nerve-stimulator-guided pudendal nerve block by pararectal approach
TRANSCRIPT
Original article doi:10.1111/j.1463-1318.2011.02720.x
Nerve-stimulator-guided pudendal nerve block by pararectalapproach
S.-H. Kim*, S. G. Song*, O. J. Paek*, H. J. Lee†, D. H. Park* and J. K. Lee*
*Department of Proctology, Pelvic Floor Disease Center and †Department of Anesthesiology, Seoul Song Do Colorectal Hospital, Seoul, Korea
Received 17 October 2010; accepted 4 May 2011; Accepted Article online 13 July 2011
Abstract
Aim Various techniques have been described for per-
forming a pudendal nerve block (PNB) and have associ-
ated problems such as multiple needle injections, the
need for special equipment and consumption of time.
This study aimed to describe a nerve-stimulator-guided
PNB using a pararectal approach and to evaluate the
safety and the efficacy of that procedure.
Method We conducted a prospective study of 53 patients
who underwent a PNB from December 2009 to July
2010. With the index finger of the left hand inserted into
anus, we guided the nerve stimulator needle along the
second finger tip on the ischial spine to the site where the
maximal contraction of the external anal sphincter could
be felt. Once the position of the needle tip had been
confirmed, the desired drug was injected. Of the 53
patients, a cohort of eight underwent manometry before
and after the pudendal block.
Results A total of 53 patients underwent the nerve-
stimulator-guided procedure: 13 patients for pudendal
neuralgia and the other 40 patients for anorectal disease.
The mean maximal resting and squeezing pressures
before the block were 55 and 161 mmHg, respectively,
compared with 35 and 67 mmHg after the block. The
PNB took just minutes to perform, was well tolerated by
the patients, and resulted in neither severe complications
nor repeated attempts.
Conclusion Nerve-stimulator-guided PNB using a para-
rectal approach proved to be easy and safe, with accept-
able patient tolerance. In addition, it can be used for a
variety of anorectal procedures where relaxation of anal
tone is required.
Keywords Pudendal nerve block, ischial spine, anal tone
What is new in this paper?
Reports exist on pudendal nerve blocks only forhaemorrhoidectomy patients. This paper describes nerve-stimulator-guided pudendal nerve block using a para-rectal approach, and its clinical application for variousanorectal diseases.
Introduction
A neural block of the pudendal nerve has been reported
to relieve postoperative pain after a haemorrhoidectomy
and to relieve pain associated with pudendal neuralgia,
which is characterized by sharp pain along the course of
the pudendal nerve [1]. Pudendal nerve blocks (PNBs)
have also been used as anaesthesia in elective surgery for
haemorrhoids [2,3]. A variety of techniques have been
previously described for approaching the pudendal nerve
via transvaginal, transperineal and transgluteal routes.
Special equipment, such as X-ray [4], fluoroscopy [5,6],
ultrasound [7] and CT [8–10] equipment, have quite
often been used to determine the correct position for the
tip of the needle. Thus, those techniques have multiple
disadvantages: a need for special equipment, a risk of
pudendal vascular injury, significant patient discomfort
and significant time to perform the technique.
The aim of this study was to evaluate both the safety
and the efficacy of a nerve-stimulator-guided PNB
(hereafter simply called a PNB) using a pararectal
approach and the physiological effect of the pudendal
nerve on the function of the anal sphincter.
Method
Fifty-three patients who underwent a PNB for varying
aetiologies from December 2009 to July 2010 were
included in this study. The PNBs were used on patients
suffering from pudendal neuralgia with no demonstrable
Correspondence to: S.-H. Kim, MD, Department of Proctology, Seoul Song Do
Colorectal Hospital, 366-144 Sindang 3-dong, Jung-gu, Seoul, Korea.
E-mail: [email protected]
� 2011 The Authors
Colorectal Disease � 2011 The Association of Coloproctology of Great Britain and Ireland. 14, 611–615 611
or recognizable organic or infectious cause. They were
also used as alternative regional anaesthesia for patients
who did not want to undergo spinal anaesthesia for
benign anorectal surgery.
Of 53 patients who underwent PNB, 40 were inter-
viewed and graded for procedural pain, which was
classified as mild (level 1), moderate (level 2) or severe
(level 3). Of the 53 patients, eight patients on whom a
PNB had been performed due to pudendal neuralgia
underwent manometry to determine the influence of the
PNB on the function of the anal sphincter, and the effect
was assessed by using an electromyogram and by
measuring the anal pressure. Patients with chronic renal
failure, coagulopathy or symptoms of bladder neck
obstruction were not eligible for inclusion in this study.
Complete and specific written informed consent was
obtained from all patients, and the procedures used in
this study were approved by the institutional review
board.
Anorectal manometry
Intraluminal pressures in the anal canal were measured
using a water-perfused, pressure-detecting probe con-
nected with an eight-channel capillary infusion system
(Mui Scientific, Mississauga, Canada). Both the resting
pressure and the maximal voluntary contraction pressure
were measured in 1-cm steps at positions from the anal
verge to 6 cm within the anal canal.
Electromyography (EMG)
Surface anal plug EMG was used to record the electrical
activity of the sphincter muscle (Cadwell Laboratories
Inc., Kennewick, Washington, USA). A plastic plug was
placed inside the anus with the patient in the decubitus
position, and the pressure was measured in the resting,
squeezing and pushing states.
Pudendal nerve block technique
Pudendal nerve block was performed with the patient in
the recumbent or jack-knife position. A pararectal
approach was used; the desired position of the puncture
point was at the top of the ischial spine. Following aseptic
preparation of the perianal region, the index finger of the
left hand was inserted into the anus and was used to
palpate the ischial spine. A bleb of local anaesthesia was
raised at the site of needle insertion, which is between
the external anal sphincter and the ischial tuberosity. The
nerve stimulator needle was then guided through the
ischiorectal fossa to a point just under the ischial spine. At
the injection point, a 22-gauge 10-cm nerve stimulator
needle (Stimulex� HNS 12, B. Braun, Melsungen,
Germany) was connected to the nerve stimulator and a
stimulating current of 1.0–2.0 mA at 1 Hz was applied.
After appropriate stimulation of the pudendal nerve was
verified (visualized as ipsilateral contractions of the
external anal sphincter), the position of the needle’s tip
was optimized in a normal fashion by preserving muscle
contractions while at the same time reducing the stim-
ulating current to 0.5–0.6 mA, after which the injection
was performed. After aspiration has excluded bleeding,
5 ml of 0.25% bupivacaine for anaesthesia or triamcino-
lone mixed with bupivacaine for pudendal neuralgia was
infiltrated around the nerve. Bilateral injections were
performed in two patients (Fig. 1).
Results
A total of 53 patients who underwent a PNB were the
subjects of this study. Among the patients, 13 were
injected for chronic pelvic pain and 40 for a benign
anorectal procedure. The male-to-female ratio for the 53
patients was 38:15. The mean age of the patients was 50
(20–89) years.
The anorectal conditions for and the pain severity after
PNB are shown in Table 1. A wide variety of anorectal
diseases, including condylomata, fissure, fistula and
abscess (except complex type), tumour and haemor-
rhoid, and various miscellaneous conditions can be
treated surgically using a PNB. Throughout this study,
maximum pain (level 3) was reported by only two
Ischial spine
2.00
Figure 1 Diagram of the pudendal nerve block technique.Intraoperative view of a right nerve-stimulator-guided pudendal
nerve block being performed, with the patient in jack-knife
position. With the index finger inserted into the anus, a nerve
stimulator needle is inserted along the ischial spine and guidedusing the nerve stimulator.
Nerve-stimulator-guided pudendal nerve block S.-H. Kim et al.
� 2011 The Authors
612 Colorectal Disease � 2011 The Association of Coloproctology of Great Britain and Ireland. 14, 611–615
patients with complex type of anorectal abscess. This
result suggests that a PNB may not be applicable to
complex types of anorectal abscess or fistula because of
the possibility of incomplete anaesthesia due to extensive
inflammation.
The mean maximal resting pressure before the block
was 55 mmHg compared with 35 mmHg after the block,
and the maximal squeezing pressure before the block was
161 mmHg compared with 67 mmHg after the block.
The decreases in the maximal resting and maximal
squeezing pressures were 36% and 58%, respectively.
The EMG also showed a decreased response, which was
proportional to the manometry result (Fig. 2).
All patients had a successful block within 10 min after
administering the anaesthesia, and all patients reported a
loss of sensation in the perianal and genital skin and had
difficulty in squeezing the anal musculature voluntarily.
Acceptable mild pain or discomfort was noted during the
infiltration of bupivacaine. Neither unintended punctures
of internal pudendal vessels nor complications, except for
mild degrees of tachycardia, hypotension and nausea
which were well controlled by fluid therapy, were
associated with the PNB (Table 2).
Table 1 Anorectal conditions, pudendal nerve block and
degrees of procedural pain.
Diagnosis and treatment
Number of
patients
Scale of
pain during
procedure
Haemorrhoids 19 1
Condyloma (intra-anal canal lesion) 5 1
Fistula, low intersphincteric 6 1
Abscess
Simple type 1 1
Complex type 2 3
Fissure
Lateral subcutaneous
sphincterotomy
3 2*
Fissurectomy 2 1
Rectal mass 2 1
Standard operations were adapted for a variety of anorectal dis-
eases.
Scale of pain: level 1, mild degree of pain; level 2, moderate
degree of pain; level 3, severe degree of pain.
*Discomfort associated with index finger insertion into the anus
before the nerve block.
Pudendal EMG-Right Rest Pudendal EMG-Right PushPudendal EMG-Right Sqeeze
Pudendal EMG-Right Rest Pudendal EMG-Right PushPudendal EMG-Right Sqeeze
10 (µV) 500 (ms), 10 (µV) 500 (ms)
EMG before PNB
500 (ms), 10 (µV)
10 (µV) 500 (ms), 10 (µV) 500 (ms)500 (ms), 10 (µV)EMG after PNB
Figure 2 Electromyography before and after pudendal nerve block. An electromyogram showing a decreased response with thepudendal nerve block in a patient with pudendal neuralgia.
S.-H. Kim et al. Nerve-stimulator-guided pudendal nerve block
� 2011 The Authors
Colorectal Disease � 2011 The Association of Coloproctology of Great Britain and Ireland. 14, 611–615 613
Discussion
The pudendal nerve is a mixed nerve (sensory and motor)
derived from the somatic component of sacral roots S2–
4, and it crosses through three anatomical regions
successively, i.e. the pelvic cavity, the gluteal region and
the perineal region [10,11]. Although a variety of
techniques for approaching the pudendal nerve have
been attempted, secondary to the significant patient
discomfort associated with multiple injections, the need
for special equipment, such as CT, fluoroscopy and
sonography equipment, and the risk of pudendal vascular
injury have limited the use of the traditional PNB. Nerve
stimulator use improves nerve localization as well as the
rate of success, and is a good method for teaching this
block.
Kovacs et al. [7] reported the safety and the effective-
ness of direct ultrasound-guided infiltration of the
pudendal nerve for relief of perineal pain, but these
authors could only perform the block indirectly by using
the ischial spine or the internal pudendal artery, instead of
the pudendal nerve, as a landmark in half of their 53
cases. There are reports regarding PNBs using a nerve
stimulator, but those techniques only involved ap-
proaches through the ischial tuberosity to find terminal
branches of the pudendal nerve, and patients had been
sedated before local anaesthesia was administered
[12,13]. Thus, those procedures had problems associated
with multiple injections to find several branches of the
pudendal nerve and the possibility of inadequate anaes-
thesia. Our technique, on the other hand, makes it
possible to block the main trunk of the pudendal nerve,
and it can be successfully applied with only a single
injection without discomfort and without intravenous
sedation.
Compared with some previously published tech-
niques, nerve-stimulator-guided PNB offers many advan-
tages over conventional techniques. It can be performed
with the patient in any position, such as prone, recum-
bent or lithotomic. Multiple injections for adequate
anaesthesia are not needed. It has a high success rate,
which is most probably due to the nerve-stimulator-
guided technique in improving the accuracy of needle
placement through visualization of contractions of the
external anal sphincter, thereby improving the chance of
an adequate nerve block.
Frenckner and Euler [14] reported the influence of a
pudendal block on the function of the anal sphincter by
comparing continuous recordings of the anal canal
pressure and the EMG activity after a pudendal block in
10 healthy persons. The maximal anal pressure was
reduced from a mean of 64 mmHg before the pudendal
block to a mean of 54 mmHg after the pudendal block,
indicating that the internal sphincter contributed approx-
imately 85% of the anal pressure at rest. This is strong
evidence for the important role played by the internal
sphincter in maintaining continence at rest [14,15].
However, our study showed that the mean maximal
resting pressure was reduced from 55 mmHg before the
pudendal block to 35 mmHg after the pudendal block,
indicating that the internal anal sphincter contributes
64% of the anal pressure at rest, and the maximal
squeezing pressure was reduced from a mean of
161 mmHg before the pudendal block to 67 mmHg
after the block. Therefore, anal tone can be sufficiently
dilated after infiltration, and our technique offers excel-
lent exposure without the discomfort associated with the
insertion of an anal retractor during an anorectal proce-
dure. This technique is not novel but, from a surgeon’s
point of view, we believe that it will be helpful for
carrying out the procedure or regional blockade for
anorectal diseases.
Conclusion
PNB via the ischial spine is safe and easy to perform, and
it can be used for regional anaesthesia for surgery of many
benign anorectal surgery conditions.
Author contribution
The authors of this paper do not have commercial asso-
ciations and have not received funding for this research.
The study was designed by Soung-Ho Kim and Seok-Gyu
Song. Acquisition of data, statistical analysis and inter-
pretation of collected data were performed by Soun-Ho
Kim and Ok Joo Paek. The manuscript was written
by Soung-Ho Kim. Revising the paper for important
Table 2 Demographics and complication: anorectal surgery vs
pudendal neuralgia.
Anorectal
surgery group
(n = 40)
Pudendal
neuralgia
group (n = 13)
Age (years) 45.9 64.4
Male ⁄ female ratio 30 ⁄ 10 8 ⁄ 5Mean duration to perform
the procedure (min)
7.5 8.5
Complications*
Tachycardia 1 0
Hypotension 1 0
Micturition by catheter 0 0
Nausea 1 0
*Tachycardia and hypotension were well controlled after fluid
therapy.
Nerve-stimulator-guided pudendal nerve block S.-H. Kim et al.
� 2011 The Authors
614 Colorectal Disease � 2011 The Association of Coloproctology of Great Britain and Ireland. 14, 611–615
intellectual content was done by Duk-Hoon Park and
Jong Kyun Lee. Final approval of the manuscript was
made by Jong Kyun Lee. All authors reviewed the
manuscript.
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