Effective postoperative pain management is essential for enhanced recovery after laparoscopic colorectal surgery. This randomized, controlled, double-blind trial will compare conventional postoperative analgesia (intravenous medications plus surgical wound infiltration) with a locoregional strategy combining a peripheral autonomic block (inferior mesenteric and superior hypogastric plexuses) and a transversus abdominis plane (TAP) block. We hypothesize that the combined strategy (BAPTAP) reduces pain intensity and opioid consumption in the first 48 hours after Left-Sided Colorectal Resection.

Postoperative pain after colorectal surgery involves both somatic and visceral components. Abdominal wall blocks target somatic nociception, whereas visceral pain often requires different approaches. Autonomic plexus blocks have shown promise in gynecologic and bariatric surgery. This study will randomize 140 adults undergoing elective laparoscopic Left-Sided Colorectal Resection to either: (1) BAPTAP (peripheral autonomic plexus block targeting the superior hypogastric and inferior mesenteric plexuses plus bilateral ultrasound-guided TAP block) in addition to standardized multimodal analgesia; or (2) Control (standardized multimodal analgesia and trocar/wound infiltration alone). Primary outcomes are pain intensity (Numerical Rating Scale) at predefined time points and cumulative opioid consumption (IV morphine equivalents) in the first 48 hours. Secondary outcomes include functional recovery milestones, adverse events, complications related to blocks or systemic analgesia, patient satisfaction, and quality of recovery via the PAIN OUT questionnaire. Randomization is computer-generated (1:1). Participants, postoperative care teams, and outcome assessors will be blinded; the anesthesiologist performing the block will not participate in postoperative assessments.

This is an interventional, randomized (1:1), parallel-assignment, double-masked clinical trial with an estimated enrollment of 140 participants, designed for supportive care (postoperative analgesia) in patients undergoing minimally invasive left-sided colorectal surgery for indications including colorectal neoplasms and diverticular disease, with outcomes focused on postoperative pain. Participants aged 18-80 years of any sex, ASA I-II, scheduled for elective laparoscopic Left-Sided Colorectal Resection at a single institution and able to understand and sign informed consent are eligible. Exclusions include known allergy to study medications (Ropivacaine), coagulation disorders, pregnancy, inability to provide consent, chronic pain on opioid therapy, and BMI > 35 kg/m². Two arms will be compared: the experimental arm receives a peripheral autonomic plexus block (targeting the superior hypogastric and inferior mesenteric plexuses) with ropivacaine 0.2% at 8 mL per site performed laparoscopically before dissection plus a bilateral ultrasound-guided TAP block with ropivacaine 0.33% at 30 mL per side, in addition to standard multimodal analgesia; the active comparator arm receives the same multimodal analgesia with trocar/wound infiltration using ropivacaine 0.33% up to 60 mL total, without autonomic plexus or TAP blocks. Masking is double (participant and outcomes assessor); the anesthesiologist who performs the block is unblinded and does not take part in postoperative care or assessments, while participants, and assessors remain blinded. The coprimary outcomes are pain intensity at rest on an NRS 0-10 at 2, 6, 12, 24, and 48 hours after surgery and cumulative opioid consumption over the first 48 hours expressed as intravenous morphine equivalents calculated as (fentanyl mg × 100) + (morphine IV mg) plus, if applicable, (tramadol mg ÷ 10); secondary outcomes include time to return of bowel function (first flatus and first bowel movement) through discharge, time to ambulation up to 48 hours, length of hospital stay during the index admission, adverse events and complications related to the TAP/autonomic blocks or systemic analgesia from the intraoperative period to 30 days postoperatively, patient-reported outcomes at 48 hours using PAIN OUT (Portuguese-validated IPO) covering pain frequency, interference with activities and mood, satisfaction, and participation, and overall patient satisfaction with pain management at 48 hours; an exploratory outcome consists of a 5-10 minute qualitative interview at 48 hours addressing expectations, trust, coping, and emotional impact.

Inclusion Criteria:

• Elective laparoscopic left-sided colorectal resection
• ASA physical status I-II
• Ability to understand the study and sign informed consent

Exclusion Criteria:

• Known allergy to study medications (e.g., local anesthetics)
• Coagulation disorders
• Pregnancy
• Inability to understand or provide consent
• Chronic pain on opioid therapy
• BMI > 35 kg/m²

We plan to share de-identified individual participant data (IPD) underlying the primary and secondary outcomes of this trial, including demographics, intraoperative variables necessary to interpret outcomes, postoperative pain scores at prespecified time points, cumulative opioid use (IV morphine equivalents), adverse events, length of stay, and discharge status. Direct identifiers and free-text notes will be removed; a re-identification key will be retained only at the site and will not be shared. Accompanying documents (final protocol, statistical analysis plan, data dictionary/codebook, blank CRFs, informed consent template, and analytic code for the primary analyses) will be provided. Access will be granted to qualified researchers with a methodologically sound proposal and IRB/ethics approval (or exemption) who sign a data-use agreement compliant with Brazil's LGPD (Law No. 13,709/2018) and institutional policies. Requests should be sent to the corresponding author.

Data will be available beginning 6 months after publication of the primary results for 36 months (extensions considered upon reasonable request).

Access will be granted to qualified researchers with a methodologically sound proposal and IRB/ethics approval (or exemption) who sign a data-use agreement compliant with Brazil's LGPD (Law No. 13,709/2018) and institutional policies.

andomization occurs at the participant level with no crossover; the anesthesiologist performing the block is unblinded and is not involved is not involved in postoperative care or outcome assessments, while participants, and assessors remain masked.