FormalPara Key Summary Points

Why carry out this study?

Interfascial plane blocks have been demonstrated to be effective in multimodal analgesia. Literature regarding the interfascial plane blocks for total laparoscopic hysterectomy (TLH) is limited.

This study aimed to evaluate whether interfascial plane blocks of erector spinae plane block and transmuscular quadratus lumborum block reduce postoperative pain and opioid consumption after TLH.

What was learned from the study?

This study demonstrated that the interfascial plane blocks of erector spinae plane block and transmuscular quadratus lumborum block both improved the quality of multimodal analgesia for TLH.

Erector spinae plane block may be more favorable due to the prolonged period of analgesia and decreased opioid consumption.

Introduction

Total laparoscopic hysterectomy (TLH) is a preferred alternative to open abdominal hysterectomy [1]. Though minimally invasive, patients may still experience significant and multifactorial postoperative pain owing to surgical manipulation [2, 3]. Based on anatomical knowledge of the visceral afferent fibers from the uterus and anterolateral abdominal wall, we considered that local anesthetic (LA) anesthetizing the ventral rami and sympathetic trunk in the thoracolumbar paravertebral space would provide somatic and visceral pain relief after TLH [4].

Interfascial plane block techniques including the erector spinae plane block (ESPB) and transmuscular quadratus lumborum block (TQLB) provide effective multimodal analgesia with technical safety and simplicity [5,6,7,8]. For ESPB, an LA is injected into the plane between the erector spinae muscle and transverse process of the thoracic vertebra, spreading the LA cephalad, caudally, and through the paravertebral space [9]. For TQLB, the LA is deposited into the plane between the quadratus lumborum and psoas major, leading to a dense block of the thoracolumbar sympathetic trunk and segmental nerves after the LA spreading through the paravertebral space [10, 11]. However, literature regarding ESPB for postoperative analgesia in TLH is limited. Meanwhile, controversy regarding the efficiency of TQLB for TLH remains. Although a study demonstrated promising results of TQLB on pain control after TLH [12], this technique failed to show a significant reduction in opioid consumption as seen in another study [4].

Therefore, we designed a randomized controlled trial (RCT) to differentiate the analgesic efficacy of ESPB and TQLB by comparing the results with a control group in patients scheduled for TLH. Additionally, we evaluated the relative efficacy of ESPB compared to TQLB. The primary outcome was cumulative sufentanil consumption at 12 h postoperatively. We hypothesized that both TQLB and ESPB would reduce the postoperative opioid consumption and pain intensity in patients undergoing TLH.

Methods

Study Design and Randomization

This prospective RCT was conducted from July 2021 to May 2022, after approval by the Ethics Committee of the Second Affiliated Hospital of Anhui Medical University (approval no. YX2021-054[F1]) on June 29, 2021 and was prospectively registered in the Chinese Clinical Trial Registry (http://www.chictr.org.cn/showproj.aspx?proj=129578, ChiCTR2100048165; principal investigator: YW) on July 4, 2021. This study was conducted in accordance with the Consolidated Standards of Reporting Trials (CONSORT) criteria [13] and in compliance with the Helsinki Declaration. Written informed consent was obtained from all patients.

Female patients who underwent elective TLH were enrolled in this study. The inclusion criteria were age between 18 and 65 years and American Society of Anesthesiologists (ASA) physical status of I–II. The exclusion criteria were a body mass index > 35 kg m−2, coagulopathy, history of opiate abuse, pre-existing chronic pain, allergy to local anesthetics or analgesics, infection at the injection site, mental or neurological disorders, severe cardiovascular disease, hepatic or renal insufficiency, and pregnancy or lactation.

Patients were randomly allocated to receive either ultrasound-guided ESPB (Group ESPB), TQLB (Group TQLB) or no intervention (Group CON) using computer software at a ratio of 1:1:1. An assistant, who was not involved in the study, prepared the randomization list and concealed group assignments in consecutively numbered, sealed, opaque envelopes. A consultant anesthesiologist who had performed over 200 TQLB and ESPB procedures and was unaffiliated with the study opened the envelopes to reveal the group allocation shortly before nerve block performance. Ultrasound-guided peripheral blocks were performed according to randomization. Thereafter, the surgeons, anesthesiologists, nurses providing postoperative care, investigators, and outcome assessors were blinded to the patients’ group allocation and did not have access to randomization until data analysis was complete.

Regional Anesthesia Technique

After arrival in the preoperative holding area, intravenous access was established and premedication (midazolam 0.02 mg kg−1 and sufentanil 0.1 μg kg−1) was administered. Vital parameters, including heart rate, electrocardiogram, blood pressure and pulse oximetry, were monitored throughout the procedure. All blocks were performed with a 22-gauge block needle using the same ultrasound machine (SonoSite M-Turbo; FUJIFILM Sonosite, Inc., Bothell, WA, USA). The patients were placed in a lateral decubitus position, and skin preparation was performed with 10% povidone-iodine. Bilateral ESPB and TQLB were performed as previously described [4, 14].

For ESPB, a linear ultrasound transducer (13–6 MHz) inside a sterile transparent plastic cover was positioned in a longitudinal orientation approximately 3 cm lateral to the midline at the T10 level to obtain a parasagittal view. After the tip of the T10 transverse process, the overlying erector spinae muscle and pleura were identified, the needle was inserted and in contact with the tip of the transverse process using an in-plane technique. After confirmation of the correct needle tip position by hydrodissection with normal saline, 25 ml of 0.4% ropivacaine was injected into the erector spinae plane between the tip of the transverse process and the erector spinae muscle on the left side. The same procedure with the same LA solution was injected at the T10 level on the right side (Fig. 1A–C).

Fig. 1
figure 1

A schematic diagram of ESPB and TQLB. A The LA injected into the erector spinae plane was expected to extend to the paravertebral space, anesthetizing the thoracolumbar ventral rami and the sympathetic trunk which innervate the uterus and anterolateral abdominal wall. B Ultrasound image of ESPB at T10. C The LA was injected into the erector spinae plane between the tip of the transverse process and the erector spinae muscle. D The LA injected into the plane between the quadratus lumborum and the psoas major was expected to extend to the paravertebral space, anesthetizing the thoracolumbar ventral rami and the sympathetic trunk which innervate the uterus and anterolateral abdominal wall. E Ultrasound image of TQLB. F The LA was injected into the interfascial plane between the quadratus lumborum muscle and the psoas major muscle. ES erector spinae muscle, SG segmental ganglion, TP transverse process, QL quadratus lumborum muscle, PM psoas major muscle, EO external oblique muscle, IO internal oblique muscle, TA transversus abdominis muscle, VB vertebral body

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For TQLB, a curvilinear ultrasound transducer (5–2 MHz) was placed in the transverse position immediately cranial to the iliac crest, at the level of the posterior axillary line. The needle was inserted in-plane in a posterolateral to anteromedial direction from the posterolateral edge of the probe until penetration of the medial part of the quadratus lumborum muscle, but without piercing the psoas major muscle. After confirmation of the correct needle tip position by hydrodissection, 25 ml of 0.4% ropivacaine was injected into the interfascial plane between the quadratus lumborum muscle and the psoas major muscle on the left side. The same procedure with the same LA solution was also injected on the right side after the patient was changed to the left lateral position (Fig. 1D–F).

In Group CON, the patients only received premedication in the preoperative holding area.

General Anesthesia Technique

After nerve block, patients were transferred to the operating room and received general anesthesia with standardized monitoring. Intravenous dexamethasone (8–10 mg) was administered to prevent postoperative nausea and vomiting (PONV). General anesthesia induction and tracheal intubation were performed using midazolam (0.05 mg kg−1), sufentanil (0.4 μg kg−1), etomidate (0.3 mg kg−1) and cisatracurium (0.2 mg kg−1). Parecoxib sodium (0.8 mg kg−1) was administered after induction for pre-emptive analgesia. Maintenance of anesthesia was achieved by continuous infusion with propofol (4–6 mg kg−1 h−1) and remifentanil (0.15–0.25 μg kg−1 min−1). The depth of anesthesia was adjusted to maintain a bispectral index target range of 40–60. Anesthesiologists administered intravenous sufentanil (5–10 μg) when the patient’s heart rate or blood pressure increased by > 20% from basal measurements.

Postoperative Management and Assessment

All patients were transferred to the post-anesthesia care unit for recovery after extubation (0 h postoperatively). A nurse blinded to the protocols instructed patients how to evaluate the incisional, visceral, shoulder and perineum pain [15] at rest and in motion using the 11-point Numeric Rating Scale (NRS), which ranges from ‘0’ (meaning no pain) to ‘10’ (meaning worst pain imaginable). Incisional pain was defined as a superficial pain, wound pain, or pain located in the abdominal wall, a pain that one can “touch”; visceral pain was defined as pain inside the abdomen, which may be deep, dull, and more difficult to localize, and may resemble a biliary pain attack; perineum and shoulder pain were defined as the sensation of pain in the perineum or shoulder, respectively. The sedation level was assessed using Richmond Agitation-Sedation Scale (RASS) [16] at 0.5 h postoperatively. Postoperative analgesia was maintained with sufentanil infusion using a patient-controlled intravenous analgesia (PCIA) device. The PCIA device administered a 3-μg bolus dose with a 15-min lock-time; no basal infusion and was initiated when the NRS score at rest was ≥ 4 or patients verbalized the need for pain relief. If three boluses of sufentanil did not alleviate pain, pentazocine 30 mg was administered intravenously as rescue analgesia. After transfer to the ward, patients used PCIA, as needed. The patient’s quality of recovery was assessed using the Quality of Recovery-15 (QoR-15) scale [14, 17, 18] at 24 h postoperatively. At 3 and 6 months postoperatively, the intensity of the patients’ average pain during the previous week was assessed using the NRS via telephone interview.

Outcomes

The primary outcome was cumulative sufentanil consumption at 12 h postoperatively. The secondary outcomes included cumulative sufentanil consumption at 24 h postoperatively; the RASS score at 0.5 h postoperatively; the NRS pain scores of incisional, visceral, shoulder, and perineal pain at rest and in motion, evaluated at 0.5, 2, 4, 6, 12 and 24 h after surgery; QoR-15 score at 24 h postoperatively; time to first PCIA; rescue analgesia requirement; time to first postoperative ambulation; block-related and anesthetic-related complications; postoperative length of hospitalization; and chronic pain in 3 and 6 months, postoperatively.

Sample Size and Statistical Analysis

The sample size was calculated based on the primary outcome of sufentanil consumption at 12 h postoperatively, using PASS V.15.0 (PASS, NCSS, USA) for Windows. Based on the results of our pilot study with six patients in each group (mean consumption of sufentanil at 12 h postoperatively was 3.5, 4.5, and 10.0 μg for Group ESPB, TQLB and CON, respectively, using a pooled standard deviation [SD] of 7.6), one-way analysis of variance (ANOVA) was selected and grouped into three groups; group allocation ratios were equal. At a power of 0.80 and an alpha error of 0.05, to account for 20% loss to follow-up, the required sample size for each group was calculated as 30. Thus, 90 participants were included in this study.

All statistical analyses were performed using SPSS Statistics (version 26.0; IBM, Armonk, NY, USA). Kolmogorov–Smirnov test and visual inspection of histograms were performed to assess data normality. Continuous variables were expressed as mean (SD) or median (interquartile range, IQR), and inter-group differences were assessed for significance using ANOVA for normally distributed data or Kruskal–Wallis test for nonparametric data followed by Bonferroni correction. Pairwise comparison for postoperative sufentanil consumption was analyzed using the Mann–Whitney U test, and by calculating the Hodge–Lehman median difference with a constructed 95% confidence interval (CI) with P < 0.0167 (0.05/3) was considered significant. Categorical variables were expressed as number (percentage) and intergroup differences were assessed using chi-squared or Fisher's exact tests in cases of expected frequency < 5. The time to first PCIA was analyzed using Kaplan–Meier survival analysis followed by log-rank test, with adjustment for multiple comparisons.

Repeated measurements of postoperative pain scores were analyzed using a linear mixed model [19, 20] to evaluate the association between NRS pain score over time and the intervention technique. This model included intervention, time and the interaction between time and intervention as the fixed effects. Time was included as a repeated effect; NRS pain scores were included as dependent variables. We corrected for comparisons between groups at multiple time points using Bonferroni correction. Assessments were 2-tailed, and statistical significance was set at P < 0.05.

Results

The CONSORT flow diagram for this trial is shown in Fig. 2. Patients were recruited from July 12, 2021 to November 26, 2021; follow-up of the last enrolled patient was completed on May 30, 2022. Initially, 106 patients were screened for suitability. Ten patients did not meet the inclusion criteria (one patient was 68 years of age, six patients were ASA III physical status, and three patients were morbidly obese with BMI > 35 kg m−2), and six patients declined to participate in the study. In total, 90 patients were enrolled and randomized. All enrolled patients were followed-up successfully; and no patients were lost to follow-up.

Fig. 2
figure 2

Consolidated Standards of Reporting Trials flow diagram of participants through each stage of the randomized trial. ASA American Society of Anesthesiologists, BMI body mass index, ESPB erector spinae plane block, TQLB transmuscular quadratus lumborum block, CON control

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The patients’ general and surgical characteristics and the intraoperative analgesic consumption are summarized in Table 1. Group ESPB and TQLB both had lower mean dosage of remifentanil than Group CON; however, only Group TQLB showed a statistically significant difference after Bonferroni correction (Group TQLB vs. CON: mean difference, 0.05 μg kg−1 min−1; 95% CI 0.01–0.09 μg kg−1 min−1; P = 0.021). There were no significant differences among the three groups regarding other parameters (Table 1).

Table 1 Patients’ and surgical characteristics and intraoperative analgesic consumptions
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The median [IQR] sufentanil consumption at 12 h postoperatively was significantly different among the three groups (Group ESPB, 0 [0, 4] μg; Group TQLB, 0 [0, 4] μg; Group CON, 6 [0, 10] μg; P = 0.019). This difference was statistically significant for Group ESPB vs. CON after Bonferroni correction (P < 0.0167 was considered significant) (mean difference = − 3; 95% CI − 6–0; P = 0.010), but not for Group ESPB vs. TQLB (mean difference = 0; 95% CI 0–0; P = 0.533) or Group TQLB vs. CON (mean difference = − 3; 95% CI − 6–0; P = 0.031). Moreover, Group ESPB had significantly lower sufentanil consumption than Group CON at 24 h postoperatively (mean difference = − 3; 95% CI − 6–0; P = 0.016). No significant differences in sufentanil consumption were found between the two block groups or between Group TQLB and CON after surgery (Table 2).

Table 2 Postoperative cumulative sufentanil consumption
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The linear mixed-effect model analysis showed that the interaction of treatment and time in NRS scores of visceral pain both at rest and in motion was significant (both P < 0.05). In comparison with Group CON at 0.5 h after surgery, Group ESPB and TQLB exhibited significantly reduced visceral pain scores at rest (Group ESPB vs. Group CON: mean difference = 1.6; 95% CI 0.8–2.4; P < 0.001; Group TQLB vs. Group CON: mean difference = 1.3; 95% CI 0.5–2.1; P < 0.001) and in motion (Group ESPB vs. Group CON: mean difference = 1.8; 95% CI 0.9–2.6; P < 0.001; Group TQLB vs. Group CON: mean difference = 1.3; 95% CI 0.5–2.2; P = 0.001). Furthermore, patients in Group ESPB maintained significantly lower visceral pain scores at rest until 4 h and in motion until 6 h after surgery (P < 0.05), while TQLB provided a prolonged pain-relief in motion until 4 h postoperatively (P < 0.05). No significant differences in visceral pain scores were found between the two block groups after surgery (Fig. 3).

Fig. 3
figure 3

NRS scores of visceral pain in the studied groups. Data are expressed as mean (standard deviation). Comparisons between groups were made using linear mixed-model analyses, showing Group ESPB and TQLB exhibited reduced visceral pain scores at rest (A) and in motion at 0.5 h postoperatively (B). Patients in Group ESPB remained significantly lower visceral pain scores at rest until 4 h postoperatively (A) and in motion until 6 h postoperatively (B). *P < 0.05 indicates statistically significant differences compared with Group CON. P values are corrected using Bonferroni correction. ESPB erector spinae plane block, TQLB transmuscular quadratus lumborum block, CON control, NRS numeric rating scale

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The time to first PCIA was significantly longer in Group ESPB than in Group CON after Bonferroni correction (P = 0.030). However, there were no significant differences between the two block groups or between Group TQLB and CON (Fig. 4).

Fig. 4
figure 4

Kaplan–Meier survival curve representing the time to first sufentanil administration of PCIA from arrival at PACU (T0). The time to first PCIA was significantly longer in Group ESPB compared with Group CON after Bonferroni correction (P = 0.030). There were no significant differences between the two block groups or between Group TQLB and CON. PCIA, patient-controlled intravenous analgesia, PACU post-anesthesia care unit, ESPB erector spinae plane block, TQLB transmuscular quadratus lumborum block, CON control

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No statistical differences were observed among the three groups for any of the following secondary outcomes: incisional, shoulder and perineum pain scores (Table S1), RASS scores, QoR-15 scores, time to first postoperative ambulation, incidence of PONV, and postoperative length of hospitalization. No cases of rescue analgesia requirement or block-related complications were observed. There were no complications of pruritus or respiratory depression. No significant differences in the chronic pain scores at 3 and 6 months postoperatively were observed among the three groups (Table 3).

Table 3 Postoperative parameters
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Discussion

Herein, the interfascial plane blocks of ESPB and TQLB provided a prolonged pain-relief after TLH. Patients receiving ESPB exhibited a delayed and less analgesic requirement of opioid after THL when compared with those in Group CON. However, no significant differences in the analgesia efficacy of ESPB and TQLB were observed.

As a novel interfascial plane block technique, ESPB can be performed more easily and safely than paravertebral block [9]. The LA spreads deep to the erector spinae muscle and is expected to extend to the paravertebral space which may provide effective analgesia by blocking both the ventral and dorsal rami of the spinal nerves [14]. ESPB performed at T10 can induce a sensory loss from T5 to L2 [21]. Based on anatomical knowledge that visceral afferent fibers from the uterus relay at T11–T12 [22], we performed bilateral ESPB at the T10 level. As hypothesized, ESPB provided visceral pain relief persistently after TLH compared with Group CON. Meanwhile, patients initiated PCIA later and consumed less sufentanil in Group ESPB, which supports bilateral ESPB as an option for TLH. Similarly, two case reports both showed promising results with ESPB performed at T8 and T10, separately, for visceral pain management after TLH [21, 23]. Thus, together with our results, bilateral ESPB performed at low thoracic level would be a prospective interfascial plane block for pain control in TLH.

In cadaveric studies regarding transmuscular quadratus lumborum injection, the dye spread to the L1 and L3 nerve roots [10], and was also found in the thoracic paravertebral space and intercostal spaces to surround the somatic nerves and the thoracic sympathetic trunk at the T9 level [11]. Therefore, we assessed this technique in TLH and found that TQLB, as ESPB, significantly reduced visceral pain scores after surgery. However, we did not find a postoperative opioid-sparing effect of TQLB, as was seen in a previous study [4]. Due to the discrepancy between the hypothesis and clinical results, we speculated that the anatomic characteristics of patients differs from those of cadavers; the post-mortem changes in temperature and lack of muscle tone may alter injectate spread compared with that in living patients [11]. Interestingly, performing TQLB after TLH [12] or depositing LA on both the anterior and posterior aspects of the quadratus lumborum muscle [22] has shown favorable results in pain management. Thus, the timing of block performance and techniques enhancing drug spread might be crucial in TQLB action.

It is worth noting that TQLB, but not ESPB, reduced the mean dosage of remifentanil when compared with Group CON. The erector spinae is a bundle of muscles and tendons; the transverse process interspace is bounded by intertransverse connective tissues. The anatomical variations may slow LA penetration through the paravertebral space, making the ESPB effective in the later phase [24].

We found no significant difference in the analgesia efficacy of ESPB and TQLB, and the statistically significant differences in postoperative pain control among the three groups were relatively small in clinical practice. Additionally, all patients experienced mild and comparable pain in incision, shoulder, and perineum even without regional blocks. We used the most potent opioid of sufentanil [25, 26] and adjunctive analgesics for multimodal analgesia [27]. Moreover, good manipulation abilities and surgical skills might have helped minimize the pain intensity, thus explaining the lack of clinically significant differences between groups. We did not find any promising results of time to first ambulation and length of hospitalization after surgery. However, it partly indicated that ESPB and TQLB did not induce lower limbs weakness. Since acute pain was treated, all patients reported high recovery scores and experienced mild chronic pain at 3 and 6 months after surgery.

This study had several limitations. First, even if the patients were sedated, they likely knew the intervention they received. However, the choice was guided by ethical considerations, and the blinding of the outcome assessors minimized biases. Second, we did not perform sensory or motor measurement because of the risk of further unblinding of patients. Third, we expected that primary outcome results would follow normal distribution and calculated the power analysis with ANOVA. However, it ended up using Kruskal–Wallis test because the primary outcome was not normally distributed, which weakened the analysis power. Additionally, Bonferroni correction was not used in the sample size calculation, which may further confirm the underpower of the study. Forth, surgical type was not standardized and the TLHs were not performed by the same surgeon. However, we considered this desirable as our inclusion criteria were close to real-world clinical practice situations.

Conclusions

In conclusion, we showed that ESPB and TQLB improved multimodal analgesia quality in patients undergoing TLH. Additionally, ESPB may be a preferred interfascial plane block technique owing to its significant reduction of postoperative visceral pain and opioid consumption after TLH.