Rhomboid intercostal block is used to block lateral cutaneous branches of intercostal nerves between T3 and T9 dermatomes. Serratus anterior plane block is used to block lateral cutaneous branches of intercostal nerves between T2 and T6, in addition, it is also known to block thoracodorsal nerve and long thoracic nerve. Both of the blocks are usually performed for postoperative analgesia following breast surgery. The primary hypothesis of the study is that FEV1 value of the patients who will receive modified radical mastectomy (MRM) and rhomboid intercostal plane (RIP) block combined with serratus anterior plane (SAP) will be higher than FEV1 value of the patients in the no-block group. The secondary hypothesis is that RIP+SAP blocks will provide reduction in the pain scores and opioid consumption in the postoperative first 24 hours.

The patients who are scheduled for MRM under general anesthesia, aged between 18-65 years and ASA scores I-II will be included in the study. Respiratory functions (FEV₁, FVC, FEV₁/FVC, PEF, FEF25-75) of the patients will be measured by a hand-held spirometry device prior to the operation in the surgical ward. The induction of anesthesia will be provided similarly in all patients, then patients will be intubated and randomly divided into two groups. One group will receive RIP+SAP block using 40 milliliters of %0.25 bupivacaine and patients in the control group will receive no block procedures. The standard analgesia will be provided by intraoperative intravenous (iv) infusion of dexketoprofen 50 mg and iv tramadol 1 mg/kg which will be administered in 15 minutes before end of the surgery. Respiratory functions of the patients will be measured at the postoperative 2nd, 4th and 24th hours. Pain intensity of the patients will be evaluated by Numerical Rating Scale (NRS) which is a scale ranges between 0 (no pain) and 10 (the worst pain that a person can stand). NRS scores will be evaluated at the postoperative 15th, 30th minutes and 1st, 2nd, 6th, 12th and 24th hours, and opioid consumption will be recorded at the postoperative 24th hour.

Inclusion Criteria:

• ASA I-II patients
• Female
• Ages between 18-65
• Patients who will receive breast cancer surgery under general anesthesia

Exclusion Criteria:

• Known respiratory diseases
• Rhinitis and atopic dermatitis story
• New York Heart Association Class equal to higher than class 2
• Respiratory diseases story in the last two weeks
• Alchol or substance or chronic opioid consumption story
• Any pain killers intake in the last 24 hours prior to surgery
• Active smokers or ex-smokers
• Body mass index over 35 kg/m2
• İnfection at the injection sites
• Known allergy to local anesthetics
• Known psychiatric diseases
• Operations longer than 3 hours

IPD will not be shared with anyone

The patients will be under general anesthesia and will not know if they received a block procedure or not.

The investigator, the data collector and the outcome assessor will be completely blind to the study groups. Only the care provider who will perform the block procedures will know the study groups.