Urology & Urogynecology > Education and Reference

The 1512M and 1512F Wire Electrodes Needle Set consists of a fine stainless steel wire electrode inserted into a #27 Gauge hypodermic needle. Insulation has been removed and the wire bent near the beveled edge of the needle so that it will be retained in the muscle as the needle is withdrawn. Insulation has also been removed from the distal end of the electrode wire to allow connection to the preamplifier with the WEAS-TP Wire Electrode Adaptor Springs.

The Model 1512M, for male patients, has a 1.5" (3.7cm) needle length. The model 1512F, for female patients, has a 1" (2.5cm) length.

1. Patient Instructions- General
   • Explain to the patient that as part of a complete urodynamic examination, it is necessary to test the activity of the urethral striated muscle.
   • The procedure will involve insertion of two fine wire electrodes into the urethral striated muscle. The electrodes will remain inserted for the duration of the examination. Some pain will be experienced with the insertion of the needles, but will quickly dissipate. In addition to the wire electrodes, a third electrode, 'ground', will be taped to the adductor tendon close to the groin.
2. General Patient Preparation
   • The wire electrodes are inserted after the urethral catheter is in place.
   • Using procedures appropriate to the insertion of a hypodermic needle, prepare the insertion sites. The insertion procedure is sex specific (refer to 3.3 for males and 3.4 for females).
   • Place the patient in the lithomy or frogleg position.
   • Instruct the patient to relax and keep as still as possible.
3. Insertion of the 1512M Wire Electrodes into the Male patient and connection of the ground electrode (see Figs. 1 -4).
   • Insert the forefinger into the rectum and locate the apex of the prostate.
   • With the thumb, palpate the angulation of the urethral catheter. This gives the penetration angle.
   • The needles should be placed at 3 and 9 o'clock on either side of the urethra in the urogenital triangle. Insert each needle approximately 1.5" deep toward the apex of the prostate (Figure 1).
     

     Note: You cannot reposition the needles for a second attempt, as the wire will snag on the patient's tissue at the needle's deepest penetration. You can only remove the needle and wire and repeat with a fresh electrode.

   • After the needle is correctly inserted, withdraw it. After the point of the needle clears the skin, grasp, with the thumb and forefinger, the newly exposed wire segment between needlepoint and skin.
   • Remove the needle from the wire.
   • Pass the wires around the testicles and tape in place as shown (Figures 2 and 3).
   • Clean the area of the adductor tendon as close to the groin as possible with OmniPrep (Life-Tech part number 11-001) and a gauze pad. Remove OmniPrep after cleaning the skin.
   • Apply electrode gel to one surface of the ground plate electrode. Tear a 10" (25cm) length of 2" (5cm) wide paper tape. Positioning the ground plate as close into the groin as possible (Figure 3), place one end of the tape on the dorsal surface of the thigh, pulling the other end over the ventral surface of the thigh.
   • Tape the ground electrode wire in place as shown (Figure 4).
4. Insertion of the 1512F Wire Electrodes into the Female patient and of the ground electrode (see Figures 5 and 6).

NOTE:  To assist in placement of the wire electrodes, palpate the bladder neck area by inserting the index finger into the vagina.

The female urethra is approximately one inch (2.5cm) long. It does not have a well-defined sphincter mechanism. Most of the striated muscle around the female urethra is located in the anterior portion directly distal to the bladder neck. Two small veins are normally visible directly anterior to the urethral meatus. The electrodes should be placed below these veins but anterior to the urethral meatus.

Spread the labia and insert the needles at 11 and 1 o'clock above the urethral meatus toward the bladder neck (Figure 5). After each needle is correctly inserted, withdraw it. When the needlepoint clears the skin, grasp, with the thumb and forefinger, the newly exposed wire segment between needlepoint and skin. Remove the needle from the wire (Note: You cannot reposition the needles for a second attempt, as the wire will snag on the patient's tissue at the needle's deepest penetration. You can only remove the needle and wire and repeat with a fresh electrode. ). Bring the wires forward, between the labia, separating about 30 degrees, and pinch each wire in a strip of tape on the lower abdomen (Figure 6).  Do not pull the wires taught. Clean the area of the adductor tendon as close to the groin as possible with OmniPrep (Life-Tech part number 11401) and a gauze pad. Remove OmniPrep with alcohol after cleaning the skin.  Apply electrode gel to one surface of the ground plate electrode. Tear a 5" (25cm) length of 2" (5cm) wide paper tape. Positioning the ground plate as close into the groin as possible, place one end of the tape on the dorsal surface of the thigh, pulling the other end over the ventral surface of the thigh (Figure 7). Tape the ground electrode wire in place as shown.

5. Connection of Wire Electrodes and Ground Electrode to the Preamplifier

• If they haven’t already been connected, insert one WEAS-TP to the EMG Electrode Cables ( - ) Black and one WEAS-TP to the EMG Electrode Cables ( + ) Red input connectors. Connect the ground electrode wire to the green () input connector (Figure 9).
• Using the WEAS-TP (Wire Electrode Adaptor Spring), bend the spring to 45 degrees and insert the silver portion of the wire (approximately 1cm) into a spring coil and release the spring (Figure 9). Do not insert the insulated (gold colored) portion of the wire into the spring loop. Repeat for the second wire electrode with a second WEAS.
• A continuity check can now be performed. Ask the patient to contract the urethral and anal sphincters. Increased EMG activity should be observed.

Note: Electrical interference present at this stage may indicate high impedance between the electrode and the preamplifier. Check electrodes at the WEAS-TP to verify that the connection was made on the insulation-free portion of the wire. Use of an electrode impedance meter may help isolate poor electrode contact.

6.  Removal of Wire Electrodes.  Upon completion of the examination:

• Release the wire electrodes from the WEAS by bending the spring slightly and pulling the wire out (Figure 11).
   
• Grasp both wires as close as possible to the insertion sites.  It is acceptable to also grasp the catheter with the wires and pull all at the same time.
• Ask the patient to turn his/her head to the side and cough.
• Quickly and sharply remove the wire electrodes. The patient will feel little pain with removal.

7.   Hazards and Warnings

• Model 1512M and 1512F are shipped sterile. Discard any units with damaged packaging.
• Although unlikely, there is some possibility that removal of the wire electrode could leave a small portion of stainless steel wire within the patient.
• Insertion of the needle in the female patient will result in some bleeding due to the vascularity of the area of penetration. Although less common, some bleeding is also possible in the male.

8.  Contraindications

• These electrodes are designed for short term, supervised use and are not intended for long term or unsupervised monitoring.
• Use of the electrodes in patients with blood dotting or bleeding disorders in contraindicated.

9.  Precautions
Wire electrodes create a direct electrical connection to the patient. Their use is cautioned in patients with cardiovascular risk. Amplifiers meeting good biomedical safety standards (e.g., ground isolated) are suggested. Care must be exercised to avoid accidental connections to hazardous voltages.