Pudendal Nerve Block Techniques for Pain Control After Hemorrhoidectomy

Context, rationale and hypothesis: Hemorrhoidectomy remains one of the most painfulambulatory surgical procedures, frequently associated with substantial postoperativeopioid consumption despite multimodal analgesia. This persistent nociceptive burden hasdirect implications for delayed recovery, unplanned admissions, and opioid‐relatedadverse events. Consequently, optimizing regional analgesic strategies is a prioritywithin enhanced recovery pathways.Pudendal nerve block (PNB), targeting sacral roots S2‐S4, has emerged as an effectiveadjunct for postoperative analgesia in anorectal surgery. Randomized trials andmeta‐analyses consistently demonstrate reductions in pain scores and opioid requirementswhen PNB is incorporated into perioperative care. However, these studies encompassheterogeneous techniques, and critically, do not address whether the anatomical level ofblockade influences clinical efficacy.From a mechanistic perspective, the pudendal nerve divides into its terminal branches‐theinferior rectal, perineal, and dorsal genital nerves‐after traversing the region of theischial spine and entering Alcock's canal. The inferior rectal nerve, which provides theprincipal sensory innervation to the anal canal and perianal region, typically branchesproximally before the pudendal nerve courses distally within the pudendal canal. Thisanatomical arrangement suggests that distal approaches to PNB, such as the transperinealtechnique, may incompletely anesthetize the inferior rectal nerve due to injection beyondthe point of branching or variable spread within the ischiorectal fossa.In contrast, the posterior transgluteal approach targets the pudendal nerve at a moreproximal location, near the ischial spine and sacrospinous ligament, where the nerveremains a single trunk. Ultrasound guidance at this level enables precise deposition oflocal anesthetic before division into terminal branches, theoretically ensuring a moreconsistent and comprehensive blockade, including the inferior rectal nerve. Thisdistinction in injection level‐proximal versus distal‐represents a fundamental butunderexplored determinant of block success.Despite increasing adoption of ultrasound‐guided regional anesthesia, there is a strikingabsence of randomized controlled trials directly comparing proximal (transgluteal) anddistal (transperineal) approaches to PNB in the context of hemorrhoidectomy. Existingevidence is therefore insufficient to determine whether improved anatomical coveragetranslates into superior clinical analgesia or reduced opioid consumption.Addressing this gap is clinically relevant for several reasons. First, inadequateblockade of the inferior rectal nerve may contribute to residual pain during defecation,a key determinant of patient dissatisfaction after hemorrhoidectomy. Second, identifyinga more reliable and reproducible technique could standardize PNB within perioperativeprotocols. Third, demonstrating superiority of a proximal approach would support broaderintegration of ultrasound‐guided regional techniques into opioid‐sparing strategies.The present trial is designed to test the hypothesis that a proximal, ultrasound‐guidedtransgluteal PNB provides superior postoperative analgesia compared with a distaltransperineal approach. By directly comparing these techniques in a randomized controlledsetting, this study seeks to determine whether anatomical optimization of nerve blockadetranslates into meaningful clinical benefit.Originality and innovative aspects: Hemorrhoidectomy remains associated with significantpostoperative pain, often requiring substantial opioid consumption. Pudendal nerve block(PNB), targeting nerve roots from S2‐S4, has demonstrated efficacy in reducingpostoperative pain and opioid requirements. Anatomically, the pudendal nerve gives riseto the inferior rectal, perineal, and dorsal genital nerves. The effectiveness of PNBdepends on the level of injection: ‐ Transgluteal (proximal) approach: blockade at the level of the ischial spine beforenerve branching ‐ Transperineal (distal) approach: injection within or near Alcock's canal afterbranching The distal approach may spare the inferior rectal nerve, leading tosuboptimal anorectal analgesia. In contrast, the proximal ultrasound‐guidedtechnique may provide a more complete and reliable block.To date, no randomized controlled trial has directly compared proximal (transgluteal) anddistal (transperineal) approaches to pudendal nerve block in hemorrhoidectomy, despiteclear anatomical rationale suggesting differences in nerve coverage and analgesicefficacy.Methods This study is a prospective, Randomized, Controlled, Parallel‐group , Superioritytrial, Assessor‐blinded The protocol follows SPIRIT recommendations, and reporting willadhere to CONSORT guidelines Setting The study will be conducted at VinMec InternationalHospital, Can THo, Vietnam. Interventions Control Group (Standard Management): Transperineal Group (Distal PNB) Spinal anesthesia protocol standardized; Ultrasound‐guidedtransperineal approach ; Injection in rectoperineal/ischiorectal fossa; Bilateral;Ropivacaine 0. 5%, 8 mL per side; Oral Paracetamol 500 mg every 6 hours; Oral Celecoxib200 mg every 12 hours ( if no contra‐indication); Rescue opioids if NRS pain values >3/10converted to MME Intervention Group: Transgluteal Group (Proximal PNB) General anesthesiaprotocol standardized; Ultrasound‐guided posterior approach; Injection near ischialspine/sacrospinous ligament; Bilateral; Ropivacaine 0. 5%, 6 mL per side; OralParacetamol 500 mg every 6 hours; Oral Celecoxib 200 mg every 12 hours (if nocontra‐indication); Rescue opioids if NRS pain values >3/10 converted to MMEThe Block Techniques:Transperineal Approach Patient Positioning The patient is placed in the lithotomyposition with slight hip abduction. Adequate exposure of the perineum is ensured understrict aseptic conditions.Ultrasound Equipment and Probe Position A high‐frequency linear transducer (10‐18 MHz) isused. The probe is placed: Transversely or slightly oblique; On the perineum, lateral tothe external anal sphincter; Over the ischio‐rectal fossa.Sonoanatomy Key structures to identify include: External anal sphincter (mediallandmark); Ischioanal (ischiorectal) fossa (hypoechoic fat‐filled space); Obturatorinternus muscle (lateral boundary); Internal pudendal artery (identified using colorDoppler). The pudendal nerve is often not directly visualized, but lies medial to theinternal pudendal artery and within or near Alcock's (pudendal) canal Needle InsertionApproach: in‐plane, typically medial to lateral; Needle: 50mm echogenic needle advancedto the ischioanal fossa, adjacent to the internal pudendal artery.Injection 8 mL of local anesthetic is injected per side. The spread should be observedwithin the ischioanal fossa Controlled by Color echo Doppler to prevent IV injection.Transgluteal Approach Patient Positioning The patient is placed in the prone position (orlateral decubitus if needed). The gluteal region is exposed and prepared under sterileconditions.Ultrasound Equipment and Probe Position A low‐frequency curvilinear probe (2‐5 MHz) or ahigh‐frequency probe in lean patients may be used.The probe is positioned transversely over the gluteal region, at the level of the ischialspine Sonoanatomy Key landmarks: Ischial spine (hyperechoic bony structure with acousticshadow); Sacrospinous ligament; Sacrotuberous ligament; Internal pudendal artery(identified with Doppler). The pudendal nerve is located medial and posterior to theinternal pudendal artery between the sacrospinous and sacrotuberous ligaments. It mayappear as a small hyperechoic oval structure, although visualization is variable.Needle Insertion Approach: in‐plane, usually lateral‐to‐medial; Needle: 50 or 80 mmechogenic needle. The needle is advanced through the gluteal muscles, toward the ischialspine region, Into the interligamentous plane (between sacrospinous and sacrotuberousligaments) Injection 6 mL of local anesthetic is injected per side. The spread of LAexpands of the interligamentous space, circumferential spread around the pudendal arterycontrolled by Color echo doppler Sample Size: Assuming a mean 48h opioid consumption at60 mg MME with a standard deviation: 30 mg and a clinically meaningful difference of 15mg (25% reduction) with an Alpha risk : 0.05 (two‐sided) and a β risk Power: 80%, therequired sample is 64 patients per group. Accounting for 10% dropout the Total samplesize: 140 patients (70 per group).Analysis of the Population: Intention‐to‐treat (ITT) (primary analysis) and Per‐protocol(sensitivity analysis) Descriptive Statistics: Continuous variables: mean ± SD or median(IQR) and Categorical variables: n (%)Primary Outcome Analysis:Comparison of cumulative MME at 48 h: If normally distributed → Student's t‐test; Ifnon‐normal → Mann‐Whitney U test Additionally: Linear regression adjusted for: Age, Sex,Surgical technique, Baseline pain Effect size: Mean difference with 95% confidenceintervalSecondary Analyses :Pain scores (repeated measures): Mixed‐effects linear models ; Fixed effects: group,time, group × time interaction; Random intercept for patientTime‐to‐event outcomes:Time to first opioid: Kaplan‐Meier analysis; Log‐rank test; Cox proportional hazardsmodelCategorical outcomes:Chi‐square or Fisher's exact test; Report relative risks with 95% CIContinuous outcomes:t‐test or Mann‐Whitney depending on distribution Handling Missing Data : Multipleimputation if >5% missing; Sensitivity analyses Significance Threshold : p < 0.05(two‐sided) Randomization Randomization and Blinding : Allocation ratio: 1:1;Computer‐generated random sequence with variable block sizes; Allocation concealment viasecure electronic systemBlinding:The patients are blinded; Outcome assessors: blinded; Data analysts: blinded; Performinganesthesiologist: not blinded Data Collection Methods: Pain opiates consumption andfunctional outcomes will be assessed at predefined time points using scales and validatedquestionnaires: NRS pain score at rest and during movement, .Lickert scale for patientsatisfaction, consumption of rescue analgesia opiates (MME), Brief Pain Inventory and QOR15 form. Data will be collected during follow‐up visits or via structured interviews.