Different Dose Esketamine and Dexmedetomidine for Supplemental Analgesia and Longterm Outcomes

Chronic postsurgical pain (CPSP) refers to pain that occurs or increases after surgery and lasts longer than 3 months. Pain can be limited to the surgical area or projected to the innervated area. The incidence of CPSP is reported from 10% to 50%, with incidence of moderate-to-severe CPSP of about 11.8%. Risk factors of CPSP include severe acute postoperative pain, long duration surgery, and related nerve injury. Spinal correction surgery is associated with severe acute postoperative pain due to large trauma and long duration, with a median pain score of 7 (interquartile range, 4 to 8) on the first day after surgery. And the incidence of persistent pain is up to 75%. Ketamine is a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonists. Ketamine has anti-hyperalgesia effects and may reduce the occurrence of CPSP by blocking NMDA receptors. Esketamine is the S-enantiomer of racemic ketamine with stronger analgesic effect and less adverse reactions. In previous studies, opioid-dependent patients who received low-dose ketamine/esketamine infusion during the perioperative period had decreased pain scores and opioid requirement at 6 weeks, 6 months, and 1 year after surgery. However, results in patients without opioid dependence are controversial. Dexmedetomidine is a highly selective α2 receptor agonist with sedative, anxiolytic, and analgesic effects. When used in the perioperative period, dexmedetomidine improves analgesia, reduces opioid consumption, and decreases opioid-related adverse reactions. Meanwhile, dexmedetomidine can prolong total sleep time, improve sleep efficiency, and increase subjective sleep quality, possibly by activating the endogenous sleep-promoting pathway. The sedative effect of dexmedetomidine may help to reduce the psychiatric adverse reactions of ketamine. However, data is lacking regarding the effect of dexmedetomidine on chronic postsurgical pain. In a previous trial of 200 patients following scoliosis correction surgery, mini-dose esketamine-dexmedetomidine in combination with opioids significantly improved analgesia and sleep quality after surgery but did not reduce CPSP. The authors speculate that increasing esketamine dose in the combination may further improve analgesia and, therefore, reduce the occurrence of CPSP.