Use of Preemptive Pudendal Nerve Block Prior to Hydrodistention for the Treatment of Interstitial Cystitis/Painful Bladder Syndrome (IC/PBS)

Painful bladder syndrome/interstitial cystitis (IC/PBS) is a disorder characterized by
chronic bladder pain or discomfort. The exact underlying etiology of IC/PBS is unknown
however several theories exist which include epithelial dysfunction, mast cell activation,
and neurogenic inflammation. Whatever the underlying inciting factor for IC/PBS, the
resulting phenotype is one of urinary frequency, urgency and bladder pain improved after
voiding. Animal studies show that as the normal bladder fills, mechanoreceptors in the
bladder wall respond to stretch through the discharge of afferent innervations or nerve
firing. In normal humans, there is no conscious perception that the bladder is filling until
a threshold volume is reached4. Patients with PBS/IC are thought to have substantially lower
cystometric bladder volumes and a heightened sensitivity to bladder filling. Mechanoreceptors
and chemoreceptors in the bladder may trigger myelinated A- delta or C-fibers found in the
smooth muscle or in the submucosa in response to bladder distention. A- delta fibers are
distributed mainly within the detrusor smooth muscle and are responsive to detrusor stretch
that occurs during bladder filling. In contrast, C-type fibers seem to be more widespread and
are distributed in the detrusor muscle, within the lamina propria and in close proximity to
the urothelium. There is considerable interest in mechanisms underlying sensitization of
C-fiber afferents, as these nerves are thought to play a key role in symptoms of IC/PBS. It
has been shown that the plexus of afferent nerves is most dense in the regions of the bladder
neck and proximal urethra. Lumbosacral afferent fibers in the pelvic and pudendal nerve, with
cell bodies in the lumbosacral dorsal root ganglion (DRG), not only sense pain but also
regulate continence and micturition. In laboratory animals, the pelvic nerve supply contains
more stretch-responsive afferent fibers and appears to be important in responses to bladder
over-distention. Neurologic changes seen after the occurrence of cystitis or other bladder
insult suggest reorganization of reflex connections in the spinal cord and changes to the
bladder afferents, that may suggest a greater role for the influence of the pudendal nerve on
bladder pain than had been previously thought.

The pudendal nerve is a peripheral nerve that is mainly composed of afferent sensory fibers
from sacral nerve roots S1, S2, and S3 and consequently it is a major contributor to bladder
afferent regulation and bladder function. Pudendal nerve entrapment often leads to
significant voiding dysfunction including urinary incontinence and over active bladder
syndrome Furthermore, because the pudendal nerve carries such a large percentage of afferent
fibers, it has been an attractive target for neuromodulation in treating refractory
overactive bladder and may be useful for modulating pain experienced in IC/PBS.

No treatment has been consistently shown to provide relief in the majority of patients with
painful bladder syndrome. Furthermore, combination treatment modalities are needed in the
majority of patients. Cystoscopy with hydrodistention is thought to be a useful therapeutic
tool in patients who are unresponsive to therapies like medication and pelvic floor physical
therapy; however, its use has only been studied in a few observational studies and is
currently listed as a third line treatment option for IC/PBS. According to the interstitial
cystitis database study experience cystoscopy with hydrodistention is reported to be the most
commonly used treatment modality for IC/PBS and published studies have reported improvement
in symptoms in 70 to 80 percent of patients while other studies have reported improvement in
only 40 percent. It has been postulated that hydrodistention works by disrupting the sensory
nerves within the bladder that may be contributing to bladder pain and enabling the
regeneration of afferent sensory nerves. Though the exact mechanism of action is unclear,
there is ample evidence to suggest the efficacy of cystoscopy with hydrodistention, in a
recent study by Chien-Ying et al, therapeutic hydrodistension was associated with an increase
in bladder capacity and significant reduction in average O'Leary- Sant symptom and problem
scores after treatment. In addition, Aihara et al who determined a positive therapeutic
outcome in 71% of patients 1 month after hydrodistention have reported similar findings. The
disadvantages of hydrodistention are that some patients experience a temporary worsening of
their symptoms immediately following the procedure and any beneficial effect often lasts
between 2-6 weeks. The immediate worsening of bladder symptoms immediately after
hydrodistention and its relatively short duration of effect are often deterrents to
recommending this therapy to patients. Given the multimodal approach to managing patients
with IC/PBS it is imperative that the investigators explore ways to prolong the efficacy of
available options and one approach that has been recently suggested is the use of preemptive
analgesia.

In 1983, Woolf proposed that persistent pain experienced after trauma or surgery is due to
posttraumatic functional changes not only in the peripheral pain receptors but also in the
dorsal horn of the spinal cord a property known as hyperexcitability. The hyperexcitable
state persists long after such stimuli cease, causing the patient to perceive pain from
stimuli normally believed to be painless a common occurrence thought to be seen in patients
with IC/PBS. Therefore, prevention of spinal hyperexcitability by blockade of the afferent
nerve pathway from surgical site to spinal cord may therefore decrease the amount and
duration of postoperative pain perception. This theory has been tested in various animal
studies and was first described by Wall in 1988. In addition, the current literature on
preemptive analgesia in gynecology is supportive of this approach. In a study by Ismail et
al, 130 patients undergoing posterior colporrhaphy were randomized to receive preemptive
pudendal nerve block with either .25% bupivacaine or normal saline. Study findings
demonstrated an average postoperative VAS score of 51.1 for the bupivacaine group compared to
23.5 in the placebo group. The investigators postulate that since the pudendal nerve is an
important contributor to bladder afferent regulation, preemptive nerve block prior to
hydrodistention may block afferent impulse transmission to the spinal cord and decrease the
initial increase in postoperative bladder pain.

Inclusion Criteria:

- All women aged greater than 18 years of age scheduled to undergo cystoscopy with
hydrodistention

- who are literate,

- English speaking and

- can provide written informed consent will be included in this study.

Exclusion Criteria:

- Patients who have intolerance or known allergies to local analgesia will be excluded.

- In addition, patients who have coagulation disorders will also be excluded as this may
increase their risks of complication from bleeding.

- Patient will also be excluded if they have a history of dementia as this may impair
their ability to follow instructions.

- Patients who are non-ambulatory and who have an inability to fully assess pain will
also be excluded.

- Patients receiving additional surgical procedures will be excluded from the study, as
the source of their pain may be difficult to decipher in the immediate post-operative
period.