Local anesthetic infiltration of the skin of the penis is useful for the repair of superficial lacerations, dorsal slits of the foreskin, or freeing entrapped skin from a zipper. Local infiltration circumferentially around the penis will provide adequate anesthesia distal to the anesthetic injection site. The circumferential subcutaneous injections can be performed directly on the penis or on the abdominal wall and scrotum surrounding the penis. While not contraindicated, some authors avoid direct infiltration of the foreskin as tissue sloughing may result.2 Local infiltration of anesthetic agents is often extremely painful for the patient. Consider premedicating the patient with parenteral benzodiazepines and/or narcotic agents.
Local anesthetic agents can be injected subcutaneously into the penis to provide distal anesthesia. If performing a dorsal slit of the foreskin, raise a skin wheal of local anesthetic solution at the base of the foreskin in the 12 o'clock position (Figure 146-2A). Insert the needle through the skin wheal aimed distally. Inject local anesthetic solution subcutaneously as the needle is advanced to the distal edge of the foreskin. Alternatively, local anesthetic solution can be circumferentially infiltrated around the penis (Figure 146-2B). This block usually requires 6 to 10 mL of local anesthetic solution in the adolescent or adult and 2 to 3 mL in a child.
Local anesthetic infiltration into the penis. A. A skin wheal is raised and local anesthetic is injected distally (dotted line). B. Circumferential infiltration of local anesthetic solution.
The objective of a penile block is to anesthetize the right and left dorsal nerves of the penis that provide sensation to the penis (Figure 146-1). The dorsal nerves should be blocked as close to the base of the penis as possible. If the block is performed too distal to the pubic bone, the posterior branches of the dorsal nerves will not be anesthetized and the ventral surface of the penis will retain sensation.5,6 Multiple effective techniques will be described to perform a penile block. The technique chosen should depend on the specific procedure to be performed, the level of patient cooperation, and the preference of the Emergency Physician.
The penis may be anesthetized where it forms along the abdominal wall.2 This block anesthetizes the nerves to the penis before they reach the penis. Form three skin wheals using local anesthetic solution on the abdominal and scrotal skin, 0.5 to 1.0 cm from the base of the penis, at the 2 o'clock, 6 o'clock, and 10 o'clock positions (Figure 146-3). Infiltrate subcutaneously with local anesthetic solution between the skin wheals to form a triangle of local anesthetic that surrounds the base of the penis. This block usually requires 8 to 12 mL of local anesthetic solution in the adolescent or adult and 3 to 5 mL in a child.
Local anesthetic infiltration around the base of the penis. Red dots represent the locations of the skin wheals.
The dorsal nerves of the penis can be anesthetized as they course onto the penis. Place a skin wheal of local anesthetic solution at the 1 o'clock and 11 o'clock positions. Slowly insert a 27 gauge needle through the skin wheals until there is a slight loss of resistance indicating penetration of Buck's fascia (Figure 146-4). Aspirate to ensure that the needle is not within a blood vessel. Inject 1 mL of local anesthetic solution at each site in the adolescent or adult and 0.3 to 0.5 mL in a child.1
The penile block anesthetizes the left and right deep dorsal nerves of the penis.
Another technique blocks the dorsal nerves as they pass through the triangular space bordered by the pubic symphysis, the corpora cavernosa, and Buck's fascia. Place a skin wheal of local anesthetic solution at the dorsal base of the penis. Insert the needle through the skin wheal and to the pubic symphysis. Withdraw the needle slightly and advance it caudally until a loss of resistance is felt, indicating that it has penetrated Buck's fascia. Aspirate to ensure that the needle is not within a blood vessel. Inject 10 mL of local anesthetic solution on each side of the suspensory ligament (midline) in the adolescent or adult and 2 to 3 mL in a child. Alternatively, the same block can be accomplished with a separate injection on each side of the midline.1,7
As the spermatic cord exits the external inguinal ring, it passes over the pubic tubercle and continues medially toward the scrotum. In this same location, the ilioinguinal nerve travels on the anterior surface of the spermatic cord and the genital branch of the genitofemoral nerve on the posterior surface. These two nerves supply sensation to the spermatic cord, epididymis, and testicle. Anesthesia of the spermatic cord in the region of the pubic tubercle will provide anesthesia to the testis and its covering, the epididymis, and the vas deferens.6 The spermatic cord block does not provide anesthesia to the skin of the scrotum. Additional subcutaneous infiltration is necessary for an incision of the scrotal skin.
This first spermatic cord block technique is useful in thin patients with a palpable pubic tubercle. Identify the pubic tubercle by palpation. Inject local anesthetic solution to make a skin wheal just medial and 1 cm below the pubic tubercle (Figure 146-5). Gently advance a 25 gauge needle laterally through the skin wheal and spermatic cord until bone is contacted. Aspirate to ensure that the needle is not within a blood vessel. Inject 3 to 4 mL of local anesthetic solution as the needle is slowly withdrawn in the adolescent or adult and 1 to 2 mL in a child. Repeat the procedure two more times using the same skin puncture site, each time passing through the cord at a slightly different angle. This block requires a total of 10 to 12 mL of local anesthetic solution in the adolescent or adult and 3 to 5 mL in a child.6
The spermatic cord can be anesthetized just below the pubic tubercle, if the tubercle is palpable. The arrows represent the three different directions required to inject local anesthetic solution.
A modified technique is used for the patient in whom the pubic tubercle is difficult to palpate. Grasp the spermatic cord between the nondominant thumb and index finger as it enters the scrotum (Figure 146-6). Place a wheal of local anesthetic solution between the fingers and above the spermatic cord. Insert a 25 gauge needle through the skin wheal. Direct the needle anterior to the spermatic cord. Aspirate to ensure that the needle is not within a blood vessel. Inject 3 to 4 mL of local anesthetic solution in the adolescent or adult and 1 to 2 mL in a child. Repeat the process on the medial and lateral side of the spermatic cord.
The spermatic cord block at the base of the scrotum. Local anesthetic solution is injected anteriorly (1), laterally (2), and medially (3) to the spermatic cord.
Alternatively, palpate the spermatic cord as it enters the scrotum.8 Trace the spermatic cord superiorly to the pubic tubercle where it exits the external inguinal ring. Trap the spermatic cord between the second and third fingers of the nondominant hand and the pubic tubercle. Place a wheal of local anesthetic solution between the fingers and above the spermatic cord. Insert a 25 gauge needle through the skin wheal. Aspirate to ensure that the needle is not within a blood vessel. Inject local anesthetic solution anteriorly, medially, and laterally to the spermatic cord as described above. Injection of local anesthetic solution around the spermatic cord as it exits the inguinal canal may be less painful than injection as it enters the scrotum.