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Abstract
Objective This study aimed to investigate the analgesic effect of an ultrasound-guided anterior quadratus lumborum block (QLB) at the L2 level on postoperative pain after laparoscopic gynaecological surgery.
Design Prospective single-centre randomised double-blind trial.
Setting University-affiliated hospital.
Participants Sixty patients aged between 18 and 65 years scheduled for laparoscopic gynaecological surgery.
Interventions Before surgery, bilateral anterior QLB was performed with 20 mL of 0.375% ropivacaine injected on each side in the QLB group, whereas equal amount of saline was administered in the placebo group.
Primary and secondary outcome measures The primary endpoint was the cumulative morphine dose in the first 24 hours, and the secondary endpoints were morphine consumption at each time interval, area under the curve (AUC) of the numeric rating scale (NRS) for pain, maximum pain intensity, incidence of moderate-to-severe pain (NRS>3), sedation score, adverse events, and time to home-readiness.
Results Cumulative morphine consumption in the first 24 hours after surgery was significantly lower in the QLB group than in the placebo group (mean difference, 14.2; 95% CI 6.3 to 22.1; p<0.001). The AUCs of NRS pain intensity scores, including visceral and incisional pain at rest and on movement, were significantly lower in the QLB group than in the placebo group (all p<0.001). The time to home-readiness was significantly shorter in the QLB group than in the placebo group (p<0.05).
Conclusion Ultrasound-guided anterior QLB at the L2 level significantly reduced morphine consumption and relieved visceral and incision pain intensity after laparoscopic gynaecological surgery, which was beneficial for enhanced recovery.
Trial registration number Chinese Clinical Trial Registry (ChiCTR-IOR-17011960).
- ultrasonography
- pain management
- adult anaesthesia
- minimally invasive surgery
Data availability statement
Data are available upon reasonable request.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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STRENGTHS AND LIMITATIONS OF THIS STUDY
This trial evaluated both visceral and incision pain intensity after laparoscopic gynaecological surgery.
We adopted the transverse oblique paramedian approach to the anterior quadratus lumborum block with the patient in a sitting position and improved the method of ultrasonic localisation at the L2 level.
Under ultrasound guidance, the local anaesthetic was safely administered to ensure both its effectiveness in providing analgesia and the safety of the process.
Because this is a clinical trial conducted at a single centre, the generalisability of the conclusions may be limited.
Introduction
Postoperative pain is a common complication of laparoscopic gynaecological surgery, with visceral pain being a prominent feature.1 2 Patients undergoing laparoscopic gynaecological surgery usually receive oral or intravenous analgesia as required. However, the analgesic effect may be insufficient, resulting in excessive use of opioids, accompanied by itching, nausea, vomiting, sedation and respiratory depression. Pain and excess opioid use are important factors that restrict enhanced recovery after surgery (ERAS).3 4
In recent years, regional anaesthesia has been increasingly used as a component of multimodal analgesia following abdominal operations, such as transversus abdominis plane block, erector spinal plane block and anterior quadratus lumborum block (QLB).5–9 Local anaesthetics in the anterior QLB spread through the thoracolumbar fascia to the thoracic paravertebral space, surrounding the somatic nervous and thoracic sympathetic trunk, which may relieve visceral pain,10–12 and provide a better analgesic effect after laparoscopic surgery.13–15
Therefore, we performed a bilateral anterior QLB at the L2 level in patients undergoing laparoscopic gynaecological surgery to observe postoperative analgesic effects. We hypothesised that anterior QLB reduces morphine consumption after laparoscopic gynaecological surgery and provides better visceral and incision pain relief. The primary endpoint was the cumulative morphine dose in the first 24 hours, the secondary endpoints were cumulative morphine dose in the 6th, 18th hour, morphine consumption at each time interval, area under the curve (AUC) of the numeric rating scale (NRS) of pain intensity, maximum pain intensity, incidence of moderate-to-severe pain (NRS>3), sedation score, adverse events and time to home-readiness (the total score reached ≥9) assessed using the Post Anaesthetic Discharge Scoring System (PADSS).
Methods
Study design and participants
Sixty patients scheduled for laparoscopic gynaecological surgery between August 2018 and December 2018 were included in this trial. Written informed consent was obtained from all patients. A Consolidated Standards of Reporting Trials checklist was used for patient enrolment and allocation (figure 1). The inclusion criteria were American Society of Anesthesiologists (ASA) physical status scores of I or II, age between 18 and 65 years, and body mass index (BMI) between 18 and 24 kg/m2. The exclusion criteria were a history of allergy to ropivacaine, chronic pain, skin pathology at the puncture site, peripheral neuropathy (such as diabetic neuropathy), coagulopathy, difficulty with communication or unwillingness to receive regional anaesthesia.
Consolidated Standards of Reporting Trials flow diagram. QLB, quadratus lumborum block.
Preoperative fasting was applied according to the clinical routine, and no preoperative medication was administered. All patients were educated to distinguish between postoperative incisional and visceral pain in the abdomen the day before surgery. Incisional pain was described as superficial pain localised to the abdominal wall. Visceral pain was described as deep abdominal pain that is difficult to localise and is mostly dull, aching or colic.1 16 Patients were also instructed to assess pain intensity using the NRS score (from 0 to 10; 0=no pain, 10=worst imaginable pain).
Randomisation and blinding
According to a random number table generated using SPSS V.22.0 statistical software (IBM Corporation, Armonk, New York, USA), patients were randomly divided into the QLB group and the placebo group (n=30). The investigational products were prepared by a nurse who did not participate in the trial. A bilateral anterior QLB was performed with 20 mL of 0.375% ropivacaine (LBGP, AstraZeneca AB, Sweden) on each side in the QLB group, whereas equal amount of saline was administered in the placebo group. All anterior QLBs were performed by an experienced anaesthesiologist. Patients and the anaesthesiologists who performed the anterior QLB, general anaesthesia and follow-up, and our statistical team who performed statistical analysis were unaware of the grouping.
Block procedure
Non-invasive blood pressure, ECG and pulse oximetry were routinely monitored when the patient arrived in the operating room. Anterior QLB was performed with patients in a sitting position, as described by Dam et al.17 After identifying the 12th rib using a low-frequency (2–5 MHz) convex probe (SonoSite X-Porte; SonoSite, Bothell, Washington) in the sagittal section, the transducer was moved medially to check the transverse process of T12 and caudally to check the transverse process of L1 and L2. The transducer was then moved at the L2 transverse process plane ventrally in a horizontal section to identify the L2 transverse process and the quadratus lumborum attached to it. A 22G needle (B. Braun Melsungen AG, Melsungen, Germany) was inserted using an in-plane method from the lateral side of the transducer and advanced anteromedially through the erector spinae (iliocostalis) and quadratus lumborum to enter the interfascial plane between the quadratus lumborum and psoas major muscles, determined by an injection of 1 mL saline; thereafter, 20 mL ropivacaine or saline was injected (figure 2A,B). As the fluid diffused, there was a hypoechoic shadow between the quadratus lumborum and the psoas major muscles (figure 2C). The same block procedure was performed on the contralateral side.
(A) Patient positioning, probe position and puncture direction; (B) preinjection image of the anterior QLB; (C) postinjection image of the anterior QLB. The arrow indicates needle. The hypoechoic shadow represents the spread of local anaesthetics. ES, erector spinae; QL, quadratus lumborum; TP, transverse process.
General and postoperative analgesia
All patients received general anaesthesia. Sufentanil (0.3 µg/kg), propofol (1–2.5 mg/kg) and cis-atracurium (0.2 mg/kg) were used for induction. After tracheal intubation, the tidal volume was adjusted to maintain the end-tidal carbon dioxide pressure between 30 and 45 mm Hg. Propofol (4–8 mg kg−1 hour−1) and remifentanil (0.1–0.2 µg kg−1 min−1) were administered through continuous infusion to maintain the bispectral index values between 40 and 60. Cis-atracurium was added whenever necessary.
Local infiltration analgesia was administered with a total of 10 mL of 0.75% ropivacaine by a trained surgeon at each trocar site for all patients when suturing the abdomen.18 Tropisetron (5 mg) and flurbiprofen (50 mg) were administered intravenously approximately 30 min before the completion of surgery. All patients received flurbiprofen 50 mg every 8 hour after surgery, and intravenous morphine infusion was started in the postanaesthesia care unit with a patient-controlled analgesia pump (ZZB-I automatic injection pump driver; Nantong Aipu Medical Instrument Co., Nantong, China) containing 100 mg morphine diluted with saline to a volume of 100 mL. Patient-controlled analgesia was programmed to deliver a bolus dose of 1 mg morphine, without background infusion, with a lockout of 5 min and limit of 10 mg/hour.
Data collection
Demographic and intraoperative characteristics, including age, ASA of anaesthesiologists classification, height, weight, BMI, surgery type and surgical duration, were recorded. The consumption of rescue analgesia in patient-controlled intravenous analgesia was also recorded, including the interval morphine requirements from 0 to 1, 1 to 6, 6 to 18 and 18 to 24 hours after surgery and cumulative morphine consumption in the 6th, 18th and 24th hour. NRS scores at rest and during movement for visceral and incisional pain intensity were recorded at 30 min, 1 hour, 2 hours, 6 hours, 18 hours and 24 hours after surgery. The AUC of the NRS scores was calculated by multiplying the time interval with the NRS scores using GraphPad Prism V.7 (GraphPad Software, San Diego, CA, USA). Moderate-to-severe pain was considered when the NRS score was >3. The incidence of moderate-to-severe pain and the worst pain intensity score were recorded. The sedation status was evaluated as mild sedation, moderate sedation, deep sedation and general anaesthesia according to the definitions developed and adopted by the ASA.19 Patients were evaluated every hour after surgery to record the time to home-readiness (the total score reached ≥9), assessed using the PADSS.20 Adverse events such as nausea and vomiting, itchy skin, local anaesthetic toxicity, hypokinesia of the lower extremity and paresthesia were recorded.
Sample size calculation and statistical analysis
In a preliminary study, 10 patients were equally divided into the QLB and placebo groups. The cumulative morphine dose in the first 24 hours after surgery (19.4±7.7 vs 29.6±15.8 mg) were compared using t-test performed by PASS V.11.0 (NCSS Statistical Software, Kaysville, UT, USA), with type I error α=0.05 and type II error β=0.1 (ie, power of 0.90). A sample size of 27 patients per group was required to determine statistically significant differences between the groups. Considering potential losses and errors, we included 30 patients in each group.
All data were analysed using SPSS V.22.0. In our study protocol, the Shapiro-Wilk test was used to evaluate continuous data to confirm normal distribution. Measured data with a normal distribution were expressed as mean±SD. Non-normally distributed data were expressed as medians (IQRs). Frequencies were used as categorical variables. Age, BMI, surgical duration and AUC of the NRS pain intensity scores were analysed using t-test. ASA classification, maximum pain intensity score, morphine dose in the intervals, sedation status and the time to home-readiness were analysed using the Mann-Whitney U test. Surgery types, incidence of moderate-to-severe pain and incidence of adverse events were analysed using the χ2 (or Fisher’s) test. Cumulative morphine dose was analysed using variance of repeated measures followed by Bonferroni test. The value of p<0.05 was considered statistically significant.
Results
General information
Seventy-five patients undergoing elective laparoscopic gynaecological surgery were considered eligible; of these, 60 were assigned and included in the final analysis (figure 1). There were no statistically significant differences between the two groups in ASA classification, age, BMI, surgery type or surgical duration (all p>0.05) (table 1).
Demographic, intraoperative characteristics and postoperative situation
Postoperative analgesics
The cumulative morphine consumption in the QLB group was significantly lower than in the placebo group in the 6th (mean difference (MD), 5.3; 95% CI 2.4 to 8.2; p<0.001), 18th (MD, 12.0; 95% CI 5.8 to 18.3; p<0.001) and 24th hour after surgery (MD, 14.2; 95% CI 6.3 to 22.1; p<0.001) (figure 3A). The morphine doses administered in the interval times from 0 to 1, 6 to 12, and 12 to 18 hours were significantly lower in the QLB group than in the placebo group (p=0.020, p=0.002 and p<0.001, respectively), however, no significant difference was noted in the morphine doses administered in intervals between 18 and 24 hours (p=0.097) (figure 3B).
(A) Cumulative morphine consumption, data are expressed as mean±SD; (B) interval morphine requirements, data are expressed as median (IQR). QLB, quadratus lumborum block. *p<0.001; #p<0.05.
Pain intensity scores
The AUCs of NRS pain intensity scores, including visceral and incisional pain at rest and on movement, were significantly lower in the QLB group than in the placebo group (all p<0.001) (figure 4A). The maximum pain intensity scores in the QLB group, including visceral and incisional pain at rest and movement, were significantly lower than in the placebo group (p<0.001, p<0.001, p=0.002 and p<0.001, respectively) (figure 4B). The incidence of moderate-to-severe visceral pain at rest and movement, as well as the incidence of moderate-to-severe incisional pain at movement in the QLB group were significantly lower than in the placebo group (p=0.002, p<0.001 and p=0.004, respectively), however, there was no significant difference in the incidence of moderate-to-severe incisional pain at rest between the two groups (p=0.085) (figure 4C).
(A) AUCs of the NRS pain intensity scores through 24 hours postsurgery, data are expressed as mean±SD; (B) maximum pain intensity scores, data are expressed as median (IQR); (C) incidence of moderate-to-severe pain intensity, data are expressed as number (%). IPAR, incisional pain at rest; IPOM, incisional pain on movement; QLB, quadratus lumborum block; VPAR, visceral pain at rest; VPOM, visceral pain on movement. *p<0.001; #p<0.05.
Sedation status, adverse events and time to home-readiness
Patients in both groups were assessed as having minimal or moderate sedation after surgery, which showed no significant difference in sedation status between the two groups (p=0.424). No significant difference was noted in the incidence of itchy skin between the two groups (p=0.371). The incidence of nausea and vomiting was significantly lower in the QLB group than in the placebo group (p=0.015). No other adverse events were observed in this study. The time to home-readiness was significantly shorter in the QLB group than in the placebo group (p=0.014) (table 1).
Discussion
This study was designed to evaluate the postoperative analgesia of the anterior QLB at the L2 level in patients undergoing laparoscopic gynaecological surgery. We found that anterior QLB significantly alleviated visceral and incision pain, reduced morphine consumption and the incidence of nausea and vomiting, and shortened the time to home-readiness.
Lu et al compared anterior QLB at the L2 versus L4 level in volunteers and found that the maximum cephalad dermatome level reached T7 and caudally reached L2 in the anterior QLB at the L2 level, and in most cases the dermatomes from T9 to L1 were blocked.21 Kadam and Howell reported that anterior QLB at the L2 level blocked the dermatomes from T8 to L1 without neurological adverse events.22 These previous studies demonstrated that the blocked range of anterior QLB at L2 covered the incision in laparoscopic gynaecological surgery; therefore, we adopted anterior QLB at the L2 level in this study. As a result, the incision pain intensity in the QLB group in this study decreased significantly. Due to carbon dioxide for pneumoperitoneum during surgery, residual blood in the abdomen after surgery, and diaphragmatic irritation, laparoscopic surgery is usually accompanied by severe postoperative visceral pain, even more than the incision pain.23 In anterior QLB, the spread of the injected solution through the thoracolumbar fascia to the paravertebral space of the lower thoracic region has a significant impact on the visceral analgesic effect of anterior QLB.10–13 However, the controversy still remains because the thoracolumbra fascia is an important anatomical structure that affects the diffusion of local anaesthetic, whether the local anaesthetic is injected in the ‘correct’ position has a crucial impact on the analgesic effect on visceral pain.24 Li et al demonstrated that the spread of local anaesthetic along the diaphragm into the T12 paravertebral space after anterior QLB was observed on the sonogram in every patient.25 In a cadaver study, the dye was injected between the quadratus lumborum muscle and the anterior layer of the thoracolumbar fascia, and produced a broad coverage of the lower to mid-thoracic region.26 Bilgin et al compared transversalis fascia plane block and anterior QLB in patients undergoing caesarean delivery, and confirmed that anterior QLB significantly reduced postoperative visceral pain and opioid consumption.27 The study by Jadon et al reported that anterior QLB prolonged the time to the first request for analgesics, reduced the dose of fentanyl, and effectively alleviated postoperative pain, however the analgesic effect of anterior QLB on visceral pain could not be verified, because the study did not differentiate between incisional pain and visceral pain, the analgesic effect of anterior QLB on visceral pain could not be confirmed.28 Similarly, Dam et al also reported the anterior QLB significantly reduced postoperative opioid consumption.7 In this study, similar to previous research findings, morphine consumption is significantly reduced at various time points and intervals in the QLB group. Additionally, we also observed a significant decrease in visceral pain intensity scores. We believe that these findings are associated with the reduction in both incisional and visceral pain in patients after anterior QLB. In addition, a previous study reported that patients with laparoscopic gynaecological surgery were often accompanied with shoulder pain, which is considered a referred pain conducted by the phrenic (C3-5) and supraclavicular (C3-4) nerves.29 Therefore, in this study, all patients were administered non-steroidal anti-inflammatory drugs and opioids to effectively relieve the postoperative shoulder pain, which was also beneficial to the ERAS protocol.
In previous studies, patients were often in a lateral decubitus position when performing the anterior QLB. When bilateral blocks were required, the patients had to change their positions during the procedure with disinfection and draping twice. In this study, we adopted the transverse oblique paramedian approach to the anterior QLB proposed by Dam et al with the patient in a sitting position,17 and improved the method of ultrasonic localisation at the L2 level. We identified the 12th rib and T12 as the initial marker for puncture positioning. The probe was scanned caudally to identify L1 and L2 successively, increasing the accuracy of block positioning. The needle was inserted in the plane from the lateral side of the transducer to avoid restriction of the transverse process.
The ERAS protocol advocates for the combination of general anaesthesia and regional anaesthesia. General anaesthesia provides satisfactory analgesia, and regional anaesthesia blocks the conduction of peripheral noxious stimuli to the central nervous system, effectively preventing hyperalgesia and achieving multimodal analgesia.30 31 In this study, the postoperative pain was significantly relieved in the QLB group compared with the placebo group. We used PADSS to evaluate the discharge time after anaesthesia, indirectly demonstrating the impact of anaesthesia on ERAS. PADSS evaluates discharge time by evaluating vital signs, ambulation, nausea/vomiting, pain, bleeding and voiding.20 32 In this study, the shorter time to home-readiness in the QLB group compared with the placebo group suggests that anterior QLB is suitable for multimodal analgesia in laparoscopic gynaecological surgery within the ERAS concept.
This study had some limitations. First, the cutaneous sensory blocked area of the patient was not detected due to the purpose of blinding, which might lead to biased results because of the potential failure of the block. Second, we did not measure the plasma concentration of ropivacaine. Although the concentration of ropivacaine used in the study did not exceed 150 mg, the safety of the study could be further improved if the concentrations were tested.
Conclusions
Anterior QLB at the L2 level significantly reduced postoperative morphine consumption in patients undergoing laparoscopic gynaecological surgery, relieved visceral and incision pain intensity, and shortened the discharge time after anaesthesia. Thus, anterior QLB at the L2 level could be used as the optimal scheme of multimodal analgesia for laparoscopic gynaecological surgery.
Data availability statement
Data are available upon reasonable request.
Ethics statements
Patient consent for publication
Ethics approval
This study involves human participants and for this double-blinded randomised trial, ethical approval was provided by the Ethical Committee of The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China, on 6 July 2018 (No. 192-02, 2017). Participants gave informed consent to participate in the study before taking part.
Acknowledgments
The authors would like to thank Dr Xuzhong Xu for his unselfish assistance in statistical analysis and study design. The authors also acknowledge the Department of Anesthesiology, Gynecology, the First Affiliated Hospital of Wenzhou Medical University and the patients enrolled.
References
Footnotes
Contributors KS and LL obtained funding. KS and QW designed the study. LY collected the data. YC was involved in data cleaning. LL analysed the data. LH drafted the manuscript. KS and QW contributed to the interpretation of the results and critical revision of the manuscript for important intellectual content and approved the final version of the manuscript. All authors have read and approved the final manuscript. KS is the study guarantors.
Funding This work was supported by the National Natural Science Foundation of China (Grant numbers 81900231; Grant numbers 82200329).
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.