# Acute Effect of One Single Application of Intravaginal Electrostimulation on Urodynamic Parameters in Patients with the Overactive Bladder Syndrome

Authors: Petra J. Voorham-van der Zalm; Rob C. M. Pelger; Henk W. Elzevier; Guus A. B. Lycklama à Nijeholt
Journal: Scholarly Research Exchange
 (2008)

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## Abstract

Introduction. We performed this study to quantify the acute effect of one single application of intravaginal electrostimulation in patients with symptoms of the overactive bladder syndrome (OAB), using urodynamic parameters.
Materials and methods. Prospectively forty female patients were consecutively selected by entry in two groups: urodynamics only and urodynamics combined with intravaginal electrostimulation. We applied intravaginal electrostimulation with a frequency of 8 Hz, pulse duration of 1000 microseconds and no pulse to rest. Urodynamic evaluations were performed according to ICS standards. Results. By comparing urodynamic measurements in both groups, it appeared that the first sensation of bladder filling, cystometric capacity, micturition volume, urethral pressure, and peak flow showed statistical significant improvement (P<.05) during intravaginal electrostimulation. Conclusion. In the present study, we were able to demonstrate an acute effect of one application of intravaginal electrostimulation on bladder function urodynamic parameters in patients with the overactive bladder syndrome. Whether our findings represent the clinical effect of intravaginal electrostimulation in patients with complaints of OAB symptoms needs to be clarified.


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## Body

## 1. Introduction

In 2002, the International Continence
Society defined the overactive  bladder (OAB) as urgency with or without
incontinence, with frequency and nocturia in the absence of local pathological
or hormonal factors (a symptom-based definition) [1]. Detrusor
overactivity (DO) incontinence is diagnosed during filling cystometry when DO
is accompanied by involuntary urine loss. However, conventional filling
cystometry is not able to register DO consistently. The reported sensitivity is
77.9% and the specificity is 38.7% [2]. Urge urinary incontinence (UI) with no detectable DO is mostly
categorized as sensory UI. Currently, the term “overactive bladder” (OAB) is
used when defining the symptom complex, disregarding the urodynamic features.Patients with symptoms of the OAB-syndrome can be treated by medication
(anticholinergics), biofeedback training, electrical stimulation, and pelvic
floor muscle (PFM) exercises. During the past decades, electrical stimulation
of the pelvic floor, bladder, sacral roots S2-S4, and pudendal nerves has been
reported to be an effective treatment option [3]. There are different techniques of electrical stimulation like
intra-anal or vaginal stimulation, tibial nerve stimulation [4], and sacral nerve stimulation [5]. Extra corporeal magnetic innervation (ExMI) therapy is a more recent
technique [6, 7]. According to previous studies, electrostimulation of the external
urethral sphincter inhibits and depresses unstable bladder contractions and
decreases the frequency of micturition [8, 9]. The lack of controlled parameters has made it difficult to evaluate
the true efficacy of intravaginal electrostimulation (ES). Moreover, the
stimulation equipment as well as the treatment regimens are not standardized
and it is difficult to draw conclusions about electrical parameters of
frequency, pulse duration, pulse-to-rest ratio, length of treatment, power, and
accurate success rates [10]. Almost three decades ago, Erlandson et al. made a first attempt to standardize the technique. Erlandson referred
not only to electrode position but also to the choice of electrical parameters
used for stimulation [11]. Most follow-up studies and
review articles refer to this study of Fall and Lindstrom [12]. Based on previous studies, induction of bladder inhibition
is most effective when using a frequency of 5–10 Hz.We performed this study to quantify
the acute effect of one single application of intravaginal ES in patients with
symptoms of the overactive bladder syndrome using urodynamic parameters.


## 2. Materials and Methods

Forty consecutive female patients, visiting our out-patient
clinic of urology and the pelvic floor center, diagnosed with urgency, frequency
and/or urge incontinence were included in this study. Women with stress
incontinence, mixed incontinence, neurogenic bladder, malignity, prolapse,
ability to comply with instructions in Dutch, and bladder pain were excluded; notwithstanding
that bladder pain could be an expression of detrusor
overactivity.
We did rule out clinical urinary tract infection; bacteriuria was not an
exclusion criterion. All women were multiparous. Also they all had
pelvic floor exercises (straining), bladder training, and urge suppression. All of them learned to
contract the pelvic floor. Stress incontinence was excluded by history, urodynamics, bladder diary,
and cystoscopy. At least two days before urodynamic investigations, anticholinergics (oxybutinine,
tolterodine) had to be stopped, which should be enough considering the
half-life of these drugs (T1/2 elimination  =  2-3, resp., 3-4 hours).We obtained medical ethical
approval of our medical ethical committee and the subjects provided informed
consent.Before urodynamic evaluation,
all patients underwent comprehensive evaluation, including patient history,
physical examination, urinary system ultrasound, and a voiding diary. All patients completed a diary in order to assess
the micturition fluid intake, frequency, and severity of the loss of urine,
micturition frequency over 24 hours and micturition volumes. A micturition
frequency of over 8 times a day and more than once over night (in absence of
cardiac failure) was considered as urge (ICS).To investigate the effect of intravaginal
electrostimulation we used the UD-2000 (Medical Measurement Systems, Enschede,
the Netherlands).
Urodynamics were performed with a four-fold microtip catheter (Gaeltec) with three-urethral
and one-bladder pressure measuring electrodes. Rectal pressure was measured
with a rectal balloon as a representative of the abdominal pressure. Activity
of the pelvic floor during urodynamic investigation was monitored by 3-surface
electrodes, 2 positioned on the perineum and 1 on the upper inner leg (reference
electrode). In between both urodynamic investigations, the pelvic floor
activity was measured with a vaginal probe
(EMG, 2 rings, V. M. P. Bioparc).Abdominal pressureis considered to be the pressure
surrounding the bladder. In current practice it is estimated from rectal,
vaginal, or, less commonly, extraperitoneal pressure or a bowel stoma. The
simultaneous measurement of abdominal pressure is essential for the
interpretation of the intravesical pressure trace. All investigations were
performed in sitting position.Urodynamics were performed according
to ICS recommendations. The word “cystometry” is commonly used to
describe the urodynamic investigation of the filling phase of the micturition
cycle.The filling phase starts when filling commences and
ends when the patient and urodynamics decide that “permission to void” has been
given. A medium-fill
rate of 30 mL/min (ICS definition medium-fill rate is 10–100 mL/min) was used
in order to prevent artificial detrusor overactivity. First sensation of filling
(FSF) and maximum cystometric capacity were measured.Cystometric capacityis the bladder volume at
the end of the filling cystometrogram, when “permission to void” is usually
given. The end point should be specified, for example, if filling is stopped
when the patient has a normal desire to void. The cystometric capacity is the
volume voided together with any residual urine (post-void residual).Maximum cystometric capacity (MCC) in patients with normal
sensation is the volume at which the patient feels that he/she can no longer
delay micturition (has a strong desire to void). Before urodynamic investigation,
patients had an explanation about FSF and MCC.The voiding phase starts when “permission to void”
is given, or when uncontrollable voiding begins, and ends when the patient
considers that voiding has finished.Flow rateis defined as the volume of fluid expelled
via the urethra per unit time. It is expressed in mL/s.Subjects were asked to void
without straining. Ultrasound was used to measure the post-void residual
volume.In all patients, two urodynamic investigations were performed in succession.Patients were submitted to urodynamics only (group I,n=20) with two urodynamic fillings within one session or urodynamics plus one
application of intravaginal electrostimulation (group II, n=20) during
the second filling
within one session.In group II, prior to the second urodynamic
evaluation, electrostimulation was applied by a pelvic floor clinician using
the Myomed 932 (Enraf
Nonius, Delft, the Netherlands) with
a vaginal probe (EMG, 2 rings, V. M. P. Bioparc).
Ultrasound was
used to measure the post-void residual volume. In both groups, patients
underwent a physical examination by the pelvic floor physiotherapist [13] in between both urodynamic investigations.A qualitative
investigation of the pelvic floor function includes a qualitative physical examination of the pelvic floor function consisting of vaginal and anal visual inspection as well as digital palpation
(including the pelvic organ prolapse quantification, POP-Q) [13]. Finally the pelvic floor
function is assessed quantitatively by biofeedback registration.Stimulation parameters were set at a frequency of 8 Hz, pulse duration
of 1000 microseconds and no pulse to rest, during 20 minutes. Stimulation
intensity was adjusted individually to a level just below a level giving
unpleasant sensations. Urodynamic procedures were repeated after the 20 minutes
of intravaginal stimulation by an experienced clinician in our department.At the end of the second bladder filling when the patient has a normal
desire to void, electrostimulation was stopped and “permission to
void” is usually given.We documented maximal detrusor pressure at micturition
(cm H2O), first sensation of bladder filling (mL), cystometric capacity (mL),
urethral pressure (cm H2O) micturition volume (mL), peak flow (mL/s), and post-void residual (PVR).
One investigation combining urodynamics and investigation of the pelvic floor
function is a standard of care at our institute. Maximum urethral pressureis the
maximum pressure of the measured profile.The investigation was a diagnostic procedure and not a
treatment. Urodynamics of both groups have been compared retrospectively. Printouts of the urodynamic evaluation with and without intravaginal
electrostimulation were assessed by a urologist. The urologist was blinded to
the treatment group.Statistical analysis was
performed using Wilcoxon and paired T-tests in SPSS 14.0. Significance was
defined asP<.05.


## 3. Results

All except one patient had been treated before with
pharmacotherapy 41, 3%, pelvic floor physiotherapy (all patients), urethral
dilatation, and 56% of patients had at least one surgical intervention.
We are a referral center and of a number of patients the exact number or the
type of surgical interventions is lacking. Between groups there was no
difference. 3% of patients in both groups were performing clean intermittent catheterization
of the bladder.All the women were multiparous. Also they had pelvic
floor exercises (straining), bladder training, and urge suppression. They all learned to contract
the pelvic floor.The mean age of patients in group I was 37 years
(range 31–65) standard deviation
(SD) 21. Seven patients were diagnosed with urgency/frequency, ten patients
with urgency/frequency and urge incontinence, and three patients with urge
incontinence.In this group, comparison of
both urodynamic evaluations revealed no significant changes between urodynamic
parameters.The mean age of patients in group II was 45 years
(range 22–67), SD 18. Ten
patients were diagnosed with urgency/frequency, one patient with urge
incontinence, and nine patients with urgency/frequency and urge incontinence.There were no significant
differences between patients in group I and group II that is between both
fillings in group I and the first filling in group II (see Table1). By comparing both urodynamic
evaluations in group II, it appeared that the first sensation of bladder
filling (FSF), cystometric capacity, micturition volume, and peak flow showed
statistical significant improvement (P≤.05) during ES. Other
urodynamic parameters improved but not statistically significant (see Table 1).
Observation during the
urodynamic investigation showed that the introduction of the probe had no
influence on urodynamic parameters in both groups.Table 1Group 1 (n=20); without stimulationGroup II (n=20); with stimulationParametersFirst
filling
(±
SEM)Second
filling
(±
SEM)P-valueFirst
filling
(± SEM)Second
filling during
intravaginal
ES
(± SEM)P-valueFirst
sensation of bladder filling (mL)164,6  ±  31,6170,5 ±29ns164,5  ±  31,6321,0  ±  38,70,001Cystometric
capacity (mL)317,3  ±  40340,3  ±  39ns337,3  ±  40,0491,4  ±  34,10,0001Micturation
volume (mL)190,3  ±  30190,5  ±  32ns197,6  ±  42,6252,1  ±  42,30,05Average
urethral pressure (cm H2O)154,1  ±  15,0163,0  ±  12ns169,1  ±  16,5160,2  ±  13,4nsPeak
flow (mL/s)11,0  ±  2,011,5  ±  1,9ns11,0  ±  2,015,7  ±  2,30,008Post-void
residual (mL/s)61,0  ±  15,075,0  ±  21,0ns63,0  ±  14,759,2  ±  17,5nsPrior to intravaginal ES, we registered no involuntary detrusor
contractions during bladder filling in this patient population (phasic detrusor
overactivity). However, as an expression of detrusor overactivity, we observed
a decreased maximum cystometric capacity at which patients could not longer
delay micturition (terminal detrusor over activity).Ultrasonography prior to urodynamic
investigation indicated no relevant PVR in the studied patient population.In this patient population the
resting urethral pressure was high; this may be related to a high percentage of
overactivity of the pelvic floor musculature in these patients (69% of patients  >  2μV).


## 4. Discussion

We were able to demonstrate an acute effect of one
application of intravaginal ES on bladder function in patients with the
overactive bladder syndrome according to current criteria (ICS) using urodynamic
parameters. Whether our findings represent the clinical effect of intravaginal
electrostimulation in patients with complaints of OAB symptoms needs to be
clarified. We believe that intravaginal electrostimulation facilitates the
voiding process by lowering the urethral pressure (see Table1).In urge incontinence, two modes of action of
electrostimulation have been described: stimulation of pudendal nerve
afferents, which results in detrusor inhibition via central reflexes, and
stimulation of efferents, which results in enhancement of pelvic floor and
urethral sphincter musculature tone, inducing detrusor inhibition via the
guarding reflex [12]. Hence, it is important to correlate the clinical results
of this treatment with functional changes in the pelvic floor musculature. During electrostimulation,
the urethral pressure is high because of the current, and after ES we noticed a better relaxation
of the urethra which facilitates the voiding process. The quantitative
investigation of the pelvic floor function consists of EMG registration of the behavior
of the pelvic floor. Because of the absence of (inter)nationally accepted
reference values, we defined, based on our experience for 18 years, a muscle tone at rest of 1-2 microvolt (μV) as normal and
a resttone above 2 μV as an elevated restone [13].In this population with symptoms
of the OAB syndrome, we have found a very high concurrence of an overactivity
of the rest tone of the pelvic floor. The urethral sphincter is an integral part of the
pelvic floor, so we believe the urethral pressure is high, as a result of this
phenomenon. We could not find any reference of this in the literature and this
(consistent) phenomenon is the focus of a present study in our department.Prior to intravaginal ES, we registered no involuntary detrusor
contractions during bladder filling in this patient population.However, as an expression of detrusor overactivity,
we observed a decreased maximum cystometric capacity at which patients could no longer delay micturition. Ultrasonography of the bladder prior to urodynamic
investigation indicated no relevant PVR in the studied patient population. The apparent post-void
residual (PVR) is due to the fact that some patients were unable to void
completely or even to void at all during urodynamics, because they were asked
to refrain from straining or due to the urodynamic setting (inhibition as
described in literature) [14].Previous studies indicated that a prolonged trial of
up to three months was needed to determine whether ES could be considered
potentially successful for a given subject. Success
can be obtained in approximately two-thirds of patients, but the therapy has
the disadvantage of the necessity of maintenance therapy [15, 16]. The success rates are usually in the range from 55% to 80%
and probably limited by the fact that no variables predictive of outcome have
been identified. It is now generally accepted that electrostimulation works via
the afferent rather than efferent nerves and effects at the level of the
supraspinal nervous system [17]. Parallel to the gate control theory for pain, it may also
be suggested that stimulation of large somatic fibers could modulate/inhibit
the thinner afferent A-delta or C fibers, thus decreasing the perception of
urgency [17, 18].The effect of intravaginal
ES on bladder, urethral, and pelvic floor function depends on several factors:
the distance to and configuration of the electrodes with respect to the appropriate
nerve fibers, the excitability of these fibers, the transfer characteristics of
the central pathways (in case of bladder inhibition), and the properties of the
peripheral effector organ. Voorham-van der Zalm et al. [19] stated that electrode placement has a profound influence on
the threshold voltage: a small dislocation of the electrode carrier was often enough
to cause a twofold or even threefold increase.Pelvic floor physiotherapy is
mostly based on experience and not evidence based. We indeed feel that in the
absence of a gold standard all efforts should be made to give us tools to hold
onto. In our experience, treatment with intravaginal ES was effective.We are not aware of previous studies that focused on
intravaginal electrostimulation and urodynamics.Whether the acute effect of
intravaginal electrostimulation we described in this study represents its
therapeutical effect as a result of 8–12 sessions is
not proven yet. However, the results underscore the rationale of intravaginal
electrostimulation in patients with symptoms of the overactive bladder syndrome.The
limitation of our study is the lack of randomization of patients.


## 5. Conclusion

In the present study, we
were able to demonstrate an acute effect of one application of intravaginal ES
(8 Hz, pulse duration 1000 microseconds and no pulse to rest) on bladder
function using urodynamic parameters in patients with symptoms of the OAB.
Whether our findings represent the clinical effect of intravaginal ES in
patients with complaints of OAB symptoms needs to be clarified.



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