EVALUATION OF DIRECT BLADDER STIMULATION WITH STAINLESS-STEEL WOVEN EYE ELECTRODES

Encouraged by recent clinical reports of micturition induced in patien ts by direct bladder stimulation, we conducted a study of optimum meth ods of direct bladder stimulation. During surgery six male cats receiv ed eight large surface-area woven eye electrodes sutured to the bladde r wall serosa, four on the bladder dome and four adjacent to the trigo ne area. Two additional small surface-area single knot electrodes were sutured in the trigone area. Suprapubic and intraperitoneal tubes wer e placed for pressure recording and bladder filling. Leg and pelvic fl oor EMG electrodes were also used for tethered recordings. One to eigh t weeks after surgery, optimum stimulation methods were evaluated as t he animal freely moved about a urodynamic recording cage. Electrodes i n the trigone region were more effective than electrodes on the dome a nd induced bladder contractions and voiding similar to spontaneously i nduced voiding with bladder filling. Large surface area, woven eye ele ctrodes, composed of multi-stranded 316LVM stainless steel wire, were more effective than smaller surface area single knot electrodes. High stimulating frequencies (40 Hz) were better than lower frequencies (10 to 20 Hz), and a 1 millisecond pulse duration was optimal. Pulsing wi th stimulating currents from 10 to 25 mA induced effective bladder con tractions with voiding when applied for 3 seconds. However, lower curr ents using longer stimulation periods were also effective. Bipolar ele ctrodes with both electrodes on the bladder wall were superior to mono polar arrangements with the positive ground electrode along the animal 's back. We concluded that in the able-bodied cat model, bladder contr actile activity for micturition can be induced with direct bladder sti mulation and with little discomfort. An effective stimulation protocol consists of capacitor-coupled monophasic pulses with large surface ar ea bipolar electrodes in the trigone region. Stimulating parameters of 40 Hz, 1 msec., 10 to 25 mA applied for 3 seconds were optimal. In ad dition, based on corrosion resistance observations, the electrodes are quite suitable for long-term studies.