LOCAL ANESTHESIA WITH ACUPUNCTURE AID

We apply acupuncture, routinely, to those who are uncomfortable with cavernosography or are nervous to skin prepare, as a necessary adjuvant of local anesthesia due to its consistent effectiveness, although its mechanism as well as its role in dedicating anesthesia is not beyond controversy. The acupoints [dots]: Hegu [LI 4], Shou San Li [LI 10], Quchi [LI 11], Neiguan [PE 6] and Shen Men [H 7], are those that are chosen regularly. The acupoint Hegu may be located at the highest point of the prominence when the thumb and the index finger are kept adducted. The Quchi point is at the lateral end of the “transverse cubital crease,” with the elbow flexed at a right angle. The point of Shou San Li may be positioned a 3-finger breadth caudally to the Quchi acupoint.

Figure 1. Schematic  illustrations of acupoints

The Neiguan is pointed 5 cm proximal to the middle point of the volar transverse carpal crease, between the flexor carpi radialis muscle and the palmaris longus tendon, with the forearm supine. The Shen Men is at the cross of the wrist proximal transverse crease and the low-lateral margin of the pisiform bone.

Methods of local anesthesia

Over the last few decades, several types of nerve blockades2,3,4,5,6 have been recommended for penile surgeries with the patients under local anesthesia rather than the well-established general or spinal anesthesia. However, either an inconvenient and unpleasant pudendal nerve block, or an adjuvant intravenous injection of sedatives, has been unavoidable. 6.7,8,9,10 We would like to describe local anesthetic methods for penile surgeries on a true outpatient basis of proximal dorsal nerve block,11,12 peripenile infiltration, penile crural block, 13 cavernous nerve blockade, and topical injection of the medial low abdominal region as necessary. We believe that these local anesthetic techniques can offer an optimal option over standard methods for varied penile surgeries.

The innervations of the human penis

The human penis is a unique structure composed of multiple fasciae layers which surround the three cylinders of erectile sinusoids, the most ideal milieu to apply Pascal's law in the human body.14 Thus, it consists of the glans penis, the corpus spongiosum with the bulb of the urethra, the paired corpora cavernosa and the bulbospongiosus, as well as the ischiocavernosus muscles. It is the most sensitized organ in the human body owing to its dense nervous distribution. 15 A full review of the nervous pathway and neurophysiology 16 of the human penis is unnecessary for the purpose of performing local anesthesia. However, one must always keep in mind the relationship between the cavernous nerve and the pudendal nerve to the bony and fibro-muscular structures of the penis, in order for the surgeon to be able to reproduce these nervous blockades. At the level of penile hilum, where the distal third urethral bulb is met, and the penile crura are formed, the fibers of the cavernous nerve are located at around the medial third of each corpus cavernosum. Some of these cavernous fibers enter the corpora cavernosa and corpus spongiosum laterally, abutting with the cavernous and urethral arteries. The remaining fibers travel distally with the dorsal nerve and enter the corpus cavernosum as well as the corpus spongiosum in various sites to innervate the mid and distal penile shaft. Meanwhile, the paired pudendal nerves, with somatomotor as well as somatosensory components, are located one-finger-breadth cranio-posterioly and are regarded as the starting point of the proximal dorsal nerve. The somatic sensory nerves originate at the receptors in the penile skin and glans penis. Subsequently, signals carrying sensory information of pain and temperature ascend via the spinothalamic tract; while vibratory stimuli are carried in the dorsal column; and touch and pressure sensations are transmitted via both pathways to the thalamus. All the transmitting signals of the motor nerve are sent from lateral to medial tracts, and visa versa for the sensory component. Therefore, a lateral blockade of a certain nerve can always result in an anesthetic effect to its medial innervating proper. It is a rule that the anatomical arrangement of the deep dorsal vein, dorsal artery and dorsal nerve is arrayed from the medial side. Although a thorough understanding of the penile neuro-anatomy is indispensable for a well performed penile implantation, the recognition of the fibro-muscular skeleton of the human penis is also a pre-requisite and is clinically meaningful, since through recognition the bony or fibro-muscular landmarks helps to precisely localize any specific nerve.

The fibro-muscular skeleton of the human penis (Fig. 2)
The traditional anatomical description of the human penis has been well established. However, it may not be detailed enough to deliver a precise fibrous landmark which is essential for adequate nerve blockade during an outpatient penile surgeries. Recent studies have reported more knowledge about the penile anatomy, which will benefit the surgeon in recognizing the detailed fibrous landmarks within the penis. This includes the tunica albuginea, 17 the exact position and relationship between the skeletal muscles and smooth muscles, 18 the upper border as well as the lower margin of the symphysis pubis and the ischial tuberosity. The tunica albuginea is consistently described as a single layer with uniform thickness and strength circumferentially.19 It is, indeed, a bilayered structure which can be divided into an inner circular layer and an outer longitudinal layer. Its thickness as well as its strength can vary much depending on its specific position. The outer longitudinal layer is an incomplete coat which is absent between the 5 and 7 o'clock positions, where two triangular ligamentous structures form. These structures, termed the ventral thickening (VT), are a continuation of the anterior fibers of the left and right bulbospongiosus muscles, respectively. A weak border is positioned ventrally between two ventral thickenings, and a hazardous prosthesis extrusion might be taken place from this region.20 On the dorsal aspect, between the 1 and 11 o'clock positions, is the region called the dorsal thickening, a radiating aspect of the bilateral ischiocavernosus muscles. It is then converging distally and arranged centrally to form a distal ligament (DL) which is located immediately above the 12 o'clock position of the navicular fossa of the distal urethra and acts as a trunk of the glans penis. 21,22 Without this strong ligament, the glans would be too weak to bear the buckling pressure generated during coitus. A surgeon should be able to feel five pre-requisite fibrous or bony landmarks of the penis prior to performing nervous blockage. First of all, the distal tip of the distal ligament can be clearly perceived if one puts the finger palm of one's index finger, for example, over the glanular tip. Secondly, the borders of the corpus spongiosum formed by bilateral ventral thickenings can be felt when one put his or her finger palm over the penoscrotal junction of the patient. This is more easily palpable if the patient is asked to make an anal constriction. Thirdly, one is able to tell whether the patient's penile hilum is fibrotic or not by feeling that the underlying suspensory ligament is free of resistance when one uses a gentle pushing force along the pubic angle or from the lateral aspect when the penile shaft is pulled away from the body axis. When the hilum is less fibrotic, it is easier to introduce the injection needle, thus allowing for a more precise proximal dorsal nerve block. In the fourth place, one has to be sure of the exact discrimination between the border of the upper border as well as the lower margin of the symphysis pubis. And last of all, the ability to palpate the ischial tuberosity.

Figure 2. Illustration of the fibro-muscular skeleton of the human penis

The corpora cavernosa are surrounded by the tunica albuginea which is a bilayered structure with an inner circular and an outer longitudinal layer with multiple sub-layers. The incomplete septum is dorsally fenestrated. The intra-cavernosal pillars, which may be considerably larger distally, are a continuation of the inner circular layer. The distal ligament is aggregated from the collagen bundles of the outer longitudinal layer of the tunica albuginea. It is an inelastic fibrous structure which forms the trunk of the glans penis. The ischiocavernosus muscle is paired and situated at the lateral boundary of the perineum. Each segment covers its ipsilateral penile crus. Meanwhile, the anterior fibers of the bulbospongiosus muscle partially spread out to encircle the corpus cavernosum and mostly insert into the ventral thickening of the tunica.

Proximal dorsal nerve block and Peripenile infiltration (Figure 3)
A 23-gauge, 1.25' (3.18-cm) disposable needle connected to a 10-ml syringe, was used to inject the local anesthetic of a 0.8% lidocaine solution prepared in an aseptic bowl pre-filled with 1.0 mL of a 1:200,000 epinephrine solution. With the bevel parallel to the longitudinal body axis, the needle is introduced in-between the suspensory ligaments along the pubic angle while the penile shaft is pulled a little caudally away from the body axis by the surgeon's left hand. Then the injection is made in three directions in order to cover the proximal dorsal nerves bilaterally. An aspiration of the syringe is made before any attempt of injection in order to avoid inadvertent entry into the vessels. Under a finger guide, the needle is withdrawn back just sufficiently to free it from being entrapped in the penile hilum. The needle is then shifted laterally and advanced to the lateral margin of the penile crus; then an injection is slowly delivered while the needle is withdrawn until the sub-cutaneous space is encountered. The needle is advanced caudally and further infiltration is made after ensuring no inadvertent entry into a vessel. The contralateral side is anesthetized in a similar fashion.

Two underlying rigid borders are felt by palpation while pushing downward from the penoscrotal junction. A right-handed surgeon requires the patient's glans penis to be held upward by an assistant's left hand with the palm of the index finger and thumb pinch the 3 and 9 o'clock positions respectively at the retrocoronal sulcus. Then, a rapid and precise puncture is made at the intersection of the medial raphe and the penoscrotal junction. Subsequently, a meticulous injection of the ventral thickening is made bilaterally from its medial margin. The peripenile infiltration is performed in a semi-circumferential manner unilaterally, and then the infiltration of the contralateral side is made in a similar fashion to complete the circle in the ventral aspect. Thus, topical infiltration to the junction between the corpus spongiosum and the corpora cavernosa is mandatory in order to avoid an incomplete block of the sensitive corpus spongiosum. Care should be taken not to puncture the paper-thin tunica albuginea of the corpus spongiosum. A gauge compression of the bleeding point for several minutes is sufficient to stop the bleeders if the spongiosal body is incidentally entered. The scrotal infiltration may be extended caudally if a water reservoir is intended to implant in the scrotal pouch or a 90-degree Z-plasty is intensionally performed. Finger guided manipulation is very helpful in the entire procedure.

Figure 3. Illustration of the proximal dorsal nerve blockage and the peripenile infiltration

The patient is put in the supine position which is suitable for the entire operation.

Proximal dorsal nerve block: The needle, with its bevel parallel to the direction of the body axis, was quickly inserted 0.5 to 1.0 cm cranial to the penopubic fold in between the suspensory ligament until the infrapubic angle was met.
Illustration of the precise positions injected: It was injected in three directions, medially and 15-degree obliquely bilaterally, in the penile hilum in order to cover the bilateral dorsal nerves.
Ventral infiltration: The peripenile space is meticulously infiltrated one and half finger-breadths below the penoscrotal junction while a finger-guided manipulation in which the index finger of the assistant's hands is used to confirm the precise position of the injection.
Illustration of its anatomical landmarks. The peripenile injection shalll be made to encircle the perile shaft. Note that the junction between the corpus spongiosum and the corpora cavernosal (arrow) i.e. 5 and 7 O'clock positions shall be exactly blocked, otherwise, an incomplete blockage will be unavoidable subsequently, the needle is withdrawn and advanced laterally to inject the lateral aspect of each corresponding crus. (This photo was reproduced by courtesy of the Journal of Andrology).

With the bevel parallel to the longitudinal body axis the needle is introduced in-between the suspensory ligaments along the pubic angle while the penile shaft is pulled a little caudally away from the body axis by the surgeon's left hand. Then the injection is made in three directions in order to cover the proximal dorsal nerves bilaterally. An aspiration of the syringe is made before any attempt of injection in order to avoid inadvertent entry into the vessels. Under a finger guide, the needle is withdrawn back just sufficiently to free it from being entrapped in the penile hilum. The needle is then shifted laterally and advanced to the lateral margin of penile crus; then an injection is slowly delivered while the needle is withdrawn until the subcutaneous space is encountered. The needle is advanced caudally and further infiltration is made after ensuring no inadvertent entry into a vessel. The contralateral side is anesthetized in a similar manner.

The glans penis is to be held upward by an assistant's left hand with the palm of the index finger and thumb pinch the 3 and 9 o'clock positions respectively at the retrocoronal sulcus. Then a rapid and precise puncture is made at the intersection of the medial raphe and the penoscrotal junction. Subsequently, a meticulous injection of the ventral thickening is made bilaterally from its medial margin. The peripenile infiltration is performed in a semi-circumferential manner unilaterally, and then the infiltration of the contralateral side is made in a similar fashion to complete the circle in the ventral aspect.

Penile crural block and Cavernous nerve blockage (Figure 4)
The penile shaft is put in a pendulous position while the patient is in a comfortable supine position. A 23G x 1.5' (3.81-cm)-long disposable needle is punctured into the skin at the intersection of the penopubic fold, one finger-breadth laterally. Under finger guidance, the needle is pushed downward vertically along the pubic angle until the medial third penile crus is targeted. It is then withdrawn a little upward before the local anesthetic solution is delivered in case of inadvertent puncture into the corpus. A bloody aspiration denotes that the corpus cavernosum is entered. An experienced hand can feel whether an inadvertent puncture through the tunica has been made since the tunica can act as a barrier in providing an intermediate resistance. An injection of a 2 to 3 ml solution is sufficient to block the neurofibers of the cavernous nerve. Under finger guidance, the needle is withdrawn sufficiently to free it from being entrapped in the penile hilum. The needle is then advanced to the lateral margin down to the ischial tuberosity. A slow and even delivery of the local anesthetic solution is made while the needle is withdrawn superficially until the subcutaneous space is met.

A 23-gauge, 1.5' (3.81-cm) disposable needle is recommended for this purpose. The penile shaft is stretched upward while the penoscrotal junction is identified. The needle is targeted at a 45° angle oblique to the coronal plane at the junction of the corpus spongiosum and the penile crus. It is advanced to about 2cm in order to block the cavernous nerve. Thus, there are two methods for performing the cavernous nerve blockade, dorsally and ventrally. An additional topical anesthetic injection is required if implantation of a three-piece prosthesis is performed. Similarly an extended anesthesia of the involved tissues is mandatory whenever surgery requires.

Figure 4. Illustration of the  Penile Crural Block and the Cavernous Nerve Blockage

The patiert is put in the supine position which is suitable for the entire operation.

The patient is put in the supine position which is suitable for the entire operation.

A. Ventral infiltration: After proximal dorsal nerve blockage is performed, the peripenile space is meticulously infiltrated one and half finger-breadths below the penoscrotal junction. Then the needle is targeted 45 oblique to the coronal plane and inserted deeper in order to block the cavernous nerve.
B. Crural blockage: the needle is quickly inserted into the subcutaneous space at the point crossing the penopubic fold and one finger-breadth bilaterally, respectively. Then it is depressed to target one-third of medial crus in order to block the cavemous nerve. Subsequently the needle is withdrawn and advanced laterally to inject the lateral aspect of each corresponding crus.(This photo is reproduced by courtesy of the International Journal of Andrology)

The penile shaft is put in a pendulous position while a 23G x 1.5' (3.81-cm)-long disposable needle is punctured into the skin at the intersection of the penopubic fold one finger-breadth laterally. Under finger guidance, the needle is pushed downward vertically along the pubic angle until the medial third penile crus is targeted. Under finger guidance the needle is then withdrawn sufficiently to free it from being entrapped in the penile hilum. The needle is then advanced to the lateral margin down to the ischial tuberosity. A slow and even delivery of the local anesthetic solution is made while the needle is withdrawn superficially until the subcutaneous space is met and then advanced laterally to inject the lateral aspect of each corresponding crus.

Local aesthesia on an outpatient basis for penile surgeries appears to be highly promising.23 The local anesthetic methods of proximal dorsal nerve block, peripenile infiltration, penile crural block, cavernous nerve blockage, and a topical injection on an outpatient basis have been proven to be reliable, simple, and safe, with fewer complications in our study. Local anesthesia offers the advantages of less anesthetic adverse effects, less morbidity, more protection of the patient's privacy, and a more-rapid return to daily activity with minimal complications.

References:

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