How do I perform a dorsal penile nerve block in a 70‑kg adult, including appropriate local anesthetic dosing and technique?

Dorsal Penile Nerve Block Technique in Adults

For a 70-kg adult, perform a dorsal penile nerve block using 10-20 mL of 0.25% bupivacaine (or 1% lidocaine with epinephrine 1:100,000-1:200,000), injected at the 10 and 2 o'clock positions at the base of the penis, just deep to Buck's fascia, with a maximum total dose not exceeding 200 mg of lidocaine or 175 mg of bupivacaine to avoid local anesthetic systemic toxicity.

Dosing Calculations for 70-kg Adult

Maximum Safe Doses

• Lidocaine with epinephrine: 7 mg/kg = 490 mg maximum (49 mL of 1% solution)
• Bupivacaine: 2.5 mg/kg = 175 mg maximum (70 mL of 0.25% solution)
• Practical volume for penile block: 10-20 mL total is typically sufficient 1, 2

Recommended Anesthetic Solutions

• Option 1: 10-20 mL of 0.25% bupivacaine (25-50 mg total dose) 1, 2
• Option 2: 10-20 mL of 1% lidocaine with epinephrine 1:100,000-1:200,000 3
• Consider buffering: Add sodium bicarbonate to reduce injection pain 4

Step-by-Step Technique

Landmark-Based Approach

1. Patient positioning: Supine with penis retracted cephalad
2. Injection sites: 10 o'clock and 2 o'clock positions at the penile base, just below the pubic symphysis
3. Needle insertion: Insert perpendicular to skin, advancing through:
   • Skin
   • Dartos fascia
   • Buck's fascia (you'll feel a "pop")
4. Injection depth: Just deep to Buck's fascia where dorsal nerves run
5. Volume distribution: 5-10 mL per side (total 10-20 mL)
6. Aspiration: Always aspirate before injection to avoid intravascular injection

Ultrasound-Guided Approach (Preferred When Available)

• Probe placement: High-frequency linear probe at penile base in transverse orientation
• Target visualization: Dorsal penile nerves appear as hypoechoic structures just deep to Buck's fascia
• Advantage: Precise needle placement reduces required volume and increases success rate 5
• This technique allows direct visualization of the fascial compartment and avoids inadvertent injection into corpora cavernosa 5

Critical Safety Considerations

Avoid Toxic Dosing

A recent 2025 case report documented severe local anesthetic systemic toxicity when 2000 mg of lidocaine was mistakenly administered instead of 200 mg, resulting in hallucinations, vision loss, and requiring intubation 6. Always double-check your dose calculation before drawing up medication.

Epinephrine Use

Despite historical concerns, epinephrine-containing local anesthetics are safe for penile blocks 4, 3. A 2014 study of 95 patients using ropivacaine/lidocaine with epinephrine showed no anesthetic complications and no necrosis 3. The 2016 AAD guidelines give this a Grade B recommendation based on Level II evidence 4.

Benefits of epinephrine include:

• Prolonged anesthetic duration
• Reduced bleeding and improved surgical field
• Decreased systemic absorption
• Extended postoperative analgesia 3

Onset and Duration

• Onset: 5-10 minutes
• Duration:
  • Lidocaine with epinephrine: 2-4 hours
  • Bupivacaine: 4-8 hours 1
  • With adjuvants (dexmedetomidine/dexamethasone): up to 24 hours 2

Common Pitfalls to Avoid

1. Excessive volume: Using 50 mL volumes is unnecessary and increases toxicity risk; 10-20 mL is adequate 5
2. Intracorporal injection: Aspirate before injecting to avoid injection into corpora cavernosa
3. Dose calculation errors: Always calculate maximum safe dose based on patient weight before drawing up medication 6
4. Inadequate depth: Injection must be deep to Buck's fascia where nerves run; superficial injection will fail
5. Skipping buffering: Adding sodium bicarbonate significantly reduces injection pain (Grade A recommendation) 4

Expected Efficacy

Studies show 67% of patients report no procedural pain, with 87% satisfaction rates when properly performed 7. The block provides adequate surgical anesthesia without requiring general anesthesia in most cases 7.