Direct bladder stimulation with suture electrodes promotes voiding in a spinal animal model: a technical report

To determine the efficacy of a new electrode for direct bladder stimulation, five male cats were instrumented during anesthesia. Multistranded, 316LVM, stainless-steel, wire electrodes were implanted on the bladder wall serosa above the trigone area. The electrodes were made with a needle attached to the end that was cut off after suturing the electrode in place. Additional instrumentation included tubes for pressure recording and filling, and hook electrodes for leg and pelvic floor EMG recording. Bladder filling and stimulation studies were conducted in tethered animals 1 to 2 weeks following recovery. Chronic studies were conducted following recovery in tethered animals. To test these electrodes in a spinal cord injury (SCI) model, a T-1 level complete lesion was performed on the above instrumented animals. Spinal animals had successful direct bladder stimulation that induced active contractions and voiding both before and after SCI, but voiding rates were higher more than 2 weeks after SCI and at larger initial bladder volumes. Optimum stimulation parameters consisted of 40 pulses per second, 300 microseconds to 1 ms pulse duration, a stimulation period of 3 to 4 s, and 10 to 40 mA. Urethral resistance, indicated by a urethral function measure, showed that stimulation had no adverse effect on urethral function, and fluoroscopy showed an open membranous urethra during stimulation and voiding. The cat has a small penile urethra that is the flow rate controlling zone. The suture electrode did not corrode, erode into the bladder, or become dislodged, and appears suitable for chronic implantation.