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Regional anaesthesia

Ultrasound-guided quadratus lumborum block for postoperative analgesia

A systematic review and meta-analysis

Korgvee, Andrus; Junttila, Eija; Koskinen, Heikki; Huhtala, Heini; Kalliomaki, Maija-Liisa

Author Information
European Journal of Anaesthesiology: February 2021 - Volume 38 - Issue 2 - p 115-129
doi: 10.1097/EJA.0000000000001368

Abstract

Introduction

Regional analgesia plays an important role in perioperative multimodal analgesic regimens for major abdominal and hip surgery. The ultrasound-guided technique provides several options for relieving postoperative pain.1 In the quest for a well tolerated and effective advanced pain therapy method as well as an alternative to overcome the risks of epidural analgesia, quadratus lumborum block (QLB) is one of the most recent and promising2,3 truncal block techniques.

Ultrasound-guided QLB was first described in 2007 by Rafael Blanco.4 The technique was probably inspired by the landmark-based transversus abdominis plane block (TAP block) and the location of the lumbar triangle of Petit.5 In the landmark-based technique, the target for the needle tip during QLB could not be described precisely, but it may be the same as in posterior TAP, which can be differentiated from lateral TAP with ultrasound.6 After further investigations, Blanco and McDonnell7 suggested two different QLB options, named QLB1 and QLB2. In QLB1, the needle tip is placed at the anterolateral edge of the quadratus lumborum muscle in a similar way as in posterior TAP. At the same time, Hebbard8 described ‘fascia transversalis block’, which resembles QLB1. In QLB2, the target point for the needle tip is located posteriorly to the quadratus lumborum muscle (Fig. 1).

Fig. 1
Fig. 1:
(a) Graphically illustrated ultrasound image of the quadratus lumborum region. (b) Ultrasound image of four different quadratus lumborum block approaches

At about the same time that Blanco described ultrasound-guided QLB2, Borglum and colleagues introduced the transmuscular quadratus lumborum block (TQLB),9,10 where the needle is inserted through the quadratus lumborum muscle into the interfascial plane between the quadratus lumborum and psoas major muscles (Fig. 1). A more detailed description of these QLB techniques, with a discussion of the anatomical concepts and theories on the potential mechanisms, has recently been published in a review by Elsharkawy et al.11 In addition, some recent publications have also described the use of intramuscular QLB.12,13

According to the literature, these QLB techniques are reported to be a usable option for postoperative analgesia in abdominal and hip surgery.14–17 The sensory blocks have been described as extending from T7 to the L1--L2 dermatomes,9,18 and some studies have even shown the spread of the injection up to the fourth thoracic dermatome.5,19 As an ultrasound-guided peripheral block, the complications and adverse effects associated with QLB are thought to be minor,11,20–22 and not as severe as with epidural block.11,23–25 However, it is a deep block that should only be used after careful consideration.11

The aim of this systematic review and meta-analysis was to evaluate the efficacy and safety of QLB for postoperative analgesia after abdominal and hip surgery in adult patients.

Methods

Protocol and registration

The manuscript was prepared according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis Protocols (PRISMA-P 2015) statement guidelines.26,27 We used a predetermined protocol that was registered with the International Prospective Register of Systematic Reviews on 7 June 2016 (PROSPERO, https://www.crd.york.ac.uk/prospero/, CRD42016039921).

Eligibility criteria

In this review and meta-analysis, we included randomised controlled trials (RCTs) and prospective observational studies that investigated the postoperative analgesic properties of ultrasound-guided single shot QLB compared with any control in patients aged at least 18 years undergoing abdominal or hip surgery. In studies with several control groups, the groups were assessed separately. The publication status required was either a full published article or abstract. Studies written in English, French, German, Swedish and Finnish were included. Retrospective studies, case reports and series, as well as studies where blocks were performed without ultrasound guidance or where catheter techniques were used were excluded.

Information sources and search

The following electronic databases were used: Ovid (MEDLINE), PubMed, Scopus, Web of Science, CINAHL and the Cochrane Central Register of Controlled Trials (CENTRAL). A search for unpublished studies was conducted in ClinicalTrials.gov. and studies not registered in the databases listed above. The https://clinicaltrials.gov/ct2/results?cond=&term=Quadratus+Lumborum+block&cntry=&state=&city=&dist= lists within relevant publications were checked for additional studies.

We performed three searches. The time frame for the first search was from inception up to 20 March 2016, for the second search from 1 January 2016 to 30 January 2018 and for the third search from 1 February 2018 to 27 June 2019. Any duplicates during the overlap between these three search periods were removed.

The search strategy was planned in collaboration with an experienced informatician (SH). The strategy was developed using medical subject headings (MeSH) and words related to the subject. It was based on three separate entities: anatomical site, regional analgesia and QLB/TAP block. First, the anatomical site and regional analgesia entities were combined by the Boolean operator ‘AND’, which was then combined with the QLB/TAP entity by operator ‘OR’ (Fig. 2). The search strategy used in Ovid (MEDLINE) is presented in Supplementary Table S1, http://links.lww.com/EJA/A387.

Fig. 2
Fig. 2:
Flowchart according to the PRISMA-P statement guidelines summarising the search strategy used as well as the retrieved, included and excluded studies.

Study selection and data collection

All literature search results from different databases were uploaded to Refworks (ProQuest), which is an online reference management software programme. The software also enabled collaboration among reviewers during the study selection process. First, one reviewer (AK) screened for duplication of the records. After deduplication, AK screened the titles of the records to exclude any totally irrelevant search results. Next, two independent reviewers (AK, EJ) screened the abstracts for potential inclusion according to the predefined inclusion criteria. The same two independent reviewers (AK, EJ) performed a full-text assessment for eligibility and, in case of disagreement, a third reviewer (MLK) was consulted.

Data extraction was undertaken by two reviewers (AK, EJ), using a standardised data extraction form (Supplementary Table S2, http://links.lww.com/EJA/A388). In studies where data was missing or was unusable for meta-analysis, or data was only presented graphically, an attempt was made to contact the corresponding authors by e-mail.

Data items

The data extracted for the study, such as publication details, study design, the number of study patients and the country in which the study was performed, are presented in Supplementary Table S2, http://links.lww.com/EJA/A388. In addition, patient characteristics and the type of surgical intervention were extracted. The data extracted for the block characteristics were the timing of the block (preoperatively or postoperatively), the block technique used and the site of injection (QLB1/TAP posterior, QLB2 or TQLB) and the local anaesthetic used along with its concentration, volume and adjuvant medications.

Outcomes, prioritisation

The primary outcome was the opioid consumption at 24 h postoperatively. The dose of opioid is presented in milligrams (mg) equivalents of intravenous morphine. Secondary outcomes were the time to the first rescue opioid analgesic, pain grades at rest and during movement at 24 h postoperatively (only pain grades scored as 0 to 10 or 0 to 100 were included as these could be converted to a numeric rating scale, NRS 0 to 10), the incidence of postoperative nausea and vomiting (PONV), pruritus, respiratory depression and sedation. Also, data from recovery scores (such as QoR-40), patient satisfaction, length of stay (LOS) in the postanaesthesia care unit (PACU) and hospital, block complications and other adverse effects were extracted.

Risk of bias

The Cochrane Collaboration's tool28 was used to assess the risk of bias. Two independent review authors (EJ, MLK) assessed the risk of bias of the studies by considering the following characteristics: randomisation sequence generation, treatment allocation concealment, blinding, completeness of outcome data, outcome reporting and other sources of bias, such as publication bias. These domains were then classified as high, unclear or low risk.

Quality of evidence

Grading of Recommendations Assessment, Development, and Evaluation (GRADE, http://www.gradeworkinggroup.org) was used to assess the quality of evidence, which was classified as high, moderate, low or very low. Assessments included the risk of bias, inconsistency, indirectness, impreciseness and other considerations (EJ and MLK). GRADEpro/GDT (https://gdt.gradepro.org/) was used to create the GRADE evidence profile.

Summary measures and synthesis of results

Article characteristics and outcomes are presented in tabulated form with a discussion of the trial methodology and results. Studies with more than two treatment arms were handled as separate study results. Meta-analyses were performed for opioid consumption and pain grades at 24 h postoperatively and the time to the first opioid analgesic with the available data presented in mean ± SD and incidence of PONV. Subgroup analyses were performed according to the comparator (placebo/no block, other peripheral block and central block) and the type of QLB (QLB1, QLB and TQLB). The Peto odds ratio method was used in PONV analyses. The software used for the meta-analyses was Stata 13.0 (Stata Corp, College Station, Texas, USA). The extent of heterogeneity was verified using I2 statistics. If there existed high heterogeneity, I2 over 50% across the included studies, the pooled mean difference and 95% CIs were calculated from the reported or raw data of the included studies using the Der-Simonian method for random effects. User manual and software for trial sequential analysis (TSA)29 were used to evaluate the risk of type I and II errors in the primary outcome with alpha 0.05 and beta 0.20 probabilities.

Those studies that reported only medians with [IQR], but without range (min and max), and the original data were not available despite our requests to the authors for the data, are reported narratively. For one study15 that had raw data available, a statistician (HH) calculated those P values not previously reported in the article. A P value less than 0.05 was considered statistically significant.

Results

Study selection

A detailed summary of the three searches performed is presented in the PRISMA Flowchart (Fig. 2). After combining the studies from these search results and five studies from other sources and removing any duplicates, 4045 studies were screened according to the title and 1126 according to the abstract. Finally, 189 full text articles were assessed for eligibility with 27 being selected for analysis.

Study characteristics and participants

In total, data from the 27 studies with 1557 patients were reviewed. Most studies were RCTs and three were observational.18,30,31 Six studies were available only as an abstract.30–35 The most common type of surgery was abdominal, with hip surgery in four studies. The type of surgery performed is described in more detail in Table 1.

Table 1 - Study characteristics, primary outcomes and reported main outcomes
Study (first author, year) Groups, n (patients) Surgery Anaesthesia Primary outcome Opioid consumption Pain grade, rest Pain grade, dynamic PONV
Aoyoma, 201630 QLBa (12)TAP, lateral (11) Laparoscopic gynaecological surgery GA Not reported
Baytar, 201948 QLB1 (54)TAPsubcost (53) Laparoscopic cholecystectomy GA Postoperative pain grade and tramadol consumption
Bhatti, 201631 TQLB (9)Fascia iliaca block (7) Hip surgery Spinal or GA Not reported
Binzer, 201332 TQLB (3)Placebo (3) Laparoscopic cholecystectomy GA Postoperative pain grade
Blanco, 201540 QLB2 (25)Placebo (23) Caesarean section Spinal Postoperative opioid consumption
Blanco, 201616 QLB2 (36)Placebo (36) Caesarean section Spinal Postoperative opioid consumption
Dam, 201946 TQLB (25)Placebo (26) Percutaneous nephrolithotomy GA Postoperative opioid consumption
Dewinter, 201845 QLB1 (50)Intravenous lidocaine (50) Laparoscopic colorectal surgery GA Postoperative opioid consumption
Faiz, 201836 TAP, posterior (38)TAP, lateral (38) Caesarean section Spinal Postoperative pain grade
Hansen, 201947 TQLB (36)Placebo (36) Caesarean section Postoperative opioid consumption
He, 201834 QLBa (30)No block (30) Hip arthroplasty Data not available
Ishio, 201751 QLB2 (35)No block (35) Laparoscopic gynaecological surgery GA Postoperative pain grade
Iwata, 201835 QLBa (17)No block (17) Laparoscopic nephrectomy GA Not reported
Kang, 201937 QLB2 (22)QLB3 (23)Epidural (22) Caesarean section Spinal Postoperative pain grade
Kilic, 201817 TQLB (22)Placebo (22) Percutaneous nephrolithotomy Spinal Postoperative opioid consumption
Krohg, 201815 QLB1 (20)Placebo (20) Caesarean section Spinal Postoperative opioid consumption
Kumar, 201849 QLB1 (35)TAP, lateral (35) Abdominal surgery GA Delay to first rescue opioid analgesic
Mieszkovski, 201841 QLB1 (28)No block (30) Caesarean section Spinal Postoperative opioid consumption
Murouchi, 201618 QLB1 (11)TAP, lateral (11) Laparoscopic gynaecological surgery GA Duration of analgesia
Parras, 201514 QLB1 (48)Femoral block (49) Hip surgery Spinal Postoperative pain grade and opioid consumption
Salama, 201942 QLB2 (30)ITM (30)Placebo (30) Caesarean section Spinal Pain grade
Shafeek, 201838 TQLB (20)TAP, lateral (20)No block (20) Laparoscopic bariatric surgery GA Not reported
Taketa, 201533 TAP, posterior (10)TAP, lateral (10) Laparoscopic gynaecological surgery GA Not reported
Tamura, 201943 QLB2 (36)Placebo (38) Caesarean section Spinal Pain grade
Tulgar, 201844 TQLB (20)L-ESPB (20)No block (20) Hip and proximal femur fracture surgery GA Postoperative pain grade
Yousef, 201850 QLB2 (30)TAP, lateral (30) Hysterectomy GA Postoperative opioid consumption
Ökmen, 201839 QLB2 (30)Placebo (29) Laparoscopic cholecystectomy GA Postoperative pain grade
aQLB type not reported; GA, general anaesthesia; PONV, postoperative nausea and vomiting; QLB, quadratus lumborum block; TAP, transversus abdominals plain block; TQLB, transmuscular quadratus lumborum block.

Block techniques were categorised as QLB1, QLB2 and TQLB. The categorisation and the details of the agents and additional analgesics used are described in Table 2. We included two studies in the QLB1 category where a posterior TAP block was performed.33,36 In one study, both QLB2 and TQLB were performed.37 The local anaesthetics used were ropivacaine, bupivacaine or levobupivacaine, with varying concentrations. The control groups varied across the studies, consisting of groups without any block or with placebo or comparative blocks. The details of the control groups are described in Table 1.

Table 2 - Block characteristics and postoperative analgesic regimens according to the type of quadratus lumborum block
Type of QLB Study (first author, year) Unilateral/bilateral block Timing of the block Local anaesthetic, concentration Local anaesthetic, amount per side Opioid used Additional analgesia
QLB1
Baytar, 201948 Bilateral Preop Bupivacaine 2.5 mg ml−1 0.3 ml kg−1 (max 20 ml) Tramadol Tenoxicam
Dewinter, 201845 Bilateral Preop Ropivacaine 2.5 mg ml−1 20–30 ml Morphine Acetaminophen Ketorolac
Faiz, 2018a36 Bilateral Postop Ropivacaine 2 mg ml−1 20 ml Meperidine Acetaminophen
Krohg, 201815 Bilateral Postop Ropivacaine 2 mg ml−1 0.4 ml kg−1 (max 30 ml) Ketobemidone Acetaminophen, ibuprofen
Kumar, 201849 Bilateral Postop Ropivacaine 2.5 mg ml−1 20 ml Morphine Acetaminophen
Mieszkovski, 201841 Bilateral Postop Ropivacaine 3.75 mg ml−1 24 ml Morphine Acetaminophen
Murouchi, 201618 Bilateral Preop Ropivacaine, 3.75 mg ml−1 20 ml Not used Acetaminophen
Parras, 201514 Unilateral Preop Levobupivacaine 1.25 mg ml−1 30 ml Morphine Acetaminophen
Taketa, 2015a33 Not reported Preop Not reported Not reported Fentanyl Not reported
QLB2
Blanco, 201540 Bilateral Postop Bupivacaine 1.25 mg ml−1 0.2 ml kg−1 Morphine Acetaminophen, diclofenac
Blanco, 201616 Bilateral Postop Bupivacaine 1.25 mg ml−1 0.2 ml kg−1 Morphine Acetaminophen, diclofenac
Ishio, 201751 Bilateral Postop Ropivacaine 3.75 mg ml−1 20 ml Not used Acetaminophen, diclofenac
Kang, 2019b37 Bilateral Postop Ropivacaine 2 mg ml−1 30 ml Morphine Not reported
Salama, 201942 Bilateral Postop Ropivacaine 3.75 mg ml−1 24 ml Morphine Acetaminophen
Tamura, 201943 Bilateral Postop Ropivacaine 3 mg ml−1 0.45 ml kg−1 Not used Acetaminophen, diclofenac, pentazocine
Yousef, 201850 Bilateral Preop Bupivacaine 2.5 mg ml−1 20 ml Morphine Acetaminophen
Ökmen, 201839 Bilateral Preop Bupivacaine 2.5 mg ml−1 0.3 ml kg−1 Tramadol Tenoxicam
TQLB
Bhatti, 201631 Unilateral Preop Levobupivacaine 2.5 mg ml−1 20 ml Morphine Tramadol
Binzer, 201332 Unilateral Not reported Ropivacaine 7.5 mg ml−1 30 ml Not reported Not reported
Dam, 201946 Unilateral Preop Ropivacaine 7.5 mg ml−1 30 ml Morphine Acetaminophen
Hansen, 201947 Bilaterl Postop Ropivacaine 3.75 mg ml−1 30 ml Morphine Acetaminophen, ibuprofen
Kilic, 201817 Unilateral Preop Bupivacaine 1.25 mg ml−1 0.2 ml kg−1 Morphine Not reported
Shafeek, 201838 Bilateral Preop Bupivacaine 1.25 mg ml−1 0.2 ml kg−1 Morphine Not reported
Tulgar, 201844 Unilateral Preop Bupivacaine 5 mg ml−1 20 ml Lidocaine 2 mg ml−1 10 ml 0.9% saline 10 ml 40 ml Tramadol Fentanyl Acetaminophen
Unable to define
Aoyoma, 201630 Bilateral Preop Levobupivacaine 3.75 mg ml−1 20 ml Fentanyl Not reported
He, 201834 Unilateral Postop Ropivacaine 3.3 mg ml−1 30 ml Sufentanil Parecoxib
Iwata, 201835 Not reported Not reported Not reported Not reported Not reported Not reported
postop, postoperatively; preop, preoperatively; QLB, quadratus lumborum block; TAP, transversus abdominis plain block; TQLB, transmuscular QLB.
aPosterior TAP.
bBoth QLB2 and TQLB groups.

The primary outcome and other reported main secondary outcomes with more detailed descriptions of each individual study are presented in Tables 1 and 2. The consumption of opioids and pain grades were assessed at time points ranging from 4 to 48 h postoperatively. Respiratory depression was reported in three studies,16,38,39 limb weakness in two37,39 and paraesthesia in one.14 Itching/pruritus was reported in seven studies16,37,39–43 and sedation in six.16,38–41,44 In one study,45 systemic toxicity-like symptoms were reported. LOS in hospital was reported in two studies.45,46

Risk of bias within and across studies and the quality of evidence

The risks of bias according to the Cochrane Collaboration's tool are described in Fig. 3. The most common reason for the risk of bias was related to blinding. There were four studies with a low risk of bias in all the assessed characteristics.15,40,46,47

Fig. 3
Fig. 3:
Risk of bias summary according to the Cochrane Collaboration's tool

The baseline of level of evidence with the primary outcome was moderate. With secondary outcomes, the level of evidence varied from low to high. The quality of evidence had to be downgraded mainly because of the risks of bias and inconsistency. The GRADE evidence profile is presented in Supplementary Table S3, http://links.lww.com/EJA/A389.

Pooled results of the included studies

Primary outcome: opioid consumption at 24 h postoperatively

The postoperative opioid consumption at 24 h was reported in 14 studies.14–17,37,38,40,44–50 Of these, the data from 12 studies with 803 patients were available as mean ± SD,14,15,17,37,38,44–50 and were included in the meta-analysis. In two studies,37,38 there were several comparators, and these were included in the analysis separately. QLB reduced postoperative opioid consumption [mean difference, −11.15 (95% CI, −15.33 to −6.96) mg, I2 = 99%]. According to the subgroup analyses based on the comparators, QLB was favoured compared with placebo/no block or other peripheral block. In one study with an epidural block as a comparator, the result favoured the epidural.37 The results of the meta-analyses are presented in Fig. 4. According to the subgroup analyses, QLB1 and TQLB were favoured, but not QLB2 (Supplemental Figure S1, http://links.lww.com/EJA/A381). However, in two studies of QLB216,40 that presented the results as median [IQR], and were not included in the meta-analysis, the postoperative consumption of opioids was reduced in patients with QLB.

Fig. 4
Fig. 4:
Forest plot showing the 24 h opioid consumption (mg)

Secondary outcome: the delay to the first opioid analgesic

The time to the first postoperative opioid analgesic was reported in 10 studies.36,38,41,42,45–50 According to the meta-analysis based on seven36,38,41,47–50 studies with 499 patients, QLB lengthened the time to the first opioid analgesic: mean difference 189.32 (95% CI, 114.4 to 264.23) min, I2 = 98%, not depending on the comparator or the type of QLB (Fig. 5 and Supplement Figure S2, http://links.lww.com/EJA/A382). In one study,47 the result favoured the comparator (placebo).

Fig. 5
Fig. 5:
Forest plot showing the time (minutes) to the first opioid analgesic

Secondary outcome: pain grades

The pain grade at rest was assessed at 24 h postoperatively in 26 studies.14–17,30–51 Of these, 11 studies with 765 patients14,15,17,34,36,37,43,48–51 presented their results as mean ± SD and these data were included into the meta-analysis (Fig. 6). Overall, there was no difference in postoperative pain scores at rest between the QLB and the comparators: mean difference −0.22 (95% CI −1.24 to 0.8), I2 = 99%. However, according to the subgroup analyses, in patients with QLB pain scores were lower when compared with patients with placebo/no block or other peripheral block. In the study where an epidural block was used as the comparator,37 the pain scores were higher in the QLB group. The type of QLB did not affect to the pain score results (Supplement Figure S3, http://links.lww.com/EJA/A383). According to the meta-analysis of pain scores during movement, based on seven studies15,34,36,37,43,48,51 with 494 patients, the result resembled the results of pain scores at rest: [mean difference 0.47 (95% CI −0.26 to 2.2), I2 = 99%] (Fig. 7 and Supplement Figure S4, http://links.lww.com/EJA/A384).

Fig. 6
Fig. 6:
Forest plot showing the postoperative pain grade at rest at 24 h
Fig. 7
Fig. 7:
Forest plot showing the postoperative pain grade during movement at 24 h

Secondary outcome: postoperative nausea and vomiting

The incidence of PONV was reported in 12 studies30,34,37–39,42,45–48,50,51 of which 11, with 744 patients, were included in the meta-analysis.30,34,37–39,42,45–48,50 The assessment time points varied widely or were not reported. Overall, QLB reduced the incidence of PONV: odds ratio (OR) 0.40 (95% CI, 0.27 to 0.58), I2 = 7% (Fig. 8). According to the subgroup analyses, the difference was noted when the comparison was with placebo/no block and central block studies but not when compared with other peripheral blocks. The study by Ishio et al.,51 used an 11-point NRS (0 to 10) in the assessment and reported a reduction in the severity of nausea in the QLB group compared with patients without block (1.4 ± 1.6 vs. 2.9 ± 2.4, P = 0.003).

Fig. 8
Fig. 8:
Forest plot showing the incidence of postoperative nausea and vomiting. Odds ratio on a log scale

Other outcomes and side-effects

Other outcomes reported (e.g. LOS in hospital, patient satisfaction) varied widely. The differences found between groups were minimal. Only Dam et al.46 reported shorter LOS in hospital in patients with QLB but there was no difference reported in the study of Dewinter et al.45

The frequencies of reported side effects (e.g. sedation, respiratory depression, limb weakness) were low. Limb weakness in two patients in the TQLB group and two patients in the epidural group was reported in the study of Kang et al.37 In the study of Ökmen et al.,39 limb weakness was reported in two patients in the QLB2 group. In the study of Dewinter et al.,45 systemic toxic symptoms of local anaesthetics after QLB were reported (arrythmias in two, tinnitus in three and a metallic taste in nine patients).

Discussion

Summary of evidence

The main findings in this systematic review and meta-analysis for the postoperative analgesic efficacy of ultrasound-guided QLB were as follows: QLB reduces postoperative opioid consumption, prolongs the time to the first rescue opioid analgesic and diminishes the incidence of PONV after abdominal and hip surgery in adult patients. Moreover, reported complications and adverse effects related to QLB are minimal.

According to this review and the meta-analysis, in patients with QLB, the cumulative opioid consumption was reduced at 24 h postoperatively and the time to the first postoperative opioid analgesic was prolonged compared with placebo, no block or other peripheral block. The results were observed in pooled analysis with a moderate-to-high quality of evidence. Recently three systematic reviews regarding QLB have been published.52–54 According to these, QLB reduces the postoperative opioid consumption after caesarean section and renal surgery. In the review of Jin et al.53 subgroup analyses were performed according to the type of surgery, and in the review of Xu et al.,54 only studies in patients with caesarean section were included. Their results are in concordance with ours. Additionally, in our review, subgroup analyses according to the control group and to the QLB type confirmed the beneficial effect of QLB. It was also supported by the lower risk of PONV in QLB groups. In the review of Kim et al.,52 lower pain scores were reported in QLB groups. Additionally, in their review, the number of included studies was lower and the analysis of the primary outcome (pain score) was performed at 48 h postoperatively.

Control groups and the type of surgery varied between the studies. In this review, studies were classified in QLB1, QLB2 and TQLB studies, and no block/placebo, other peripheral block and central block studies. The type of surgery was reported in the association of meta-analysis of the primary outcome. According to the subgroup-analyses based on the comparators, QLB was superior compared with placebo/no block or other peripheral block. In only one study with an epidural block as the comparator,37 the results clearly favoured the epidural block, which may indicate the superiority of the epidural block as a regional analgesic technique. This issue will only be clarified when the ongoing studies comparing the epidural block with QLB are completed.55–57

So far, none of the three types of QLB can be regarded as being superior to another. In our review, the beneficial effect was noted for all types of QLB. According to the subgroup analysis, the heterogeneity of the study results was the highest with TQLB. Unfortunately, there is a scarcity of studies that compare different QLB techniques. However, according to the nomenclature used and ultrasound images available in the abstract, Aoyama et al.30 compared posterior TAP (which might actually be QLB1) and QLB2 and found no differences between the groups. Additionally, in a recently published study of Ökmen and colleagues,58 there was no difference in postoperative tramadol consumption between posterior QLB (QLB2) and lateral QLB (QLB1) after laparoscopic cholecystectomy. In contrast, another recently published study59 reported that posterior QLB (QLB2) diminished the postoperative sufentanil consumption compared with posterior TAP block (described as QLB1 placement) in patients after laparoscopic colorectal surgery.

PONV are well known side effects of opioids, and therefore, it would be expected that the frequency and intensity of PONV are lowered in proportion to the reduction in postoperative opioid consumption.60 Our results support this assumption but the reporting of PONV varied between studies, and we therefore, pooled all the reported nausea and/or vomiting incidences together. One pitfall in interpreting these results is that we were unable to evaluate the amount and the type of opioids used during surgery. Additionally, the use of antiemetics was incompletely reported.

The differences in pain scores at rest or during movement were minor. However, this is not necessarily a sign of equality between the compared methods of analgesia because, according to modern standards of practice, all patients should be offered equally effective analgesic treatment. Moreover, in interpreting the differences, one should keep in mind the inevitable inaccuracy of pain scores because of their subjective nature. In addition, clinically significant scores, that is, grading less than 4 cm in VAS or equal is considered to be an acceptable level of postoperative pain.61

Leg weakness is the most commonly reported side effect after QLB,20,21 which was also the case in the studies included in this review.37,39 One explanation for this could be the infiltration of local anaesthetic close to the lumbar plexus. No other complications or adverse effects caused by QLB were reported. On the basis of these reports, QLB seems to be a reasonably well tolerated regional analgesia technique. However, even though no severe permanent complications have been reported, the risk of intra-abdominal or even liver or kidney puncture should be considered.62 In addition, when a large amount of local anaesthetic is used in QLB, absorption to the blood circulation may be notable. Toxic local anaesthetic blood concentrations have been reported with TAP block63 but, according to the literature, local anaesthetic concentrations have not risen as high after QLB.18 However, in the study of Dewinter et al.,45 several patients with suspected systemic local anaesthetic toxicity after QLB were reported. Notably, in their study, plasma ropivacaine concentrations in the patients suffering from these signs did not exceed the reference value for toxicity and clonidine was used as an adjuvant, with which comparable side-effects are reported. Additionally, several studies44,46,47 using higher doses of local anaesthetics did not report toxic symptoms. Still, further investigations to ensure the safety aspects are mandatory.

As a result of positive clinical experiences and study results, there has been an exponential rise in the number of ongoing and published studies. Most of the studies included in this review were published in 2018 and 2019, and many others are ongoing. There have also been several case reports with promising results, where QLB has been used in paediatric patients64,65 and even in infants.66

One of the main challenges in future studies is the changing nomenclature of the QLB block. It may be called QLB1, QLB2, TQLB or even QLB 3, or simply QLB -- as Blanco et al.5 has determined for QLB2.16 Further, posterior TAP block is usually the same as QLB1. In the review by Elsharkawy et al.,11 it is recommended that the terminology should be changed to lateral (QLB1), posterior (QLB2) and anterior (TQLB) QLB approaches.

Limitations

The high heterogeneity (Supplemental Figure S5, http://links.lww.com/EJA/A385) in our results has many explanations. Firstly, the type of QLB, the surgery and the control group varied between the studies. Secondly, the number of patients in the individual studies was low in some studies. This is understandable, considering the life span of performing ultrasound-guided truncal blocks. Thirdly, the concentrations and the volume of local anaesthetic varied between the studies. Therefore, we tested our results with meta-regression, which took into account the one-side dose of local anaesthetic but it had no effect on the results. Fourthly, many studies with high risk of bias were included in this review. Despite of that, only RCTs with moderate or low risk of bias were included in the quantitative analyses. Additionally, according to the TSA performed for the primary outcome, the number of patients is sufficient and confirmed our results further (Supplemental Fig S6, http://links.lww.com/EJA/A386). Fifthly, in some studies, the type of QLB or the comparator block were not defined precisely, or the ultrasound figure did not match the description: primarily, we relied on the description. Sixthly, some of the studies were published as abstracts or presented the data in an unusable way. Of the 13 authors contacted, only 4 responded and provided the additional data requested, which prevented us from including all the possible data available in the meta-analysis. We do not believe that the inclusion would change the conclusions of this review. Seventhly, as the institution where the investigators were practicing defined the study populations, most of the studies were undertaken on gynaecological or obstetric patient populations. Eighthly, the use of additional analgesics, such as NSAIDs or acetaminophen, was not taken into account in the analyses, as these were incompletely reported. Finally, different QLB techniques and the opioids are combined in this review and meta-analysis.

Conclusion

QLB reduces postoperative opioid consumption with minimal adverse effects. QLB appears to be an applicable option for postoperative analgesia after abdominal and hip surgeries. However, more studies are required, especially on the local anaesthetic used and its concentration and safety profile in the different types of QLB and patient populations. Also, in our opinion, the site of the QLB injection deserves more careful analysis, especially in different types of abdominal surgery. Finally, a unifying the nomenclature is mandatory.

Acknowledgements relating to this article

Assistance with the study: we thank Saila Huuskonen for her help during the development of the search strategy.

Financial support and sponsorship: none.

Conflicts of interest: none.

Presentation: none.

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