Description of the studies
Results of the literature search
There were 1,141 citations identified by the initial database search. Figure 1 shows the PRISMA flowchart. After deleting duplicates, 42 RCTs (32 full reports and ten abstracts) provided the data for this systematic review. The included studies were completed between 2012 and 2019. The Table 1 lists the population, intervention, and control characteristics of the trials included.
Table 1 Characteristics and key outcomes of included randomized-controlled trials Risk of bias
Figure 2 shows the risk of bias in all domains for each study included. The risk of bias was unclear in most domains for all ten abstracts.12−21 Of the 42 included studies, eight were assessed as high risk of bias in at least one domain.13,22−28 Six studies were assessed as low risk of bias in all domains.29−34 The remaining 28 studies had an unclear risk of bias in at least one domain. Reasons for the risk of bias judgement for each study can be found in eAppendix 3 (ESM). The authors of two studies disclosed receiving compensation/honorarium from a RA device/drug company that was not directly related to the study.22,34
Technical performance
All QLBs in the included studies were performed using an ultrasound-guided single-injection technique by an experienced anesthesiologist. The QLBs were performed bilaterally for all abdominal surgeries and unilaterally for all hip and urologic procedures.
Three main anatomical variations of the QLB are described in the literature, depending on the location of the LA deposition (Fig. 3). The nomenclature for QLB in the literature is inconsistent. For the purpose of this review, we will use the anatomical terminology lateral, posterior, and anterior QLB. Lateral QLB, also known as “QLB-1” is a technique similar to “transversalis fascia plane block,” which involves the deposition of LA at the anterolateral border of the quadratus lumborum muscle. Posterior QLB, also known as “QLB-2”, involves LA injection at the posterior aspect of the quadratus lumborum muscle. Anterior QLB, also known as “transmuscular QLB” or “QLB-3”, involves the deposition of LA between the anterior border of the quadratus lumborum muscle and the anterior thoracoabdominal fascia.
The type, concentration, and volume of LA injected varied by individual trials. The dosing regimen is summarized in the eTable (ESM). Regarding dose, nine of the trials used a weight-based dosing regimen of either 0.2–0.3 mg·kg−1 of bupivacaine30,35−38 or 0.2–0.4 mg·kg−1 of ropivacaine.27,34,39,40 Thirty-one trials used a predetermined LA volume between 15 and 30 mL per injection.12,13,14,15,16,17,18,21,22,23,24,25,26,28,29,31,32,33,41,42,43,44,45,46,47,48,49,50,51,52,53 The dosage regimen or the type of LA was not stated in two of the abstracts.19,20 With respect to LA type, 19 trials used ropivacaine (0.2–0.75%)12,14,17,18,22,24,27,29,31−34,39−41,46,49,50,53 and 15 used bupivacaine (0.125–0.5%).13,15,16,21,23,26,30,35−38,42,44,45,51 Three trials used an admixture of LA (bupivacaine with lidocaine),28,43,52 and three trials used levobupivacaine.25,47,48
Type of surgery
All studies involved adult patients undergoing various abdominal or hip procedures. The Table 1 lists the types of surgeries. The included studies used QLB for the following surgical procedures: Cesarean delivery (14 studies),13,15,24,27,30,33−35,39,42,43,48,50,53 gynecological surgery (four studies),12,44,47,49 abdominal general surgery (11 studies),14,17,20,21,29,32,37,38,41,45,46 orthopedic surgery (six studies),16,18,22,23,25,52 and urological procedures (seven studies).19,26,28,31,36,40,51
Comparators
All trials compared a specific QLB with either placebo or another analgesic technique. Two trials directly compared different anatomic approaches of QLB.45,53 The comparators used were placebo,13,17,22,29−31,33,34,36,37,39,40,46,48,50 no block,18,19,23,24,28,43,47,49,51,52 other RA techniques (TAP block,12,14,20,21,27,35,38,41,42,44 femoral nerve block,25 fascia iliaca block,16 erector spinae [ESP] block,52 epidural analgesia,26 and intrathecal morphine [ITM]),15,39,50,53 and systemic analgesia techniques (lidocaine infusion32 and paracetamol infusion20).
Outcomes studied
The Table 1 shows the outcomes investigated by each RCT. All included studies, with the exception of four studies,12,14,15,40 reported pain scores at varying time intervals. The reported time interval ranged from arrival to the postanesthesia care unit (PACU) to 48 hr after surgery. All included studies except three12,20,42 reported opioid consumption at various time intervals ranging from arrival to the PACU to 72 hr after surgery. Twenty-eight studies reported the incidence of nausea and vomiting.15,17,18,22,24,28−35,37−40,42−44,46−53 Fifteen studies measured time to first analgesic request.23,24,27,29,31−33,38,41,42,44,45,49−51 Fourteen studies assessed “postoperative pruritus,”15,18,22,24,28−30,35,37,39,48,50,51,53 ten assessed “time to ambulation,”20,25,29,31,33,34,40,45,50,53 nine looked at “patient satisfaction,”14,17,23,25,28,29,38,42,50 six reported on “length of hospital stay,”20,23,31,32,46,47 five assessed “motor weakness in lower limbs,”28,37,40,51,53 and three reported on the “quality of recovery.”14,47,48 One study looked solely at intraoperative hemodynamic changes.21
Data analysis
The studies included in this systematic review had significant heterogeneity with regard to the type of surgery, comparator groups, and outcomes measured. Therefore, the planned quantitative synthesis (meta-analysis) was only conducted for QLB vs placebo or no block for patients undergoing Cesarean delivery. The main outcomes of each study are summarized in the Table 1.
The pooled data for Cesarean delivery
There were seven studies comparing QLB (any type) with placebo or no QLB that were felt to be clinically homogeneous enough for results to be pooled for Cesarean delivery outcomes (Fig. 4).9,24,30,33,43,48,50 The pooled estimates from four studies (two posterior, one anterior, and one lateral QLB) showed that opioid use was reduced by 24.1 mg (95% CI, 17.3 to 30.9) OME in the first postoperative 24 hr in the QLB group compared with placebo or no block. Similarly, pooling of estimates from three different studies (each using different QLB types) showed the time to first analgesic request was 8.1 hr longer (95% CI, 2.3 to 14.0) in the QLB group compared with the placebo or no block group. Nevertheless, no statistical differences were observed in 24-hr pain scores at rest or with the incidence of nausea and vomiting between the QLB and no QLB groups (Fig. 4). There were not enough studies assessing pain scores with activity to allow data pooling.
Lateral QLB
Eleven studies used a lateral approach to QLB. Nine studies involved abdominal surgeries12,13,24,32,34,41−44 and two studies involved hip surgeries.22,25 Four studies were assessed as high risk of bias in at least one domain.13,22,24,25 Two studies were assessed as low risk of bias in all domains.32,34 The remaining five had an unclear risk of bias in at least one domain.
Cesarean delivery
Five RCTs studied lateral QLB for lower segment Cesarean delivery. Four of these compared lateral QLB with placebo or no block13,24,34,43 and one compared lateral QLB with TAP block.42 When compared with placebo or no block, the lateral QLB group consistently showed lower opioid requirements in the first 24 hr after surgery. Two studies showed no difference in pain scores13,34 whereas two studies showed a reduction in pain scores at rest during the early postoperative period.24,43 No study reported a significant difference in the incidence of nausea and vomiting between the groups.24,34,43 One study comparing lateral QLB with TAP block found no significant difference in pain scores, nausea/vomiting, or time to first analgesic request between the two groups.42 Importantly, no studies compared lateral QLB to ITM or examined the benefit of adding lateral QLB to a multimodal analgesic regimen that included ITM.
Non-obstetric abdominal surgery
Three studies compared lateral QLB with the TAP block. One of these studies looked solely at intraoperative hemodynamic changes and found no difference between the groups.12 Kumar et al. reported a statistical but not clinically meaningful reduction in opioid consumption and 24-hr pain scores. Yousef et al. showed a lower mean (standard deviation [SD]) 24 hr intravenous morphine use [10.0 (3.8) vs 14.5 (3.4) mg] and visual analogue scale (VAS) pain scores [1.9 (0.3) vs 3.2 (0.4)] in the QLB group for total abdominal hysterectomy.44 The latter two studies showed a significantly longer time to first analgesic request in the QLB group.41,44 One study comparing lateral QLB with intravenous lidocaine for laparoscopic colorectal surgery did not find a significant difference between groups regarding analgesia, nausea/vomiting, time to first analgesic request, recovery of intestinal function, and length of stay.32
Hip/orthopedic surgery
One RCT compared the transversalis fascia plane (TFP) block (anatomically similar to lateral QLB) with a placebo for iliac crest bone graft.22 The TFP block group had less opioid consumption at eight hours, with no difference at 24, 48, and 72 hr. Similarly, the pain scores were comparable at all time points measured. A second study compared lateral QLB with a femoral nerve block for hip hemiarthroplasty and found a reduction in mean (SD) opioid consumption [9.7 (7.0) vs 17.0 (11.2) mg intravenous morphine equivalent (IME)] but a clinically insignificant reduction in pain scores at 24 hr.25
Posterior QLB
Twelve studies used the posterior approach to QLB. Six of them used it for Cesarean delivery.27,30,35,39,48,50 Four studies used it for general surgical procedures,29,37,38,46 and two for gynecological procedures.47,49 One study was assessed as a high risk of bias.27 Two studies were assessed as low risk of bias in all domains.29,30 The remaining nine had an unclear risk of bias in at least one domain.
Cesarean delivery
Of the six studies in the Cesarean delivery population, four studies compared posterior QLB with placebo or no block for patients who did not receive ITM. Two studies found lower opioid use and reduced pain scores with activity in the early postoperative period in the QLB group.30,50 The other two studies found no difference in opioid use or pain scores between groups.39,48 None of the studies observed a difference in the incidence of nausea and vomiting between the posterior QLB and placebo groups.
Two studies compared posterior QLB with TAP block and found lower median [interquartile range (IQR)] opioid use postoperatively in the QLB group (6.0 [4.8–16.0] vs 16.5 [8.0–33.3] mg IME).27,35 While Blanco et al. did not find a difference in pain scores, Verma et al. found significantly lower mean (SD) 72-hr postoperative VAS activity pain scores in the QLB group compared with the TAP block [20 (8.5) vs 35(5.1)].
Two studies compared posterior QLB with ITM.39,50 Salama found a significantly lower 48-hr mean (SD) intravenous morphine use [18 (9.6) vs 42.8 (10.4) mg], pain scores at rest and with activity, and nausea/vomiting in the QLB group. Tamura et al. found lower rest and activity VAS pain scores and opioid use in the ITM group compared with the QLB group for up to six hours after surgery, but no significant difference thereafter. Nevertheless, the incidence of moderate to severe pruritus was significantly higher in the ITM group. Finally, two studies did not observe any analgesic benefit of adding posterior QLB to an analgesic regimen that included ITM.39,48
Non-obstetric abdominal surgery
Of the six studies in the non-obstetric population, five compared posterior QLB to placebo for non-obstetric abdominal surgeries. Three of them did not find any postoperative analgesic benefit of posterior QLB compared with placebo29,46,47 whereas two other studies found lower postoperative opioid use and lower 24-hr pain scores (at rest and with activity) for the QLB group.37,49 Ishio et al. reported a significant difference in the time to first analgesic request and the incidence of nausea and vomiting between the groups. One study compared posterior QLB with TAP block and found no difference in any observed outcomes.38
Anterior QLB
Thirteen studies used an anterior approach to QLB. Two studies used this method for Cesarean delivery.15,33 Six studies used the anterior approach for urological surgery, two for laparoscopic surgical procedures, and three for orthopedic hip surgery. Overall, three of these included studies were assessed as high risk of bias at least in one domain.23,26,28 Two studies were assessed as low risk of bias in all domains.31,33 The remaining studies had an unclear risk of bias in at least one domain.
Cesarean delivery
Hansen et al. compared anterior QLB with placebo in patients undergoing Cesarean delivery.33 They found lower mean (SD) 24-hr opioid use [65.3 (47.9) vs 94.3 (60.0) mg OME], and lower early postoperative numerical rating pain scores in the QLB group. Nevertheless, postoperative nausea/vomiting (PONV) or time to ambulation was not significantly different between the groups. Felfel compared anterior QLB with ITM and found no difference in 24-hr morphine consumption between the groups.15 However, there were fewer side effects, such as nausea, vomiting, and pruritis in the QLB group.
Non-obstetric abdominal surgery
Of the two studies for the general surgery population, Vamnes et al. compared anterior QLB to placebo for laparoscopic cholecystectomy and found no significant difference in analgesia between the groups. Bhoi et al. compared anterior QLB with TAP block for laparoscopic inguinal hernia repair and found lower 24-hr opioid consumption, higher dermatomal coverage, and longer block duration in the QLB group.14
Three studies compared anterior QLB with placebo or no block for percutaneous nephrolithotomy and found improved analgesia consistently.31,36,51 Similarly, Zhu compared anterior QLB with placebo for laparoscopic nephrectomy and found lower opioid use, shorter time to mobilization, less PONV, and less time to recovery of intestinal function in the QLB group.40 Yayik et al. found that anterior QLB improved intraoperative analgesia during extracorporeal shock wave lithotripsy and success of lithotripsy when compared with no block. Finally, Rahendra et al. compared anterior QLB to continuous epidural for donor nephrectomy and did not find any analgesic benefit.
Hip/orthopedic surgery
Kukreja et al., in a recent RCT, showed lower OME consumption at 24 hr (mean difference, 17.1 mg; 95% CI, 5.0 to 29.1) and 48 hr (mean difference, 36.1 mg; 95% CI, 9.4 to 62.9) in the QLB group compared with no block for total hip arthroplasty. The pain scores were lower at 24 hr (mean difference, 1.8 points; 95% CI, 0.6 to 2.9). Nevertheless, no significant difference in pain scores was observed at 12 hr or 48 hr. The QLB group had higher patient satisfaction scores. The study did not report any data on opioid-related side effects. Hashmi et al. compared anterior QLB with fascia iliaca block and did not find any difference in analgesic outcomes. Similarly, Tulgar et al. did not find any difference in analgesic outcomes when anterior QLB was compared with the lumbar ESP block.
Comparison of anatomic approaches of QLB
Ahmed et al. compared posterior QLB with anterior QLB for patients undergoing unilateral inguinal hernia repair. They found no clinically relevant difference in 24-hr morphine consumption in the anterior compared with the posterior QLB group, but a longer mean (SD) time to first analgesic request in the anterior compared with the posterior QLB group [20.1 (6.2) vs 12.0 (8.4) hr]. Similarly, the pain scores were lower in the anterior QLB group at 12 hr but not at 24 hr after surgery.
Kang et al. compared a combined technique of both anterior and posterior QLBs with either anterior or posterior QLB alone for Cesarean delivery. They found that pain scores (at rest and with activity) and morphine consumption were lower in the combined technique group compared with either the anterior or posterior technique alone.
Dermatomal spread with QLB
Four studies assessed the dermatomal blockage of QLB. Black et al. observed a consistent involvement of L1 with TFP block (lateral QLB). Nevertheless, spread to T12 or above was observed in less than 30% of patients. Parras et al. observed that lateral QLB analgesia covers the dermatomes from T10 to L1. Bhoi et al. found higher dermatomal coverage with anterior QLB (T8) compared with the TAP block (T9).
Adverse events
Okmen et al. reported two cases of quadricep weakness in 30 patients who received posterior QLB for laparoscopic cholecystectomy.37 Similarly, Kang et al. reported two cases of lower limb weakness in 24 patients who received anterior QLB for Cesarean delivery. No studies using lateral QLB reported lower limb weakness.
Dewinter et al. detected a higher incidence of subjective LA systemic toxicity symptoms (metallic taste) in the QLB group compared with lidocaine infusion and placebo.32 Nevertheless, serum ropivacaine levels in these patients were not within the toxic range on arrival to the PACU, and there were no serious adverse events. The remaining studies included in this review did not report any adverse events.