Ultrasound guided dorsal penile vs pudendal nerve blocks for circumcision
Myron Yaster MD, Rita Agarwal MD, Fabian Okonski MDI
It’s really hard to believe that until the mid 1980s most physicians believed that the newborn neither experienced nor remembered pain. In its extremes this led to surgery without anesthesia. A breakthrough, game changing study by Lynne Maxwell and colleagues1 forever changed that notion. In her study, newborns undergoing circumcision either received a penile nerve block or not. The study conclusively showed that the newborn did experience pain and the pain could be blocked/prevented with anesthesia (the penile nerve block).
The penile nerve block in the Maxwell et al.1 study was performed using surface landmarks. In today’s PAAD, Boisvert-Moreau et al.2 compared ultrasound guided penile vs ultrasound guided pudendal nerve blocks for circumcision. The ultrasound images in the article are terrific. I must admit though, that I was spectacularly unsuccessful when I tried to identify the penile nerves using ultrasound and fell back to simply using surface landmarks. Additionally, the ultrasound technique requires a second pair of hands to retract the penis while doing the block. I concluded “why bother”? I’m curious what you do in your practice. I ( RA) asked my colleague at Stanford and Lucile Packard Children’s Hospital Dr Fabian Okonski to comment on this, as someone who has had a lot of experience with both these blocks using U/S, nerve stimulation (pudendal blocks) and surface anatomy techniques. His comments are listed below the article review.
PS: Dr. Lynne Maxwell did her penile block study while a fellow at the Johns Hopkins Hospital and went on to having a remarkable career. She is a Robert M. Smith award winner and a regular contributor to the PAAD. MY
Original article
Frédérique Boisvert-Moreau , Bruno Turcotte, Natalie Albert, Narcisse Singbo, Katherine Moore, Ariane Boivin. Randomized controlled trial (RCT) comparing ultrasound-guided pudendal nerve block with ultrasound-guided penile nerve block for analgesia during pediatric circumcision. Reg Anesth Pain Med. 2023 Mar;48(3):127-133. PMID: 36396298
Circumcision remains one of the most common surgical procedures performed in North America. How best to provide anesthesia and analgesia remains to be determined. Some advocate for caudal blockade, others for dorsal penile nerve (or ring) block, and more recently ultrasound guided, out of plane, pudendal nerve block.3 A previous study by Tutuncu et al.4 comparing ultrasound guided pudendal nerve block to surface landmark dorsal penile nerve block found that the pudendal nerve block provided better analgesic efficiency compared to the penile nerve block and lasted for 24 hours after operation. In today’s PAAD, the authors compared ultrasound guided penile dorsal nerve block to ultrasound guided pudendal nerve block.
For those of you who are unfamiliar with these techniques, the ultrasound images and the description of how to do the blocks in this article are terrific. What did they find? Both techniques work and provide equal post operative analgesia. Intraoperatively, the dorsal penile nerve block comes on faster than the pudendal nerve block. Finally, surgeons preferred the pudendal nerve block because unlike the penile nerve block, local anesthetic diffusion in subcutaneous tissues did not distort the surgical anatomy.
I (MY) must admit that I am unconvinced that ultrasound guidance for the penile nerve block is worth the effort. Further, using surface landmarks at the END of the case will minimize surgeon dissatisfaction with distortion of the surgical anatomy and because of its speed of block onset should not negatively affect post operative analgesia.
Fabian Okonski: In our practice, it is routine for the surgeon to do a dorsal penile nerve block using the traditional landmark approach prior to circumcision. However, the efficacy is far from perfect. This is most likely due to 1. the inaccuracy of the landmark approach, and 2. incomplete coverage of the ventral surface of the penis by the DPN. Since the ventral surface likely has significant contribution from branches of the perineal nerve, complete anesthesia of the foreskin/glans area is best accomplished with a proximal block such as the pudendal block (before the bifurcation of the dorsal penile nerve and the perineal nerve) or more commonly, DPN block in conjunction with ventral infiltration of local. Earlier descriptions of incomplete anesthesia using DPN block alone substantiate this. This recent paper refutes this assertion, claiming equivalence of DPN block and pudendal. Hmmm. Who is right?
It can be difficult to reliably feel the "pop" necessary to identify passage of Bucks fascia using sharp hypodermic needles. It is likely that many of these traditional DPN blocks fail due to poor placement. Ultrasound for this block is also challenging, however, fortunately the nerves themselves do not need to be visualized, rather simply depositing local anesthetic near the dorsal arteries bilaterally, below Bucks fascia essentially guarantees success. Studies do substantiate this.
But this is where the pudendal nerve block shines. It is relatively easy to perform and very reliable. Also, it appears to last longer than both DPN or caudal blocks. The greatest success rate comes from combining nerve stimulation with ultrasound guidance. This is my approach when doing pudendal blocks for hypospadias surgery, though the ultrasound only approach has many adherents.
Is an ultrasound guided pudendal nerve block, or ultrasound guidance for DPN worth the trouble for circumcision? Hard to say, though my personal opinion is that if you are going to bother with nerve blocks, then near 100% efficacy should be the goal. Circumcision pain has been managed relatively effectively without these "fancy" techniques for decades, so yes maybe all that is too much for little gain. It is important, though, to NOT extend this seemingly reasonable success to more complex penile surgery. DPN block, with or without ultrasound, is not, in my opinion, adequate for hypospadias surgery or other complex repairs. Pudendal block or caudal block is far more likely to achieve good anesthesia/analgesia in that setting.
What do you think? Let Myron know and he’ll post in a reader response.
References
1. Maxwell LG, Yaster M, Wetzel RC, Niebyl JR. Penile nerve block for newborn circumcision. ObstetGynecol. 1987 1987;70(3 Pt 1):415-419. Not in File.
2. Boisvert-Moreau F, Turcotte B, Albert N, Singbo N, Moore K, Boivin A. Randomized controlled trial (RCT) comparing ultrasound-guided pudendal nerve block with ultrasound-guided penile nerve block for analgesia during pediatric circumcision. Regional anesthesia and pain medicine. Mar 2023;48(3):127-133. doi:10.1136/rapm-2022-103785
3. Gaudet-Ferrand I, De La Arena P, Bringuier S, et al. Ultrasound-guided pudendal nerve block in children: A new technique of ultrasound-guided transperineal approach. Paediatric anaesthesia. Jan 2018;28(1):53-58. doi:10.1111/pan.13286
4. Tutuncu AC, Kendigelen P, Ashyyeralyeva G, et al. Pudendal Nerve Block Versus Penile Nerve Block in Children Undergoing Circumcision. Urol J. May 3 2018;15(3):109-115. doi:10.22037/uj.v0i0.4292