Peroral Endoscopic Myotomy (POEM) has become an established, minimally invasive therapy for achalasia and esophageal motility disorders. Submucosal tunnelling is a critical phase of POEM and requires meticulous haemostasis to avoid bleeding, loss of orientation, reduced visibility, and prolonged procedural time.

The current standard method of vessel coagulation during POEM involves conventional coagulation under CO₂ insufflation using the hybrid knife (HK). However, this approach can require additional hemostatic devices-most commonly coagulation forceps-particularly when dealing with large-calibre vessels or resistant bleeding.

A novel technique-underwater preventive coagulation-leverages water as a conductive medium. Preliminary evidence suggests that:

• electrosurgical current in water is focalized at the interface of the vessel,
• allowing a soft sealing of the vessel wall,
• reducing the risk of vessel rupture or unintended deep thermal injury,
• and potentially eliminating the need to convert to coagulation forceps. Pilot data from our center demonstrate that underwater prophylactic sealing of large vessels during POEM is feasible, safe, and associated with markedly reduced need for rescue coagulation forceps. The technique is already used in practice but lacks systematic evidence from prospective randomized trials.

This study is designed to provide high-quality evidence on whether underwater vessel coagulation improves haemostatic efficiency, reduces intra-procedural bleeding, and minimizes device changes during POEM.

All POEM procedures will be performed under general anesthesia in the supine position using Fujifilm high-definition gastroscopes with a 2.8 mm channel and transparent distal cap.

Steps (Both Arms)

1. Identify the esophagogastric junction (EGJ).

2. Inject saline + methylene blue submucosally.

3. Create a 2 cm mucosal incision at 5-6 o'clock position, 10 cm above EGJ.

4. Enter the submucosal space.

5. Perform submucosal tunnelling down to EGJ and 2-3 cm into cardia.

6. Perform vessel haemostasis according to group allocation:

   • Underwater coagulation (intervention)
   • CO₂-based conventional coagulation (control)

7. Perform circular myotomy (with occasional full-thickness myotomy when indicated).

8. Close the mucosal entry using hemostatic clips.

9. Record procedure time, instrument exchanges, bleeding events, and forceps usage.

Equipment

• Hybrid Knife (Erbe Elektromedizin GmbH)
• VIO 3 generator + ERBEJet 2 water-jet system
• Methylene-blue tinted saline
• Electrosurgical settings: ENDO CUT Q 2-3-3 for mucosal incision and myotomy

Primary Objective

To compare the proportion of POEM patients requiring rescue haemostasis with coagulation forceps (for active bleeding) between:

1. Underwater preventive vessel coagulation, and 2. Conventional vessel coagulation under CO₂ insufflation. Secondary Objectives

1. To compare composite forceps use (rescue + prophylactic) between groups.
2. To evaluate the frequency of prophylactic-only forceps use.
3. To compare total number of forceps applications per procedure.
4. To determine differences in intra-procedural bleeding episodes.
5. To compare procedural efficiency (procedure time, number of instrument exchanges).
6. To compare hematological and inflammatory markers (Hb drop, Hct, CRP, WBC).
7. To compare delayed bleeding rates within 30 days.
8. To evaluate overall complication rates (intra- and post-procedural).
9. To assess patient-reported outcomes (pain, tolerability). A prospective, randomized, open-label, parallel-group, controlled clinical trial.

Study Arms Intervention Arm: Underwater Coagulation

• Vessel coagulation performed entirely underwater using the Hybrid Knife.
• SWIFT COAG: E3 (89 W) for POEM.
• Physiological saline instilled to completely displace air around the target vessel.

Control Arm: Conventional Coagulation (CO₂ Setting)

• Standard vessel isolation and coagulation under CO₂ insufflation.
• SWIFT COAG: E3 (89 W) for POEM.

Inclusion Criteria:

1. Age ≥ 18 years
2. Diagnosis of achalasia or esophageal motility disorder planned for POEM
3. Ability to provide informed consent

Exclusion Criteria:

1. Anticoagulant or antithrombotic therapy not safely stoppable
2. Known coagulopathy or platelet disorder
3. Esophageal/gastric varices
4. Previous POEM or Heller's myotomy
5. Prior treatment for same condition
6. Inability or refusal to consent
7. Visualized vessels smaller than the HK inner diameter (1.2 mm)

120 (60 in each arm)