Acupuncture for postoperative ileus: Advancement and underlying mechanisms

Abstract

Postoperative ileus (POI) remains a prevalent and significant challenge following abdominal surgeries, precipitating patient distress, prolonged hospital stays, and escalated medical expenditures. Conventionally addressed via pharmacological interventions, POI is increasingly being explored through adjunctive therapeutic strategies, with acupuncture gaining recognition as a promising option. Acupuncture has demonstrated encouraging potential in promoting gastrointestinal motility in patients with POI. Moreover, recent research has shed light on the therapeutic mechanisms underlying its efficacy. This article aims to present a comprehensive overview of acupuncture as a treatment for POI, highlighting advancements in clinical research and recent elucidations of its mechanistic underpinnings. It aspires to contribute a pivotal reference point for scholars and enthusiasts keen on garnering a deeper understanding of acupuncture’s role in managing POI.

Key Words: Acupuncture; Gastrointestinal motility; Mechanism; Patients; Postoperative ileus

Core Tip: This article emphasizes that postoperative ileus (POI), a prevalent issue after abdominal surgeries, causes significant patient distress and financial burdens. Traditionally managed with drugs, POI is now explored with additional therapies, notably acupuncture, which shows potential in enhancing gastrointestinal motility. The article provides a comprehensive review of acupuncture for POI, featuring clinical advancements and new insights into its mechanisms. It serves as a crucial reference for scholars and enthusiasts seeking a deeper understanding of acupuncture’s application in POI management.

INTRODUCTION

Postoperative ileus (POI) is a common complication following surgery, characterized by a temporary reduction or cessation of normal bowel function. It results in patient discomfort, delayed recovery, prolonged hospital stays, and increased healthcare costs[1]. Traditional treatments for POI include pharmacological interventions, which may have limited efficacy and potential side effects[2]. As a result, researchers and healthcare providers are increasingly exploring alternative therapies, such as acupuncture, as a complementary approach for managing POI.

Acupuncture, a key component of traditional Chinese medicine, involves the insertion of thin needles into specific points on the body to promote healing. Recently, numerous studies have investigated the effectiveness of acupuncture in managing POI, with promising results. Research has shown that acupuncture can improve bowel motility and reduce the duration of POI, leading to faster recovery and shorter hospital stays for patients[3,4]. The underlying mechanisms behind the efficacy of acupuncture for POI are not yet fully understood, but several theories have been proposed. One theory suggests that acupuncture stimulates the release of neurochemicals that alleviate inflammation and pain, thereby promoting bowel function[5]. Additionally, acupuncture modulates the autonomic nervous system, which regulates gastrointestinal motility. Acupuncture may help restore normal bowel function in patients with POI, by promoting the balance the sympathetic and parasympathetic nervous systems[6].

CLINICAL ADVANCEMENTS

In recent years, numerous randomized controlled trials have explored the efficacy of acupuncture and electroacupuncture (EA) in treating POI. Wang et al[4] reported a significant reduction in the duration of POI in patients undergoing laparoscopic surgery for colorectal cancer who received EA compared to those in the sham EA group, highlighting a reduced risk of prolonged POI. Similarly, another clinical trial showed that EA significantly decreased the duration of POI and postoperative analgesic requirements following laparoscopic colorectal cancer surgery compared to no acupuncture or sham acupuncture[7]. Additionally, Yang et al[8] demonstrated that combining traditional Chinese medicine formula simo decoction with acupuncture significantly decreased the incidence of POI, shortened hospital stays, and achieved superior efficacy compared to chewing gum in patients undergoing colorectal cancer surgery. Furthermore, Jung et al[9] found that acupuncture enhanced bowel motility in patients with POI after distal gastrectomy compared to those who did not receive acupuncture. A prospective, randomized, controlled pilot study conducted by Chae et al[10] revealed that acupuncture shortened the duration of POI following gastric surgery, potentially contributing to improved postoperative recovery outcomes. Moreover, a study indicated that combining simo decoction with acupuncture reduced the incidence of POI after liver cancer surgery and decreased hospital stays. In contrast, chewing gum could potentially reduce the risk of intestinal obstruction but did not impact the length of hospitalization[11].

Chen et al[12] demonstrated that transcutaneous EA effectively improved bowel motility, reduced POI post open gastrectomy, resulting in shorter hospital stays. In clinical practice , the commonly used acupuncture points for the treatment of POI mainly include Zusanli (ST36), Zhigou (SJ6), Hegu (LI4), Sanyinjiao (SP6), Tianshu (ST25), Shangjuxu (ST37), Taichong (LV3), and Quchi (LI11). Researchers have also explored the varied effects of acupuncture at different acupoints in improving POI. For instance, Yang et al[3] reported that compared to standard therapy, EA at ST36 combined with standard treatment significantly promoted postoperative bowel function recovery in patients undergoing laparoscopic colorectal cancer resection, while EA at ST25 did not exhibit the same effect. However, conflicting perspectives exist regarding the effectiveness of acupuncture in treating POI. For instance, an randomized controlled trial by Meng et al[13] concluded that acupuncture may not prevent prolonged POI after colorectal cancer surgery once it has developed in the studied population.

Numerous systematic reviews and meta-analyses have investigated the effectiveness of acupuncture or EA in managing POI. The comprehensive review by Chen et al[14] highlighted the positive correlation between EA and improved gastrointestinal recovery, along with reduced pain severity following colorectal surgery, underscoring the potential benefits of integrating EA into perioperative care for enhanced patient outcomes. Zhao et al[15] demonstrated that the combination of acupuncture with enhanced recovery after surgery protocols can effectively facilitate recovery from POI following colorectal cancer surgery, offering a promising therapeutic approach. Additionally, Chen et al[16] identified EA and transcutaneous EA as safe and efficacious modalities for enhancing gastrointestinal motility in patients recovering from abdominal surgery, although their efficacy in alleviating postoperative pain remains inconclusive. In another study, Liu et al[17] demonstrated that acupuncture interventions for POI following colorectal cancer surgery may significantly aid in restoring gastrointestinal function, emphasizing the precise efficacy of EA at the ST36 acupoint. Ye et al[18] suggested that acupuncture may play a potential role in reducing POI following gastrointestinal surgery. However, they emphasized the need for further research to improve the overall quality of evidence and ensure the safety of acupuncture interventions. Furthermore, the analysis by Zhang et al[19] highlighted a significant reduction in time to first defecation in colorectal cancer POI patients treated with acupuncture, emphasizing the therapeutic importance of lower He-sea points like ST36 and ST37 in managing POI and restoring intestinal motility.

MECHANISMS OF ACTION

Numerous studies have explored the potential mechanisms underlying the role of acupuncture in improving POI. Yang et al[20] found that EA could suppress intestinal inflammation and promote gastrointestinal motility in POI mice. The mechanism involves EA activating the Janus kinase 2/signal transducer and activation of transcription 3 signaling pathway mediated by α7 nicotinic acetylcholine receptor in macrophages, leading to a reduction in the production of inflammatory cytokines. Additionally, EA can inhibit the expression of gamma absorptiometry aminobutyric acid receptors in the dorsal motor nucleus of the vagus nerve, thereby activating the vagus nerve and improving inflammation. Similarly, Liu et al[21] discovered that EA alleviate intestinal inflammation and motility disorders in POI mice by activating the α7 nicotinic acetylcholine receptor signaling pathway mediated by the vagus nerve, independent of the spleen. Gao et al[22] also found that the effect of EA in treating POI is primarily achieved through the stimulation of the vagus nerve by Th1 cells and the inhibition of inflammatory responses. However, Fang et al[23] suggested that the regulatory effects of EA primarily improves gastrointestinal transit function by stimulating neurons of the solitary tract nucleus, rather than activating the cholinergic anti-inflammatory pathway. Research by Okada et al[6] indicated that abdominal surgery induces intestinal transit delay via the sympathetic pathway mediated by α-adrenergic receptors, while EA can treat POI by modulating the autonomic nervous system. Murakami et al[5] found that EA enhances gastrointestinal motility in a POI mouse model, with regulatory effects on small intestinal slow waves, as well as postoperative analgesic effects, likely mediated through autonomic-cytokine pathways. Additionally, Deng et al[24] discovered that acupuncture may improve POI by regulating the macrophage interleukin-6/microRNA-19a/C-kit signaling pathway. Current research suggests that acupuncture or EA improves POI through mechanisms involving anti-inflammatory responses, cholinergic anti-inflammatory pathways, the sympathetic and vagus nervous systems, the nucleus of the solitary tract, etc. However, further research is required to validate these findings or to explain the mechanism of acupuncture from other perspectives.

CHALLENGES AND FUTURE DIRECTIONS

The field of acupuncture therapy for POI still faces several challenges and uncertainties that need to be addressed. One of the key issues is the lack of standardized acupuncture treatment protocols in clinical research, with various acupuncture techniques and acupoints being utilized. It is crucial to establish standardized acupuncture protocols (including the selection of specific acupuncture points, frequency, duration, and intensity), focusing on specific acupoints for POI treatment. Additionally, the current clinical evaluation criteria are predominantly subjective, highlighting the need for more objective gastrointestinal motility assessment tools, such as intestinal motility monitoring devices. Furthermore, there is a scarcity of long-term follow-up studies on the outcomes of acupuncture treatment for POI, with existing research primarily focusing on patients during hospitalization. Severity assessments of conditions of the patients are often lacking, resulting in a deficiency of evidence regarding the effectiveness of acupuncture on patients of different disease severity levels. There is a scarcity of research examining the therapeutic differences among various acupuncture methods, including manual acupuncture, EA, and auricular acupuncture, in treating POI. Consequently, it remains uncertain which acupuncture technique is the most effective for POI treatment. In the realm of clinical research, there is a pressing need for future large-scale, multicenter, randomized, sham acupuncture-controlled clinical trials to further validate the effectiveness of acupuncture in POI treatment. In basic research, many studies lack depth, highlighting the importance of adopting novel methodologies to delve deeper into the mechanisms underlying the effectiveness of acupuncture in improving POI.

CONCLUSION

Acupuncture represents a significant advancement in the management of POI, providing a safe and efficacious alternative to pharmacological interventions. Acupuncture has the potential to reduce recovery time, enhance patient comfort, and optimize overall surgical outcomes by targeting the underlying mechanisms of POI and enhancing bowel function. Despite the increasing body of evidence supporting acupuncture for POI, further research is warranted to elucidate its precise mechanisms of action, establish standardized treatment protocols, explore long-term outcomes, and effectively integrate acupuncture into multimodal postoperative care strategies.