Effect of Caudal and Penile Block on Hypospadias Repair Complications
Effect of Caudal and Penile Block on Hypospadias Repair Complications
Hypospadias is one of the most common genitourinary (GU) malformations, seen in approximately
 1 of 250 male live births. Common methods of local anesthesia administration for hypospadias
 surgery include caudal and dorsal penile nerve blocks. While both methods are known to be
 effective with minimal risk, the effect on post-operative complications is not
 well-established. The purpose of this randomized controlled trial is to evaluate if caudal
 versus dorsal penile nerve block results in higher rates of post-operative complications.
Hypospadias is a one of the most common genitourinary (GU) malformations, seen in
 approximately 1 of 250 male live births, characterized by proximal location of the urethral
 meatus, dorsal hooded foreskin with incomplete ventral fusion, and ventral curvature of the
 penis. Hypospadias repair includes several standard steps including urethroplasty,
 mobilization of adjacent flaps for urethroplasty coverage, rotation of penile skin flaps and
 circumcision. In order for the surgeon to operate in a clean and relatively bloodless field,
 tourniquets and local epinephrine injection have been used. In a rabbit hypospadias repair
 model, the authors used both tourniquet and local epinephrine infiltration to maintain a
 clear surgical field, and showed increased apoptotic urethral myocytes on TUNNEL assay and
 collagen deposition in the epinephrine cohort. The study also showed structural changes in
 the mitochondria on scanning electron microscopy in the epinephrine cohort. This is the only
 hypospadias study demonstrating pathologic changes in the urethra after tourniquet or
 epinephrine injection. While single stage hypospadias surgical techniques have standardized
 significantly over the two decades, surgical complications can still occur in up to 28% of
 patients. Complications include urethrocutaneous fistulas, meatal stenosis, glans dehiscence,
 urethral strictures, and urethral diverticulum. Risk factors for hypospadias surgical
 complications have been extensively published and include: proximal urethral location,
 previous operation, glans width <14 mm, no urethroplasty coverage layers, surgeon learning
 curve, and age <4 years old.

 The majority of hypospadias surgical complications need to be revised surgically and this
 results in significant financial and emotional burden for the family. The financial impact of
 hypospadias visits, repairs, and reoperations on society is largely unknown. A single study
 in 2000 noted that $16.6 million was spent on operative and outpatient hypospadias care and
 17,000 total outpatient hypospadias visits were made that year. No recent studies are
 available and the cost to the patient per surgery and per surgical complication repair is
 also unknown. Multiple objective hypospadias surgical questionnaires have been developed to
 characterize postoperative appearance of the skin, meatus, urinary stream, and presence of
 fistula. These studies have only been validated by the same institution and data correlating
 questionnaire scores to complications is sparse.

 Penile sensation is derived primarily from the dorsal nerve of the penis. Ventrally there is
 some innervation to the frenulum that is derived from the perineal nerve branches. The dorsal
 nerve of the penis is a branch of the pudendal nerve which is supplied from sacral nerves.
 Common methods for penile block, which are performed by the hypospadias surgeon, include
 dorsal nerve penile block (DNPB) or penile ring block. The DNPB involves infiltration of
 local anesthetic using a short beveled needle in the subpubic location at the 10 and 2
 o'clock positions such that the dorsal nerve of the penis is blocked as it enters the base of
 the penis. The penile ring block is performed by infiltration of local anesthetic in the
 subcutaneous tissue at the base of the penis. One prospective study showed that DNPB was
 significantly better than ring block. Success rates of DNPB have been noted to be anywhere
 from 90-100% in children undergoing circumcision. Complications from DNPB are exceptionally
 rare at <0.1% including hematoma and local tissue edema.

 Caudal block is a commonly performed regional block by anesthesiologists for hypospadias
 surgery. It involves blockade of the same nerve pathway described above, at a more proximal
 location, by infiltration of the caudal epidural space through the sacral hiatus. The
 procedure is performed usually in the lateral position. Anatomic landmarks are defined by an
 equilateral triangle formed by the bilateral posterior superior iliac spines, and the sacral
 hiatus. Initially a short beveled needle or small gauge angiocatheter is inserted into the
 sacral hiatus at a 45 degree angle and then once a "pop" is heard, the angle is "dropped" to
 0 degrees and the needle is advanced. Aspiration is performed and in the absence of
 cerebrospinal fluid or blood, a local anesthetic is injected. Complications are exceptionally
 rare at the rate of <0.003% and include local anesthetic toxicity, neurological injury or
 infection and success rates of up to 96% have been reported.

 Penile physiology and blood flow parameters after DNPB and caudal block are largely unknown.
 Very few studies show the effects of distal organ perfusion after regional blockade. One
 study looking at children undergoing caudal block for urologic procedures found that caudal
 block using 1.5 ml/kg of 0.15% ropivicaine increased the dorsalis pedis arterial parameters:
 increased peak velocity 24%, volume flow 76%, arterial diameter 20%. The authors proposed a
 sympatholytic mechanism as the reason for these physiologic changes. Another randomized
 controlled trial primarily looking at post-operative pain outcomes in hypospadias repair
 patients also found increased penile volumes of 27% in the caudal block arm, with the
 proposed mechanism also being sympatholytic. Finally, there have been case reports in which
 the sympatholytic effects of caudal blocks are used to treat glans ischemia after
 circumcision.

 Penile analgesia after caudal block is approximately equal to that of DNPB. A meta-analysis
 of the circumcision analgesia literature, analyzing over 700 patients showed analgesic
 equivalence of caudal versus parenteral analgesia. Also in the meta-analysis, caudal block
 was found to be equivalent to DNPB with increased motor blockade found in the caudal block
 arm. One randomized controlled trial assessing analgesia requirements in children undergoing
 hypospadias repair after caudal block and penile block found that penile block resulted in
 superior pain control. However, another randomized controlled trial found that caudal block
 resulted in superior pain control as compared to penile block. After either bock, there are
 usually no significant alterations in mean arterial pressure.

 Recently, the association between caudal block and hypospadias surgical complications has
 been theorized and has drawn international interest amongst pediatric urologists and
 anesthesiologists. A randomized controlled trial of 54 distal hypospadias repair patients,
 half assigned to caudal block and half to penile block, showed that all urethrocutaneous
 fistulas were seen in the caudal block arm. Even though the primary outcome was
 post-operative pain control between the groups, the authors theorized that caudal blocks lead
 to sympathetic blockade, penile engorgement, tissue edema, and increased hypospadias surgical
 complications. A nested case control series comparing 45 fistulas and 90 controls showed no
 association between fistulas and caudal block. The authors found fistula to be associated
 with proximal urethral location, penile epinephrine injection, and longer operative times.
 Unpublished data presented at the 2015 American Urologic Association in New Orleans by Routh
 et al. showed that in a retrospective single surgeon series of 452 primary hypospadias repair
 patients, half which had caudal block and half which had penile block, caudal blockade was
 highly associated with hypospadias surgical complications even after adjusting for operative
 time (OR 3.9 (1.3-12.1)); p= 0.0008. This is the only study to date that has been powered
 appropriately to assess the association between caudal block and hypospadias complications.
 Thus, there is clinical equipoise regarding the utilization of caudal block versus penile
 block for post-operative pain control and also in minimizing surgical complications in
 hypospadias repair.
Inclusion criteria:

 -  Age 4 months to 4 years

 -  ASA score I and II

 -  Primary hypospadias repair in one stage including distal, midshaft, and proximal
 repairs

 Exclusion criteria:

 -  Age <4 months or >4 years

 -  ASA score >II

 -  Genetic syndromes

 -  Previous hypospadias operations

 -  Staged hypospadias repair operations

 -  Spinal dysraphism or other contraindications to caudal block

 -  Infection at the block site

 -  Refusal of consent by the parents

 -  Unwillingness of the anesthesiologist or surgeon to participate