A 32-year-old multiparous woman at term is in the second stage of labor. After 1.5 hours of active pushing, the fetal head is at +3 station in the OA position with good flexion. Fetal heart rate is reassuring. The obstetrician decides to perform a low forceps delivery to shorten the second stage. Which is the drug of choice for perineal anesthesia?

## Perineal Anesthesia for Low Forceps Delivery **Key Point:** Bupivacaine 0.5% via pudendal nerve block is the preferred local anesthetic technique for operative vaginal delivery when epidural anesthesia is unavailable or inadequate, because it provides dense perineal anesthesia with longer duration and lower systemic toxicity risk. ### Local Anesthetic Techniques for Operative Vaginal Delivery | Technique | Agent & Concentration | Onset | Duration | Coverage | Toxicity Risk | |-----------|----------------------|-------|----------|----------|---------------| | **Pudendal nerve block** | Bupivacaine 0.5% | 5–10 min | 2–3 hours | Perineum, lower vagina | Low | | **Local infiltration** | Lignocaine 1% | 1–2 min | 30–60 min | Superficial perineum only | Moderate | | **Epidural top-up** | Chloroprocaine 2% | 5–10 min | 30–45 min | Perineum + lower abdomen | Moderate | | **Paracervical block** | Prilocaine 1% | 3–5 min | 1–2 hours | Cervix only (NOT perineum) | High (fetal bradycardia) | **High-Yield:** The **pudendal nerve block with bupivacaine 0.5%** is the **first-line local anesthetic** for operative vaginal delivery because: - Blocks the pudendal nerve (S2–S4), which innervates the perineum, external genitalia, and anal sphincter - Provides dense anesthesia for perineal stretching and episiotomy - Longer duration (2–3 hours) allows time for repair - Lower systemic toxicity (bupivacaine is cardiotoxic but at lower risk with pudendal block dosing: typically 10 mL of 0.5% = 50 mg) - Does NOT cause fetal bradycardia (unlike paracervical block) **Clinical Pearl:** Pudendal nerve block is often combined with perineal infiltration (lignocaine 1%) for additional superficial anesthesia and to reduce the total bupivacaine dose. **Mnemonic:** **PPN** = **P**udendal nerve block with **P**erfect perineal anesthesia for **P**rocedural delivery. **Warning:** Paracervical blocks carry a **high risk of fetal bradycardia** (up to 30% incidence) due to direct fetal absorption and are contraindicated in operative vaginal delivery. Lignocaine infiltration alone provides only superficial anesthesia and is inadequate for forceps application. [cite:Obstetric Anesthesia: Principles and Practice 5e Ch 19; RCOG Green-top Guideline 26]