Does Ultrasound-Guided Quadratus Lumborum Block Improve Pain after Hysterectomy.

Objective: Determine whether the quadratus lumborum block (QLB) is an effective adjunct to control postoperative pain during the first 24 hours after minimally invasive hysterectomy.

Prospective cohort observational study of patients who underwent laparoscopic or robotic hysterectomy. Patients either received a QLB or did not. Initial postoperative pain scores were recorded in the postanesthesia recovery area using a numeric rating scale. Patients were then called to collect 24-hour scores and analgesic medication usage. The primary outcome was the 3-hour pain score. Secondary analysis evaluated use of analgesic medication.

Fifty patients were enrolled in the study: 25 patients in the no-QLB cohort and 25 patients in the QLB group. The median postoperative pain scores (out of 10) were 4, 2, and 6 at 1, 3, and 24 hours in the no-QLB group. Scores were 5 (P = .541), 3 (P = .418), and 6 (P = .358), respectively, in the QLB group. A total of 11 of 25 patients at 1 hour, 8 of 25 patients at 3 hours, and 21 of 25 patients at 24 hours used analgesia postoperatively in the no-QLB group, compared to 11 of 25 patients at 1 hour (P = 1.0), 18 of 25 patients at 3 hours (P = .005), and 23 of 25 patients at 24 hours (P = .384) in the QLB group. Opioid, acetaminophen, and ibuprofen usage was not significantly different between groups.

There was no significant pain difference between the no-QLB and QLB groups. Patients who received a QLB were more likely to receive pain medication 3 hours after surgery. Thus, the use of a QLB does not appear to be a suitable adjunct for postoperative pain.

Hysterectomy, Minimally invasive surgery, Quadratus lumborum block (QLB)

The overall decrease in morbidity associated with advances in minimally invasive surgery has transformed the concept of postoperative management, given lower complication rates, decreased blood loss, earlier mobilization, and rapid postoperative recovery.1 Laparoscopic procedures can be associated with longer operative times2; however, minimally invasive surgeons may also be referred more challenging patients with elevated body mass indexes (BMIs), more complex pathologies, and adhesive disease. Increased operative time and increased amount of surgical dissection can make control of postoperative pain all the more problematic. This challenge has led to the development of directed, multimodal protocols specific to management of postlaparoscopy surgery pain in an effort to decrease the amount of additional administration of narcotic medication and improve postoperative pain control.3 Regional blocks utilizing local anesthetic agents may play a role in multimodal protocols. A prior study assessing the effect of transversus abdominus plane (TAP) block for postoperative analgesia in patients undergoing total laparoscopic hysterectomy did not show a difference in the amount morphine consumption or pain score measurements.4 More recently, the utilization of the quadratus lumborum block (QLB) has been shown to effectively alleviate somatic and visceral pain in the upper and lower abdomen in patients undergoing abdominopelvic surgery. A systematic review and metanalysis of 16 studies published by Jin et al showed QLB significantly reduced postoperative pain in cesarean delivery and renal surgeries.5 The QLB provides analgesia spanning from the T4 to L1 dermatomal levels in the thoracolumbar plane to provide a broad sensory level analgesic effect. The approach involves injecting local anesthetic under ultrasound guidance into the plane posterior to the quadratus lumborum muscle and middle layer of thoracolumbar fascia.5,6 Data regarding the effect of QLB in patients undergoing laparoscopic gynecologic surgery has been conflicting. Thus, this study aimed to further evaluate whether a QLB is an effective analgesic adjunct to control postoperative pain, focusing specifically on patients undergoing laparoscopic benign hysterectomy.

This was a single-site, prospective cohort study in a large, urban community hospital in Brooklyn, NY. The study was approved by the Internal Institutional Review Board at our institution. Patients were eligible for recruitment if they were between the ages of 18 and 65 years old and scheduled to undergo laparoscopic or robotic assisted hysterectomy for benign indications. Patients were excluded if they had a known history of adverse reaction to bupivacaine, if there was a concern for gynecologic malignancy, if the patient was pregnant, or if the patient's weight was less than 40 kg. The control group consisted of patients who did not undergo a QLB (no-QLB group). The study group was made up of patients who underwent a QLB after induction of general anesthesia, immediately prior to beginning of surgery. Administration of the QLB was decided based on surgeon, anesthesiologist, and patient preferences. The QLB included 20 mL of 0.25% bupivacaine and (133 mg) 5 mL of liposomal bupivacaine per side. The block was done bilaterally. Therefore, a total of 40 mL of 0.25% bupivacaine and 10 mL of liposomal bupivacaine was administered. Apart from the QLB, patients in both the no-QLB and the QLB groups received a total of 30 mL of 0.25% bupivacaine and 10 mL of liposomal bupivacaine injected locally superficially into the laparoscopic incisions sites, which is routinely done at our institution. Sociodemographic and clinical data were collected including age, BMI, history of abdominal and pelvic surgeries, intraoperative adhesions, operative time, and preoperative pain score Postoperatively, pain scores were documented at 1, 3, and 24 hours using a 1-to-10 numeric rating scale (NRS). The NRS was also used to document preoperative pain scores. In addition, analgesic medication administered in the postoperative recovery unit as well as oral analgesic medication was documented for the first 24 hours postoperatively. Patients were given pain diary to take home and record every time they take pain medication along with pain scores. Any adverse events were documented. The primary outcome was the pain score at 3 hours. The secondary outcome was difference in pain scores, at 1 hour, 24 hours, as well as analgesic medication usage in the first 24 hours. For statistical analysis, means of 4.0 (standard deviation [SD] 2.1) and 1.8 (SD 1.3) NRS pain scores at 3-hour postanesthesia recovery were used, as a previous study showed a statistically significant difference with NRS pain scores of twice or more in the study arm versus the control arm.7 Assuming equal numbers in each study arm, 90% power for a 2-sided Satterthwaite-adjusted t test would be achieved for N = 18 per group, assuming a significance level .05. We assumed the difference between the means to be 2.0. Twenty-five patients per group were planned in each arm to account for the possibility of screen failures postenrollment. All numeric variables were summarized with median and 25th–75th percentile and compared across groups using the Mann–Whitney U test. All categorical variables were summarized with frequency and percentage and compared between groups using a χ2 test. SPSS software was used for statistical analysis and a P value of .05 was considered significant.

Fifty patients were deemed eligible and enrolled; no patients refused to participate or were excluded. 25 patients were enrolled in the no-QLB and 25 enrolled in the QLB group. Table 1 describes the demographic data of the patients in both groups. Age, BMI, previous abdominal surgery, and specimen weights were not significantly different between the groups. Fewer patients in the no-QLB group had surgery via a robotic approach versus the QLB group (5/25 vs 23/25 P ≤ .001). The same fact is evident from the number of incisions with a median of 3 incisions in no QLB group and 5 incisions in QLB group (P < .001). Table 1. | No QLB N = 25 | QLB N = 25 | P Value | | |---|---|---|---| | Age | 46 (42–49) | 48 (43–51) | .33 | | BMI | 28.3 (25–33) | 31 (25.7–33) | .691 | | Number of incisions | 3 (3–3) | 5 (5–5) | <.001 | | Previous abdominal surgery | 14 (56%) | 18 (72%) | .239 | | Specimen weight (g) | 230 (150–580) | 210 (140–450) | .892 | | Robotic approach | 5 (20%) | 23 (92%) | <.001 | All numeric variables were summarized with median and 25th-75th percentile and compared across groups using the Mann–Whitney U test. All categorical variables were summarized with frequency and percentage and compared across groups using a χ2 test. Table 2 shows median postoperative NRS pain scores and whether any analgesic medication was used at the 1, 3 and 24-hour postoperative intervals. Postoperative pain scores showed no significant difference. Analgesic medication used at 1 and 24 hours did not differ significantly. However, analgesic medication used was significantly lower in the no-QLB group 8/25 (32%) patients versus 18/25 (72%) in QLB at 3-hour interval (P = .005). Table 2. | Non-QLB N = 25 | QLB N = 25 | P Value | | |---|---|---|---| | Preoperative pain score | 0 (0–0) | 0 (0–0) | .669 | | 1-hour postoperative pain score | 4 (0–7) | 5 (2–7) | .541 | | 3-hour postoperative pain score | 2 (0–4) | 3 (1–4) | .418 | | 24-hour postoperative pain score | 6 (4–7) | 6 (5–8) | .358 | | Any pain medication at 1 hour | 11 (44%) | 11 (44%) | 1.000 | | Any pain medication at 3 hours | 8 (32%) | 18 (72%) | .005 | | Any pain medication at 24 hours | 21 (84%) | 23 (92%) | .384 | All numeric variables were summarized with median and 25th–75th percentiles and compared across groups using the Mann–Whitney U test. All categorical variables were summarized with frequency and percentage and compared across groups using a χ2 test. Table 3 shows median usage of different classes of pain medications that included acetaminophen and opioids at 1, 3, and 24-hour intervals. No significant difference was seen in any class of medications used at 1, 3, and 24 hours. Table 3. | Time and Pain Medication | Non-QLB N = 25 | QLB N = 25 | P Value | |---|---|---|---| | 1-hour opioid | 1 (4) | 5 (20) | .08 | | 1-hour acetaminophen | 1 (4) | 2 (8) | .56 | | 3-hour opioid | 8 (32) | 10 (40) | .57 | | 3-hour acetaminophen | 2 (8) | 2 (8) | 1 | | 24-hour acetaminophen | 650 (0–1,300) | 975 (0–1,300) | .98 | | 24-hour ibuprofen | 1,200 (600–1,600) | 860 (600–1,600) | .96 | All categorial variables are summarized as N (%). All numeric variables were summarized with median and 25th–75th percentiles and compared across groups using the Mann–Whitney U test. Table 4 highlights secondary outcomes including operative time, length of stay, previous abdominal surgeries, and presence of intraoperative adhesions. None of the variables were significantly different between the no-QLB and QLB groups except operative time. The operative time was significantly shorter in the no-QLB group compared to the QLB group (160 vs 199 minutes, P = .008). Table 4. | No QLB n = 25 | QLB n = 25 | P Value | | |---|---|---|---| | Operative time (minutes) | 160 (143–185) | 199 (150–265) | .008 | | Length of stay (minutes) | 240 (225–270) | 255 (210–360) | .448 | | Adhesions | 12 (48%) | 15 (60%) | .239 | All numeric variables were summarized with median and 25th–75th percentiles and compared across groups using the Mann–Whitney U test. All categorical variables were summarized with frequency and percentage and compared across groups using a χ2 test. Table 5 shows the indications for minimally invasive hysterectomy. The most common indication was abnormal uterine bleeding. Only the QLB group had patients with endometriosis. Table 5. | Indication | QLB | No QLB | |---|---|---| | Abnormal uterine bleeding | 72% | 92% | | Endometriosis | 8% | 4% | | Endometrial hyperplasia | 16% | 4% | | Chronic pelvic pain | 4% | 0% |

Our study did not show that QLB had any positive effect on postoperative pain. Additionally, pain medication use was not decreased by QLB. Furthermore, surgical time was 40 minutes longer in the QLB group (199 vs 160 minutes) even though the specimen weights and amount of adhesions did not differ significantly between the groups. The longer operative time in the QLB group could potentially explain the increased analgesic medication usage in the QLB group at 3 hours. A robotic approach was also used more in QLB group compared to no-QLB group. Dam et al and Kukreja et al studies have shown efficacy of QLB in surgeries including laparoscopic nephrectomy, and total hip arthroplasty respectively,8,9 but Tanggaard et al study did not show QLB efficacy in laparoscopic hemicolectomy.10 The literature has been conflicting in the role of QLB in gynecologic surgeries. Naaz et al concluded that a QLB was more effective than a TAP block in reducing postoperative pain scores in the first 24 hours after patients underwent abdominal hysterectomy.11 Ishio et al performed a randomized control trial in which QLB was administered to half of the patients which demonstrated reduced postoperative pain scores at 0, 1, 3, and 24 hours postoperatively after laparoscopic gynecologic surgery that included procedures such as myomectomy, cystectomy and oophorectomy. In a study done by Choi, pain after laparoscopic hysterectomy is different in duration, severity and characteristics compared to other laparoscopic procedures like laparoscopic cholecystectomy, ventral hernia repair and fundoplication.12 It is possible that other gynecological laparoscopic surgeries may be associated with less visceral pain compared to hysterectomy. Conversely, Fujimoto et al performed a randomized control QLB trial which demonstrated no significant difference in postoperative pain scores after undergoing major laparoscopic gynecologic surgeries including hysterectomy.13 A recent randomized trial assessing QLB conducted on 70 patients scheduled for laparoscopic hysterectomy showed no significant difference in pain score or opioid consumption.14 The primary outcome was opioid consumption during the first 12 hours postoperatively, and the medication used for QLB was ropivacaine. Another study was performed in which patients undergoing laparoscopic hysterectomy were randomized to oblique subcostal transversus abdominis plane (OSTAP) which was compared to QLB group. The group with QLB showed reduced morphine consumption 17.2 vs 26.1 mg with P = .010. The morphine doses were significantly lower at various time intervals and the time to first need for morphine was lower. The NRS scores were also lower in QLB group compared with OSTAP.15 Another randomized controlled trial with 37 patients in each group undergoing total laparoscopic hysterectomy compared the opioid consumption and pain scores in group that received QLB versus no QLB group. The results showed decrease in fentanyl dose used and visual analogue pain score.16 All the above-mentioned studies used ropivacaine in QLB group. The median analgesic dose data was skewed, as it showed minimal medication usage in both groups at 1 and 3 hours, including opioid use. This could be due to the additional superficial bupivacaine and liposomal bupivacaine used in both groups. Our study is the first study that used a short acting anesthetic (bupivacaine) combined with liposomal bupivacaine (longer duration). The longer operative time in the QLB group could potentially explain the increased analgesic medication usage in the QLB group at 3 hours. More number of ports due to robotic approach used with total of 5 abdominal incisions could also add to the increased pain medication requirement, perhaps due to the larger and increased number of ports. Additionally, the increase in operative time in the QLB group could be related to robot usage as well. There is a possibility that a small sample size could have limit us from seeing significant changes in pain score or medication used at 1-, 3-, and 24-hour intervals. In future, a larger study with large sample size could be done to evaluate the results of this study and efficacy of QLB in minimally invasive hysterectomies. Endometriosis patients should be randomized to both groups, compared to our study, where they were not. As patients with endometriosis and chronic pelvic pain have different pain threshold and pain medication requirement, care should be taken to make sure patients are randomized to avoid bias. The strengths of the study included its prospective nature and that this is the first study to analyze use of liposomal bupivacaine QLB in laparoscopic hysterectomy. Also, by using liposomal bupivacaine and bupivacaine combination in the QLB, we were able to assess for both short and longer-term postoperative effects. Most studies have used bupivacaine alone, ropivacaine, or levobupivacaine in the QLB. Limitations of the study included the risk of selection bias and the inability to control for confounding. The sample size was small though it was consistent with power analysis that was achieved from a prior study.

There was no significant pain difference between the no-QLB and QLB groups at 1, 3, and 24 hours postoperatively. Patients who received a QLB were more likely require pain medication 3 hours after surgery. Thus, the use of a QLB does not appear to be a suitable adjunct for postoperative pain management in the setting of minimally invasive benign hysterectomy. Further research is needed to assess which groups of patients will benefit from a QLB.

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