Optimal approach to ultrasound-guided quadratus lumborum blocks for postoperative analgesia in elective caesarean section: protocol for systematic review and meta-analysis

Abstract

Introduction

Ultrasound-guided quadratus lumborum blocks are commonly used for postoperative analgesia during caesarean section. Ultrasound-guided quadratus lumborum blocks can be performed through four approaches, including lateral, posterior, anterior, and intramuscular quadratus lumborum blocks. This systematic review and meta-analysis aims to determine the optimal approach to ultrasound-guided quadratus lumborum blocks for postoperative analgesia in elective caesarean section.

Methods and analysis

The PubMed, EMBASE, Cochrane Library and Web of Science databases will be systematically searched from their inception to 30 July 2024. Randomised controlled trials that compared the analgesic effects of different ultrasound-guided quadratus lumborum block approaches in elective caesarean section will be included. Only publications in English will be eligible for inclusion. The total postoperative analgesic consumption over 24 hours will be the primary outcome. The time to first analgesic request, postoperative pain scores at rest and during movement, and incidence of adverse effects will be secondary outcomes. RevMan V.5.4 will be used for the statistical analysis. Network meta-analysis will be used for indirect comparisons between different approaches across studies. The Grading of Recommendations Assessment, Development and Evaluation approach will be used to assess the quality of evidence for each outcome.

Ethics and dissemination

Ethical approval was not required. The results of this study will be submitted to peer-reviewed journals.

PROSPERO registration number

CRD42024503694.

STRENGTHS AND LIMITATIONS OF THIS STUDY.

• This study aims to determine the optimal approach for postoperative analgesia via ultrasound-guided quadratus lumborum blocks in elective caesarean section, which can provide better analgesia with fewer adverse effects.

• Subgroup analysis and meta-regression will be used to explore potential heterogeneity and will allow recommendations for the preferred approach to ultrasound-guided quadratus lumborum block for certain conditions.

• The Grading of Recommendations Assessment, Development and Evaluation tool will be used to assess the quality of evidence for each outcome.

• High clinical heterogeneity may exist among the included studies due to the many contributors, such as the local anaesthetics and adjuvants used for nerve block, the duration of surgery, the anaesthesia type and intraoperative analgesic use, and the definition of outcomes.

• The number of trials that directly compare different approaches involving the use of ultrasound-guided quadratus lumborum blocks in caesarean section, as well as the sample sizes of each intervention group, may be relatively small.

Introduction

Ultrasound-guided quadratus lumborum blocks are widely used for postoperative analgesia in patients undergoing elective caesarean section. Accumulating evidence indicates that ultrasound-guided quadratus lumborum blocks can alleviate pain intensity, reduce total postoperative analgesic consumption and decrease the incidence of adverse effects after caesarean section.¹,³ Previous studies have also suggested that ultrasound-guided quadratus lumborum blocks are superior to other commonly used nerve blocks, namely, transversus abdominis plane blocks, for patients receiving caesarean section.⁴,⁶ Therefore, the use of ultrasound-guided quadratus lumborum blocks is an effective choice for multimodal analgesia for caesarean section.⁷,⁹

Currently, ultrasound-guided quadratus lumborum blocks can be generated through four major approaches, including lateral,⁷ posterior,¹⁰ anterior¹¹ and intramuscular quadratus lumborum blocks.¹² An increasing number of randomised controlled trials (RCTs) have investigated and compared the analgesic effects of different approaches involving the use of quadratus lumborum blocks for postoperative analgesia in elective caesarean section,¹³,¹⁶ but the results have not always been consistent.

This systematic review and meta-analysis aims to determine the optimal approach to ultrasound-guided quadratus lumborum blocks for postoperative analgesia in elective caesarean section.

Methods and analysis

Study registration and reporting

This protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO, CRD42024503694). This protocol is reported according to the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols guidelines.

Search strategy

Two authors (YL and NW) will systematically search the PubMed, EMBASE, Web of Science and Cochrane Library databases from their inception to 30 July 2024. The search terms will include “quadratus lumborum block”, “cesarean section”, “cesarean delivery” and “randomized controlled trials”. English language restriction will be applied. The detailed search strategy for all the databases is shown in online supplemental file 1.

Inclusion and exclusion criteria

The inclusion criteria for the included studies: (a) Study type: RCTs; (b). Participants: patients undergoing caesarean section; (c). Comparisons: different approaches of ultrasound-guided quadratus lumborum blocks and (d) Primary outcomes: total postoperative analgesic consumption over 24 hours; secondary outcomes: the time to first analgesic request, postoperative pain scores at rest and movement at 2 hours, 4 hours, 8 hours, 12 hours and 24 hours, and the incidence of adverse effects. Studies that do not meet the abovementioned criteria will be excluded.

Study selection

Two authors (YL and NW) will independently identify the relevant studies by first reading their titles and abstracts. Then, the full texts of these identified studies will be reviewed to determine whether they will be included. A discussion with the third author (DZ) will be performed if any disagreement exists. Figure 1 shows the flow chart of the study selection process.

Figure 1. Flow chart for study selection.

Data extraction

Two authors (YL and NW) will independently perform data extraction, including publication year and settings, participant characteristics, sample numbers, quadratus lumborum block approach, anaesthesia type, surgery length, local anaesthetics and adjuvants, comparisons, outcomes, and postoperative analgesia strategy.

Risk of bias assessment

Two authors (YL and NW) will use the Cochrane Collaboration tool to assess the risk of bias of the included RCTs. Major items, including random sequence generation and allocation concealment (selection bias), blinding of participants and personnel (performance bias), blinding of outcome assessment (detection bias), incomplete outcome data (attrition bias) and selective reporting (reporting bias), will be evaluated, and the estimated results will be reported as ‘high’, ‘low’ or ‘unclear’. When there is suspicion of or direct evidence for selective reporting, we will ask the authors for additional information. For example, authors could supply the study protocol and full information for outcomes reported inadequately. Moreover, for outcomes mentioned in protocol but not reported, authors could be asked to clarify whether those outcomes were analysed, and if so to provide the data. In addition, sensitivity analysis will also be used to investigate the possible impact of selective outcome reporting. Disagreements will be discussed with another author (DZ).

Statistical analysis

Data processing and statistical analysis will be conducted using RevMan V.5.4 software. Dichotomous data will be presented as risk ratios with 95% CIs, and continuous data will be calculated as the mean difference with 95% CI. Direct meta-analysis will be performed for comparisons between the same two approaches across studies. Network meta-analysis will be used for indirect comparisons between different approaches tested across different trials. For example, the results from a direct comparison of approach A versus approach B and approach A versus approach C will be able to be generated as a result of an indirect comparison between approach B and approach C (approach A as a common comparator). A network plot will show the network geometry and node connectivity. The results of the RANK command (p value) in STATA 14.0 software will be used to rank the efficacy of different interventions. The statistical heterogeneity will be indicated by the I² test results. A fixed-effect model will be used to pool the data if I²<50%, whereas a random-effect model will be used if I²>50%, which suggests high heterogeneity. Subgroup analysis and meta-regression will be further used to determine the source of heterogeneity based on several factors, such as the local anaesthetics and adjuvants used for nerve block, the duration of surgery, the anaesthesia type and the use of intraoperative analgesics. Sensitivity analyses will be performed to assess the reliability of the pooled results. Finally, the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach will be applied to assess the quality of evidence. A p<0.05 indicates statistical significance.

Patient and public involvement

None.

Ethics and dissemination

Ethical approval is not required as this systematic review and meta-analysis will be based on published data. The results will be submitted to peer-reviewed journals.

Discussion

Different approaches involving ultrasound-guided quadratus lumborum blocks are currently used in elective caesarean section to provide postoperative analgesia, but their advantages or weaknesses remain controversial. This systematic review and meta-analysis aims to determine the optimal approach to ultrasound-guided quadratus lumborum blocks for postoperative analgesia in elective caesarean section, which will provide better analgesia with fewer adverse effects.

However, several issues should be considered. First, high clinical heterogeneity may exist among the included studies due to the many contributors, such as the local anaesthetics and adjuvants used for nerve block, the duration of surgery, the anaesthesia type and intraoperative analgesic use, and the definition of outcomes. Subgroup analysis and meta-regression will be used to explore potential heterogeneity and will allow recommendations for the preferred approach to ultrasound-guided quadratus lumborum block for certain conditions. Second, the number of RCTs that directly compared different approaches of ultrasound-guided quadratus lumborum blocks used for elective caesarean section, as well as the sample size of each intervention group, may be relatively small, which may influence the reliability of the pooled results. However, we will use the GRADE tool to assess the quality of evidence for each outcome. Finally, it should be noted that the divergence in postoperative analgesia strategies may affect the accuracy of the pooled results.