What is the proper technique for performing a dorsal penile block on a patient, considering their medical history and potential complications?

Dorsal Penile Block Technique

Anatomical Approach and Needle Placement

The subpubic (median) approach is the preferred technique, involving a single midline injection into the subpubic space where the dorsal penile nerves run before entering the base of the penis. 1

Subpubic (Median) Technique - Recommended Primary Approach

• Insert a short bevel needle in the midline at the base of the penis, directing it toward the posterior inferior aspect of the symphysis pubis 1, 2
• The needle enters the subpubic space where bilateral diffusion of local anesthetic has been demonstrated in 100% of patients when contrast medium was added 2
• This single-injection technique targets both dorsal penile nerves simultaneously in the fascial compartment 1
• Aspirate before injection to avoid intravascular administration 3

Alternative Bilateral Technique

• Each dorsal penile nerve can be blocked separately at the penile root using injections at the "10 o'clock and 2 o'clock" positions 4, 2
• This approach may be preferred in adults as contralateral diffusion with unilateral injection occurs in only 60% of patients 2
• However, the bilateral technique requires two punctures versus one with the median approach 2

Supplemental Infiltration

• Add subcutaneous infiltration of the penile root circumferentially to improve analgesia quality, as the ventral penile nerves also require coverage 2
• This can be performed as a ring block around the base of the penis 4

Local Anesthetic Selection

Use bupivacaine 0.25-0.5% without epinephrine as the first-line agent for prolonged postoperative analgesia lasting approximately 10 hours. 3, 1, 2

Dosing Guidelines

• Bupivacaine: Maximum dose 1.3 mg/kg without epinephrine or 3.0 mg/kg with epinephrine 3
• Lidocaine: Maximum dose 4.4 mg/kg without epinephrine or 7.0 mg/kg with epinephrine (shorter duration than bupivacaine) 3, 1
• Ropivacaine 0.2%: Alternative with intermediate duration, maximum 2.0 mg/kg without epinephrine or 3.0 mg/kg with epinephrine 3
• Volume: Use 0.1 mL/kg body weight for the subpubic injection 1
• Calculate total dose in mg/kg before administration to prevent local anesthetic systemic toxicity 3

Critical Safety Consideration Regarding Ropivacaine

• Avoid ropivacaine 0.75% concentration due to a reported case of temporary glans ischemia occurring 40 minutes post-injection, requiring treatment with intravenous iloprost 5
• Theoretical vasoconstrictive properties of ropivacaine at higher concentrations may pose ischemia risk to end organs 5

Epinephrine Controversy - Evidence-Based Update

Contrary to traditional teaching, epinephrine can be safely added to local anesthetic for penile blocks based on recent evidence. 3, 6

Supporting Evidence

• A retrospective study of 95 patients receiving penile ring blocks with ropivacaine/lidocaine plus epinephrine showed zero anesthetic-related complications 6
• Benefits include prolonged anesthetic effect, reduced bleeding, improved surgical field visualization, and relatively painless infiltration 6
• No necrosis related to epinephrine use occurred due to the rich vascular anatomy of the penis 6

Practical Recommendation

• If using epinephrine, employ the lowest effective concentration (typically 1:200,000) 3
• Have lipid emulsion available for treatment of local anesthetic systemic toxicity 3

Ultrasound Guidance Option

Ultrasound guidance can improve accuracy by precisely targeting the dorsal penile nerves in the fascial compartment just deep to Buck fascia. 3, 4

• This technique potentially increases block success rates and reduces required local anesthetic volumes compared to landmark-based approaches 4
• Traditional landmark-based techniques may require up to 50 mL of local anesthetic due to technical imprecision 4
• Ultrasound visualization prevents inadvertent injection into the corpora cavernosa 4

Adjunctive Measures

• Add sodium bicarbonate to local anesthetic to reduce pain during infiltration 3
• Combine with multimodal analgesia including NSAIDs and acetaminophen for optimal pain control 3

Technique Success and Safety Profile

• The subpubic approach was successful in 100% of 100 pediatric patients in a prospective evaluation 1
• In 80 adult patients, only 3 of 33 receiving additional sedation/general anesthesia had partial block failure 2
• Venous blood reflux may occur (4% in one series), requiring needle withdrawal and reinsertion 1
• No complications occurred in the landmark-based series when proper technique was followed 1, 2

Contraindications

• Active systemic, cutaneous, or urinary tract infection 7
• Known allergy to local anesthetics being used 3