi, K. (2021). Effects of subanesthetic intravenous ketamine infusion on neuroplasticity-related proteins in male and female sprague-dawley rats. Ibro Neuroscience Reports, 11, 42-51.
https://doi.org/10.1016/j.ibneur.2021.06.005