This current study was designed to evaluate the analgesic efficacy of preoperatively ultrasound-guided single-injection QLB in patients undergoing RAPN under general anesthesia for perioperative analgesia. The main findings of this study are that the QLB provided superior analgesia at early postoperative stage resulting in lower pain scores and less opioid consumption and adverse reactions. We found that the preventive implement of QLB did reduce pain scores at rest during any time-point up to 24 hours. VAS scores at movement were significantly lower in the QLB group at all observed intervals except at 4 hours postoperatively. Similarly, the consumption of intraoperative remifentanil or postoperative morphine during the first 6 hours but not thereafter was significantly lower in the QLB group than in the control group. Hence, the QLB seem to be a useful analgesic method with a typical patient-controlled analgesia for RAPN.
Ultrasound-guided QLB technique was first described by Blanco [11, 12], and the benefits of QLB for postoperative pain relief and opioids-sparing effect have been reported by several randomized controlled trials and case reports[2, 5, 6, 8–10, 19–30]. All approaches have been proved the synergistic efficacy for multimode analgesia, especially for QLB2 or QLB3 after laparoscopic surgery, cesarean section and total hip arthroplasty. This is the first randomized, double-blinded controlled trial study that has compared the the preventive implement of QLB2 block to a standard perioperative analgesic regimen when applied in RAPN. For most studies, the QLB2 (posterior approach) was chosen as its targeted injection was more superficial and be focused much more tightly and can be easily positioned. Our findings echo most of previous trials. Irwin et al. [10]investigated the posterior approach for postoperative pain relief after caesarean section, and showed a reduction in median (IQR [range]) visual analogue scale pain scores at 6 h postoperatively. However, opioid consumption was similar in both groups during the first 24 hours after surgery. Kukreja et al. [29]have also demonstrated the benefits of opioid-sparing analgesic effect of the anterior quadratus lumborum block in total hip arthroplasty. The true mechanism of action of the QLB is not completely known. One of the important diffusion mechanisms of either anterior or posterior approaches is that local anesthetic spread to the paravertebral space region to achieve effective analgesia in the desired dermatomes. However, the postulation of local anaesthetic consistently tracking into the anterolateral penetration of quadratus lumborum and anterior thoracolumbar fascia has been called into question [31, 32]. It remains to be seen whether a different approach, such as the intramuscular or lateral, would provide superior or longer lasting analgesia.
The multi-modal analgesia consists of preoperative prophylactic analgesia, combined different analgesic medication, local infiltration anesthesia, and patient-controlled intravenous analgesia has become a routine standard for the postoperative pain management in our surgical center. We did not directly compare the use of QLB with sham block group (same volume of saline) or other approaches or epidural analgesia. We felt that the aforementioned analgetic scheme has remarkable efficacy in pain relief, especially for patients who are involved in the enhanced recovery programs. Therefore, this study focused on whether the QLB may enable an increased analgesic effect and the role it plays in the combination of a typical multi-modal analgesia[33, 34]. A recent study by Aditianingsih et al. [2]compared the anterior approach with epidural analgesia in patients underwent laparoscopic donor nephrectomy. They demonstrated that the morphine consumption and pain scores at 24 hours after surgery were comparable. A propensity score matching analysis has reported that postoperative pain was not significantly different between the different operation mode (robot-assisted partial nephrectomy vs laparoscopic partial nephrectomy)[35]. A third arm in our study may have been beneficial in discerning whether the QLB has assistant effects when compared to“no block” pattern.
Postoperative pain management has always been a core value to enhanced recovery after surgery. We took this opportunity to use the 15-item quality of recovery score (QoR-15) developed by Stark et al. [36]as a secondary outcome measure. As the pain scores were the highest within 24 hours after surgery in accordance with previous studies, severe pain is associated with a series of adverse reactions after surgery and anesthesia. The QoR-15 providing a quantitative measure of comfort, emotional wellbeing, and physical functioning has the ability to assess functional recovery rather than pain, which may become more relevant supplementary information. In this study, there were significant statistical differences in terms of five sub-items (Have had a good sleep, Able to look after personal hygiene, urination and defecation unaided, Moderate pain, Severe pain and Nausea or vomiting) and total scores between the groups at 24 hours after surgery. Therefore, it seems like that single-injection QLB is not merely used to relieve acute pain. Besides, it serves as a supportive role for improving the overall health status at the early stages after surgery.
Limitations
There are some of limitations to our study. Firstly, VAS scores with movement at 6 hours postoperatively was chosen as the primary outcome measure. VAS scores in a pilot study and this study were tested to conform to a normal distribution. Then we chosen a Student’s t test for pain scores at all the predetermined intervals. Secondly, we did not check sensory dermatomal levels, assess visceral pain, record lower extremity weakness and accurately calculate the duration of the QLB to explain the characteristic of sensory blockade. The main purposes of this study were to compare pain scores and opioid consumption between two groups. Thirdly, some studies have proposed the problem of “rebound pain” phenomenon after single-shot peripheral nerve block, which defined as very severe pain when peripheral nerve block wears off. It is not so rare problem in clinical practice and could reach 40% of patients undergoing orthopedic procedures [37], but pathophysiological mechanisms remain unknown. The QoR-15 collected all the related data at 24 hours postsurgery, such as Have had a good sleep and Severe pain, which might provide a bit of tracing data in regard to rebound pain. However, we have not observed that severe pain interferes with sleep and complain of severe discomfort when QLB wore off. In the future, randomized controlled trials may be needed to include all the aforementioned indicators, which might have impacted pain management program and patient satisfaction.