Majority of patients after surgery complain about moderate to severe pain. This is due to inadequate postoperative pain relief which may lead to delay in recovery, prolonged hospital stay, increased medical costs and mental as well as emotional impairment [1].

Every patient perceives pain differently, thus; there arises requirement for many different ways to treat pain. Since the time when enhanced recovery after surgery program was introduced, there have been changes in expectations of both physician as well as patient needs in terms of pain management perioperatively aiming to reduce opioid intake [2].

A single therapy isn’t useful, therefore a multimodal therapy for management of pain is employed whenever possible, which   comprises of analgesics acting directly. Examples of directly acting analgesics include opioids,  acetaminophen, nonsteroidal anti-inflammatory drugs; neuraxial analgesics include epidural, spinal or both; Peripheral blocks and local infiltration [3].

In the past, pain relief was given mainly as required by intramuscular (i.m.) injections consisting of opioids which were the main agents for post operative analgesia. The patient-controlled analgesia (PCA), epidural analgesia and regional blocks have now gained popularity as they are known to be more effective [1]. When used along with peripheral nerve blocks, PCA aims to reduce post-operative pain. PCA pump also allow patient to control his desired level of analgesia which tends towards patient satisfaction [4].

Therefore, the need for multimodal analgesia came to decrease opioid consumption and to regulate pain pathways acting via various mechanisms. Also, having the advantage of additive activity while reducing adverse events with a larger dose of any single analgesic. The advantages of Peripheral nerve blocks (PNB) are various which help in improving outcomes clinically. PNBs have also been linked with improvement in post operative control of pain and decrease in the utilization of opioids in majority of surgical procedures. Other benefits of PNBs includes a decrease in hospital stay, and improved recovery postoperatively This is performed by injecting anaesthetic drug at a specific region in the vicinity of nerve that stops the transmission of pain pathways reaching brain, resulting in analgesia [3].

With the advent of ultrasound; a number of Musculo-fascial plane blocks have emerged for management of pain post various surgeries. Depending upon the nerves being blocked there are various inter fascial plane blocks described such as Lumbar plexus block, Transverse abdominis plane block (TAP), Quadratus lumborum block(QLB), Transversalis fascia block, Erector spinae plane block (ESPB) and Retro laminar block(RLB)  [5].

With the guidance of ultrasound, Quadratus lumbar block can be given which provides good analgesia in multiple operations ranging from abdominal to lumbar fascia, it being a type of regional block. It is further subdivided into four types- (QLB1) in which local anaesthetic drug is inoculated in the antero-lateral area, (QLB2) being in between quadratus lumborum and erector muscle, (QLB3) at the quadratus lumborum and the psoas major muscle, and (QLB4) in quadratus lumborum [6].

Anterior Quadratus lumborum block is another upcoming modality frequently applied at L4 for analgesia cover but the approach at L2 shows a better and wider spread of the block than L4 approach. Anterior QLB at L2 has a broad spectrum of block acting mainly on sensory pathway than any other technique, ranging between T4 to L2, besides this it provides good pain relief of pain from viscera. 

Post lap nephrectomy; pain usually extends at T8-T12 dermatomal segments. Majority of preoperative sensory block will be ranging from T9-L1 after the block at L2 which should cover pain post lap nephrectomy. After a while the extend of this plane may become even broader. In this study we will study application of QLB2 at L2 level [7].

Anterior Quadratus lumborum block post operative is considered superior than other approaches. Various studies have shown that quadratus lumborum block (QLB) is effective in postoperative pain relief, demonstrating the accessibility and advantage of ultrasound guided trunk nerve block for pain control postoperatively for lap surgeries [8].

One of the major limitations of QLB is that it is a deep block and has its puncture site in near proximity to the incision, which may restrict the timing of application of block to certain extend. Hence appropriate options for the application of truncal nerve block for Laparoscopic surgery are not satisfactory [9].

So, recently various PVB techniques have been the target of many researches, one of those approaches is RLB. It was observed that RLB would be more on the lines of working via the PVB approach, that is, by “deep” infiltration. RLB is known to be a compartment/interfacial plane block. In this approach, local anaesthetics are observed to infiltrate the superior part of cost-transverse ligament and move to the paravertebral space, whereas tip of the needle does not reach the space [10]. On the other hand, it shows properties of poor diffusion around craniocaudal extension, thus, a single injection hinders the application of this technique. Clinically, through various studies it was speculated that by giving three injection points, retrolaminar block would take care of post operative analgesia in a better way than a local infiltration analgesic.

When pain is assessed, it is noted that laparoscopic nephrectomies produce equal or slightly less pain than open nephrectomies, In comparison with open nephrectomy, laparoscopy dominates with the merits of decreased intraoperative bleeding, faster recovery time and earlier recovery of gastrointestinal functions [11].  In few studies it was noted that if the pain persisted, it lead to the activation of pain pathways thus ultimately causing postsurgical chronic pain [12].

It has been noted that pain after laparoscopic nephrectomy is not only associated with Pfannenstiel incision as well as deep intra-abdominal pain [13] but along with the trocar placement, the area of somatic analgesia needed by intraperitoneal approach. So, Laparoscopic nephrectomy pain shows multifactorial origin; low abdominal incisions, pelvic organ nociception, port pain, residual pneumoperitoneum leading to shoulder tip discomfort, nerve lesions by Trocar insertion, urinary catheter discomfort being few of the things that occurs.

Therefore, laparoscopic nephrectomy undergoing patients experience large amount of postoperative pain, to the point where they need intravenous opioids. To tackle this, we require a multimodal analgesia cover ranging from IV, oral drugs to neuraxial techniques to reduce acute and chronic pain [7].

Pain relieved by other techniques such as NSAIDS, analgesia by epidural, systemic opioids are not as effective as regional block with local anaesthetic.[13]

For the quantification of pain, Verbal rating scales either (mild/moderate/severe) are clinically used and shows the advantage of assessing the nature of pain [14].

There have been several studies about the effectiveness of QLB with other blocks such as Erector spinae block and TAP block but not between anterior QLB at L2 level with Retro Laminar block, in our study we aim to compare these two and determine the analgesic requirement along with the post operative comfort the patient gets after application of these novel blocks reducing the acute pain after surgery along with preventing chronic post-surgical pain.

Sample size calculation

The primary objective of the study is to assess the post-operative analgesic effect in terms of pain scores assessed using NRS between three groups. For the sample size calculation, we assumed a difference of 1 in NRS between any two groups as clinically significant, thus sample size of 21 patients per group were considered necessary to detect statistical significances with an effect size of 1.0 at alpha 0.05 and power of 90%.[23]

The sample size for the comparison between groups was calculated based on the following formula:

The formula for calculated sample size is given below

n = (σ1 2 + σ2 2 ) . [Z 1- α/2 + Z 1- β] 2

(M1 - M2) 2

= (1 2 + 1 2 ).[1.96+1.282] 2

(1) 2

= (1+ 1)*10.51

1

= 21.02

where Z α/2  is the critical value of the Normal distribution at α/2 (e.g. for a confidence level of

95%, α is 0.05 and the critical value is 1.96), Z β  is the critical value of the Normal distribution at

β (e.g. for a power of 90%, β is 0.1 and its critical value is 1.282) and σ 1 and σ 2 are the

Standard deviations of the two groups and M1 and M2 are the means of two groups.