Nerve block techniques utilized in post-bariatric surgery: a narrative review

Abstract

Pain relief following bariatric surgery (BS) can be difficult because many patients have obstructive sleep apnea and are more prone to breathing problems caused by excessive opioid use post-surgery. Using nerve blocks is an effective alternative since they enhance patient comfort and decrease the side effects of opioids. In our review, we comprehensively reviewed present methods to alleviate pain after BS including the transversus abdominis plane block (TAPB), the erector spinae plane block (ESPB), the quadratus lumborum block (QLB), the external oblique intercostal block (EOIB), and the rectus sheath block (RB), aiming to summarized the respective and relative advantages of each nerve block for post-BS analgesia. The review concluded that TAPB is the optimized post-BS nerve block for somatic pain and ESPB relieves somatic and visceral pain which can both be combined with RB. Anterior QLB relieves visceral pain and EOIB can be done without the interference of fat. This review also identified key points for future research to improve post-BS nerve blocks.

Introduction

Obesity ranks among the most prevalent health issues globally [1]. Bariatric surgery (BS) has become the most effective treatment of obesity. Nevertheless, BS usually results pain from the abdominal wall and internal organs [2]. Inadequate postoperative pain control can inevitably result in slower recovery and reduced health [3]. Current methods for post-BS pain have certain disadvantages. Opioids have a strong analgesia, but obese patients are likely to have breathing issues during sleep, and opioids could potentially worsen their breathing, leading to complications or death. Hence, the Enhanced Recovery After Surgery guidelines recommend reducing post-BS opioid use [4]. And non-steroidal anti-inflammatory drugs could lead to the post-BS complications, including anastomotic leaks and peptic ulcers [5, 6]. Local anesthetics offers the fewer systemic side effects, yet they might have a short duration and limited efficacy in managing visceral pain [7]. While nerve blocks provide longer analgesia, lower pain scores, less opioid consumption and better recovery [8,9,10,11,12,13,14,15]. Regional anesthesia applies anesthesia drugs directly to the nerves, so that patients can maintain a lower pain level for longer and the drug consumption in nerve block anesthesia is usually less than that of local anesthesia [16]. Regional anesthesia includes epidural analgesia and nerve blocks. Epidural analgesia often leads to procedural failure due to the difficulty of positioning an epidural catheter [17]. A retrospective study showed that patients under epidural analgesia had a higher rate of wound infection [18]. Therefore, it’s crucial to include nerve block techniques in a multimodal post-BS pain management to decrease opioid use and enhance pain control. Nerve blocks decrease postoperative pulmonary complications, nausea, vomiting, and length of stay [19]. This study reviewed current nerve block techniques utilized in post-BS including the transversus abdominis plane block (TAPB), the erector spinae plane block (ESPB), the quadratus lumborum block (QLB), the external oblique intercostal block (EOIB), and the rectus sheath block (RB), summarizing their analgesia efficacy on the somatic and/or visceral pain after BS. It also identified key points for future research to improve post-BS nerve blocks. Moreover, it’s the first comprehensive review of all kinds of nerve block techniques currently available after BS.

Transversus abdominis plane block (TAPB)

The TAPB, introduced by Rafi in 2001, is a peripheral nerve block that targets the anterolateral abdominal wall [20]. The TAPB targets the space between the internal oblique and transversus abdominis muscles, through which the thoracolumbar nerves from spinal segments T6 to L1 pass, providing sensory innervation to the anterolateral abdominal wall. Figure 1 illustrates the positioning of the TAPB needle and the spread of local anesthetic.

Fig. 1

The positioning of the transversus abdominis plane block needle and the spread of local anesthetic

The TAPB has been shown to enhance pain relief both early and late after BS, as well as to decrease the opioids need [21,22,23,24,25,26]. Various methods have been utilized in the TAPB [27,28,29]. The subcostal technique aims at the transversus abdominis plane in the front abdominal wall, ranging from the xiphoid process to the anterior-superior iliac spine. It is mainly used for upper abdominal surgeries as it affects nerves T6 to T12. The lateral approach involves injecting local anesthetic into the TAP at the midaxillary line and is more effective for lower abdominal procedures, targeting nerves T10 to T12. The oblique subcostal method targets the same anterior nerve rami as the subcostal approach. It begins under the ribcage at the anterior axillary line and moves downward toward the iliac crest. Lastly, the posterior approach focuses on the transversus abdominis plane at the level of Petit’s lumbar triangle or the anterolateral part of the quadratus lumborum muscle. The subcostal approach to the TAPB is often preferred due to its superior analgesic effect in the upper abdomen and the broader distribution of the local anesthetic. Furthermore, the subcostal technique strives for proximity to the costal margin and aligns with the midclavicular line to enhance the outcomes [5]. Notably, the pre-incisional administration of the TAPB for BS is suggested to be more effective than post-incisional, due to the preemptive analgesic effect that prevents the establishment of altered sensory processing pathways in response to surgical stimulus [30].

Considering its mode of action, the TAPB is effective in relieving somatic pain, but not visceral pain, following BS. As a result, it is often deemed more fitting for open surgical incisions compared to minimally invasive laparoscopic techniques [28]. In the cadaveric study conducted by Milan et al. [31], dye was administered into the subcostal, lateral, and posterior compartments of the transversus abdominis plane. The study showed that the subcostal approach had the greatest spread of dye. Conversely, a number of studies reported in the literature have indicated promising outcomes for the application of TAPBs in laparoscopic procedures including BS [32,33,34]. These conflicting outcomes could potentially be attributed to the varying techniques employed for the TAPB and the differing intra-abdominal pressures that arise throughout the BS procedures.

A significant issue related to TAPBs after BS is pinpointing the precise location for their placement. Hebbard et al. [35] described an ultrasound-guided TAPB in 2007, which ensures the local anesthetic is injected into the space between the internal oblique and transversus abdominis muscles. And it has been successfully employed by numerous researchers for analgesia after BS [23, 36]. Performing an ultrasound-guided TAPB in morbidly obese patients undergoing BS can be difficult because of the altered ultrasonographic clarity caused by excessive fatty tissue, challenges in needle placement due to the significant depth from the skin to the target area, and the obscured ultrasound image due to the pressure from laparoscopy. As a result, obtaining consistent results with the TAPB after BS may require a substantial learning process [37]. Furthermore, it can be challenging to incorporate an ultrasound machine into the operating room, and many surgeons may not be well-versed in its use. Performing a TAPB after BS with laparoscopic guidance eliminates the need for additional ultrasonography setup, allowing surgeons to avoid injecting the local anesthetic into the peritoneal cavity. They can also clearly observe the transversus abdominis muscle bulge or Doyle’s internal bulge sign, which confirms the correct placement of the local anesthetic [38, 39]. Recent research has confirmed the accuracy of the post-BS block placement in the correct plane and its comparable effectiveness in controlling postoperative pain to that of the ultrasound-guided method [40, 41]. Additionally, the literature has documented complications from ultrasound-guided TAPBs, such as liver puncture, which are linked to the difficulty in clearly visualizing the needle during the procedure [42]. Performing a TAPB with laparoscopic guidance after BS enables full visualization of the needle, thus preventing the reported iatrogenic injuries. However, it lacks the precision of ultrasonography in defining the interfacial planes and the surrounding muscles. Hence, it is necessary to use ultrasonographic confirmation of the local anesthetic spread in the initial learning phase [43].

A meta-analysis discovered that the TAPB had a significant impact on reducing postoperative pain scores at 0–4 h and 24 h following laparoscopic BS [44]. Nevertheless, the half-life of traditional bupivacaine is between 8 and 10 h, making it less effective for prolonged pain relief. A potential reason is that while bupivacaine has a brief half-life in the bloodstream, it might provide a more extended analgesic effect when used for direct nerve blockade [45]. Furthermore, the optimal timing for administering a TAPB is likely during the post-BS period [44]. Administering the TAPB after BS significantly decreased 24-hour opioid usage compared to that before BS. However, De Oliveira et al. [44], discovered that a preoperative TAPB has advantageous preemptive analgesic effects, particularly on 24-hour opioid usage and early rest pain scores, as compared to a postoperative block. However, these findings might be partly due to the use of ropivacaine in the two postoperative TAPB studies analyzed by De Oliveira et al., while the preoperative TAPB studies predominantly utilized bupivacaine. Bupivacaine was determined to provide a more extended duration of analgesia than ropivacaine when used for peripheral nerve blocks [46]. Taking into account the pharmacokinetics of bupivacaine and ropivacaine, the effect of TAPB on reducing post-BS opioid use is expected to be most significant within the first 24 h.

Recently, the relatively long-acting liposomal bupivacaine (LB) has been used for TAPBs in BS, offering the benefit of prolonged analgesia lasting up to 96 h [47]. A few comparative studies have demonstrated a marked decrease in total opioid consumption and better pain scores beyond the 24-hour mark after BS [47,48,49], while Wong, KA et al. [39] concluded that the LB did not lead to a significant decrease in overall opioid use or in pain levels among patients who underwent BS in a randomized controlled trial (RCT). Further studies are needed to study the utilization of LB in TAPBs for laparoscopic BS, and assess the effect of varying volumes and concentrations of local anesthetics, diverse TAPB techniques, and the timing of TAPB on opioid usage.

Erector spinae plane block (ESPB)

The erector spinae muscle complex consists of the spinalis, longissimus, and iliocostalis muscles. These muscles extend vertically along both sides of the vertebral column, starting from the sacrum and reaching up to the base of the skull. Forero et al. [50] introduced the erector spinae plane block (ESPB), a technique that has enjoyed significant popularity over the past ten years. ESPB is an innovative method of regional anesthesia. In this procedure, a local anesthetic is administered deep into the erector spinae muscle, targeting the fascial plane. From this point, the local anesthetic is designed to spread both caudally and cranially [51]. Studies conducted on cadavers have demonstrated that ESPB impacts both the dorsal and ventral branches of the spinal nerve. Additionally, it has been observed that the local anesthetic spreads to the surrounding paravertebral space. This diffusion results in a comprehensive sensory block for both somatic and visceral structures in the abdominal region. Therefore, ESPB’s capacity to block both somatic and visceral nerves enables it to address the two primary sources of pain following BS [51]. Figure 2 has shown the positioning of the ESPB needle and the spread of local anesthetic.

Fig. 2

The positioning of the erector spinae plane block needle and the spread of local anesthetic

This block has been employed for a range of surgical applications, including thoracic, abdominal, and cardiac operations [52, 53]. So far, a limited number of studies have explored the application of ESPB in BS, with all suggesting potential advantages in terms of reducing opioid consumption and managing pain. The initial findings on its use in morbidly obese patients undergoing BS were reported in a case series involving three individuals [54]. In that study, bilateral ESPBs were administered at the T7 transverse process level to alleviate postoperative pain following BS, yielding promising outcomes. The randomized study by Abdelhamid et al. [55] evaluated three different methods for post-BS pain management in patients who recieved laparoscopic sleeve gastrectomy. Patients who underwent bilateral ESPB experienced reduced pain scores compared to those who received other techniques, especially during the initial 12 h post-BS. In the ESPB group, both the total 24-hour post-BS opioid consumption and the total 24-hour post-BS paracetamol consumption were markedly lower than in the control group, which was administered opioid analgesia. The randomized study by Mostafa et al. [56] assessed the effectiveness of ESPB at the T7 level versus a control group that received a sham block. In the study, the emphasis was on managing post-BS pain and monitoring the consumption of opioids during BS. ESPB offered superior pain control compared to the control group in the first 8 h after BS. However, from 12 to 24 h after BS, the pain scores between the ESPB group and the controls were not significantly different. Nonetheless, Zengin, SU et al. [51] highlighted that the benefits of the ESPB in managing post-BS pain lasted for a full 24 h, with no patients in the study requiring additional analgesic intervention. The discrepancies between the two sets of findings could be attributed to the higher dosage of the blocking agent employed in the latter study, as well as variations in the level at which the block was administered. Furthermore, the use of opioids via patient-controlled analgesia (PCA) may have obscured the additional pain relief of the ESPB beyond the 8-hour after BS in Mostafa’s study. This is a period when patients have typically become adept at using the PCA system. In the latest RCT conducted by Pongkwan J et al. [57], there were no notable variations in postoperative morphine use or pain levels for obese patients undergoing laparoscopic BS, irrespective of whether they had an ESPB or not. Although the ESPB group experienced a statistically significant reduction in pain scores compared to the control group at both post-BS 6 and 12 h, this reduction did not hold clinical relevance, and ESPB did not lead to a decrease in post-BS opioid usage.

Discrepancies among the trials may stem from the unpredictable distribution of the anterior rami of spinal nerves following ESPB, as indicated by conflicting data from cadaveric and radiological studies [58, 59]. Furthermore, a separate study noted that ESPB did not result in any alterations in somatosensory evoked potentials [60], indicating inadequate distribution of local anesthetic to the paravertebral space that may lead to the insufficient analgesia in the current study. Differences in the types of bariatric surgeries performed and the multimodal analgesic protocols used could potentially affect the outcome of the study. The study by Pongkwan J et al. had a smaller percentage of laparoscopic sleeve gastrectomy cases compared to the study by Mostafa et al., which could have influenced the severity of post-BS pain. While Mostafa et al.‘s study relied solely on intravenous paracetamol, Pongkwan J et al.‘s study promoted a multimodal analgesic approach. This strategy might have provided extra analgesic benefits, leading to a significant reduction in pain scores and morphine needs during the post-BS period. Consequently, the variation in the analgesic effect’s duration could be due to the varying techniques employed (such as the thoracic level targeted, the dosage or concentration of the local anesthetic, the approach to post-BS pain relief, and the specific type of BS), and these factors could potentially be the focus of upcoming studies.

ESPB is considered a secure and straightforward procedure, as it is performed away from critical bodily structures. Nonetheless, it is imperative to remain vigilant about possible complications in obese patients undergoing BS, including the risks of pneumothorax, accidental intravascular injection, and systemic toxicity from local anesthetics [61]. Furthermore, the presence of excessive body fat in obese patients undergoing BS can complicate the ultrasound imaging process because of the ultrasound beam’s reduced penetration and the inadequate needle length. These challenges could make it technically challenging to carry out peripheral nerve blocks. Nevertheless, such technical hurdles can be mitigated by the operator’s advanced skill set and the use of high-quality equipment [56].

Quadratus lumborum block (QLB)

The concept of the QLB was introduced by Blanco in 2007 [62] and it has been utilized in post-BS analgesia in recent years. Figure 3 illustrates the positioning of the QLB needle and the spread of local anesthetic.

Fig. 3

The positioning of the quadratus lumborum block needle and the spread of local anesthetic

The QLB technique is categorized into four distinct types, each defined by the location where the medication is applied: the lateral QLB, the posterior QLB, the anterior QLB, and the intramuscular QLB. The local anesthetic spreads along the thoracolumbar and endothoracic fasciae, entering the paravertebral space and extending cranially to the T10 level. The analgesic effect of QLB is because of the blockade of pain receptors and the inhibition of both high-threshold and low-threshold mechanoreceptors of sympathetic neurons situated in the superficial layer of the thoracolumbar fascia by the local anesthetic [63]. Research conducted in the past has shown that employing QLB in abdominal surgery can result in decreased reliance on opioids and offer pain relief for up to 24 h [64, 65]. The same analgesic effect has been shown in BS. Tarek M et al. [66] determined that patients who received posterior QLB during laparoscopic sleeve gastrectomy experienced longer-lasting postoperative pain relief compared to those who had ESPB. However, he also noted that the posterior QLB procedure is more challenging and time-consuming than ESPB. The anterior QLB is recommended for BS due to its solid anatomical and theoretical foundation. Elsharkway H et al. [67] showed that the medication spread to the levels between T7 and L2, reaching up to T6, when the subcostal anterior approach was used at the L1-L2 level in a cadaver. Furthermore, in a cadaver study, it was observed that the dye extended into the thoracic paravertebral space, the intercostal space surrounding the somatic nerve, and even reached the thoracic sympathetic trunk [68]. Thus, the range of this plane can efficiently alleviate pain stress for patients during the postoperative period of BS, encompassing both visceral pain and pain from the abdominal wall incision. Present clinical studies have indicated that the anterior QLB has a swift onset, a sustained duration of effect, and covers a wide area of blockage, which is the first choice of four types of QLB for the pain relief after BS [69].

In the latest RCT conducted by Liao W et al. [70], the expected local anesthetics distribution of QLB after BS can effectively block the visceral nerves by extending to the paravertebral area. When carrying out nerve blocks below the ribs, the block plane is capable of reaching from T6 to L2 [70]. The anterior QLB procedure was conducted within the fascial plane that separates the quadratus lumborum muscle from the psoas major muscle. Compared to more superficial block techniques utilized after BS, like the TAPB block and lateral QLB, the anterior QLB’s benefit stems from its deeper positioning, which may facilitate a more extensive spread within the paravertebral region [71]. Because of the possible paravertebral spread noted in certain research, the anterior QLB could provide more reliable analgesia for visceral pain [68]. Nevertheless, since the injection site for the anterior QLB is positioned deeper anatomically and nearer to the abdominal organs, the technical requirements for executing the anterior QLB after BS are more stringent [72]. Future research should focus on technologies that can aid in performing post-BS anterior QLB, including tools like laparoscopes and ultrasound devices. Notably, the reported complications of anterior QLB include local anesthetic toxicity, bleeding risk of anticoagulant patients, and muscle weakness of quadriceps femoris [72, 73].

External oblique intercostal block (EOIB)

EOIB is an advanced technique of post-BS analgesia for the upper midline and lateral regions of the abdominal wall. Elsharkawy et al. [74] elucidated the possible mechanisms behind it, which showed staining of both the lateral and anterior branches of the intercostal nerves from T7 to T10 in a cadaver study. EOIB is executed by positioning the ultrasound probe in a paramedian sagittal orientation at the T6-7 level, allowing for the visualization of the external oblique and intercostal muscles. The local anesthetic is then injected beneath the external oblique muscle. Figure 4 demonstrates the positioning of the EOIB needle and the spread of local anesthetic.

Fig. 4

The positioning of the external oblique intercostal block needle and the spread of local anesthetic

Given the successful outcomes of the EOIB in upper abdominal procedures, Sami and colleagues [5] also incorporated the EOIB into their BS practices. The current research indicates that the EOIB has produced satisfactory outcomes [75]. EOIB offers considerable advantages, as it can be applied in regions not impacted by the excess fat. Thus, obesity can’t hinder the EOIB. As more clinical trials are conducted to further assess its efficacy, the EOIB is poised to become a top choice for post-BS analgesia.

Rectus sheath block (RB)

RB offers dependable pain relief for surgeries including the central part of the abdominal wall and has a high success rate when ultrasound guidance is used during the procedure [76]. It has become increasingly favored for single-incision laparoscopic surgeries and other operations that require a midline approach [77, 78]. With the aid of direct visualization through an in-plane technique, RB is straightforward to administer, poses minimal risk of puncturing the peritoneum, and can offer extended pain relief [79]. Figure 5 illustrates the positioning of the RB needle and the spread of local anesthetic.

Fig. 5

The positioning of the rectus sheath block needle and the spread of local anesthetic

Currently, surgeons have combined RB with TAPB and ESPB for post-BS analgesia. Sami et al. [5] discovered that the use of RB combined with subcostal TAPBs was more effective in reducing both resting and dynamic pain scores after BS. Significantly, their study’s findings suggested that the subcostal TAPB and RB might positively impact post-BS visceral pain, contradicting the prevailing belief that TAPBs do not alleviate such pain [21]. Further trials are necessary to determine if the RB contributes to the alleviation of visceral pain in this combined approach. Sami et al. [75] found that using both bilateral EOIBs and bilateral regional blocks together could decrease the amount of post-BS rescue analgesia needed. We anticipate that future clinical trials will explore the combination of RB with various other nerve block techniques for post-BS analgesia, and that examining the analgesia effect of RB in isolation following BS will also hold substantial importance.

Conclusion

TAPB technique is currently the most effective nerve block for post-BS somatic pain relief. Performing the TAPB under laparoscopic vision is more convenient and cleare for somatic pain relief than ultrasound-guided TAPB and it’s required to confirm LB’s prolonged analgesic efficacy in TAPB for BS. ESPB is relatively safe which relieves both somatic and visceral pain, although there are difficulties in the ultrasound imaging process. The anterior QLB provides visceral pain relief with the technical difficulty due to the injection site. EOIB can be administered without the interference of the subcutaneous fat, offering unique advantages for BS. RB has shown its efficacy when combined with TAPB or ESPB. Moreover, the thoracic level of the block, the dosage and concentration of the local anesthetic, the techniques assisted for the block, the timing of the block, and the type of BS can all influence the efficacy of nerve block techniques after BS, which should be focus on in upcoming research.