Comparative Study between Ultrasound Guided Erector Spinae Plane Block versus Paravertebral Block for Postoperative Pain Relief in Patients Undergoing Unilateral Modified Radical Mastectomy

INTRODUCTION

Breast cancer is a serious medical problem because one out of every eight women will develop the disease during her lifetime. Acute postoperative pain raises the likelihood of chronic postoperative pain, so proper perioperative pain management is critical. Breast procedures are frequently accompanied with postoperative pain, nausea, and vomiting, all of which can negatively impact the patients' perioperative experience. ^{1, 2}

Although opioids are commonly used to treat acute post-mastectomy pain, they can have a number of negative side effects, including drowsiness, nausea, vomiting, and respiratory depression. Despite the fact that thoracic epidural analgesia and PVB have been linked to significant complications such as pneumothorax and total spinal anaesthesia, they have

become the gold standard for breast surgery. Because of the use of ultrasound in RA, various novel blocks have been developed that can give analgesia for breast procedures with less adverse effects. ^{3, 4}

The dorsal and ventral rami of the thoracic and abdominal spinal nerves are blocked using ESPB, a novel regional block in which LA is injected between the ESM and TP under US guidance. A single injection at the level of the T5 caused cranio-caudal spread between C7 and T8 in a cadaver model, according to radiological imaging. This explains the widespread sensory block noted in case reports, which is at least as widespread as the spread seen with PVB. However, no previous studies compared the simplicity of this method to the gold standard PVB. ⁵

The aim of the current study was to compare the efficacy of the US guided PVB and the ESPB in decreasing the intensity of postoperative pain following unilateral MRM.

PATIENTS AND METHODS

After approval of the Ethics Committee of the Faculty of Medicine – Al-Azhar University and a written consent from each patient, a sample size of 46 patients underwent unilateral MRM under GA at Al-Azhar University hospitals (ElHussein and Sayed Galal) were enrolled in the study.

Study Design: prospective randomized controlled single blinded clinical study.

The patients were randomly divided into two equal groups using closed envelope method: Group I (ESPB) Erector Spinae Plane Block: 23 patients received preoperative ESPB with GA. Group II (PVB) Paravertebral Block: 23 patients received preoperative PVB with GA.

Group I and Group II achieve 91.250% power to detect a difference of (1) in postoperative VAS between both groups with standard deviation for both groups of (1) and a significance level (alpha) of 0.05 using a two-sided Mann-Whitney test after nonparametric adjustment.

Randomization: Patients have been allocated to one of the study groups at random using a computer-generated table, with the randomized sequence hidden in sealed opaque envelopes.

Exclusion criteria: Patients who refused to participate in the study, those with allergy to any of LA drugs or any included medications, reconstructive breast surgery, coagulopathy or patients on anti-coagulant, patients with psychiatric disorder, pregnancy, and patients less than 18 years old.

Preoperative evaluation: The patients were evaluated the day before surgery with a thorough medical history, clinical examination, and regular laboratory tests. All patients were told about the surgery and taught how to use the patient-controlled analgesia (PCA) pump (Master PCA, Fresenius vial S.A., France) and VAS, which is a 10-cm line with 0 cm indicating no pain and 10 cm indicating the most severe pain.⁶

Preanaesthesia preparation: Before the operation, all patients were present at block room, where the blocks were administered following the insertion of a peripheral IV line and the attachment of a multichannel monitor (Drager vista 120, Dragerwerk AG & Co. KGaA, Germany) that displayed heart rate (beats/min), mean non-invasive arterial blood pressure (mmHg), and oxygen saturation (%). ( percent ). Prior to the blocks, all of the patients were given intravenous midazolam (0.05 mg/kg) and fentanyl (25ug). 7 30 minutes following the anaesthetics, all patients were moved to the operating room (OR).

Group I: ESPB was carried out in this group with perfect aseptic method. 8 Left- or right-sided ESPB was conducted with the patients in the sitting position, depending on the operative side, using a high-frequency (higher resolution than low-frequency) linear US probe (L25n, 13-6MHz, Sonosite S-Nerve, Sonosite Inc., USA). High-frequency probes provide a superior resolution but a lower penetration capability.⁹

Group II: PVB was carried out in this group under strict aseptic conditions. 8 PVB was conducted with a low-frequency (since more depth was needed to see the pleura) curved US probe with the patients in the sitting position, depending on the surgical side (C60n, 2-5 MHz, Sonosite S-Nerve, Sonosite Inc., USA). Low-frequency probes, on the other hand, penetrate deeper but have worse resolution. ⁹

After checking for sensory dermatomes from the 2nd thoracic vertebra to the 6^th, GA was induced to both groups. The anaesthetic technique in both groups was induced with fentanyl (1ug/kg) and propofol (2mg/kg), Tracheal intubation was facilitated with cisatracurium (0.15 mg/kg), anaesthesia was maintained with isoflurane (1-2%) in 100% oxygen and incremental doses of cisatracurium (0.03 mg/kg) guided by nerve stimulator (TOF-Watch SX, Organon, ireland) train of four (TOF) was kept at 2 and fentanyl (25 μg) was given when HR and/or MABP increases more than 20% above pre-induction levels. Controlled ventilation was maintained at a tidal volume of (6 ml/kg) and at a rate of (10 breath/min), maintaining the end-tidal CO₂ at (32-35 mmHg) using the ventilator (Fabius GS- Drager-Germany). Anaesthesia was stopped at the end of the procedure, residual neuromuscular block was reversed with atropine 0.01 mg/kg and neostigmine 0.04 mg/kg, the trachea was extubated, and the patients were transported to the postoperative anaesthesia care unit (PACU) for the next 24 hours. A PCA pump (Master PCA, Fresenius vial S.A, France) was prepared by dissolving 20mg of nalbuphine in 20mL of normal saline to make 1mg/mL concentration of opioid solution. Patients were given the option of using PCA on their own. The PCA was set to a 2mL bolus with a 10-minute lockout duration. There was no infusion in the background.¹⁰

All patients were given 30mg ketorolac /8 hours IV as a standard postoperative analgesia in both groups.

All patients were subjected to:

Duration of the procedure in minutes was measured starting from administration of the LA drug (lidocaine 2%) until the complete injection of the 30 ml of 0.25% bupivacaine.

The examination of the sensory blockade was judged using an ice pack every 5 min for 20 min preoperatively as the onset of the block was identified at T4 dermatome.

The extension of the block was examined after 20 minutes and was identified as upper and lower limit of partial loss of cold sensation at dermatomes levels from T2 to T6.

Degree of sensory block was measured using an ice pack every 5 min for 20 min preoperatively by the used scale at T4 dermatome.

Duration of the block, time of first request of postoperative analgesia, total dose of consumed nalbuphine and satisfaction level.

Postoperative complications: LA toxicity, haematoma at the site of injection, pneumothorax, PONV, hypotension or bradycardia.

Statistical analysis:

The IBM SPSS software programme version 20.0 was used to analyse the data that was supplied into the computer. (IBM Corporation, Armonk, NY) Number and percent were used to describe qualitative data. The Kolmogorov-Smirnov test was employed to ensure that the distribution was normal. Range (minimum and maximum), mean, standard deviation, and median were used to characterise quantitative data. The significance of the acquired results was assessed at a 5% level. To calculate the difference between two or more sets of qualitative variables, use the Chi square test (2). The mean and standard deviation (SD) were used to express quantitative data (Standard deviation). ANOVA with repeated measures (repeated measures ANOVA): To compare more than two periods or stages of normally distributed quantitative variables, use the Post Hoc test (Bonferroni adjusted) for pairwise comparisons (HR, MABP). The Mann Whitney test is used to compare two groups with improperly distributed quantitative characteristics (VAS at rest & movement, degree of sensory block at T4, onset of the sensory block at T4, total dose of nalbuphine consumption in 24 hours).

RESULTS

Age: In group I, the age of the patients ranged between 47and 81years with a mean value of 62.96± 7.56 years, in group II, it ranged between 45 and 83 years with a mean value of 62.09±10.95 years. Body weight: In group I, the weight of the patients ranged between 73and 105 kg with a mean value of 85.35±8.62 kg, in group II it ranged between73 and 103 kg with a mean value of 86.04±9.37 kg. Comparing both studied groups, there was no significant difference between the two groups regarding the age (p= 0.756) and the weight (p=0.795) (Table 1).

The total dose of nalbuphine consumption in postoperative 24 hours in Group I ranged from 2 to 6 with a mean of 3.33 ± 1.63 mg, while it ranged from 2 to 6 with a mean of 3.14 ± 1.57 mg in Group II. There was no significant difference between both groups as regard the total dose of nalbuphine consumption in postoperative 24 hours (p = 0.836) (Table 2).

Satisfaction was measured using verbal rating scale for satisfaction (1-5) at the end of the study. In Group I patient verbal rating score was 3 in 2 (8.7 %) patients, 4 in 4 (17.4%) patients and 5 in 17 (73.9%) patients. While in Group II was 3 in 3 (13 %) patients, 4 in 5(21.7%) patients and 5 in 15(65.2%) patients. There was no significant difference between both groups as regard patient satisfaction (Table 3).

There were no complications recorded except for PONV, 1 patient in Group I and 2 patients in Group II and were treated by IV ondansetron 4mg. There was no significant difference between both groups as regard PONV (Table 4). There were no LA toxicity, haematoma at the site of injection, pneumothorax, hypotension or bradycardia.

Table 1: Comparison between the two studied groups as regard the demographic data.

Table 2: Comparison between the two studied groups as regard the total dose of nalbuphine (mg) consumption in 24 hours.

Table 3: Comparison between the two studied groups as regard patient satisfaction at the end of 24 hours.

Table 4: Comparison between the two studied groups regarding complications.