In this study, it was aimed to evaluate the effects erector spina plane block (ESPB) on postoperative opioid consumption in the first 24 hours and pain scores after colorectal surgery.

Colorectal surgery can be applied for many reasons, among these reasons, colorectal cancer (CRC) takes the first place. With the understanding of the pathophysiological effects of analgesics better, the use of regional techniques in providing analgesia for patients undergoing colorectal cancer surgery has come to the fore. Depending on the surgical procedure, pain faced by patients is an important problem that must be deal with in the postoperative period.

In this study, the hypothesis was determined as "Pre-operatively, erector spina plane block (ESPB) performed as part of multimodal analgesia reduces postoperative morphine consumption and pain scores."

The patients were divided into two groups :

Group ESP (erector spinae plan):

In this group, patients will be administered bilateral ESPB (total of 40 ml, %0.25 bupivacaine) in addition to IV morphine patient-controlled analgesia (PCA) for the first 24 postoperative hours.

Group GA (general anesthesia):

In this group, patients will be administered only IV morphine patient-controlled analgesia (PCA) for the first 24 postoperative hours.

Inclusion Criteria:

• Patients aged between 18 and 65 years
• ASA I , II patients
• BMI<35 kg/m2 (body weight <100 kg , >45 kg)
• Patients who underwent colorectal surgery

Exclusion Criteria:

• Patients who underwent abdominoperineal resection
• Patients who were evaluated as unsuccessful block in the dermatomal examination performed after the block was applied.
• Patients diagnosed with OSAS
• Pregnancy and breastfeeding
• Contraindication of regional anesthesia (coagulopathy, abnormal INR, thrombocytopenia, infection at the injection site)
• Hypersensitivity to local anesthetics or a history of allergy
• Patients with a history of opioid use longer than four weeks
• Patients with severe psychiatric diseases such as psychosis or dementia that limit cooperation with the patient.
• Patients with anatomic deformity ( advanced scoliosis and kyphotic patients. Patients with pectus carinatum and pectus excavatum-like chest deformity )
• Patients who do not want to participate
• Patients who have had previous colorectal surgery, excluding diagnostic biopsies
• Patients who could not be reached by phone to inquire about their pain score at 3rd month.

The patients were randomly divided into two groups of 30 patients each. In the system where computer generated random numbers (SPSS v23.0, IBM, NewYork, USA) were used, ESP and GA groups were determined at a ratio of 1:1. Sealed and sequentially numbered envelopes were created. One hour before the operation, an experienced anesthesiologist, who was not involved in the intraoperative and postoperative follow-up of the patient and would only perform the block procedure, opened a sealed opaque sealed envelope to learn the group that the patient would be included in. There were two different physicians who performed intraoperative and postoperative follow-up. Both of the follow-up physicians were blind to the patient group. The care provider and investigator were also blinded to the participant.