EFFICACY OF QUADRATUS LUMBORUM BLOCKS IN ROBOTIC NEPHRECTOMY- A RETROSPECTIVE REVIEW.

Abstract: With the implementation of enhanced recovery pathways (ERAS) in kidney surgeries, regional techniques are being considered an important aspect of multimodal analgesia. Abdominal blocks such as quadratus lumborum block (QLB) have been used as an effective analgesic in abdominal surgeries, however their ecacy in kidney surgery remains unknown. To our best knowledge, there are no clinical studies exploring the relationship between QLBs and post-operative opioid consumption in robotic laparoscopic nephrectomy. Study Objectives: Assess analgesic ecacy between QLB and postoperative opioid consumption in robotic laparoscopic nephrectomy. Design and Setting: A retrospective chart review was conducted by querying the electronic medical record system of 2,200 bed tertiary academic hospital center in New York City. Outcomes: The primary measured outcome was postoperative morphine milli equivalent (MME) consumption for the rst 24 hours. Secondary outcomes include intra-operative MME, as well as postoperative pain scores measured on a visual analogue scale (VAS) scale at 2, 6, 12, 18, and 24 hours post-operatively. Results: The mean total post-operative MME in the pQLB group was 11 [4, 18] and 15 [5.6, 28] in the control group (p =.001). There was a signicant reduction in intra-operative MME in the QLB group in comparison to the control group. This reduction was not seen in post-operative MME. There was no signicant difference in pain scores at any of the measured time points up to 24 hours post-operatively. Conclusion: Our study provides compelling support that ultrasound guided QLB signicantly decreased intra operative opioid requirements but did not have the same effect on postoperative opioid requirements following robotic kidney surgeries in the context of an ERAS pathway.


Abstract
Abstract: With the implementation of enhanced recovery pathways (ERAS) in kidney surgeries, regional techniques are being considered an important aspect of multimodal analgesia. Abdominal blocks such as quadratus lumborum block (QLB) have been used as an effective analgesic in abdominal surgeries, however their e cacy in kidney surgery remains unknown. To our best knowledge, there are no clinical studies exploring the relationship between QLBs and post-operative opioid consumption in robotic laparoscopic nephrectomy. Study Objectives: Assess analgesic e cacy between QLB and postoperative opioid consumption in robotic laparoscopic nephrectomy. Design and Setting: A retrospective chart review was conducted by querying the electronic medical record system of 2,200 bed tertiary academic hospital center in New York City. Outcomes: The primary measured outcome was postoperative morphine milli equivalent (MME) consumption for the rst 24 hours. Secondary outcomes include intra-operative MME, as well as postoperative pain scores measured on a visual analogue scale (VAS) scale at 2, 6, 12, 18, and 24 hours post-operatively. Results: The mean total post-operative MME in the pQLB group was 11 [4,18] and 15 [5.6, 28] in the control group (p =.001). There was a signi cant reduction in intra-operative MME in the QLB group in comparison to the control group. This reduction was not seen in post-operative MME. There was no signi cant difference in pain scores at any of the measured time points up to 24 hours post-operatively. Conclusion: Our study provides compelling support that ultrasound guided QLB signi cantly decreased intra operative opioid requirements but did not have the same effect on postoperative opioid requirements following robotic kidney surgeries in the context of an ERAS pathway. Keywords: Kidney surgeries, Robotic laparoscopic nephrectomy, quadratus lumborum block (QLB), enhanced recovery pathways (ERAS) Introduction: Approaches to contemporary urologic procedures range from open incisions to minimally invasive or robotically-guided techniques (1). Contributions to postoperative pain patients undergoing these surgeries may include the size of incision, location of port sites, pelvic organ nociception, discomfort due to urinary catheter, or diaphragmatic irritation from residual pneumoperitoneum (2,3). Inadequately controlled postoperative pain may have harmful physiologic and psychological consequences that potentially increases perioperative morbidity and mortality (4,5). Poor control of acute post-operative pain is associated with a higher incidence of progression to chronic pain (6). Excellent pain control is a cornerstone of enhanced recovery after surgery (ERAS) pathways, and speci cally, multimodal analgesia after renal surgeries has yielded bene cial peri-operative outcomes such as improved functional recovery, reduced incidence of post-operative nausea and vomiting (PONV), mitigation of adverse effects of narcotics, all culminating in shorter hospital lengths of stay and increased patient satisfaction (7).
With varying success, regional anesthetic techniques such as neuraxial anesthesia, transverse abdominis plane (TAP) blocks and lumbar plexus blocks have been employed as part of ERAS protocols for renal surgeries. Similarly, systemic opioids, non-steroidal anti-in ammatory drugs (NSAIDS), magnesium and lidocaine have also been studied (8). The posterior quadratus lumborum block (pQLB) is an abdominal truncal block rst described by Blanco in 2007 (9). He characterized it as an ultrasound (US) guided posterior TAP block (9). Anatomically, pQLB involves the injection of local anesthetic (LA) into a contiguous TAP interfascial plane that extends posteriorly to the thoracolumbar fascia (TLF) investing the quadratus lumborum muscle superiorly. The analgesic effect is produced by LA spread along these fascial planes targeting intercostal nerves that provide sensory innervation to the abdominal wall.
Potential spreading patterns in cephalo-caudad as well as antero-posterior directions have been described, with potential involvement of paravertebral or neuraxial spaces (8).
Three types of QLB have been described and have anatomical names which describe the location of LA deposition around the QL muscle: QL1 or lateral, QL2 or posterior, and QL3 or transmuscular. Other modi cations such as the paramedian sagittal oblique (PSO) and transverse oblique paramedian (TOP) orientations (10) also exist. These types of QLBs add complexity and diversity, but uncertainty to the e cacy of QLB in general. Based on the available literature on e cacy, ease of block placement, and complication pro les, we have adopted the pQLB as part of our ERAS protocol for robotic nephrectomies.
Previous studies have shown that the addition of pQLB to a regimen of morphine and NSAIDs to be associated with a signi cant reduction in opioid consumption in abdominal surgeries (11,13). However, All patients were monitored using standard ASA monitors and neuromuscular blockade was administered to facilitate endotracheal intubation after anesthetic induction. All anesthetics were maintained with inhaled agents. All patients received opioids intraoperatively at the discretion of the anesthesia practitioner depending on the intraoperative MAP and heart rate.
Patients were positioned in lateral decubitus position with operative side up. Posterior QLB were performed under direct visualization with an ultrasound machine (Sonosite Inc., Bothell, WA, USA) using a 13 − 6 MHz broadband curvilinear probe. Blocks were performed by an attending anesthesiologist, or by a resident or a fellow under direct supervision, either prior to surgical incision or after the dressing was applied at the end of surgery. Blocks were placed with an insulated 22-gauge 50 mm block needle (Pajunk, Geisingen, Germany) inserted in an in-plane medial to lateral approach. After negative aspiration, 30 millimeters (ml) of long acting LA (0.25% bupivacaine or 0.2% ropivacaine) was injected in 5 mL aliquots, with direct visualization of spread in the intersection of pQLB and the TAP fascial planes.
Surgery was performed by two surgeons at the hospital locations, all specializing in robotic guided laparoscopic nephrectomies. We excluded open procedures or surgeries that were converted to open incisions. We also excluded patients who were administered patient-controlled analgesia (PCA) postoperatively or patients who received other forms of regional anesthetics.
The surgical incisions for robotic guided laparoscopic partial nephrectomy involved 3-4 keyhole incisions each measuring 1 cm in the abdomen. All patients were expected to remain in the hospital for 48 hours after surgery.

Outcomes:
The primary measured outcome was postoperative morphine milli equivalent (MME) consumption for the rst 24 hours. Secondary outcomes include intra-operative MME, as well as postoperative pain scores measured on a VAS scale at 2, 6, 12, 18, and 24 hours post-operatively. Intra operative MME was calculated based on total intraoperative consumption of ketamine, remifentanil, fentanyl, hydromorphone and morphine. Post-operative MME was calculated based on total administration of fentanyl, hydromorphone, morphine and oxycodone. Peri-operative consumption of acetaminophen, gabapentin and ketorolac was also calculated.
Intraoperative maintenance anesthetic either volatile anesthetic or monitored anesthesia care after endotracheal intubation was recorded.

Statistical Analysis:
Descriptive data are reported as a number (%), mean (± standard deviation) or median (interquartile range [IQR]). For group comparisons, two-sample t-test or the Wilcoxon-Mann-Whitney tests was used for continuous data, and Chi-square or Fisher Exact test was used for categorical data, as appropriate. Linear regression models were built to compare the log-transformed intraoperative and postoperative MME use between the pQLB and control groups. Covariates such as age, gender, American Society of Anesthesiology (ASA) status, diabetes, hypertension, anesthesia team (resident or certi ed nurse anesthetist CRNA), anesthesia method (volatile anesthetic or total intravenous anesthesia TIVA), surgical duration and hospital site were adjusted between the two groups.
Logistic regression model using the generalized estimating equations method was used to compare the incidence of severe pain (pain score ≥ 7) between the two groups during the rst 24-hour period following surgery, and to test whether this incidence difference was the same over time. Odds ratios of reporting severe pain (visual analogue scale VAS of more than 7) at 2, 6, 12, 18 and 24 hours post operatively and the corresponding con dence intervals derived from the empirical standard errors were recorded. Analysis was performed using SAS 9.4 (SAS Institute Inc., Cary, NC). All tests were 2-sided and statistical signi cance was de ned as a p value < 0.05, unless speci ed.

Results:
Out of the total 722 patients identi ed, 148 were excluded based on predetermined criterion. Two hundred eleven of the 554 patients who underwent laparoscopic/robotic assisted partial nephrectomies, received a pQLB as part of their analgesic strategy (Fig. 1).
Demographic data appear in Table 1. There was no signi cant difference between groups. Blocks were administered prior to surgical incision in 90.52% (191) and 9.48% (20) after closure.
The median surgical duration was 136 [IQR 118, 161] minutes in the pQLB group and 151 [120,182] minutes in the control group (p = 0.001). The median total intraoperative MME in the group receiving the pQLB was 10 [3,25], compared to 55 [40,85] in the group that did not receive the block (p = 0.001).
Speci cally, total intra-operative fentanyl administration was signi cantly reduced in the pQLB group (p = 0.007). The mean total post-operative MME in the pQLB group was 11 [4,18] and 15 [5.6, 28] in the control group (p = .001) ( Table 2). After covariate adjustment between the two groups, the reduction in post-operative MME in the pQLB group was not signi cant.
The median pain scores at various time points(2,6,12,18,24hours) ranged from 2 [IQR 0-5] to 4[IQR 0-6] for the pQLB group, and 2 [IQR 0-5] to 3[IQR0-5] in the control group( p value > 0.05)( Table 3). Additionally, there was a trend towards greater reduction of intraoperative MME when block was placed after surgery (Table 4). There was no signi cant difference in pain scores during the rst 24 hours between the two groups. However, the odds of having severe pain tends to be consistently higher in the pQLB group (Table 5).     Discussion: This is a retrospective review of patients who underwent robotic and laparoscopic kidney surgeries. There was a signi cant reduction in intra-operative MME in the group of patients who received a pQLB in comparison to the control group. This reduction was not seen in post-operative MME, nor was there any signi cant difference in pain scores at any of the measured time points up to 24 hours postoperatively.
Managing postoperative pain in kidney surgeries presents a unique set of challenges. In our multimodal analgesic and ERAS pathways, avoidance of NSAIDs and opioids is prudent owing to concerns of nephrotoxicity with accumulation of active and nondialyzable metabolites (12). The possibility of impaired creatinine clearance must be considered when dosing other opiates as well. With the increasing numbers of kidney surgeries occurring worldwide, further exploration of modern analgesic techniques is timely (18). Ultrasound guided regional anesthesia is highly bene cial after abdominal surgery. Truncal blocks such as TAP blocks have been performed in donor nephrectomies and was found to have reduced pain scores and reduced morphine consumption during the rst 24 hours post-operatively (14,15). Li et al performed a placebo controlled randomized control trial in partial and radical nephrectomy and found that preoperative TAP block was effective in reducing intra-operative and post-operative opioid consumption but had no effect on pain scores and length of stay (16 The timing of the performance (pre or postoperatively) of the pQLB is an important factor that is rarely studied. The pre-incision pQLB timing in our study was not associated with reduction of total MME for both the intra-operative and post-operative periods, with the odds ratio of having lower pain scores if the block was performed after the conclusion of surgery. Surgical incision triggers an in ammatory reaction to damaged tissues that induces central sensitization of pain pathways. It has been proposed that antinociceptive protection provided by pre-emptive treatments should extend into the postoperative period to effectively cover the in ammatory phase. In turn, pre-emptive analgesia focuses on minimizing central sensitization and potentially decreasing the incidence of developing chronic neuropathic pain. (24) Similar to our study, Olanipekun et al conducted a study comparing pre incisional and post incisional ilioinguinal and iliohypogastric nerve block to control post-operative pain in children after herniotomy.
They concluded that though the mean pain scores were lower in the pre-incision group at 6 hours, they were higher at 24 hours in comparison to the post-operative block group. (25) Our study has limitations that are inherent to a retrospective study. Anesthetic practices and regional anesthetic techniques were not controlled nor standardized, thus the true e cacy and effectiveness of pQLB could be underreported. Randomized controlled trials assessing the e cacy should focus on standardization of techniques including the types of QLB utilized. The size of our surgical cohort was su cient to demonstrate statistical signi cance. Despite pQLB being performed in patients under general anesthesia, because patients, surgeons, anesthesiologists, nor perioperative personnel were not blinded from the techniques, placebo effects might have in uenced the narcotic demands in the pQLB group, and nonblinded practitioners could introduce further bias.
In conclusion, our study provides compelling support that ultrasound guided pQLB signi cantly decreased intra operative opioid requirements but did not have the same effect on postoperative opioid requirements following robotic kidney surgeries in the context of an ERAS pathway. Figure 1 FLOW DIAGRAM