Bilateral Dorsal Penile Nerve Block: Technique and Safety
For bilateral dorsal penile nerve block, use 0.2-0.5% bupivacaine or ropivacaine at a maximum dose of 2.5 mg/kg (bupivacaine) or 3 mg/kg (ropivacaine), injected at the base of the penis in the subpubic space, avoiding midline dorsal vessels and the ventral urethra. 1
Anesthetic Choice and Dosing
Preferred Local Anesthetics
Ropivacaine is the preferred agent due to lower systemic toxicity and reduced motor blockade compared to bupivacaine 2. The most recent pediatric guidelines (2025) specifically recommend ropivacaine as the primary choice across all regional blocks 2.
Specific Dosing Recommendations
For peripheral nerve blocks including penile block:
- Bupivacaine 0.25%: Maximum 1 ml/kg (= 2.5 mg/kg) 1
- Levobupivacaine 0.25%: Maximum 1 ml/kg (= 2.5 mg/kg) 1
- Ropivacaine 0.2%: Maximum 1.5 ml/kg (= 3 mg/kg) 1
For adults: A 2025 study demonstrated safe use of 20 ml of 0.25% bupivacaine (50 mg total) for dorsal penile nerve and ring block 3. Another adult case used 20 ml of 0.25% bupivacaine successfully 4.
Volume Considerations
Use 0.1 ml/kg body weight for the subpubic approach, divided between two injection sites 5. This low-volume technique is effective because precise perineural administration doesn't require complete circumferential spread 2.
Injection Technique
Anatomical Approach
The subpubic space technique involves two punctures:
- Insert a short-bevel needle into the two compartments of the subpubic space where dorsal nerves run before entering the penile base 5
- Inject at the 2 o'clock and 10 o'clock positions at the base of the penis to avoid midline dorsal blood vessels/nerves and the ventral urethra 6
Ultrasound Guidance
Ultrasound guidance is recommended as the current gold standard for regional blocks, allowing direct visualization of anatomic structures and reducing complications 2. A 2025 pediatric study confirmed ultrasound-guided dorsal penile nerve block (DPNB) effectiveness 7.
Safety Precautions
Critical Dosing Errors to Avoid
Never exceed maximum recommended doses. A 2025 case report documented severe local anesthetic systemic toxicity (LAST) when 2000 mg lignocaine was administered instead of the intended 200 mg, resulting in hallucinations, vision loss, and requiring intubation 8. This emphasizes the importance of:
- Calculate dose based on mg/kg before drawing up medication
- Double-check concentration and volume calculations
- Use ideal body weight for obese patients 9
Maximum Safe Doses
With epinephrine:
Without epinephrine:
In infants <6 months: Reduce amide local anesthetic doses by 30% due to immature hepatic clearance 10, 2.
Epinephrine Use
Epinephrine can be safely added to penile blocks. A retrospective study of penile ring blocks during circumcision showed no anesthetic-related complications with epinephrine use [11, @69@]. The 2016 dermatologic surgery guidelines support epinephrine use for penile skin surgery, though studies remain limited 11.
Vascular Precautions
If venous blood reflux occurs, withdraw and reinsert the needle 5. Avoid intravascular injection by:
- Aspirating before injection
- Injecting slowly
- Avoiding the midline dorsal neurovascular bundle
Recognition and Treatment of LAST
Local anesthetic systemic toxicity occurs in 8 per 100,000 pediatric regional procedures 2. Manifestations include:
- Loss of consciousness
- Tonic-clonic convulsions
- Bradycardia, tachyarrhythmias, or asystole
Treatment protocol:
- Immediate lipid emulsion therapy: 20% Intralipid at 1.5 ml/kg over 1 minute 2
- Continuous infusion: 0.25 mg·kg⁻¹·min⁻¹ 2
- Repeat boluses: Twice at 5-minute intervals if needed 2
- Standard resuscitation measures
- Have lipid emulsion readily available wherever blocks are performed 9
Timing with Other Local Anesthetics
Do not perform penile block within 4 hours of other local anesthetic interventions to avoid cumulative toxicity 9. Similarly, don't start other nerve blocks until 4 hours after discontinuing any local anesthetic infusion 9.
Duration of Analgesia
Bupivacaine provides significantly longer postoperative pain relief than lidocaine 5. Expected durations:
Adjuvants for Extended Duration
Dexmedetomidine (1-2 µg/kg) can extend block duration 2. A 2025 study showed that adding dexmedetomidine (70 µg) plus dexamethasone (4 mg) to bupivacaine significantly improved analgesia and reduced opioid consumption for 24 hours after penile prosthesis surgery 3.
Special Populations
Pediatric Considerations
Age-specific pharmacokinetics matter. Neonates and infants <6 months have:
- Reduced hepatic clearance of local anesthetics 10, 2
- Larger free drug fractions increasing toxicity risk 2
- Prolonged elimination half-lives 2
Former preterm infants require extended post-procedure monitoring due to altered drug metabolism and increased apnea risk 10.
Patients on Anticoagulation
Exercise caution but penile block is not absolutely contraindicated. The risk of hematoma formation is lower than with deep blocks, but monitor for bleeding complications 12.