Problem Statement: The Brindley Method is the only implantable stimulator available for micturition control following SCI. Although good outcomes have been shown with this device, it is limited by the need for invasive surgical procedures including a sacral afferent neurectomy. Alternatively, our long-term goal is to develop minimally invasive and staged stimulation methods for SCI bladder control. Our Objectives for this study includes the evaluation of a new Peterson, bipolar electrode that has been developed for this application by Synapse Biomedical Inc (Oberlin, OH). This electrode will be tested in two areas of SCI lower urinary tract problems: 1) short duration bladder contractions that do not empty the bladder;2) high urethral resistance caused by skeletal urethral sphincter contractions that prevents urination. Proposed methods in anesthetized dogs with electrical stimulation (E-STIM) to produce high urethral resistance will include testing the new electrode on bladder and pudendal nerves separately and then in combination to determine effects on urination.
Aim 1 (Bladder nerves): To investigate if moderate-frequency E- STIM of bladder nerves with Peterson bipolar and monopolar electrodes can produce high-pressure bladder contractions without pelvic floor activation.
Aim 2 (Pudendal nerves): To demonstrate that Peterson bipolar electrodes can be used to block the pudendal nerve with high-frequency E-STIM in a model of high urethral resistance (proximal pudendal nerve stimulation) and compare the blocking effects to a standard nerve cuff electrode.
Aim 3 : (combined nerves): Combined E-STIM of bladder and pudendal nerves in the model of high urethral resistance will result in urination with bladder emptying. Methods: Twelve dogs will be studied under anesthesia during this 1-year, pilot investigation. Animals will be instrumented for lower urinary tract recording and to evaluate the effects of E- STIM.
Aims 1 to 3 will all be conducted in each of the animals. Physiological recording will include bladder, urethral, colonic, rectal and anal pressures. Also recorded will be urinated volume and flow as well as rating by palpation of pelvic floor and lower limb muscles and recording their movement with tubes filled water tubes. The bladder will be filled with 40 ml of isotonic saline for single nerve testing and 80% of cystometric capacity for combined nerve stimulation studies for urination. Probe electrodes will be used first to locate nerves followed by implanting the Peterson bipolar electrodes. Current-response testing will be conducted to show the effects of stimulation over a wide range of currents. Moderate frequency stimulation will be applied to the bladder nerves to produce bladder contractions and urination. 6 to 10 KHz frequency, square-wave stimulation of the pudendal nerves will be used to block the nerve and reduce urethral resistance. The animal model of high urethral resistance will be proximal pudendal nerve stimulation. Statistical analysis will be done by one-way ANOVA or Student t-test with paired data for single comparisons. Post hoc comparisons will be made using the Student-Neuman-Keuls test. All data will be presented as Mean + SEM. Relevance to the VA mission: The development of the bipolar Peterson electrode is an important step in technology transfer of minimally invasive and staged stimulation methods for bladder control following SCI. Current studies will show the acute effects of the Peterson bipolar electrode for this application. The minimally invasive methods needed to implant this electrode will assist in this long term goal. 1
Significance of Research Initial hospital and rehabilitation costs for SCI can currently exceed $271,000 for paraplegia and follow-up hospital charges can exceed $27,000 per year.1,33 A significant amount of this cost is related to secondary complications of the lower urinary tract including urinary tract infections.5,6,34,35 Thus, the long-range goal of our laboratory is to develop methods for bladder management that do not rely on catheters. Both the staged and minimally invasive methods to be investigated here could contribute to this goal.1 Bladder nerve stimulation is a promising approach for inducing urination;2 the proposed pudendal nerve blocking techniques are promising for management of high urethral resistance.1 Thus, results from these studies will contribute to our long-term goals. Veteran with SCI have the same concerns as other patients with this injury living in the community. Thus, results will apply equally to Veterans with SCI.