Evaluation of Ultrasound-guided Erector Spinae Plane Block for Postoperative Analgesia in Laparoscopic Sleeve Gastrectomy: A Prospective, Randomized, Controlled Clinical Trial

This study will help us in understanding the role of erector spinae block (ESPB) for postoperative pain control in patients undergoing upper GI laparoscopy surgeries. The surgeries included in this group include laparoscopic cholecystectomy, laparoscopic gastrectomy, laparoscopic umblical or epigastric hernia repair. Patients aged between 18 and 65 years, scheduled to undergo any upper GI laparoscopy surgeries with an ASA score of 1 or 2 will be included in the study. This is a prospective randomised controlled trial which will compare two groups receiving either erector spinae block or no block for postoperative pain control after upper GI laparoscopy surgeries

Research Proposal and significance Postoperative analgesia should include strategies to reduce side effects. Intravenous analgesics are generally considered to be adequate for pain management in upper GI laparoscopic surgeries. However opioids can lead to nausea, vomiting and itching while NSAIDs affect the gastric, hepatic and renal systems and wound healing. Reducing opioid requirements during the perioperative period is among the current goals of enhanced recovery programs. The objective is to reduce all potential opioid-related side-eﬀects. Therefore, multimodal analgesics including regional blocks decrease the use of other analgesics and therefore decrease side effects.

Objective The aim of this study is to evaluate the eﬀect of Erector spinae block (ESPB) on postoperative pain in upper GI laparoscopy surgeries, which leads to both visceral and somatic pain.

Research review In this study, the surgeries included in upper GI laparoscopic surgeries are laparoscopic cholecystectomy, laparoscopic gastrectomy, laparoscopic umblical or epigastric hernia repair.

n upper GI laparoscopy surgeries, postoperative pain is caused by two reasons; one is somatic pain from the trocar entry incisions and additionally peritoneal distention and diaphragm irritation due to high intra-abdominal pressure and CO2 insufflations lead to visceral pain as well. Therefore, any analgesic protocol for these surgeries must be effective on both sources of pain.

Regional block techniques studied and considered part of multimodal anesthesia include transversus abdominis plane block (TAP), oblique subcostal transversus abdominis plane block (OSTAP or STAP) and paravertebral block. Apart from paravertebral block, these techniques only effect somatic pain and can therefore be inadequate in some cases. Ultrasound Guided paravertebral block is an advanced regional anesthesia technique. When considering that the pleura forms one boundary of the paravertebral space, ESPB can be considered an easier technique to perform. It is also safer because the needle remains behind the transverse process. However, non-inferiority studies comparing ESPB and paravertebral block are required. Erector Spinae Plane Block (ESPB) - first recently described for the treatment of thoracic neuropathic pain, is a peri-paravertebral regional anesthesia technique that has since been reported as an effective technique for prevention of postoperative pain in various surgeries. In ESPB, local anesthetic is reported to be administered in to the interfascial plane between the transverse process of the vertebra and the erector spinae muscles, spreading to multiple paravertebral spaces. Case reports have reported that ESPB effects both the ventral and dorsal rami and leading to blockage of both visceral and somatic pain. Anatomical dissection indicates that the likely mechanism of action is diffusion of local anaesthetic anteriorly through the connective tissues and ligaments spanning the adjacent transverse processes and into the vicinity of the spinal nerve roots. This is consistent with other reports of successful analgesia following injection into a similar tissue plane in the thorax.

Tulgara et al in their study has shown that ultrasound guided bilateral single shot ESPB performed before general anesthesia induction in LC patients signiﬁcantly lowered NRS at rest in the ﬁrst 3h and lead to less analgesia requirement in the ﬁrst 24h when compared to a control group.

Methodology Patients aged between 18 and 65years, scheduled to undergo any upper GI laparoscopy surgeries with an ASA score of 1 or 2 will be included in the study. Written informed consent for general anesthesia and all procedures will be obtained from all patients. Patients who refused enrollment or later requested removal for the study, those who are unable to give informed consent and patients with either contraindications for regional anesthesia, known allergy to local anesthetics, bleeding diathesis, use of anticoagulants or corticosteroids, inability to operate patient controlled analgesia (PCA) system, psychiatric disorders or use of psychiatric medications and conversion to open laparotomy will not be included in the study.

There will be two groups of patients: control group (Group A) and ESPB group (Group B). Upon ward admission, a random ID will assigned to each patient. Simple randomization in the operating room will performed using the closed envelope method to determine which group the patient would be included in.

The random ID assigned to each patient will be used when collecting all patient data in the ward postoperatively. The anesthesiologist performing the simple randomization will also perform the block but will not play any role in the collection of postoperative data or its analysis.

General anesthesia and surgical technique will be the same for both groups. Standard monitoring procedures included pulse oximetry, electrocardiography, and noninvasive arterial pressure will be performed prior to anesthesia. Baseline heart rates, systolic and diastolic blood pressures, and mean arterial pressures will be recorded before anesthesia. Induction will performed using propofol 2-3 mgkg-1, fentanyl 100μg and Cisatracurium 0.2 mgkg-1. 0.8-1.0 MAC sevoﬂurane and 0.05-0.1 μg/kg/min remifentanil infusion will be used for anesthesia maintenance. Remifentanil dosage will be adjusted according to hemodynamic parameters, up to 2 μg/kg/min. Standard perioperative intravenous analgesia protocol will include paracetamol 1g and Lornoxicam 16 mg.After completion of surgery, patients will be extubated once TOF ratio of \>0.9 is acheived and transferred to the recovery room. Local anesthesia will not be applied to wounds. Pneumoperitoneum will be evacuated in all patients at the end of surgery. All patients will receive 8 mg Dexamethasone and 1 mg Granisteron as antiemtics.

All blocks will be performed in lateral position after general anesthesia induction. ESPB will be performed under ultrasonographic guidance using a linear 6- to 10-MHz ultrasound probe. The linear ultrasound transducer will be placed in a longitudinal parasagittal orientation 3cm lateral to the T9 spinous process. The erector spinae muscles will be identiﬁed superﬁcial to the tip of the T9 transverse process. A 21-gauge 10-cm needle will be inserted using an in-plane superior-to-inferior approach or an outplane approach. The tip of the needle will be placed into the fascial plane on the deep (anterior) aspect of erector spinae muscle. The location of the needle tip will conﬁrmed by visible ﬂuid spread lifting erector spinae muscle oﬀ the bony shadow of the transverse process on ultrasonographic imaging. A total of 10-15 mL of 0.2% ropivacaine will be injected each side.

The Numeric Rating Scale (NRS) will be used to evaluate postoperative pain. The NRS is a segmented numeric version of the visual analog scale (VAS) in which a respondent selects a whole number (0-10 integers) that best reﬂects the intensity of his/her pain. It is considered a one dimensional measure of pain intensity in adults. The 11-point numeric scale ranges from '0' representing one pain extreme ("no pain") to'10' representing the other pain extreme ("pain as bad as you can imagine" or "worst pain imaginable"). Changes in NRS at rest and on movement will be recorded at intervals.

All patients will be followed using a standardized postoperative analgesia protocol which includes Morphine PCA. Morphine at a concentration of 1mg/ml is included in our PCA protocol (total volume 100mL.) PCAs will be set as no basal infusion and 1 mg bolus doses with a 10 min lock out time. PCA will be commenced when the patient arrives in the recovery room. For rescue analgesia during the ﬁrst hour in the recovery room, 2 mg Morphine will be used if NRS≥4/10. The dosage will be repeated every 20 min if NRS \> 4/10. Paracetamol 1g / 8h will be used during ward follow-up. If NRS \< 2 and the patient refuses pain medication, this dosage will be skipped. As rescue analgesia in case of the pain score≥4/10 on NRS during 1-24h, Lornoxicam 16 mg IV will be performed. If the pain remains at same level in following 1h period Morphine 2 mg IV will be added. Patient will receive 1 mg Granisetron IV if complains of nausea/vomiting.

Primary outcome measures at commencement of the study will be NRS pain score at 18th hours postoperatively both at rest and when coughing. Secondary outcome measures will be routine (paracetamol or morphine PCA) or rescue analgesic use within the ﬁrst 24h. In addition to the above measures, NRS pain scores will measured at other time intervals like 30 minutes, 1 hour, 2 hours, 6 hours, 12 hours and 24 hours postoperatively. Also, shoulder pain during the ﬁrst 24 h and presence of postoperative nausea and vomiting will be noted. The severity of both nausea and sedation will be assessed by patients on a 4 point scale (none, mild, moderate, and severe). Nurses will note any vomiting in the recovery room or on the ward. Finally, the number of patients receiving Granisetron will be recorded.

The null hypothesis of our study is that there is no diﬀerence in pain scores between ESPB and a control group receving standard analgesic regimen in patients undergoing upper GI laparoscopic surgeries.

For sample size calculation, we used the study by Tulgara et al (16) done on laparoscopic cholecystectomy with pooled standard deviation of 0.725 and margin of error (d) as 0.6 units on NRS scale at α=0.05 and power 80 %.

The sample size was calculated using the formula n = 2 ( Zα + Zβ) 2 X σ2/d2

where Zα = 1.96 ( 95% confidence interval), Zβ = 0.84 ( 80% power), σ = 0.725, d = 0.6 Sample size calculated from this formula came out to be 22 in each group and with 10 % dropouts/attrition, it was 25 patients in each group.

SPSS 16.0 Statistical package programme (SPSS, Chicago, IL, USA) will be used for statistical analysis. Descriptive statistics will be expressed as mean ± standard deviation. Univariate analysis compare in groups means using a 2-sample, independent t-test assuming equal variances for continuous variables. For data without normal distribution, Mann Whitney U test will be performed. Ratios will be compared using Chi-Square. Categorical variables will be compared using Fisher exact test. A p-value of\<0.05 is considered statistically signiﬁcant. NRS will be analysed using repeated measures analysis.

.

Eligibility Criteria:
Inclusion Criteria:

* Patients aged between 18 and 65years, scheduled to undergo any upper GI laparoscopy surgeries with an ASA score of 1 or 2 will be included in the study. The surgeries included in this group include laparoscopic cholecystectomy, laparoscopic gastrectomy, laparoscopic umblical or epigastric hernia repair.

Written informed consent for general anesthesia and all procedures will be obtained from all patients.

Exclusion Criteria:

* Patients who refused enrollment or later requested removal for the study, those who are unable to give informed consent and patients with either contraindications for regional anesthesia, known allergy to local anesthetics, bleeding diathesis, use of anticoagulants or corticosteroids, inability to operate patient controlled analgesia (PCA) system, psychiatric disorders or use of psychiatric medications and conversion to open laparotomy will not be included in the study.