This study aims to assess whether transmusculr quadratus lomborum block (QL block) can reduce postoperative pain after cytoreductive surgery and hyperthermic intra-peritoneal chemotherapy (CRS and HIPEC). Patients will be randomly assigned to either QL block group or control group. Ultrasound-guided bilateral transmuscular quadratus lomborum block will be performed in QL block group using 0.375% ropivacaine. Multimodal analgesic regimen including acetaminophen, nonsteroidal antiinflammatory drugs (NSAIDs), and rescue opioids will be used in every patient. Primary outcome is opioid consumption for 24 hours after surgery. Secondary outcomes included pain scores, time to first rescue analgesics, quality of recovery score, length of hospital stay.