Effect of Deep Neuromuscular Blockade and a Preoperative Low-Residue Diet on Intra-operative Surgical Field Conditions During Vaginal Natural Orifice Transluminal Endoscopic Surgery (vNOTES) Hysterectomy: A 2×2 Factorial, Assessor-Blinded Randomized Controlled Trial

The field is scored with the vNOTES-OVI, a 3-point index (0 = inadequate, 1 = adequate only with instrument bowel-retraction, 2 = optimal/clear), adapted for vNOTES from the team's prior objective visualisation index in conventional laparoscopy. At each 1 mmHg step a 3-second clip is recorded with a fixed scanning choreography (right adnexa → midline/cephalic boundary → left adnexa); the consensus (median) of the blinded assessors defines, per participant, the lowest pressure at which the field is adequate (OVI ≥ 1; primary) and at which it is optimal (OVI = 2; secondary).

Deep relaxation is rocuronium by continuous infusion to a post-tetanic count of 1-2 (no train-of-four twitches); standard relaxation is rocuronium by intermittent bolus to a train-of-four count of 1-2. Relaxation depth is monitored quantitatively and fully reversed (train-of-four ratio ≥ 0.9 confirmed) before extubation in every participant; the reversal agent is sugammadex in all four groups (neostigmine is not used), and because sugammadex dosing follows block depth (≈ 2 mg/kg moderate, ≈ 4 mg/kg deep) the dose differs by the NMB factor by necessity, so it is recorded per participant and reported by arm (collinear with NMB depth, it is examined only in a sensitivity analysis, not added as a covariate to the factorial nausea model). The step-down field measurement descends from 12 mmHg to 6 mmHg in 1 mmHg steps with a 60-second equilibration at each step. The preoperative low-residue diet (diet arms) restricts daily intake to less than 10 g of dietary fibre for the three days before surgery - permitting refined grains, well-cooked or canned skinless and seedless vegetables, peeled or canned fruit, tender meat, fish, eggs, and moderate dairy, while avoiding whole grains, raw fruits and vegetables, legumes, nuts, seeds, and dried fruit - and participants receive a written diet information sheet; no group receives mechanical bowel preparation. The primary outcome is assessor-blinded (assessors score de-identified video with pressure and group removed); the operating surgeon is blinded to allocation and the data analyst analyses with groups coded; the anaesthesia team is necessarily unblinded to relaxation depth but does not score the outcome. The internal pilot (≈ 10-15 per group) is used for blinded sample-size re-estimation; detecting an interaction typically requires several times the sample size of a main effect.