nerve-stimulator-guided pudendal nerve block by pararectal approach

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Original article doi:10.1111/j.1463-1318.2011.02720.x Nerve-stimulator-guided pudendal nerve block by pararectal approach 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 for haemorrhoidectomy patients. This paper describes nerve- stimulator-guided pudendal nerve block using a para- rectal approach, and its clinical application for various anorectal 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] Ó 2011 The Authors Colorectal Disease Ó 2011 The Association of Coloproctology of Great Britain and Ireland. 14, 611–615 611

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Page 1: Nerve-stimulator-guided pudendal nerve block by pararectal approach

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

Page 2: Nerve-stimulator-guided pudendal nerve block by pararectal approach

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

Page 3: Nerve-stimulator-guided pudendal nerve block by pararectal approach

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

Page 4: Nerve-stimulator-guided pudendal nerve block by pararectal approach

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

Page 5: Nerve-stimulator-guided pudendal nerve block by pararectal approach

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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� 2011 The Authors

Colorectal Disease � 2011 The Association of Coloproctology of Great Britain and Ireland. 14, 611–615 615