Single-point ultrasound-guided iliohypogastric-ilioinguinal-genitofemoral nerve block for inguinal hernia surgery in older adult patients: a randomized controlled trial

Introduction

An inguinal hernia typically manifests as a mass in the groin region. It is caused by a defect of the abdominal wall in the groin area, forming a hernial sac structure protruding at the body surface. Tissues or organs from the abdominal cavity can protrude into the hernial sac through defects in the abdominal wall. Subsequently, the hernial ring can compress the contents of the hernia, leading to an incarcerated hernia. The prevalence of inguinal hernias is 27–43% in men and 3–6% in women (1). Currently, over 20 million individuals worldwide undergo surgery for inguinal hernias every year (2); older adults are at a higher risk (3,4) and often have underlying conditions such as hypertension, diabetes, coronary heart disease, and chronic bronchitis, which can lead to their poor tolerance to both the surgery and anesthesia. Ultrasound-guided nerve block has minimal effects on the circulation and respiratory function of patients and has been successfully used for inguinal hernia repair (5,6), leading to reduced postoperative pain, decreased need for analgesic medications, and lower risk of complications (7). This technique is thus highly suitable for inguinal region analgesia, especially among older adult patients undergoing hernia surgery.

Iliohypogastric nerve-ilioinguinal nerve (IHN-IIN) block has shown promise in providing effective postoperative analgesia for inguinal hernia surgery (8), but complaints of pain at skin incision and reactions to intraoperative traction on the hernial sacs are common, necessitating further investigation. Although genitofemoral nerve (GFN) block has been recognized for its potential role in analgesia during and after inguinal hernia repair (9-11), it is rarely performed in clinical practice. In this study, we developed modifications to the technique for performing IHN-IIN block and GFN block (IHN-IIN-GFN) using a single puncture approach and evaluated its potential application in inguinal hernia surgery for older adult patients. We present this article in accordance with the CONSORT reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-24-787/rc).

Methods

Study design

This single-blinded, randomized controlled trial was conducted to assess the prospective feasibility of a single-point ultrasound-guided IHN-IIN-GFN nerve blockage in open anterior inguinal hernia repair among older adult patients. Participants were randomly allocated into two treatment arms: the IHN-IIN block group (group A) and the IHN-IIN-GFN block group (group B) (Figure 1). The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). Ethical approval for the study was granted by the Ethics Committee of The First People’s Hospital of Yunnan Province on April 21, 2020 (No. KHLL2020-KY016). Written informed consent was obtained from all participating patients.

Figure 1 Flowchart of patients included in this study.

Patients

All patients underwent unilateral open anterior inguinal hernia repair (the Lichtenstein technique). The inclusion criteria were as follows: American Society of Anesthesiologists (ASA) grade I–III, body mass index (BMI) ≤28 kg/m², age ≥60 years, no cognitive impairment, no coagulopathy, no infection at the puncture site, and no allergy to local anesthetics. Meanwhile, the exclusion criteria were as follows: ASA grade IV–V, severe heart failure, pulmonary embolism, pulmonary hypertension, other conditions that would limit cooperation, bilateral surgery, or a history of previous lower abdominal surgery. We enrolled 42 male patients undergoing open inguinal hernia surgery at The First People’s Hospital of Yunnan Province from June 2018 to December 2019.

Anesthetic methods and interventions

All patients received oxygen in the supine position with monitoring of mean arterial pressure (MAP), heart rate (HR), respiration rate (RR), oxygen saturation (SpO₂), and electrocardiography (ECG). Peripheral venous access in the upper extremities was established for all patients, followed by a continuous infusion of sodium chloride (500 mL; National Drug Standard: H53020729; Kunming Nanjiang Pharmaceutical Co., Ltd., Kunming, China) at a rate of 7 mL/kg/h. Sufentanil (0.1 µg/kg; National Drug Standard: H20054171; Yichang Renfu Pharmaceutical Co., Ltd., Yichang, China) was injected intravenously before nerve block was performed.

IHN-IIN block (group A)

The nerve block was performed under guidance of an ultrasound device (CX50; Philips., Amsterdam, the Netherlands). Patients were handled in the supine position and draped with a standard sterile cover. A high-frequency linear array probe (10–12 MHz) was positioned at the anterior superior iliac spine and along the line joining it to the umbilicus and adjacent to the anterior superior iliac spine on the side of the surgery (Figure 2A). The iliac bone, iliac muscle, external oblique, internal oblique, and transverses abdominis muscles were visualized from the outer side of surgery to the inner layers, with identification of the deep iliac circumflex artery, IHN, and IIN positioned between the internal oblique and transversus abdominis muscles (Figure 2B). We chose the lateral side near the anterior superior iliac spine as the puncture point, using a 22-G puncture needle (Kindly Medical Devices Co., Ltd., Wenzhou, China) for IHN-IIN blockage. The in-plane approach was employed during nerve block procedures. Confirmation of needle tip placement was achieved by injecting 1 mL of saline, which was followed by the administration of 10 mL of 0.375% ropivacaine (75 mg/10 mL; National Drug Standard: JX20110023; AstraZeneca, Cambridge, UK) for nerve blockage (Figure 2C).

Figure 2 Probe position, needle puncture site, and sonographic image of the ilioinguinal nerve, iliohypogastric nerve, and genitofemoral nerve. (A) The position of the probe during the ilioinguinal-iliohypogastric nerve block. The red dot shows the iliac bone. (B) Ultrasound shows the iliohypogastric and ilioinguinal nerves. (C) Diffusion of local anesthetic agents during ilioinguinal-iliohypogastric nerve block. (D) The position of the probe during the genitofemoral nerve block. The red dot shows the iliac bone. (E) Ultrasound shows the genitofemoral nerve. (F) Diffusion of local anesthetic agents during genitofemoral nerve block.

IHN-IIN-GFN block (Group B)

After completion of the IHN-IIN block (using the same methods as described above), the needle was retracted to the skin, and a low-frequency probe (3.5–5 MHz) was substituted for the axis sector scan and centered on the same puncture point (a high-frequency probe could be used in patients with a BMI lower than 23.9 or a psoas muscle depth of less than 6 cm; Figure 2D). The probe was then slightly rotated counterclockwise, guiding the ultrasound beam diagonally outward and toward the lower region and identifying the iliac bone and iliac and psoas major muscles on the deep side. The common branch of the GFN was situated at the superior aspect of the ventral side of the psoas major muscle (Figure 2E). The needle remained visible throughout the puncture process. The in-plane approach was also employed, and water separation was performed with 1 mL of saline to confirm the needle tip. A solution of 5 mL of 0.375% ropivacaine (75 mg/10 mL; National Drug Standard: JX20110023; AstraZeneca) was administered for GFN blockage (Figure 2F). The blocked region encompassed the lower abdomen, groin area, proximal and anterior thigh, medial thigh, and perineum. The surgical procedure started within 15–30 minutes after the block.

Intraoperative medications

Dexmedetomidine at a rate of 0.2–0.7 µg/kg/h and flurbiprofen at a dosage of 1 mg/kg were administered throughout the surgical procedure. For rescue analgesia, either intravenous 5–10 µg of sufentanil or local infiltration with 5–10 mg of 1% lidocaine (0.1 g/5 mL; National Drug Standard: H41023668; Suicheng Pharmaceutical Co., Ltd., Xinzheng, China) was administered.

Recording of indicators

Postoperative pain was assessed with the numerical rating scale (NRS) score, from 0 (no pain) to 10 (maximum pain). The primary endpoint was defined as the NRS score in the post-anesthesia care unit (PACU). The secondary endpoint included the NRS score at 4 and 12 h after surgery, intraoperative additional anesthetic consumption, intraoperative traction pain (scoring: 0 points for no pain, 1 point for facial struggling, and 2 points for facial struggling along with evident body movements), sinus bradycardia (scoring: 0 points for a HR above 60 bpm or between 90% and 110% of the baseline, 1 point for a HR below 60 bpm or above 80–120% of the baseline, and 2 points for a HR below 50 bpm), nausea and vomiting (scoring: 0 points for no symptoms, 1 point for only nausea, 2 points for vomiting), postoperative urinary retention (scoring: 0 points for no symptoms, 1 point for difficulty in urination, 2 points for requirement of urethral catheterization), and drowsiness (scoring: 0 points for no drowsiness, 1 point for feeling abnormally tired, 2 points for exhibiting symptoms such as snoring, deep sleep, or requiring external awakening such as shaking or clapping). Since postoperative groin pain could also present with symptoms similar to quadriceps weakness, which is commonly associated with a femoral nerve block, we did not intentionally assess whether an inadvertent femoral nerve block occurred during the GFN block.

We also recorded the operation time, the MAP, HR, RR, and SpO₂ at baseline (T0), before skin incision (T1), 1 min after skin incision (T2), after dissection of the hernial sac (T3), at mesh placement (T4), and at the end of the surgery (T5). Evaluation of chronic pain at 3 and 6 months after surgery was obtained by telephone follow-up.

Sample size

The sample size estimation was performed using PASS version 15.0.13 software (NCSS, Kaysville, UT, USA). Based on our preliminary trial results (unpublished) in which the IHN-IIN-GFN block was performed, the pain score at 12 h after surgery decreasing over 0.9 compared with IHN-IIN block (3.1±0.9) was considered to be clinically significant, and the sample size needed for each group was estimated to be 20, with a dropout rate of 10%.

Randomization

All the patients were given a sequential number from 1 to 42, and each received a corresponding random number generated by SPSS 26 (IBM Corp., Armonk, NY, USA). The random number generated was 20189999. The program was then set as a random sample by selecting exactly 21 from the 42 cases. The patients with filtered number 0 were placed into group A, while those with filtered number 1 were placed into group B.

Blinding

This was a single-blind study in which only patients were blinded to the details. The nerve block operator was not informed about the specific grouping until just before the procedure. The experimental data were divided into three parts (vital signs, operative complications, and NRS between the two groups) and analyzed respectively by three researchers (each responsible for one part) in a blinded fashion. The blinding of PACU physicians to the anesthesia protocols was applied to both patient groups.

Statistical analysis

Patients with missing values were excluded only from the relevant analysis. The data were analyzed according to the intention-to-treat (ITT) method. All data were analyzed using SPSS 21 (IBM Corp.) and are expressed as the mean ± standard deviation (x±s). Comparisons of serial measurements (MAP, HR, RR, SpO₂, and NRS score) were performed with repeated-measures analysis of variance (ANOVA). The independent samples t-test was used for comparisons between groups. Categorical data are presented as numbers and percentages, and the comparisons between groups were completed using the χ² test, Fisher exact test, or rank-sum test. A two-sided P value <0.05 was considered significant.

Results

From June 2018 to December 2019, 42 patients who underwent inguinal hernia surgery in The First People’s Hospital of Yunnan Province were included. One was allergic to lidocaine, and one declined the procedure the night before the surgery. Finally, a total of 40 patients, 20 in each group, completed the entire trial. These patients were followed up until 6 months after surgery, during which time none withdrew from the trial (Figure 1).

Patients and surgical characteristics

There were no significant differences in the clinical characteristics between the two groups (P>0.05) (Table 1). However, the duration of anesthesia in group A was significantly shorter than that in group B (P<0.05) (Table 1).

Respiratory and hemodynamic data

There were no differences in preoperative respiratory or hemodynamic parameters between the two groups (P>0.05). The MAP in the group A was significantly higher than that in group B at T2, T3, and T4 (P<0.01), and the HR in group A was also higher than that in group B at T2 and T3 (P<0.05) (Figure 3). At T5, the MAP and HR of the two groups tended to be stable. In addition, at T3, T4, and T5, the RR of group A was significantly higher than that of group B (P<0.05), but there was no significant change in SpO₂ (P>0.05) (Figure 3).

Figure 3 Patient’s vital signs at different time points. *, P<0.05, compared to group A. Group A, iliohypogastric-ilioinguinal nerve block group; group B, iliohypogastric-ilioinguinal-genitofemoral nerve block group. T0, preoperative baseline; T1, before skin incision; T2, 1 min after skin incision; T3, after dissection of the hernia sac; T4, at mesh placement; T5, at the end of the surgery. RR, respiratory rate; HR, heart rate; MAP, mean arterial pressure; SpO₂, pulse oxygen saturation.

Analgesic effect and complications

There were no significant differences in the incidence of intraoperative or postoperative negative side effects between the groups (Tables 2,3). The additional doses of sufentanil and lidocaine in group A were significantly higher than those in group B (P<0.05) (Table 4), and the intraoperative traction pain score and incidence of postoperative complication score were also higher in group A compared to group B (P<0.05) (Table 5).

Postoperative pain profiles

The NRS scores in group A were significantly higher than those in group B (P<0.01), but there was no significant difference in NRS scores between the two groups at 12 h after surgery (P>0.05) (Table 6). All patients completed telephone follow-ups, and four patients (three in group A and one in group B) complained of mild pain in the groin area (Table 7), with the pain becoming more severe during heavy physical work. No patient complained of pain at 6 months after surgery (Table 7).

Discussion

To the best of our knowledge, this paper is the first report on single-point IHN-IIN-GFN nerve block with ultrasound. Our results showed that this strategy achieved a more complete inguinal blocking effect.

It has been proven that regional anesthesia is superior to general anesthesia in reducing acute pain after open anterior inguinal hernia repair (12). Ultrasound-guided nerve block using a lower dosage of local anesthetic drugs can be highly effective (13,14) and can provide anesthesiologists more choices when managing older adult patients who cannot tolerate general or spinal anesthesia. In a previous study, IHN-IIN block showed favorable outcomes for postoperative analgesia in patients who underwent open anterior inguinal hernia repair (8), which was further confirmed in our study. However, incisional pain and reactions to surgical traction were still challenging issues for which GFN block was required.

The GFN originates from the lumbar plexus. It descends along the anterior surface of the psoas muscle and divides into the femoral and genital branches. As there is considerable variety in the GFN’s distribution (10) and as it is difficult to accurately locate it in the groin area (15) even with computed tomography (CT) (16) and magnetic resonance imaging (MRI) (17), GFN block is challenging and complicated to perform. However, blocking the GFN does improve pain relief during inguinal hernia surgery (4,18,19), even if just one branch of the GFN is blocked. Cho et al. (20) blocked the femoral branch of the GFN under ultrasound guidance and achieved a good analgesic effect in the area below the groin. Huang et al. (10) found that blocking the genital branch of the GFN was the key to effective analgesia in the surgical field of the groin area in children. Frassanito et al. (11) reported that blocking the genital branch of the GFN via intraspermatic injection of local anesthetics could provide enhanced pain relief following inguinal hernia surgery, although this could increase the risk of spermatic cord injury. Shanthanna (21) demonstrated that the pain area was not completely covered in the treatment of groin pain simply through IHN-IIN block and that the groin pain was significantly relieved by additionally blocking the genital branch of the GFN. These results suggest that both the femoral and genital branches of the GFN can be relevant in the treatment of groin pain. This also prompts speculation as to whether the two branches of the GFN and the IHN and IIN can be blocked at the same time through ultrasound guidance.

Iwanaga et al. (22) found that the two branches of the GFN have complicated interlacing at different positions in their respective paths. After further autopsy analysis, they believed that it was more precise to name the branches of the GFN the intermediate branch and the side branch. This indicates that it would be less effective to block only a single branch of the GFN. As Kale et al. (23) suggest, it may be necessary to track the GFN in a retrograde manner to a more proximal location, taking into account the intertwining nature of its two branches.

Using a high-frequency ultrasound probe, we were able to trace the genital and femoral branches of the GFN, observing that it descends deeply into the groin before diverging. The thinner genital branch poses challenges in accurate identification with a low-frequency probe (24). Therefore, we further examined the anatomy and procedures related to GFN. One study reported that when the needle tip is placed on the surface of the psoas major muscle under the guidance of CT, drug injection and radiofrequency ablation can cause obvious numbness at the sensory area of the GFN (25). Using MRI, Fritz et al. (26) also found that the GFN originates from the front of the psoas major muscle at the level of the anterior superior iliac spine. Tammam et al. (27) attempted to inject drugs directly into the surface of the psoas muscle under laparoscopy to complete IHN-IIN-GFN block and found that this led to a better postoperative analgesic effect than did transversus abdominis plane block. Despite the challenges of identifying these nerves concurrently using ultrasound (28), one study found that the superficial region of the psoas major muscle could be the optimal location for blocking the GFN. Therefore, in our study, after completing the IHN-IIN block, we withdrew the needle to the skin and held it until a low-frequency probe was placed near the anterior superior iliac spine to explore the ilium, iliac muscles, and psoas muscle. We then inserted the needle into the surface of the psoas muscle to block the general GFN. Thus, IHN-IIN-GFN block was completed via a single point of puncture and contributed to a better analgesic effect in the groin area. However, we strongly advise that only experienced and well-trained anesthesiologists perform this procedure.

The occurrence of persistent inguinal pain following surgery is a prevalent challenge that significantly impacts patients’ quality of life, and during the past decades the frequency of chronic postoperative groin pain has far surpassed that of hernia recurrence (29), which might be related to poor postoperative acute pain management. We believe that a well-implemented nerve block could effectively relieve acute pain after surgery in a cost-effective manner and that blocking the GFN can improve postoperative acute analgesia in the groin area. By the end of the observation period, none of the patients experienced chronic pain. Nevertheless, the study’s small sample size and short duration of follow-up hindered a comprehensive analysis of the long-term outcomes of the patients, indicating the need for further research focused on long-term pain.

The small sample size and the absence of double-blind tests were the two major limitations of our study. In addition, we did not evaluate the incidence of inadvertent femoral nerve block resulting from the diffusion of local anesthetic after IHN-IIN block or more directly following the GFN block. Moreover, the pain and discomfort surgical procedure might also have biased the test results due to the different subjective tolerance of the patients.

Conclusions

Performing an ultrasound-guided IHN-IIN-GFN block through a single puncture point is a feasible clinical approach. This strategy provides appropriate intraoperative and postoperative analgesia in older adult patients undergoing open anterior inguinal repair and significantly reduces postoperative complications, which is conducive to patients’ recovery and has the potential to emerge as a novel analgesic option for inguinal hernia surgery.

Acknowledgments

Funding: The study was supported by National Natural Science Foundation of China (No. 81300973), the Yunnan Provincial Ten Thousand Talents Program - Famous Doctor (No. YNWR-MY-2019-060), the Key Project of Basic Research Program of Yunnan Province (No. 202101AS070047), the Basic Research Programs of Yunnan Province (Nos. 202101AY070001-251, 202201AY070001-178, and 202201AY070001-263), and the Special Fund of the Applied Basic Research Programs of Yunnan Province Associated with Kunming Medical University (No. 202301AY070001-056).

Footnote

Reporting Checklist: The authors have completed the CONSORT reporting checklist. Available at https://qims.amegroups.com/article/view/10.21037/qims-24-787/rc

Trial Protocol: Available at https://qims.amegroups.com/article/view/10.21037/qims-24-787/tp

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-24-787/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Ethical approval for the study was granted by the Ethics Committee of The First People’s Hospital of Yunnan Province (No. KHLL2020-KY016). Written informed consent was obtained from all patients who participated. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013).

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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