In this study, we found that an esketamine-based opioid-sparing anaesthetic protocol could shorten the recovery time of gastrointestinal function after benign gynaecological laparoscopic surgery and reduce the incidence of PONV, but had no significant effect on the postoperative feeding time and duration of postoperative hospitalisation.
The recovery of postoperative gastrointestinal function, which is commonly assessed using time to exhaustion, time to defecation, bowel sounds, and imaging, is an important prognostic factor for POI patients [2, 3, 8, 11, 12]. However, as the time of first postoperative exhaustion is the most commonly used method [3], this index was also used in this study. The recovery of postoperative gastrointestinal function is influenced by various factors, such as the surgical approach, operative time, surgical trauma, intraoperative blood loss, intestinal manipulation, intraoperative fluid volume, postoperative feeding time and postoperative activity time, and perioperative opioid consumption [8, 12, 13]. Among them, opioid consumption is the most concerning factor for anesthesiologists [13, 14].
Opioid consumption is strongly associated with impaired gastrointestinal motility and postoperative intestinal obstruction. Studies have found higher opioid consumption in patients with intestinal obstruction compared with patients without intestinal obstruction [13, 14]. Opioids exert a dose-dependent inhibitory effect on intestinal motility due to the presence of several opioid receptor types in the intestine, such as κ, µ, and δ. Among them, κ and µ receptor agonists modulate cholinergic transmission in the mesenteric plexus [15, 16]. All three subtypes of opioid receptors have been identified in the submucosal and intramuscular plexus neurons. In humans, mu-opioid receptors are present on immune cells in the lamina propria, submucosa, and interosseous neurons. In addition to the direct effects of opioids on gastrointestinal motility, opioids may also affect fluid transport and produce antisecretory effects. Following intravenous, intramuscular and epidural administration of opioids, inhibitory effects are detected in gastrointestinal function [15, 16]. The use of an opioid-sparing anaesthetic protocol reduces intraoperative opioid consumption, thereby mitigating the effects of opioids, which in turn facilitates postoperative recovery of gastrointestinal function.
Reducing opioid consumption is an increasing practice in anaesthesia. Epidural combined with general anaesthesia is the most commonly used opioid-sparing anaesthetic protocol in abdominal surgery [17–20]. Previous studies have shown that epidural anaesthesia can effectively reduce perioperative opioid consumption in gynecologic surgery and postoperative pain [17, 21]. However, because of side effects, such as hypotension, lower extremity muscle weakness and urinary retention, epidural anaesthesia is not widely used in gynecologic surgery [22, 23]. Moreover, some studies have shown that epidural anaesthesia does not have a decisive advantage over general anaesthesia in gynecologic surgery [24, 25]. The other protocols for opioid-sparing anaesthesia include transversus abdominis plane block (TAP) or lumbar square block (QLB) combined with general anaesthesia. TAP is widely used because it is simple to perform, but it does not reduce intraoperative opioid consumption and does not have an absolute analgesic advantage over postoperative wound infiltration in gynecologic patients [26]. QLB has the potential to be widely used as a local anaesthetic and may also have a visceral analgesic effect. A randomized controlled trial (RCT) found that post-QLB significantly improved postoperative gynecologic laparoscopic pain for up to 24 h and reduced intraoperative opioid use compared with a placebo[ 27]. However, QLB is complex and not available to all anesthesiologists. Therefore, opioid-sparing anaesthesia via non-opioid analgesics is a convenient option.
Tu et al. found that propofol combined with esketamine had good safety and reliability in the induction of anaesthesia, improved hemodynamics, improved surgical stress and inflammatory response, shortened anaesthesia time, and promoted postoperative cognitive recovery [10]. A meta-analysis by Wang et al. showed that low-dose esketamine combined with sufentanil for spinal fusion patients not only improved postoperative analgesia but also reduced the need for opioids and reduced the incidence of postoperative nausea and vomiting and delayed recovery of gastrointestinal function, without affecting the time to resuscitate [28]. In this study, the use of an esketamine-based opioid-sparing anaesthetic protocol resulted in faster resuscitation after general anaesthesia, shorter postoperative gastrointestinal recovery time, and reduced incidence of PONV, which are consistent with previous studies.
A postoperative analgesic protocol of wound infiltration plus oral NSAIDs was used for benign gynecologic laparoscopic surgery in our centre. Previous studies have shown that wound infiltration provides good postoperative analgesia in patients undergoing gynecologic laparoscopy [19]. Similarly, oral NSAIDs drugs have also been shown to provide good analgesia in postoperative analgesia in gynecologic laparoscopic patients [29, 30]. In this study, the follow-up of postoperative analgesia found satisfactory analgesia in both groups.
The analgesic rescue was required in 19.4% of patients in the conventional anaesthesia group at 24 h postoperatively compared with 11.4% in the opioid-sparing anaesthesia group. However, the difference between the two groups was not statistically significant. This may be explained that the application of esketamine reduced intraoperative sufentanil and remifentanil consumption. Yamashita et al. showed that large intraoperative applications of remifentanil can cause postoperative hyperalgesia [31]. Mauermann et al. confirmed that increased intraoperative fentanil consumption could increase postoperative opioid consumption and pain in patients. Although no studies have demonstrated that sufentanil causes postoperative hyperalgesia, since it belongs to the same fentanyl family, it is reasonable to conclude that sufentanil may also increase the risk of developing postoperative hyperalgesia. Reducing opioid consumption may reduce the incidence of hyperalgesia. Studies on postoperative hyperalgesia have also shown that the use of NMDA agonists such as ketamine could effectively reduce the incidence of postoperative hyperalgesia [32, 33], thereby improving acute postoperative pain and reducing opioid consumption. The present study used an esketamine-based opioid-sparing anaesthetic regimen that reduced intraoperative opioid consumption. Further esketamine application reduced the incidence of postoperative hyperalgesia, thus showing a difference in the 24-h postoperative analgesic rescue between the two groups. The lack of statistical difference between the two groups may be due to the small sample size, and further studies using larger samples are needed to verify this effect.
This study has several limitations. First, this study was a single-centre, small sample size study, and whether the protocol has the same effect on patients in other centres can only be confirmed by a larger multicenter study. Second, this study did not include a control group with different esketamine doses, and it remains to be studied whether smaller doses of esketamine can further reduce the incidence of adverse effects. Third, although the study observed the patients' postoperative psychiatric condition, patients were not evaluated using an assessment scale. Therefore, further studies using a psychiatric assessment scale are needed to confirm whether the dosage of esketamine used in this study affects patients. Fourth, this study was limited to benign gynecologic laparoscopic surgery, and it is worthwhile to continue to investigate whether this protocol is feasible for other types of surgery and whether the effective dose of esketamine will change.
In conclusion, an esketamine-based opioid-sparing anaesthetic protocol can shorten the recovery time of gastrointestinal function after benign laparoscopic surgery in gynaecology, reduce the incidence of PONV, and promote early recovery of patients. In addition, the application of esketamine may reduce the postoperative opioid dose requirement of patients.