Effectiveness of erector spinae plane block for analgesia in breast surgery was documented in previous studies. Rhomboid intercostal block may be beneficial for analgesia in breast surgery. The aim of this study is to compare the peri-operative analgesic effect of rhomboid intercostal block with erector spinae plane block in mastectomy operation. This trial was designed as prospective randomized single-blind study. The included patients will be assigned into two groups: RIB-Group where the patients will receive ultrasound-guided rhomboid intercostal block and ESP-Group where the patients will receive ultrasound-guided erector spinae plane block prior to the operation. Primary outcome will be peri-operative pain scores and secondary outcomes will be peri-operative opioid consumption and peri-operative hemodynamic effect of these blocks.

Postoperative analgesia in breast surgery is important in reducing morbidity and mortality. Intravenous or oral analgesics may be used for this purpose. Ultrasound-guided fascia plane blocks are used to provide effective analgesia in mastectomy operations. Effectiveness of erector spinae plane block for analgesia in breast surgery was documented in previous studies.

Rhomboid intercostal block may be beneficial for analgesia in breast surgery. Both blocks have the advantage of unilateral application in unilateral mastectomy operations. When administered pre-operatively, it also provides per-operative analgesia and may reduce per-operative opioid consumption. These blocks are applied under ultrasound-guidance with single injection. Since the site of injection is relatively superficial (between the back muscles and ribs) and applied under ultrasound-guidance, mechanical complications is expected to occur less. These low-cost blocks also may reduce the usage of high-cost and high-risk opioids after surgery. These blocks unilaterally anesthetize the nerves innervating the thoracic region and the axilla, thus providing effective per-operative and post-operative analgesia in mastectomy operations.

The aim of our study is to compare the rhomboid intercostal block with erector spina plane block in mastectomy in terms of intraoperative and postoperative analgesia in mastectomy operation. Our hypothesis is rhomboid intercostal block may reduce peri-operative pain as effective as or more effectively than erector spina plane block. Secondary hypothesis is rhomboid intercostal block may reduce peri-operative opioid consumption as effective as or more effectively than erector spina plane block. Thus, the study is defined as block technique comparison.

Eighty patients aged between 29-79 years who are planned mastectomy under general anesthesia will be included in the study. Patients with severe cardiac and respiratory disease, severe coagulation disorder, body mass index greater than 35, refusal of regional block and patients having local infection in block application area, contraindication of the standardized drugs in the study and patients with insufficient postoperative analgesia requiring more potent opioids will be excluded from the study.

The patients who meet the study criteria will be assigned into two groups by using computerized randomization. Patients who do not give consent will also be excluded from the study. All patients will be sedated with midazolam and fentanyl prior to block application. First group (RIB-Group) of patients will receive ultrasound-guided rhomboid intercostal block prior to the operation under sedation. Patients in the second group (ESP-Group) will receive ultrasound-guided erector spina plane block under sedation. Since both procedures will be performed from the same site, the study was considered as a single blind.

All patients will be intubated after induction of general anesthesia with Propofol 2 mg / kg, Rocuronium 0.6 mg / kg and Fentanyl 1.5 µg / kg. Mixture of Desflurane 6% concentration in 50% air and 50% oxygen will be used for the maintenance of general anesthesia. Patients in both groups will receive 1 µg / kg of fentanyl when pain occurs during surgery. Pre-operative and post-operative blood pressure, heart rate, oxygen saturation, end-tidal carbon dioxide values of patients in both groups will be measured and recorded at determined time intervals.

Patients will be followed for 48 hours after the operation. In the postoperative period, acetaminophen 1 g three times a day will be administered routinely in context of multimodal analgesia. Intravenous tramadol 1 mg/kg will also be administered depending on patient need up to 4 times a day. Total amount of perioperative opioids will be recorded. Per-operative and post-operative opioid consumption will be calculated separately. Pain assessment will be evaluated by using a verbal analog scale (asking patients to give a pain score between 0 and 10. Score of 0 means worse pain ever and score of 10 means no pain). Complications related to the block procedure will be also recorded. If there is pain that requires more potent opioids such as morphine, the block will be considered as unsuccessful.

Inclusion Criteria:

• Patients who are planned mastectomy under general anesthesia

Exclusion Criteria:

• Patients with severe cardiac and respiratory disease
• Severe coagulation disorder
• Body mass index greater than 35 kg/m2
• Refusal of regional block
• Patients having local infection in block application area
• Contraindication of the standardized drugs in the study
• Insufficient postoperative analgesia requiring more potent opioids

The two interventions will be performed at the same thoracic region using the same technique as so; there participant will be blinded to the study. The investigator who performs the intervention will be unblinded. The investigator who will follow up the patients and collect the postoperative pain data will be blinded.