Introduction Enhanced recovery with focus on quick recovery and increasing mobilisation of the patients are considered pivotal in current up to date surgical pathways. In combination with ever shifting minimal invasive surgical techniques this has changed the postoperative pain management drastically.

Multimodal analgesia has become the cornerstone of postoperative pain management, with an increasing emphasis on developing procedure-specific recommendations and guidelines. Regional anesthesia also still plays a crucial role in this multimodal approach, enhancing pain control while minimizing opioid consumption and associated side effects.

While regional is still key, the thoracic epidural anesthesia is no longer considered the gold standard. Instead, the focus has shifted to other techniques, the fascial plane blocks. However, the efficacy of these methods remains a subject of debate. Initially, studies on these blocks showed increasingly beneficial effects, but the number of studies reporting neutral outcomes has increased over time. This can be attributed to the fact that most wall blocks, primarily target somatic pain originating from the abdominal wall. These blocks do not facilitate the spread of local anesthetics to the paravertebral space, leaving the ventral branches of the spinal nerves, which transmit visceral pain, unaffected.

In the course of this editorial we will examine the quadratus lumborum blocks and their impact on surgery at this moment.

Discussion The Quadratus lumborum blocks (QLB) were first described by Blanco et al in 2007.¹ Three to even four modifications were made (QLB 1,2,3 and even a 4^th not universally accepted) Recently a delphi consensus paper to standardize nomenclature consolidated more anatomical precise nomenclature (Posterior, Lateral and Anterior QLB)²

A systematic review of the evidence was published 4 years ago. Unfortunately heterogeneity, risk of bias and lack of results when compared to the other fascial plane blocks resulted in a sobering conclusion. Moreover most trials were performed using one of the three techniques without enough thorough background or anatomical sense. More research was definitely needed.³

The lateral Quadratus lumborum block (LQLB) was the first of the proposed variations. It’s exact injection point is actually similar to a posterior transverse abdominis plane block (TAP). Initial trials showed efficacy compared to placebo or no regional techniques.⁴ In anatomical view it targets the thoracolumbar fascia at the lateral border of the quadratus lumborum muscle next to the aponeurosis formed of the abdominal wall muscles (external and internal oblique and transverse abdominis) It lies extremely close to the fascia transversalis too. (See figure 1)

Most of these studies involved postoperative pain following caesarean section. The procedure-specific postoperative pain management (PROSPECT) still has the (lateral) QLB as a recommendation in its current update.⁵

In more recent double blinded trials investigating colorectal surgery with correct blinding methods the results were less positive.⁶ This ineffectiveness is likely due to advances in minimally invasive surgical techniques. Laparoscopic surgery, with increased use of low flow/low pressure pneumoperitoneum and fewer entrance ports, has significantly reduced the severity of somatic wall pain. However, these advancements have not mitigated visceral pain, which remains largely unaffected and still requires systemic opioids for effective management.

The posterior quadratus lumborum block (PQLB) was a second variation and the injection point is the posterior border of the quadratus lumborum muscle, next to the transverse process and the erector spinae muscle group. In this regards it could be considered as an early variant of the erector spinae plane block. The PQLB has been used for almost all the same indications as the lateral version. This includes abdominal, gynaecological and renal surgery. A recent systematic review looking only at this posterior version again identified the huge research gaps. Bias, heterogeneity and lack of effect when compared to other more effective techniques like intrathecal morphine.⁷

In our expert opinion the posterior technique lacks anatomical backing targeting mostly the posterior rami in the thoracolumbar fascia. It is therefor also probably the least investigated technique and should probably be avoided altogether.

An emerging alternative was the anterior quadratus lumborum block (AQLB), first described by Borglum et al. and also previously known as the transmuscular quadratus lumborum block (TQLB or QLB3).⁸ (see figure 2) The AQLB potentially offers superior postoperative pain control. Analgesia from an AQLB is achieved through the paravertebral and craniocaudal spread of local anesthetics, which cover the lateral cutaneous branches of the thoracoabdominal nerves T4-T12/L1 (ventral rami). Several cadaveric studies have demonstrated that the dye used in AQLB spreads into the thoracic paravertebral space, intercostal spaces surrounding somatic nerves, and even the thoracic sympathetic trunk.

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Abstract C26 Figure 1

Injection points of AQLB with spread, figure copyright of UZ Leuven LOCAL group. PMM: psoas major muscle; QLM: Quadratus lumborum muscle ; ESM: Erector spinae muscle group

Despite its potential, clinical evidence supporting the efficacy of the AQLB remains limited, consisting primarily of small studies and case reports focused on caesarean sections and kidney surgeries.^9–11 More extensive clinical trials are still needed to establish the AQLB’s effectiveness in providing better postoperative pain management across various surgical fields.

Unfortunately more recent trials examining the efficacy of the AQLB in colorectal surgery have shown no effect when compared to placebo.^{12 13}

At this moment we cannot recommend the addition of this block to any other mid to upper abdominal surgery either. Especially because the QLB’s also have their fare share of caveats. First of all the AQLB is considered a deep block by recent regional guidelines.¹⁴ This removes one of the essential advantages fascial plane blocks have over neuraxial techniques, namely safety. Indeed when using ultrasound doppler; as recommended; the steep slope to advance the needle into the AQLB position is often dotted with lumbar arteries. Secondly patient positioning in both lateral right/left decubitus position for needling adds a layer of difficulty and challenge to the technique. It is also time-consuming and does not add to patient comfort. Thirdly, needling in a steep position with a curvilinear probe requires a great deal of experience or training. Fourthly obese patients could add a whole extra layer of challenge to these already significant downsides.

The fourth modified QLB was the so-called intramuscular (in the psoas major muscle) or QLB4. As we see no indication for this block, it is potentially dangerous targeting the lumbar plexus without good identification and also leads to a motor block we can not support the use of this block, nor endorse any clinical indication for it. It is best omitted from any practice setting in our opinion.

There are a few specific niche indications which we would like to elaborate further on.

The AQLB frequently covers dermatomes at L1 up to T10 covering much of the anterior hip and lateral iliac crest region. As such some have proposed to use this block for iliac bone grafting.¹⁵ In our clinical experience we have often used this as rescue block in postoperative care units when bone grafting was the primary culprit of pain. It might also be considered as a sole anesthetic technique.

The so-called shamrock approach to the lumbar plexus lying in the psoas muscle, is not a QL block, however thorough knowledge of the anatomy helps identify the target quickly. In our clinical practice we use this block for extensive unilateral surgery and pediatric orthopedic cases in combination with catheters. (see figure 3) This technique was common knowledge for some, however got attention trough the paper by Sauter et al.¹⁶

Conclusion The QLB disperses local anesthetic broadly, typically achieving sensory inhibition from T7 to L1. This should make it effective for postoperative pain relief in the abdominal and pelvic areas. Consequently, QLBs are commonly utilized to manage pain following abdominal, obstetric, gynaecologic, and urologic surgeries. Evidence is poor however and apart from its use in post caesarean pain relief there are no hard recommendations. The anterior QLB still remains the most likely anatomical candidate for postoperative pain relief.

Using the shamrock sign to identify lumbar plexus, or using its unique sensory block at the hip and iliac crest for bone graft surgery are specific indications that need more research.

It remains an expert technique requiring significant experience and should not be considered as a first line option in regional anesthesia for postsurgical pain.

References

1. Blanco R. Tap block under ultrasound guidance: the description of a ‘no pops’ technique. Regional Anesthesia & Pain Medicine 2007;32:130.

2. El-Boghdadly K, Wolmarans M, Stengel AD, et al. Standardizing nomenclature in regional anesthesia: an ASRA-ESRA Delphi consensus study of abdominal wall, paraspinal, and chest wall blocks. Regional Anesthesia & Pain Medicine 2021;46:571–80.

3. Uppal V, Retter S, Kehoe E, McKeen DM. Quadratus lumborum block for postoperative analgesia: a systematic review and meta-analysis. Canadian Journal of Anesthesia/Journal canadien d’anesthésie 2020;67:1557–75.

4. Blanco R, Ansari T, Girgis E. Quadratus lumborum block for postoperative pain after caesarean section: A randomised controlled trial. European Journal of Anaesthesiology 2015;32:812–8.

5. Barazanchi AWH, MacFater WS, Rahiri JL, et al. Evidence-based management of pain after laparoscopic cholecystectomy: a PROSPECT review update. British Journal of Anaesthesia, 2018.

6. Dewinter G, Coppens S, Van de Velde M, et al. Quadratus lumborum block versus perioperative intravenous lidocaine for postoperative pain control in patients undergoing laparoscopic colorectal surgery: a prospective, randomized, double-blind controlled clinical trial. Annals of Surgery 2018;268:769–75.

7. Lin C, Wang X, Qin C, Liu J. Ultrasound-guided posterior quadratus lumborum block for acute postoperative analgesia in adult patients: a meta-analysis of randomized controlled trials. Therapeutics and Clinical Risk Management 2022;18:299–313.

8. Børglum J, Moriggl B, Jensen K, et al. Ultrasound-guided transmuscular quadratus lumborum blockade. BJA: British Journal of Anaesthesia 2013;111.

9. Hansen CK, Steingrimsdottir GE, Dam M, et al. Anterior quadratus lumborum catheters for elective cesarean section: a double-blind, randomized, placebo-controlled trial. Acta Anaesthesiologica Scandinavica 2024;68:254–62.

10. Dam M, Hansen CK, Poulsen TD, et al. Transmuscular quadratus lumborum block for percutaneous nephrolithotomy reduces opioid consumption and speeds ambulation and discharge from hospital: a single centre randomised controlled trial. British Journal of Anaesthesia 2019;123:e350–8.

11. Dam M, Hansen CK, Poulsen TD, et al. Transmuscular quadratus lumborum block for percutaneous nephrolithotomy reduces opioid consumption and speeds ambulation and discharge from hospital: a single centre randomised controlled trial. British Journal of Anaesthesia 2019;123:e350–8.

12. Tanggaard K, Hasselager RP, Hølmich ER, et al. Anterior quadratus lumborum block does not reduce postoperative opioid consumption following laparoscopic hemicolectomy: a randomized, double-blind, controlled trial in an ERAS setting. Regional Anesthesia & Pain Medicine 2022:rapm-2022-103895.

13. Coppens S, Somville A, Hoogma DF, et al. The effect of anterior quadratus lumborum block on morphine consumption in minimally invasive colorectal surgery: a multicentre, double-blind, prospective randomised placebo-controlled trial. Anaesthesia 2024;79:54–62.

14. Horlocker TT, Vandermeuelen E, Kopp SL, Gogarten W, Leffert LR, Benzon HT. Regional Anesthesia in the Patient Receiving Antithrombotic or Thrombolytic Therapy: American Society of Regional Anesthesia and Pain Medicine Evidence-Based Guidelines (Fourth Edition). Regional Anesthesia and Pain Medicine, 2018.

15. Sondekoppam RV, Ip V, Johnston DF, et al. Ultrasound-guided lateral-medial transmuscular quadratus lumborum block for analgesia following anterior iliac crest bone graft harvesting: a clinical and anatomical study. Canadian journal of anaesthesia = Journal canadien d’anesthesie 2018;65:178–87.

16. Sauter AR. The ‘Shamrock Method’ - a new and promising technique for ultrasound guided lumbar plexus blocks. BJA: British Journal of Anaesthesia 2013;111.