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Module 2 of 12
Local Anesthesia & Pain Management
By Dr. Yehonatan Kaplan (M.D., Fellow ACMS)Published: 2025-03-01Updated: 2026-03-10Reviewed: 2026-03-10
Learning Objectives
- Compare the pharmacology of commonly used local anesthetics (lidocaine, bupivacaine)
- Calculate maximum safe dosing for lidocaine with and without epinephrine
- Perform named nerve blocks for facial dermatologic surgery
- Apply evidence-based techniques to minimize injection pain
- Understand the rationale and preparation of tumescent anesthesia
Anesthetic Agents
Local anesthetics work by reversibly blocking sodium channels in nerve fibers, preventing depolarization and signal transmission. The two classes. Amides (lidocaine, bupivacaine) and esters (procaine, tetracaine). Differ in metabolism and allergic potential. Amides are metabolized hepatically and true allergies are extremely rare. Esters are hydrolyzed by plasma cholinesterases and can cause allergic reactions via their PABA metabolite.
Lidocaine
Lidocaine is the workhorse of dermatologic surgery. Onset is rapid (1–2 minutes for infiltration), duration is 1–2 hours without epinephrine and 2–4 hours with epinephrine.
Maximum safe dosing:
• Without epinephrine: 4.5 mg/kg
• With epinephrine: 7 mg/kg
For a 70 kg patient using 1% lidocaine (10 mg/mL):
• Without epi: 4.5 × 70 = 315 mg = 31.5 mL
• With epi: 7 × 70 = 490 mg = 49 mL
Clinical Pearls
- 1% lidocaine = 10 mg/mL. A simple conversion for dose calculation
- Lidocaine toxicity presents as perioral numbness, tinnitus, metallic taste → seizures → cardiac arrest at extreme doses
| Property | Without Epinephrine | With Epinephrine |
|---|---|---|
| Onset | 1–2 minutes | 1–2 minutes |
| Duration | 1–2 hours | 2–4 hours |
| Max dose | 4.5 mg/kg | 7 mg/kg |
| Max for 70 kg (1%) | 31.5 mL | 49 mL |
| Concentration | 0.5%, 1%, 2% | 1:100,000 or 1:200,000 |
Bupivacaine
Bupivacaine provides significantly longer duration (4–8 hours) at the cost of slower onset (5–10 minutes). Maximum dose: 2.5 mg/kg with epinephrine. Commonly used as a 0.25% or 0.5% solution. Particularly useful for procedures expected to cause significant postoperative pain or for nerve blocks where prolonged anesthesia is desired.
Cardiotoxicity risk is higher than lidocaine. Bupivacaine binds cardiac sodium channels more avidly and recovery is slower. For this reason, bupivacaine should be used judiciously and never in large volumes.
Important Warnings
- Bupivacaine has a narrower therapeutic index than lidocaine. Cardiac toxicity can occur at lower relative doses
- Intralipid (20% lipid emulsion) should be available when using bupivacaine as rescue therapy for local anesthetic systemic toxicity (LAST)
Epinephrine
Epinephrine (adrenaline) is added to local anesthetics at concentrations of 1:100,000 or 1:200,000. Benefits include: prolonged anesthetic duration, reduced bleeding via local vasoconstriction, slowed systemic absorption (allowing higher total doses), and improved surgical field visualization.
The myth that epinephrine is contraindicated in digits, ears, nose, and penis has been definitively debunked. Multiple large studies and meta-analyses confirm the safety of lidocaine with epinephrine in digital blocks without any reported cases of digital necrosis.
Clinical Pearls
- Epinephrine in digits is safe. The myth persists from the era of procaine + epinephrine, not modern lidocaine formulations
- Wait 7–15 minutes after injection for full vasoconstrictive (hemostatic) effect before incision
Buffering with Sodium Bicarbonate
Commercial lidocaine is acidic (pH 3.5–5.0) for shelf stability. Adding 8.4% sodium bicarbonate at a ratio of 1:10 (1 mL bicarbonate per 10 mL lidocaine) raises the pH to near-physiologic levels, which:
• Significantly reduces injection pain (the acidity of unbuffered lidocaine causes the burning sensation)
• May slightly accelerate onset by increasing the proportion of non-ionized (active) form
Limitation: buffered lidocaine has a shorter shelf life (~1 week refrigerated) and should be prepared fresh.
Topical Anesthetics
EMLA (eutectic mixture of lidocaine 2.5% + prilocaine 2.5%) requires 60-minute application under occlusion for effective anesthesia. LMX (liposomal lidocaine 4–5%) achieves comparable effect in 30 minutes without occlusion. Topical anesthetics are most useful for reducing injection pain in anxious patients and for pediatric procedures.
Injection Techniques & Nerve Blocks
Effective pain control in dermatologic surgery relies on proper technique as much as pharmacologic choice. The following principles and named blocks form the foundation of anesthetic delivery.
Pain Reduction Strategies
Evidence-based techniques to minimize injection discomfort:
Key Points
- Use 30-gauge needles. Thinner gauge = less pain on skin entry
- Inject slowly (30 seconds per mL). Rapid injection distends tissue painfully
- Buffer with sodium bicarbonate (1:10 ratio)
- Warm the anesthetic to body temperature (37°C)
- Apply vibration or ice adjacent to the injection site (gate control theory)
- Inject through wound edges or previously anesthetized tissue when possible
- Distract with conversation or counting
Named Facial Nerve Blocks
Regional nerve blocks provide wide-field anesthesia with minimal tissue distortion. Ideal for Mohs surgery where tissue architecture must be preserved.
Clinical Pearls
- For nasal surgery: bilateral infraorbital blocks + dorsal nasal nerve block provides complete nasal anesthesia
- Always aspirate before injecting near named vessels to avoid intravascular injection
| Block | Target Nerve | Injection Site | Area Anesthetized |
|---|---|---|---|
| Supraorbital / Supratrochlear | V1 branches | Supraorbital notch + medial brow | Forehead, anterior scalp |
| Infraorbital | V2 branch | 1 cm below orbital rim, mid-pupillary line | Cheek, lateral nose, upper lip |
| Mental | V3 branch | Below 2nd premolar at mental foramen | Chin, lower lip |
| Auriculotemporal | V3 branch | Anterior to tragus, above zygomatic arch | Temple, anterior ear |
| Great auricular | C2-C3 | Mid-sternocleidomastoid, Erb’s point | Ear, angle of mandible |
Digital Nerve Block
Digital blocks anesthetize the entire finger or toe. The traditional technique uses two dorsal injections at the web spaces, targeting the paired digital nerves. Inject 1–2 mL of plain lidocaine (without epinephrine historically, though epi is now considered safe) on each side of the digit at the level of the metacarpophalangeal joint.
The single subcutaneous injection technique (transthecal or volar approach) requires only one injection point and is equally effective.
Tumescent Anesthesia
Klein’s tumescent technique uses highly dilute lidocaine (0.05–0.1%) with epinephrine in large volumes of normal saline to achieve widespread anesthesia with excellent hemostasis. Originally developed for liposuction, it is valuable in dermatologic surgery for large excisions, extensive Mohs cases on the scalp, and large flap reconstructions.
Standard formula: 500–1000 mL normal saline + 25–50 mL of 1% lidocaine with epi + 12.5 mL of 8.4% sodium bicarbonate. This produces a final lidocaine concentration of approximately 0.05–0.1%.
The slow systemic absorption from tumescent delivery allows total lidocaine doses up to 55 mg/kg. Far exceeding the standard 7 mg/kg limit. Peak plasma levels occur 12–14 hours post-injection.
Clinical Pearls
- Tumescent technique is excellent for large scalp Mohs cases. Provides both anesthesia and hemostasis
- The blanching and turgor of tumescent tissue indicate adequate delivery
Related Tools & Resources
References
- [1]Robinson JK, Hanke CW, Siegel DM, Fratila A. Surgery of the Skin: Procedural Dermatology, 3rd Edition. Elsevier. 2019.
- [2]Zide BM, Swift R. How to block and tackle the face: Sensory and motor nerve blocks. Plast Reconstr Surg. 2006. doi:10.1097/01.prs.0000185866.98032.d3
About This Article
Author: Dr. Yehonatan Kaplan, M.D., Fellow ACMS
Last Medical Review:
Audience: Dermatologic Surgeons
Clinic: Kaplan Clinic · DermUnbound Research Program