Lateral Quadratus Lumborum Block Versus Transversus Abdominis Plane Block in Laparoscopic Surgery

This prospective randomized, observer-blinded paralleled groups study was conducted following the tents of the Declaration of Helsinki. This study was approved by the local institutional ethics committee and local institutional review board of Fayoum university hospital and written informed consent was obtained from 50 adult patients scheduled for elective laparoscopic abdominal surgical procedures (inguinal hernia repair-missed IUCD extraction-appendectomy-ovarian vein ligation) between July 2019 and February 2020.

Patients were randomly allocated into two groups (QLB group n=25 and TAPB group n=25) using computer generated random numbers kept in separate opaque envelopes that were opened by the study investigator just before the block. The patient and the data collector were unaware of the group allocation till the end of the study.

Pre-operative assessment (History, examination and investigations) was done (according to the local protocol designed to evaluate the patients). Demographic characteristics: age, weight, height and BMI were recorded in preoperative assessment of patients. All patients received 150 mg Ranitidine oral tablet at night and on the morning just before the operation as a premedication. Before surgery, the participants received education about the VAS pain score (0-10) (where 0 = no pain and 10 = worst comprehensible pain) and the details of the nerve block procedures. After a 6 hrs fasting, the patients were taken to the operation theatre.

Upon arrival to the operating room standard monitors (Pulse oximeter, noninvasive blood pressure monitoring, capnography and electrocardiogram) were applied and continued all over the operation, an 18 gauge peripheral intravenous (IV) cannula was inserted, IV midazolam 0.03 mgkg-1, metoclopramide 10 mg, and ceftriaxone 1 gm were administered to all patients as premedication then pre-oxygenation with O2 100% for at least 3 min then induction of anesthesia was done with fentanyl 1μgkg-1, propofol 1.5-2 mgkg-1 and atracurium 0.5 mgkg-1. Anesthesia was maintained by volume controlled ventilation (VCV) tidal volume 6-8 mlkg-1 with oxygen and air (50:50) with target of EtCO2≈ 35-40 mmHg, isoflurane 1:1.5 % volume concentration and atracurium 0.1 mgkg-1 every 20-30 minutes.

The study solution was prepared in two syringes each contained 20 ml of bupivacaine 0.25%. By the end of surgery and before recovery from general anesthesia, either blocks were done using a high-frequency ultrasound probe Active Array L12-4 (8-13MHz) of an ultrasound machine (Philips clear vue350, Philips healthcare, Andover MA01810, USA) and a 22-gauge, 50 mm echogenic needle (Stimuplex D; B Braun, Germany).

For the ultrasound-guided quadratus lumborum block group, the patient was placed in lateral position and skin sterilization was done with povidone iodine. Then a high frequency linear probe was placed above the iliac crest to recognize the three layers of the abdominal wall muscles. Transversus abdominis was traced posteriorly until the transversus aponeurosis appeared, then the probe tilted slightly caudal to enhance the appearance of transversus aponeurosis. QL was identified medial to the aponeurosis of transversus abdominis muscle. Then the needle was inserted from supero-anterior to postero-inferior and advanced using in plane technique till the needle tip reached the anterolateral border of the QL at its junction with transversalis fascia. After negative aspiration (to exclude intravascular injection), the correct needle position was confirmed by hydrodissection using 1mL of normal saline. Then 20 mL of 0.25% bupivacaine was applied. The same technique was performed on the other side.

For the ultrasound-guided TAP block, skin sterilization was done with povidone iodine. The probe was placed in the mid-axillary line above the level of the anterior superior iliac spine, then slided cranially till the three abdominal wall muscles identified (External oblique muscle (EAO), internal oblique muscle (IOM) and transverse abdominis muscle (TAM)). The needle was advanced using in-plane technique till it reached the transvers abdominis plane between the IOM and TAM, the correct needle position was proved by hydrodissection using 1 mL of normal saline. An injection of 20 mL of 0.25% bupivacaine was applied. The same technique was performed on the other side.

After performing the block anesthesia was discontinued and tracheal extubation was done once the patient fulfilled the extubation criteria. Patients were transferred to post-anesthetic care unit (PACU), where they were discharged from the PACU after a modified Aldrete score≥9. Visual analogue scale (VAS) was used to assess postoperative pain. All patients received analgesics according to the local institutional protocol as following (paracetamol 1gm IV infusion/8 hrs and ketorolac 30 mg IM/12 hrs.). A postoperative rescue analgesia with morphine sulfate IV was given to patients with VAS >4 at a bolus dose of 3 mg increments with a maximum dose of 15mg per 4 hours or 45mg per 24 hours.

Sample size was estimated using G*Power© software version 3.1.9.2 (Institute of experimental psychology, Heinrich Heine University, Dusseldorf, Germany)149 with total opioid consumption among the two groups as the main primary outcome. Previous similar researches150 demonstrated that the effect size between the two groups was expected to be large of 1.12 and it calculated that 42 patients (21 patients per group) would provide to achieve a power of 95% with type I error rate of 0.05. However, we assigned 50 patients (25 patients per group) to compensate for data loss. The collected data were organized, tabulated and statistically analyzed using SPSS software statistical computer package version 22 (SPSS Inc, USA). Data were tested for normality using shapiro-wilks test. Numerical variables such as age, body weight, height and BMI were normally distributed and were described as mean ± standard deviation (SD). An independent t-test was used to compare the mean values of the two groups. Other variables were not normally distributed and were presented as median and interquartile range (IQR); Mann-Whitney U test was used as a test of significance. The time-to-event variable (time to analgesic request) was evaluated using the Kaplan-Meier method, and the logrank test was used to compare the groups. Qualitative data were presented as numbers and percentages, and the chi-squared test was used to determine significance. A two-sided P-value of <0.05 was considered statistically significant.