Heart failure with preserved ejection fraction: uncertainties and dilemmas.

Many uncertainties surround the syndrome of heart failure with preserved ejection fraction (HFpEF), which was the topic reviewed in an Expert Meeting at the University of Ferrara. This concluded that the absence of clear diagnostic clinical criteria was the major barrier to progress. There was general agreement that symptoms or signs of heart failure, normal LVEF despite an elevated plasma concentration of natriuretic peptides, and signs of abnormal LV relaxation, LV filling, LV hypertrophy, or left atrial enlargement, or diastolic dysfunction supported the diagnosis. However, HFpEF, like all heart failure syndromes, is heterogeneous in aetiology and pathophysiology, rather than being a single disease. HFpEF may account for about half of all patients with heart failure. The classical risk factors for developing HFpEF include age and co-morbidities, notably hypertension, atrial fibrillation, and the metabolic syndrome. When complicated by increasing congestion requiring hospital admission, the prognosis is poor; 30% or more of patients will die within 1 year (nearly two-thirds die from cardiovascular causes). Patients with chronic stable symptoms have a much better prognosis. Despite many clinical trials, there is no solid evidence that any treatment alters the natural history of HFpEF. Several treatments have shown promising early results and are now being tested in substantial randomized clinical trials. Further basic research is required to better characterize the disease and accelerate progress. Our review highlights the many difficulties encountered in performing randomized clinical trials in HFpEF, often due to difficulties in characterizing HFpEF itself.

Research priorities for urological care following spinal cord injury: recommendations of an expert panel.

OBJECTIVE: A multidisciplinary panel of experts from Canada and the United States was convened by the Ontario Neurotrauma Foundation (ONF) to establish research priorities in the area of urological care following spinal cord injury (SCI). DESIGN: The panel reviewed a synthesis of published literature in five areas of urology, identified emerging opportunities in the private and public sector, and used a modified Delphi approach to reach consensus on priorities for funding. RESULTS: The panel recommendations included: clinical trials of the safety and efficacy of M3 receptor specific anti-muscarinic agents for bladder hyperactivity in SCI patients; development and testing of protocols for sacral nerve electrostimulation without sacral afferent neurectomy for management of micturition - including selective stimulation of sacral nerve fibers, high frequency blocking of the pudendal nerve to minimize the risk of urethral sphincter co-contraction and genital nerve stimulation for bladder inhibition and incontinence management; clinical trials of the efficacy and safety of intra-urethral valve catheters; trials of the efficacy of probiotics for bacterial interference i.e. to reduce colonization by uropathogens and manage the dual problems of infection and pathogen resistance to anti-microbials: innovations in the prevention or treatment of stone disease (ureteral, bladder and kidney). CONCLUSIONS: The recommendations form the strategic priorities of the ONF SCI grants program for Ontario-based investigators and their partnerships with out-of-province collaborators and organizations.

Use of a neuromuscular stimulator to increase anal sphincter pressure.

OBJECTIVES: The objective of this study was to determine if short periods of electrical stimulation with perianal electrodes could increase anal pressures. MATERIAL AND METHODS: Anorectal responses to electrical stimulation were evaluated in five healthy SCI patients. Anorectal pressures were recorded with a small pressure-recording balloon before, during, and immediately following stimulation. A battery-powered stimulator with self-adhering surface electrodes, two inches in diameter was used. Stimulating parameters consisted of 300 micros pulse duration, 35 Hz stimulating frequency. A current response study was conducted by using short periods of electrical stimulating with currents from 0-100 mA until a maximal pressure was recorded. Each current setting was conducted for 13.2+/-9.7 s before increasing to the next higher current, and fatigue was reduced by including a 5-minute rest between stimulations. RESULTS: Four of the five subjects had strong anal contractions with perianal stimulation. Increases in pressure ranged from 38 to 125 cm H2O based on maximal responses at currents ranges of 60 to 100 ma. Even during the short periods of stimulation used here, fatigue was apparent. There was an average drop of 11% in anal pressure over the 13 s of stimulation. Rectal pressures were unchanged with perianal stimulation. CONCLUSIONS: Perianal stimulation with surface electrodes is an approach that might be considered in the future for management of fecal incontinence in individuals with spinal cord injury. Further studies are needed to assess the feasibility of using chronic perianal surface electrical stimulation to sustain anal sphincter contractions.

Characteristics of persons with spinal cord injury as documented by use of an interactive data system.

RATIONALE: Physicians need information about their rehabilitation practices that shows the types of patients being seen and the outcomes for their rehabilitation programs. In order to obtain more information on secondary medical complications and prevention programs, and to provide the information to the spinal cord injury (SCI) rehabilitation team, an interactive data management system was developed. RESULTS: Initial findings for the first 99 patients with SCI were presented for staff review. Demographic information indicated that patients typically lived in private residences, had at least a high school education, and had annual incomes < $20,000. There were nearly equal numbers of paraplegic and tetraplegic patients; 63% of patients were more than 50 years of age and 69% were more than 10 years post-injury. Over 80% of the patients reported satisfactory health, were physically active, and had adequate transportation. Paraplegic and tetraplegic patients had similar profiles for secondary complications. CONCLUSIONS: The SCI staff was surprised that greater than 35% of patients with SCI reported current problems with spasticity, pain, and pressure ulcers. The staff was interested in obtaining additional patient-perception information including the severity of each problem, how the problem interfered with daily activity, and the desire for additional care. The staff felt that patients were reporting problems more often to the interviewer than to their physician. There was unanimous support for the ongoing collection of patient-perception information.

Modified alpha wrap techniques for dynamic urethral graciloplasty in an animal model.

Urethral sphincter reconstruction with a stimulated skeletal muscle flap has been used for treatment of severe intrinsic sphincter deficiency. Urethral strictures and failures were reported in some of the initial experiences. The etiology of these problems is not known, but elevated resting urethral pressures and excessive urethral displacement with stimulation are possible causes. We modified two operative techniques in forming dynamic urinary graciloplasty (DUG) in an attempt to minimize resting urethral pressure without stimulation and urethral mobility during stimulation. Two types of DUG were used. In the first group, a small flap (partial muscle wrap) from the gracilis muscle with an attachment site on the muscle was constructed in four dogs. In the second group, three dogs with a modified alpha wrap and proximal attachments were used. All of the gracilis muscle wraps were stimulated using an implanted programmable pulse stimulator with electrodes attached over the motor nerve. Following a 2-week, postrecovery period, urethral pressure measurements were obtained with and without stimulation. Five weeks were used for stimulation to condition the muscle. This was followed by 4 weeks of continuous stimulation. Thus, devices were implanted for 11 weeks. Before conditioning of the muscles was initiated, the partial muscle wrap pressure at rest was 42 +/- 27 cm H2O, which was higher than the incomplete alpha wrap resting pressure of 20 +/- 4 cm H2O. Stimulated partial flap pressure was 161 +/- 50 cm H2O, and stimulated modified alpha wrap pressures was 71 +/- 27 cm H2O. After conditioning with the modified alpha wrap, the resting and stimulated pressures were unchanged from before conditioning. Technical problems precluded collection of data during the conditioning period in dogs with partial flaps. During stimulation, the partial muscle wrap demonstrated marked deviation, whereas the modified alpha wrap had minimal urethral movement. Postmortem evaluation indicated no urethral stricture or fistula formation with either of the two types of wraps. The modified alpha wrap had several positive features. Advantages over the partial wrap were minimal resting pressures, reduced urethral mobility, and adequate sustained pressures during stimulation. Therefore, in contrast to the partial gracilis muscle wrap, aspects of the incomplete alpha wrap should be considered further for DUG.

Estimating detrusor pressure at home in pediatric patients with myelomeningocele.

PURPOSE: We evaluated a method of estimating detrusor pressure at home in patients with myelomeningocele who perform clean intermittent catheterization to empty the bladder. MATERIALS AND METHODS: Patients with myelomeningocele who perform clean intermittent catheterization underwent cystometry. At home they determined bladder pressure before draining a full bladder and after partial draining with the bladder almost empty. Home estimate of detrusor pressure was calculated using the formula, full bladder pressure - almost empty bladder pressure. RESULTS: A total of 4 boys and 5 girls with a mean age plus or minus standard deviation of 9.6+/-7.9 years who were enrolled in our study made 16.9+/-15.2 home bladder pressure and volume recordings weekly each during a mean of 5.8+/-4.3 months. Mean bladder capacity determined at home was significantly greater than cystometric capacity (354+/-185 versus 250+/-146 ml.). At a mean home and cystometric volume of 190+/-110 ml. full bladder pressure at home was not significantly different from cystometric vesical pressure (31.0+/-8.8 versus 27.5+/-7.5 cm. water). At a mean volume of 23+/-15 ml. mean home almost empty bladder pressure was not significantly different from cystometric abdominal pressure at full and almost empty volumes (14.1+/-5.5 versus 17.0+/-7.4 and 15.5+/-5.8 cm. water). Mean home estimate of detrusor pressure was not significantly different from cystometric detrusor pressure (17.0+/-6.3 versus 10.2+/-9.2 cm. water). CONCLUSIONS: Estimation of detrusor pressure at home is reliable and accurate in patients who perform clean intermittent catheterization. These pressure determinations may be used as a baseline for rapid identification of changes in bladder function.

Evaluation of a suture electrode for direct bladder stimulation in a lower motor neuron lesioned animal model.

The purpose of this study was to evaluate a "suture" type electrode for direct bladder stimulation in an animal model of a lower motor neuron lesion. During an initial surgery, five male cats were instrumented under anesthesia using multistranded, 316 LVM, stainless-steel, wire electrodes implanted on the bladder wall serosa above the trigone area. Electrodes were constructed with a needle attached to the end that was removed after suturing the electrode in place. Additional instrumentation included urinary bladder catheters (tubes) for pressure recording and filling, and hook type electrodes for leg and pelvic floor electromyography recording. Chronic bladder filling and stimulation studies were conducted in tethered animals three to four weeks following surgery. To test these electrodes in a spinal cord injury model, a lower motor neuron lesion was performed including the sacral cord and complete nerve roots at L6 and below. These animals were evaluated during weeks 3 and 10 after injury. Direct bladder stimulation induced active contractions and voiding both before and after spinal cord injury. Effective stimulation parameters consisted of 40 pulses per s, 300 micros to 1 ms pulse duration, a stimulation period from 3 to 4 s, and a stimulation current from 10 to 40 mA. Fluoroscopy revealed an open membranous urethra during stimulation and following stimulation. A small diameter penile urethra was observed to limit flow. Postmortem evaluation of the suture electrode revealed no abnormalities such as corrosion, migration into the bladder lumen or displacement. These findings indicate that suture electrodes are suitable and effective for short-term implantation in the lower motor neuron animal model.

Indications for a home standing program for individuals with spinal cord injury.

Additional analyses were conducted on a recently published survey of persons with spinal cord injury (SCI) who used standing mobility devices. Frequency and duration of standing were examined in relation to outcomes using chi square analyses. Respondents (n = 99) who stood 30 minutes or more per day had significantly improved quality of life, fewer bed sores, fewer bladder infections, improved bowel regularity, and improved ability to straighten their legs compared with those who stood less time. Compliance with regular home standing (at least once per week) was high (74%). The data also suggest that individuals with SCI could benefit from standing even if they were to begin several years after injury. The observation of patient benefits and high compliance rates suggest that mobile standing devices should be more strongly considered as a major intervention for relief from secondary medical complications and improvement in overall quality of life of individuals with SCI.

Optimization of sacral ventral root stimulation following SCI: two case reports with six-month follow-up.

Sacral ventral root stimulation in conjunction with sacral dorsal rhizotomy has been effective in promoting voiding in individuals with upper-motor-neuron spinal cord injury. We report on two patients who had variable voiding responses to stimulation during the first six months after electrode implantation. We used videourodynamic records and daily voiding records to characterize their voiding difficulties. Different methods were used to improve voiding, including seating adjustments and changes in stimulation parameters. The first patient was unable to empty his bladder on a regular basis with stimulation using 24 pulses per sec stimulating frequency for the first two months after implantation. Voiding was substantially improved by using 35 pulses per sec. At the end of six months, he is regularly emptying his bladder with stimulation and is on an every-second-day bowel program. However, his bowel program has been irregular. The second patient had very good voiding when stimulation was applied in bed, but he had poor voiding with high residual volumes when sitting in his wheelchair. Voiding was improved when he used a wheelchair cushion that was cut out in the back or lifted his buttocks off the chair. These procedures appeared to reduce perineal pressures. This patient has bowel care on alternate days and his bowel care time has been reduced following implantation of the device. Neither of the patients experienced an erection with the device. Both patients feel positive about their implant experience.

Botulinum toxin injections for voiding dysfunction following SCI.

Botulinum toxin (BT) injections have been used successfully to treat spastic muscle conditions, including detrusor-sphincter dyssynergia (DSD) seen in spinal cord injury (SCI) patients. In our urology clinic, we used BT to treat three SCI patients who had voiding dysfunction, using a transperineal needle with electromyographic (EMG) monitoring. Two of the patients reported excellent results following the treatment. One patient, with whom the staff had difficulty doing intermittent catheterization (IC), improved significantly. The other patient had improved voiding with an external catheter and minimal urinary residual. The third patient had no improvement of leg spasms with his voiding dysfunction and required a sphincterotomy. Although patients may need repeat injections, BT is minimally invasive and easy to administer with no side effects. Overall, BT injection is an excellent method of managing voiding in SCI patients, especially those on continuous external catheters and with IC management who refuse or are not good candidates for surgery.

Home bladder pressure monitoring in children with myelomeningocele.

PURPOSE: We evaluate a pressure gauge used at home for patients with myelomeningocele on clean intermittent catheterization to provide a system for inexpensive frequent monitoring of bladder pressures. MATERIALS AND METHODS: Subjects with myelomeningocele using clean intermittent catheterization underwent cystometry in the laboratory. At home they obtained weekly volumes and bladder pressures before and after emptying. Home estimate of detrusor pressure was defined as full bladder pressure minus empty bladder pressure. Medication changes, subject position and urinary tract symptoms were noted. RESULTS: A total of 11 subjects 10.5+/-7.3 years old have been enrolled and have made 16.7+/-12.6 weekly home bladder pressure and volume recordings in 4.7+/-3.1 months. Bladder capacities measured at home were 132+/-47% of cystometric capacities. At volumes of data overlap home full pressures (31+/-10 cm. water) were not statistically different from cystometric vesical pressures (25+/-9 cm. water). Home empty pressures (7+/-4 cm. water) were similar to cystometric abdominal pressures (14+/-8 cm. water). Home estimates of detrusor pressures (23+/-7 cm. water) magnified differences in full and empty pressures, and were significantly greater than cystometric detrusor pressures (11+/-11 cm. water). In 2 subjects significant increases in home full pressures occurred, which were associated with cessation of anticholinergic medication and infection. CONCLUSIONS: Home monitoring of bladder pressure is a simple, inexpensive and accurate method of obtaining frequent bladder pressures in patients with myelomeningocele. These pressures are consistent over a large range of volumes and times, and could potentially be used to identify quickly changes in patient condition.

Home monitoring of bladder pressure and volume in individuals with spinal cord injury and multiple sclerosis.

Individuals with spinal cord injury and multiple sclerosis are at high risk for developing kidney dysfunction due to high bladder pressures. We have developed a device for frequent monitoring of bladder pressures at home in those patients who use intermittent catheterization to empty their bladders. Of eight subjects enrolled in the study, only five conducted home recording of pressure. Vesical and abdominal pressures measured at home were significantly lower than clinical cystometric pressures. However, subtracted detrusor pressures obtained from home records and cystometric records were not significantly different. The home detrusor pressures were consistent over a large time and volume range. Therefore, the home monitoring method could be used to establish a normal range of bladder pressures at home and to rapidly identify high bladder pressures in advance of upper urinary tract deterioration.

Follow-up assessment of standing mobility device users.

The use of standing devices by spinal cord-injured subjects was investigated through a national survey of a sample of individuals who returned their manufacturer's warranty card to two companies. We obtained a 32% response rate (99/310). The majority of respondents were male (87%) with a median age between 41 and 50 years. Seventy-seven percent were paraplegic and 21% were quadriplegic. Forty percent had between 1 and 5 years experience with their device, and 84% of those responding were currently using their standing device. Forty-one percent used their standing device one to six times a week; two-thirds stood between 30 minutes and 1 hour for each use. Less than 10% of subjects experienced any side effects, such as nausea or headaches, from standing. Twenty-one percent of subjects reported being able to empty their bladder more completely. There was also a favorable response by some individuals on the effects of the standing devices on bowel regularity, reduction of urinary tract infections, leg spasticity, and number of bed sores. Finally, 79% of subjects highly recommended use of standing devices to other people with spinal cord injury. The positive responses of individuals using standing devices is a strong recommendation for the assistive technology community to make these devices more available to individuals with spinal cord injury.

Urodynamic verification of noninvasive back-pressure recordings from the urinary bladder.

Obstructive voiding is best evaluated with urodynamics, especially simultaneous measurement of bladder-pressure and urine flow rates. As an alternative to catheterization for urodynamics, noninvasive back-pressure methods using an external condom system have been introduced. This device uses one side tube in the condom for pressure recording and an outlet tube that is clamped for short periods of time during voiding. However, there have been problems with accurate back-pressure recording, including leaking, clamping techniques, hydrostatic pressures associated with pressure recording below the level of the symphysis pubis, and assessment of back pressures in relation to bladder and detrusor pressures. To address these issues, we have modified the condom for passing a catheter into the urethra for simultaneous direct bladder and back-pressure recording. The clamping device on the outlet tube also has been modified to produce back flushing of urine in addition to clamping. Hydrostatic issues have been addressed by making pressure recordings at the level of the symphysis pubis. Seven patients with obstructive symptoms were evaluated using these new devices. Back pressures were not statistically different than detrusor pressures recorded with a urethral catheter. Thus, the modifications have improved back-pressure recording techniques. The use of noninvasive back-pressure recording may be an important adjunct in the evaluation of obstructive uropathy.

Short-term bladder-wall response to implantation of microstimulators.

This study examined the histological response of the bladder wall serosa to the implantation of wireless microstimulators secured with a single polypropylene suture. Two to three microstimulators were implanted in each of three casts for an eight week implantation period to allow sufficient time for a bladder-wall injury-response to develop. Gross observation revealed encapsulation of the microstimulators with no perforation to the bladder lumen or migration from the bladder wall. Histological evaluation confirmed that all the microstimutators were encapsulated with a thin connective tissue sheath and a thickened subserosal layer. There was no remarkable difference in tissue morphology compared with normal bladder wall sections for five of seven stimulators. Two microstimulators in one cat revealed a moderate to severe inflammatory response confined to a small area around the stimulator. In a second cat, a suture extended through the bladder wall. The microstimulators were observed with a scanning electron microscope after explantation. The electrode surfaces, bonding interface between silicon and glass and insulating films that were exposed to biological fluids were carefully inspected. All these observations indicate that the glass capsule reliably protected the sealed cavity of the microstimulators from moisture. These results indicate the microstimulator should be considered for further studies such as effects of stimulation and long-term implantation.

Multielectrode nerve cuff stimulation of the median nerve produces selective movements in a raccoon animal model.

In this study, an electrode system consisting of twelve small platinum dot electrodes imbedded in a spiral silicone rubber insulating cuff was used to investigate the feasibility of selective (regional) stimulation of the median nerves of the raccoon. Acute experiments in four raccoons consisted of functional responses observations, isometric force recordings from tendon attachments and postmortem fascicular mapping. Functional responses (elbow, wrist and/or digit flexion, pronation and/or thumb abduction) to selective stimulation were noted as dependent upon cuff electrode configuration (longitudinal tripole with and without field steering, as well as a transverse bipolar arrangement) and current level (threshold, 1/2 maximal, maximal). Muscle force recruitment curves (force as a function of stimulus amplitude) were plotted for flexor digitorum superficialis, flexor digitorum profundus, flexor carpi radialis, palmaris longus and pronator teres of three raccoons. Fascicular maps at the level of the nerve cuff were created indicating the approximate position of innervation to each of the aforementioned muscles, as well as other innervation such as paw fascicles, sensory fascicles, and elbow innervation (such as coracobrachialis). The greatest selectivity was observed at or near threshold current levels. In all four raccoons studied, a threshold electrode choice and stimulation strategy could be identified enabling selective production of either digit flexion, wrist flexion and/or digit and wrist flexion. It was possible to elicit a selective pronation response at threshold in three of the four animals. Selective elbow flexion at threshold could be produced in all four experiments. With stronger currents, additional movements were usually induced. The raccoon therefore appears to be a suitable, if challenging, animal model for further development of not only nerve cuff electrode approaches but perhaps other stimulation electrode technologies prior to human neuroprosthetic studies.

Testing peripheral somatosensory neuroprostheses by recording from raccoon cortex.

A topologically organized representation of the body surface exists within the mammalian somatosensory cortical areas such that stimulation of a part of the body surface will produce a response in a localized region of the contralateral somatosensory cortex. Because of this topography, we propose that the selectivity of a peripheral somatosensory neuroprosthetic electrode array can be tested by noting whether the locus of maximum activation in the cortex moves in a consistent manner when differing portions of the array are stimulated. We further propose that the raccoon might well be the ideal animal in which to test this hypothesis, since the raccoon has a rather unique cortical somatosensory area where each digit is represented in individual subgyri around the tri-radiate sulcus. To demonstrate the feasibility of this concept, a pilot study was carried out in one raccoon under barbiturate anesthesia. The median nerve was stimulated via selective quadrants of a nerve cuff array of four tripolar electrodes implanted around the nerve. Cuff stimulation produced short-latency evoked surface potentials in the digit areas of the raccoon first somatosensory cortex. Response selectivity could be demonstrated, as could a separation between thresholds for producing movement or producing cortical evoked potentials. The sensory and motor responses elicited were consistent with the orientation of the median nerve within the cuff as determined by a postmortem identification of the muscle innervation pattern of the nerve.

Feasibility of implant driven micturition in paraplegic dogs.

OBJECTIVE: This study evaluates the feasibility of using existing technology for implant driven micturition in paralyzed dogs (part I) and also examines a less invasive technique for implant driven micturition (part II). STUDY DESIGN: Part I. Sacral nerve root dimensions and bladder and urethral pressure responses to intradural and extradural sacral nerve root stimulation were measured to determine the optimal location and size for sacral nerve root electrodes. Part II. Sacral nerve roots were stimulated via wire electrodes introduced into the S2 foramina. ANIMALS OR SAMPLE POPULATION: Ten dogs (five dogs in part I and five dogs in part II). METHODS: Part I. Microtip pressure transducers were used to monitor bladder and urethral pressure responses to sacral nerve root stimulation with tripolar hook electrodes. After euthanasia, sacral nerve root, and spinal canal dimensions were measured. Part II. Bipolar electrical stimulation of the sacral nerve roots was performed by introducing wire electrodes into the S2 foramina. Bladder and urethral pressures were recorded as in part I. RESULTS: Part I. Stimulation of SI produced an increase in urethral, but not bladder, pressure. Stimulation of S2 or S3 produced increases in bladder pressure and decreases in urethral pressure. Intradural and extradural nerve roots were not significantly different with respect to nerve dimensions or effects on nerve stimulation. Part II. High bladder pressures were achieved, but effective voiding could not be produced, primarily because of urethral resistance. CONCLUSIONS: Part I. Extradural implantation was determined to be the most appropriate site based on ease of dissection, nerve root dimensions, and decreased risk of iatrogenic trauma. Enough space is available to implant two to four tripolar spiral nerve cuffs. Part II. Transforaminal sacral nerve root stimulation did not effectively empty the bladder. CLINICAL RELEVANCE: Clinical trials in paraplegic dogs are necessary to evaluate the number of sacral nerve cuff electrodes necessary to produce effective bladder emptying.

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.

Do direct current electric fields enhance micturition in the spinal cat?

Changes in micturition behavior and motoneuron ultrastructure were studied in spinal cats to determine the effects of direct current (DC) electric field treatment. Adult cats received a complete injury at T8. A treatment group with an implanted 15 microA DC source and electrodes positioned near the lesion site was compared with non-treatment groups that were either operated or unoperated. Both bladder emptying with Crede and the withdrawal reflex were improved in the treatment group compared with the non-treatment group. Urodynamic procedures showed that high urethral resistance and pelvic floor activity following spinal injury was partially reduced in the stimulated cat, indicating inhibition of the urethral sphincter. The ultrastructural analysis of Onuf's nucleus suggested a similar synaptic input in all three groups. In conclusion, possible activation of inhibitory processes and/or neural plasticity best explain the early improvement of bladder function seen following electrical stimulation.