Effective management of postoperative pain in breast cancer surgery is essential to minimize the risk of developing postmastectomy pain syndrome.The aim of this study is to evaluate the effectiveness of combining bilevel erector spinae plane (ESP) block with a single preoperative oral dose of tizanidine in improving postoperative analgesia in patients undergoing mastectomy surgery.

It is hypothesized that the combination of bilevel ESP block and single-dose oral tizanidine will provide superior postoperative analgesia compared to bilevel ESP block alone in patients undergoing mastectomy.

Introduction:

Effective management of postoperative pain in breast cancer surgery is essential to minimize the risk of developing postmastectomy pain syndrome, a chronic condition that significantly impacts patients' quality of life. Multimodal analgesia, which combines pharmacological and non-pharmacological strategies, has been shown to enhance postoperative pain control and reduce opioid consumption. In recent years, regional anesthesia techniques have become increasingly favored for perioperative pain management in breast surgeries. The ESP block has gained popularity due to its simplicity, safety profile, and effectiveness in thoracic and breast surgeries. Its analgesic action is attributed to the craniocaudal spread of local anesthetic into the costovertebral foramina and epidural space, resulting in blockade of both ventral and dorsal rami of the spinal nerves and providing unilateral thoracic analgesia.The bilevel ESP block, which involves administering the block at two distinct thoracic levels, has been proposed to enhance the spread of local anesthetic and improve analgesic coverage, particularly in the anterolateral chest wall and axillary regions commonly involved in mastectomy.

Tizanidine has been shown to reduce perioperative opioid and anesthetic requirements, stabilize hemodynamic responses to tracheal intubation, and minimize postoperative complications such as shivering and myocardial ischemia. Previous studies have demonstrated its effectiveness in reducing postoperative pain across a variety of surgical procedures, including laparoscopic cholecystectomy, thyroidectomy, anorectal surgery, hernia repair, and orthognathic surgery.Given the potential synergistic effects of combining regional anesthesia with systemic analgesics, this study aims to evaluate the efficacy of combining bilevel ESPB with a single oral dose of tizanidine for postoperative pain control in patients undergoing mastectomy.

Aim of the Study:

The aim of this study is to evaluate the effectiveness of combining bilevel erector spinae plane (ESP) block with a single preoperative oral dose of tizanidine in improving postoperative analgesia in patients undergoing mastectomy surgery.

Sample Size Calculation:

Sample size was calculated using Power Analysis and Sample Size software program (PASS) version 3.1.9.2 for windows (2017). The primary outcome will be time to first analgesic request. In a pilot study performed on 10 patients using bilevel ESP block, the mean (SD) of time to first analgesic request was 21 (6.5) hours. Using a two-sided hypothesis test with a significance level of 0.05, assuming alpha = 0.05 and beta = 0.2 (power = 80%) and using a two-sided two-sample unequal-variance t-test, 39 subjects will be required in each group to detect 20 % difference between groups which is considered the minimal clinically important difference. To allow for subject dropouts, 45 subjects will be assigned to each group.

Methods; The study will be conducted in Mansoura oncology centre on 90 patients who will be scheduled for mastectomy surgery under general anesthesia. Informed written consent will be obtained from all subjects in the study after ensuring confidentiality. 90 eligible patients will be randomly assigned to 2 equal groups (Bilevel ESP block group) and (Bilevel ESP block+ tizanidine group) according to computer-generated table of random numbers using the permuted block randomization method. The group allocation will be concealed in sequentially numbered, sealed opaque envelopes which will be opened only after obtaining the written informed consent.

The study protocol will be explained to all patients along with VAS after enrollment into the study. They will be kept fasting according to pre-operative ASA recommendations prior to surgery. Basic demographic characters including age, gender, and BMI will be recorded.

The peri-operative management will be identical in both groups. All patients with planned modified radical mastectomy will be assessed preoperatively by detailed medical history taking, clinical examination, Electrocardiography (ECG), and basal laboratory investigations as complete blood count (CBC), coagulation profile (PT, INR), blood glucose level, liver and renal function tests (liver enzymes, serum bilirubin, albumin and serum creatinine).

Statistical Methods:

The collected data will be coded, processed, and analyzed using SPSS program (version 22) for Windows. Normality of numerical data distribution will be tested by Shapiro-Wilk test. Continuous data of normal distribution will be presented as mean ± SD and will be compared with the unpaired student's t test. Non-normally distributed data will be presented as median (range) and will be compared with the Mann-Whitney U test. Categorical data will be presented as number (percentage) and will be compared with the Chi-square test. All data will be considered statistically significant if P value is ≤ 0.05.

Inclusion Criteria:

1. American Society of Anesthesiology (ASA) ІІ patients.
2. Scheduled for unilateral modified radical mastectomy.
3. BMI levels between 18.5- 35 Kg/m2.

Exclusion Criteria:

1. Patient's refusal.
2. Altered mental status or un-cooperative patients.
3. History of known sensitivity to the used anesthetics.
4. Bleeding or coagulation diathesis.
5. Infection or redness at the injection site.
6. Cardiac, renal, hepatic, hematological disease, peptic ulcer, gastrointestinal bleeding, and central or peripheral neurological disease.
7. Chronic pain.
8. Participants used analgesics routinely within the last 24 h.

Female

A single investigator will assess the patients for eligibility, obtain written informed consent, open the sealed opaque envelopes containing group allocation, prepare all injections and oral medication needed for the study. Another investigator blinded to the study group will give oral drug and perform block. In addition, the study subjects and the resident assessing the outcome will be blinded to the study group.