Autonomic Neural Field Block for Visceral Pain in Minimally Invasive Left-Sided Colectomy

Background and Rationale

Effective postoperative pain control is a cornerstone of enhanced recovery after surgery (ERAS) pathways in colorectal surgery. Adequate analgesia facilitates early mobilization, pulmonary hygiene, gastrointestinal recovery, and timely hospital discharge. Despite widespread adoption of ERAS protocols and multimodal, opioid-sparing analgesic strategies, postoperative pain following left-sided colectomy remains a clinically relevant and persistent challenge. A substantial proportion of patients continue to experience moderate to severe pain in the early postoperative period, which may contribute to increased opioid consumption, postoperative nausea and vomiting (PONV), delayed functional recovery, and prolonged length of stay.

Current perioperative analgesic approaches in colorectal surgery predominantly address somatic pain pathways. These strategies include non-opioid analgesics, opioid-based regimens, local anesthetic infiltration, neuraxial techniques, and transversus abdominis plane (TAP) blocks. While effective in reducing abdominal wall and incisional pain, these modalities do not specifically target visceral postoperative pain, which is mediated through autonomic afferent neural pathways. Visceral pain arises from bowel distension, traction, ischemia, and inflammatory processes affecting the colon and mesentery and is transmitted primarily via sympathetic and parasympathetic fibers. This component of postoperative pain is qualitatively distinct, often diffuse and poorly localized, and frequently associated with nausea, ileus, and other autonomic symptoms.

Neuraxial techniques may provide effective visceral analgesia but are invasive, resource-intensive, and associated with potential adverse effects such as hypotension and urinary retention. As a result, many contemporary ERAS pathways have moved away from routine neuraxial analgesia, creating an unmet need for effective, targeted visceral pain control that is compatible with minimally invasive surgical workflows and ERAS principles.

Targeted modulation of autonomic neural pathways involved in visceral afferent transmission represents a potential strategy to address this gap. The superior hypogastric plexus and inferior mesenteric plexus play central roles in transmitting visceral sensory input from the left colon and rectum and are anatomically consistent structures routinely encountered during left-sided colorectal resection. Intraoperative autonomic neural field block targeting these plexuses may offer a mechanistically distinct approach to perioperative analgesia that complements existing somatic-focused techniques.

Description of the Intervention

The autonomic neural field block is performed intraoperatively during elective minimally invasive (laparoscopic or robotic) left-sided colonic or rectal resection with primary anastomosis constructed above the peritoneal reflection. Following establishment of pneumoperitoneum and trocar placement according to surgeon preference, standard minimally invasive dissection is carried out.

Dissection exposes the inferior mesenteric plexus in proximity to the origin of the inferior mesenteric artery and the superior hypogastric plexus at the level of the sacral promontory. These anatomic landmarks are routinely visualized during left-sided colorectal surgery and do not require additional dissection beyond standard operative technique.

An insulin needle connected to an anesthesia extension set is introduced through a 10-12 mm auxiliary port and attached to a syringe containing a diluted local anesthetic solution. All air is purged from the system prior to injection. Each plexus is infiltrated with approximately 5-7 mL of local anesthetic solution, administered incrementally in 1 mL aliquots. Aspiration is performed prior to each injection to confirm the absence of intravascular placement, and adequate tissue infiltration is confirmed visually. The surgical procedure then proceeds according to standard operative practice. When an extraction incision is used, any remaining local anesthetic solution may be infiltrated into the incision prior to closure.

Perioperative Analgesic Management

The autonomic neural field block is intended to complement, rather than replace, established multimodal perioperative analgesic strategies. Additional analgesic interventions, including TAP blocks, non-opioid medications, and opioid administration, are performed according to institutional ERAS protocols and surgeon or anesthesiologist discretion. This pragmatic approach allows evaluation of autonomic neural blockade within real-world clinical environments and across varying perioperative practices.

Study Design and Registry Framework

This study is a prospective, multicenter observational registry designed to systematically collect perioperative analgesic and recovery outcomes in patients undergoing minimally invasive left-sided colectomy who receive an intraoperative autonomic neural field block. The registry is descriptive and hypothesis-generating and does not mandate a comparator group. Use of additional analgesic modalities, including TAP block, is recorded but not standardized.

Participating centers collect perioperative data using standardized case report forms. Data capture includes patient demographics, operative details, analgesic interventions, and postoperative recovery metrics. The registry is designed to facilitate assessment of feasibility, reproducibility, and variability of outcomes across institutions and practice settings.

Outcome Measures

The primary outcome is postoperative opioid consumption, expressed as morphine milligram equivalents (MME), during the first 24 hours following surgery. Secondary outcomes include cumulative opioid consumption during the first 48 postoperative hours, intraoperative analgesic requirements, incidence of postoperative nausea and vomiting, antiemetic use, length of hospital stay, and readiness for discharge based on ERAS-aligned criteria. Patient-reported pain outcomes are collected during hospitalization and through the first postoperative week after discharge.

Safety and Feasibility

Feasibility outcomes include the ability to perform the autonomic neural field block under direct visualization without deviation from standard operative technique or prolongation of operative time. Adverse events potentially related to the intervention, including bleeding, vascular injury, or hemodynamic instability temporally associated with the block, are recorded. The registry does not alter routine postoperative monitoring or follow-up.

Data Analysis and Future Directions

Data from this registry will be summarized using descriptive statistics. The registry is not powered to assess comparative efficacy but is intended to generate preliminary data regarding analgesic patterns, recovery trajectories, and variability across centers. These findings will inform the design of future comparative or randomized studies, refine patient selection, and help define the role of autonomic neural modulation within ERAS-aligned perioperative pain management strategies for colorectal surgery.