Abstract

Background

The quadratus lumborum block (QLB) is an effective technique to provide analgesia for upper and lower abdominal surgeries. There are various approaches described in the literature, but the best approach is still to be explored. This study aims to compare the analgesic efficacy of three different approaches of QLBs.

Methods

Sixty-five patients, aged 18–70 years posted for elective laparoscopic abdominal surgery under general anesthesia were enrolled after taking written informed consent. QLB was given using bupivacaine 0.25% 40 mL with injection dexmedetomidine 1 mcg/kg in all the groups. In Group 1 and Group 2, the drug was injected into the anterior and posterior aspects of the muscle respectively. In Group 3, a combination of the anterior-posterior approach was used. Pain scores at various intervals along with analgesic consumption and complications were observed.

Results

The demographic variables, hemodynamic parameters, and complications were comparable among the three groups. There were statistically significant differences between treatment groups in fentanyl requirement as assessed using the Kruskal-Wallis test (P = 0.012). Pairwise post-hoc analysis between block groups showed that the differences between Group 1 & Group 2 and Group 2 & Group 3 were significant (P = 0.0098 and P = 0.013). The tramadol requirement was comparable in all the groups (P = 0.75). Patient satisfaction was significantly higher in Group 3 compared to other groups (P = 0.024).

Conclusion

Further studies can be planned to evaluate the best approach for QLB in terms of perioperative analgesia, which remains a dilemma in this pilot study. The anterior, posterior, and combined anterior-posterior QLB approaches appear equally efficacious as a component of multimodal analgesia in laparoscopic abdominal surgeries.

Keywords

analgesia, bupivacaine, laparoscopic surgical procedures, postoperative pain, quadratus lumborum block, regional anesthesia

---

Introduction

The advantages of the laparoscopic approach over the open abdominal approach are early mobilization, lesser blood loss, fewer infections, less postoperative morbidity, and shorter hospital stay but at the cost of longer operative time.^1,2 Laparoscopic approaches are known to be less traumatic and were found to receive inadequate pain relief as compared to aggressive major surgeries.^3,4 The quadratus lumborum block (QLB) has an evolving role in postoperative analgesia for lower abdominal surgeries. It may also help reduce perioperative opioid consumption. Blanco et al.⁵ first described the QLB as a variation of the transverse abdominis plane (TAP) block where he deposited local anesthetic solution adjacent to the anterolateral aspect of the QL muscle. Later, posterior QL block was described where the local is injected on the posterior surface of the QL muscle.⁶ Børglum et al.⁷ suggested a trans muscular approach, with the local anesthetic placed anteriorly to the QL muscle. This approach was associated with the less redundant anterolateral spread and achieved extensive thoracolumbar spread. The best approach for analgesia is still not known. Therefore, we have planned this study to explore the better approach of QLB for postoperative pain management in laparoscopic abdominal surgeries.

Methods

After approval from the institutional ethics committee (T/IM-NF/ Anaesth/18/71), CTRI registration, CTRI/2019/04/018612 [Registered on: 15/04/2019] was done, adult American Society of Anesthesiologists (ASA) grades I and II patients aged 18–70 years, posted for elective laparoscopic abdominal surgery under general anesthesia were enrolled after written informed consent was obtained. They were provided with a patient information sheet having all the details about the study. ASA III and IV patients, patients with neurological deficits and laparoscopic surgeries converted to open were excluded. Anesthesiologists who are well-versed in the ultrasound-guided (USG) QLB participated in this study. Patients were randomly allocated into three groups by using opaque sealed envelopes containing a computer-generated randomization schedule.

All patients were premedicated with ranitidine (150 mg) the night before and two hours before anesthesia. Standard fasting guidelines were observed for all the patients. Pre-induction monitoring included electrocardiogram, blood pressure, heart rate (HR), peripheral oxygen saturation (SpO₂), and central venous pressure/urine output (UO) in indicated cases. Following pre-oxygenation for 3 minutes, all patients were given intravenous (i.v) midazolam (0.04 mg/kg), fentanyl (2 mcg/kg), and induction of anesthesia was achieved using propofol (1.0–2.5 mg/kg). After the adequacy of mask ventilation was checked, vecuronium bromide (0.1 mg/kg i.v) was administered and the trachea was intubated with 8.5 and 7.5 size endotracheal tubes in male and female patients, respectively. SonoSite M-Turbo ultrasound machine (SonoSite, Inc. Bothell, WA, USA) with a curvilinear 5–2 MHz transducer was used after covering it with the sterile transparent sheet. The lateral abdominal wall was cleaned and scanned between the rib cage and iliac crest. The transducer followed the abdominal muscles, and fascia transversalis until the QL and psoas muscles were identified. Bupivacaine 0.25% 40 mL with injection (inj.) dexmedetomidine 1 mcg/kg was used in all the groups.

In Group 1 (anterior QL block) (n = 20): 20 mL was injected into the anterior aspect of the muscle on both sides; in Group 2 (posterior QL block) (n = 21): 20 mL was injected into the posterior aspect of the muscle on each side, and in Group 3 (combination of anterior and posterior QL Block) (n = 21): 10 mL was injected into the anterior aspect of the muscle and 10 mL on the posterior aspect bilaterally. Anesthesia was subsequently maintained with isoflurane in a mixture of 50% O₂ in air and inj vecuronium and inj. fentanyl (50 mcg) aliquots were given as and when necessary, according to hemodynamic monitoring. The end-tidal carbon dioxide (ET CO₂) was maintained at 35–45 mm Hg. Neuromuscular blockade was antagonized with 50 mcg/kg neostigmine and 10 mcg/kg glycopyrrolate i.v. at the end of surgery. All the patients were given multimodal analgesia with inj. Paracetamol 1 gm i.v every 8 hours. Inj. Tramadol 1 mg/kg was kept for rescue analgesia if Visual Analog Scale (VAS) score ≥ 4. Patients were reassessed after 30 minutes and if still, VAS score remained ≥ 4, inj. Fentanyl 1 mcg/kg was given. VAS charting was done for 12 hours and patient satisfaction (not satisfied [NS]/satisfied [S]/very satisfied [VS]) was recorded at the end. Both the patient and the nursing staff involved in the study were blinded. Mean arterial pressure, HR, SpO₂, and postoperative VAS values were recorded at 0, 1, 2, 4, 8, 12,16, 20, and 24 hours. First hemodynamic measurements in the recovery were recorded as “0” hour values. Age, sex, weight, surgical procedure, duration of surgery, analgesic consumption, and complications were also observed.

Sample Size

Assuming one one-point change in VAS score to be clinically significant,⁸ with 90% power, two-sided 5% significance, and the effect size of 0.5, a pilot trial sample size per treatment arm of 15 is needed in all three groups. We have enrolled 65 patients for the study after considering dropouts and loss to follow-up.

Statistical Analysis

Statistical analysis was performed using R, a software environment for statistical computing and graphics (R version 3.6.1). Categorical variables were expressed as counts or percentages. The Chi-square test was used to compare the categorical variables between different block groups. The normality of numerical variables was analyzed by the Shapiro-Wilks test. Parametric numerical variables were expressed as mean ± standard deviation and nonparametric numerical variables were expressed as median ± interquartile range. The comparison of nonparametric variables between different independent block groups was done by the Kruskal-Wallis test. The post-hoc analysis between paired groups was done by Dunn’s test with bonferroni corrections to find out statistical significance. A P-value of ≤ 0.05 was considered statistically significant.

Results

The consort flow chart of study participants is illustrated in Figure 1. The baseline demographic variables were comparable in all the groups (Table 1). The median VAS score at different time intervals in the three-block groups is comparable (Table 2). The hemodynamic variables such as systolic blood pressure, diastolic blood pressure, mean blood pressure, and HR at different time intervals were comparable between the three-block groups. The outcome variables in the three-block groups are shown in (Table 3).
Figure 2 illustrates the box plot depicting the fentanyl requirement between different block groups and the pair-wise comparison for statistical significance. The fentanyl requirement between block groups was statistically significant (P = 0.012). The fentanyl requirement in Group 2 is significantly less compared to Group 1 (P = 0.0098) and in Group 2 compared to Group 3 (P = 0.013). The tramadol requirement was comparable in all the block groups (P = 0.75). The patient satisfaction among the block groups was statistically significant (P = 0.024). The overall complications recorded were comparable in all the three block groups (Table 3).

Discussion

This prospective randomized trial compared the role of three different approaches of QLB namely anterior, posterior, and combined anterior and posterior approaches for perioperative analgesia in laparoscopic abdominal surgeries under general anesthesia. No significant difference was found in VAS scores between the groups, nor was there any difference in the 24-hour consumption of rescue analgesia, tramadol. The intraoperative consumption of fentanyl was the least in the posterior approach as compared to the other groups. Patient satisfaction was significantly better in Group 3 (combined anterior and posterior approach) as compared to the other two groups. The overall complications recorded were comparable in all three groups, with most of the patients having no complications. Demographic parameters in terms of gender distribution and age groups were comparable among the groups. The median age varied from 37.5 years to 42.5 years.

QLBs by either of the three approaches had a favorable effect on the VAS Score with the VAS score in all three groups being less than 4, although there is not a significant difference in VAS score among the groups. Hence QLB by any of the approaches is effective in reducing postoperative pain after laparoscopic abdominal surgeries until 24 hours.

Our study is in accordance with the meta-analysis by Kim et al.⁹ which has suggested that QLB by any approach is effective in reducing postoperative pain after abdominal surgeries. However, in opposition to our study on subgroup analysis, they found that pain scores at rest showed a statistically significant difference based on the approach of QLB (P = 0.02, I² = 75.7%). Posterior QLB had an improved pain score 12 hours postoperatively surgery (MD, –3.06 [95% CI, –4.16 to –1.95]) but the effect of anterior QLB on the pain scores was not significant (MD, –2.40 [95% CI, –5.17 to 0.36]). They have attributed this to the heterogeneity of the studies that they included. Hence, further randomized controlled trials are needed to reach a definitive conclusion.

QLB was first presented as a USG abdominal wall block by Rafael Blanco as a variant of the TAP block, where the drug was deposited deep into the transversus abdominis aponeurosis.¹⁰ Later Blanco introduced a modified technique for QL block with a drug deposition just posterior to the QL muscle.⁶ Børglum et al.⁷ have described a trans-muscular approach where the drug was deposited anterior to the QL muscle and behind the psoas muscle.

Thereafter some studies have proven it to be useful after spinal anesthesia in cesarean deliveries.^11,12 A few have compared it with TAP block for postoperative analgesia after cesarean section¹³ as well as other surgeries including laparoscopic cholecystectomies¹⁴ where they have found it more effective. Our study is supported by that of Murouchi et al.¹⁵ who have found QL block to have a more widespread and longer-lasting effect when compared to TAP block in laparoscopic ovarian cystectomies.

QL block is helpful for both somatic and visceral pain, unlike the TAP block which mainly controls somatic pain. It also provides a wider sensory block from T4 to L1 as compared to the TAP block. Cadaveric studies have proven that the drug spreads to the thoracic paravertebral space and sympathetic nerves in the thoracolumbar fascia in QLB. Hence, theoretically, it might provide longer and better analgesia than the USG-guided TAP block.¹¹

There was no significant difference in the 24-hour consumption of rescue analgesic, tramadol among the groups. This is supported by a meta-analysis by Jin et al.¹⁶ that QLB has an opioid-sparing effect in a variety of surgeries. However, we found that intraoperative fentanyl consumption was the least in the posterior approach as compared to the other groups, although the VAS score was not significant among them. This is an indirect indicator that the posterior approach has a better analgesic effect in the intraoperative period. We presumed this could be attributed to the faster onset of action of the posterior approach as compared to the anterior approach. However, supporting evidence is unclear and conflicting. The mechanism of action of the different approaches of QL blocks is still controversial. The drug spreads along the middle thoracolumbar fascia intertransverse area when deposited posterior to the QL muscle. In posterior QLB, the presence of a lumbar inter-fascial triangle is a potential route for medial, lateral, and craniocaudal local anesthetic spread.¹⁷ Anterior QLB injectate may spread to the lumbar nerve roots and branches in the lumbar plexus in addition even up to the thoracic paravertebral space. Thus, the anterior approach on the contrary may have a better analgesic effect.⁵

Patient satisfaction was significantly higher in Group 3 (combined anterior and posterior approach group) as compared to the other two groups. This is similar to the favorable effect on patient satisfaction that Singh et al.¹⁸ had observed in a few cases using the combined approach of anterior and posterior QLB for analgesia after laparoscopic abdominal hysterectomy.

The overall complications recorded were comparable in all three groups. Only eight reports of minor complications limited to dizziness, nausea, and vomiting were noted. Although theoretically QLB is a deep block and hence there are chances of injury to the surrounding deeper structures, using ultrasound guidance, knowledge of the relevant anatomy, and technical expertise, it can be performed safely. There has been a report of hypotension and tachycardia due to sympatholytic in a case report.¹⁹ Patient satisfaction was optimum in all three approaches, with the best comfort being in the combined anterior and posterior approach. The posterior approach is presumed to have the fastest onset of action, having the best opioid-sparing effect during the intraoperative period.

Conclusion

The best approach for QLB in terms of adequate intraoperative and postoperative analgesia remains a dilemma in this pilot study. As far as postoperative analgesia is concerned, the three approaches that we have included in our study vis a vis anterior, posterior, and combined anterior and posterior QLB are equally efficacious as a component of multimodal analgesia in laparoscopic abdominal surgeries.

Acknowledgments

Thank you to all the patients and theatre staff.

Conflict of Interest

There are no conflicts of interest.

---

References