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Biomedical subjects

S Bross

Publications and source records attributed to S Bross.

31 records · Page 2Linked to original sources
PubMed2001

Therapeutic administration of an endothelin-A receptor antagonist after acute ischemic renal failure dose-dependently improves recovery of renal function.

Endothelin (ET) is known to reduce glomerular filtration rate and renal blood flow and is a possible mediator of acute renal failure (ARF). We recently demonstrated that the administration of a very high dose of the ET(A)-receptor antagonist LU 135252 (LU) accelerates recovery from postischemic acute renal failure by an improvement of renal perfusion in a rat model. The aim of this study was to investigate whether this effect of LU is dose dependent. ARF was induced in rats by clamping both renal arteries. Serum creatinine was measured and endogenous creatinine clearance and fractional sodium excretion were calculated up to 4 days after acute ischemia. Rats were treated either with the selective ET(A)-receptor antagonist LU or with vehicle only after reperfusion. LU in doses of 0.5, 1, or 5 mg/kg per day was infused via a femoral vein using an osmotic minipump. Serum creatinine was increased approximately eightfold after induction of ARF. Creatinine clearance decreased from 4.35 +/- 0.26 ml/min before acute renal failure to 0.15 +/- 0.02, 0.54 +/- 0.1, and 1.49 +/- 0.19 ml/min on days 1, 2, and 4 after ischemia (p < 0.05). Fractional sodium excretion increased from baseline 0.77 +/- 0.05% to 7.5 +/- 1.21 % on day 1 and 8.53 +/- 1.34% on day 2 (p < 0.05). Treatment with LU improved kidney function dose relatedly. There was no significant change in creatinine clearance, but compared with controls, with doses of 0.5 mg/kg per day and 1 mg/kg per day (0.28 +/- 0.1, 0.88 +/- 0.22, and 1.93 +/- 0.24 ml/min on days 1, 2, and 4), we noted a significant increase under 5 mg/kg per day (day 1: 0.62 +/- 0.17 ml/min; day 2: 1.38 +/- 0.26 ml/min; and day 4: 2.45 +/- 0.21 ml/min; p < 0.05). Fractional sodium excretion decreased dose-relatedly to a maximally 2.48 +/- 0.58% on day 1 and 2.25 +/- 0.71 % on day 2 after treatment with the highest dose when compared with untreated control rats (p < 0.05). Our data support the hypothesis that ET plays a major role in ARF. It can be concluded from these results that recovery from ischemic ARF is significantly and dose-dependently enhanced by treatment with a selective ET(A)-receptor antagonist.

Acute Kidney Injury↗
PubMed2001

Combined evaluation of detrusor pressure and bladder wall thickness as a parameter for the assessment of detrusor function: an experimental in vivo study.

PURPOSE: We developed a new method for assessing detrusor function, including active detrusor pressure in relation to bladder wall thickness. This parameter should enable the determination of bladder wall tension, defined as detrusor force per cross-sectional area of bladder tissue. MATERIAL AND METHODS: In acute studies in 8 male foxhounds sacral anterior roots S2 to S3 were placed into a modified Brindley electrode. The bladder was stimulated at different intravesical volumes with bladder filling in 50 ml. stages up to 700 ml. and intravesical pressure was measured and registered. The volume of bladder tissue was determined following cystectomy. Bladder tissue volume and bladder wall thickness were correlated with intravesical pressure during stimulation, resulting in the determination of detrusor force per cross-sectional area in N./cm.2 bladder tissue. RESULTS: The curve of the intravesical pressure rise during stimulation between 0 and 700 ml. showed a rapid incline with a maximum mean of 70.8 cm. water at 100 ml., followed by a slow decline. The bladder wall tension curve had an approximately symmetrical course with a slow incline, a maximum mean of 10.15 N./cm.2 at 350 ml. and a subsequent slow decline. CONCLUSIONS: The different curves of intravesical pressure and bladder wall tension show that these parameters are not identical. Combining detrusor pressure with bladder wall thickness enables further information on detrusor function to be obtained. Therefore, the clinical assessment of bladder wall tension may become a promising supplement to standard diagnostic methods with predictive value in patients with disturbed micturition.

Animals↗
PubMed2000

[Volumetry of the urinary bladder with implantable ultrasound sensors].

Experimental studies revealed that the contractile response of the urinary bladder to sacral anterior root stimulation depends on the actual bladder volume. Furthermore, no clinical relevant technique is available for continuous monitoring of the bladder wall distension respectively bladder volume in paraplegic patients. The presented study investigates the reliability of especially developed implantable ultrasound sensors as a sensoric system for continuous monitoring of the bladder volume. In six anaesthesized pigs two ultrasound sensors, one transmitter and one receiver, were implanted on the bladder wall at different locations (latero-lateral, dorsal-ventral, rostral-caudal). After closing the abdominal wall, the bladder was filled in 50 ml steps up to 250 ml. After each filling step the running time of the ultrasound signal was measured. In all experiments reproducible results and a high correlation of the measured running times with bladder volume were observed. The latero-lateral configuration of the sensors seemed to be most confidential. The presented study indicates that bladder volumetry with implantable ultrasound sensors is possible with minimal technical prerequisites. This promising technique for continuous bladder volumetry could play an important role in the development of an intelligent and autoadaptive neurostimulator of the urinary bladder in paraplegic patients.

Animals↗
PubMed1999

Smooth muscle fatigue due to repeated urinary bladder neurostimulation: an in vivo study.

The presented study investigates the influence of different pause lengths between two consecutive stimulations of the S3 roots on intravesical pressure during bladder neurostimulation. In eight male foxhounds (aged 7-18 months), laminectomy and placement of a modified Brindley electrode were performed. In four series with different pause lengths between two consecutive stimulations (1, 3, 5, and 15 min), the maximum intravesical pressure was measured during stimulation. The changes in intravesical pressure were registered in these four series, each series with six stimulations. A 15-min interval elapsed before the commencement of each series. In the series with a pause length of 15 min, the consecutive stimulations did not result in significant changes in maximum intravesical pressure. In the 5-min series, a significant decrease in intravesical pressure was not observed after the third stimulation. In the 3-min series, a significant decrease was seen at almost every stimulation (average decrease of 3.8% per stimulation) and in the 1-min series, a significant decrease was also observed at almost every stimulation (average decrease of 5.9% per stimulation). The results of repeated bladder neurostimulation demonstrate that the maximum intravesical pressure is dependent on the pause length between two consecutive stimulations. The detrusor muscle showed reversible and short-lived signs of fatigue. This implies the importance of a minimum 5-min interval between two subsequent stimulations. A pause length <5 min leads to a falsification of the results and thus to lower validity of the investigation.

Animals↗
PubMed1999

Recording the evoked canine detrusor electromyogram.

With increasing interest in detrusor disorders and possible detrusor myopathies, a method for recording the detrusor electromyogram (detrusor-EMG) would probably greatly assist the diagnosis of various bladder dysfunctions. Therefore, we investigated the electromyographic activity of the detrusor during sacral root stimulation and during spontaneous bladder contractions in six anesthetized dogs. In all experiments, a high correlation of detrusor-EMG recordings with bladder contraction was observed. Analysis in the time domain and power spectrum analysis revealed the most clear correlation of detrusor-EMG with intravesical pressure rise in a frequency band above 3 Hz. The spike duration was 100 to 250 ms with an amplitude of 100 to 500 microV. Low-frequency activity below 1 Hz was mainly presumed to be artifacts due to fluid movement under the electrode. Our trials indicate that smooth muscle EMG recordings from the detrusor smooth musculature are possible. The exact physiological relevance of the signal in the sub-Hertz domain (<1 Hz) is still uncertain. The presented animal model allows the pathophysiologic investigation of various pathologies of bladder dysfunction and detrusor myopathies. Neurourol. Urodynam. 18:687-695, 1999.

Animals↗
PubMed1999

Restoration of bladder function in spastic neuropathic bladder using sacral deafferentation and different techniques of neurostimulation.

PURPOSE: Conventional sacral anterior root stimulation (SARS) results in simultaneous activation of both the detrusor muscle and the external urethral sphincter. We evaluated the possibilities of different neurostimulation techniques to overcome stimulation induced detrusor-sphincter-dyssynergia and to achieve a physiological voiding. MATERIAL AND METHODS: The literature was reviewed on different techniques of sacral anterior root stimulation of the bladder and the significance of posterior rhizotomy in patients with supraconal spinal cord injury suffering from the loss of voluntary bladder control, detrusor hyperreflexia and sphincter spasm. RESULTS: The achievement of selective detrusor activation would improve current sacral neurostimulation of the bladder, including the principle of "poststimulus voiding". This is possible with the application of selective neurostimulation in techniques of anodal block, high frequency block, depolarizing prepulses and cold block. Nowadays, sacral deafferentation is a standard therapy in combination with neurostimulation of the bladder because in conclusion advantages of complete rhizotomy predominate. CONCLUSIONS: The combination of sacral anterior root stimulation and sacral deafferentation is a successful procedure for restoration of bladder function in patients with supraconal spinal cord injury. Anodal block technique and cryotechnique are excellent methods for selective bladder activation to avoid detrusor-sphincter-dyssynergia and thus improve stimulation induced voiding.

Denervation↗
PubMed1999

Tailored laminectomy: a new technique for neuromodulator implantation.

PURPOSE: Neuromodulation of sacral roots is an alternative mode of therapy for patients with urge incontinence or detrusor hypocontractility. We investigated the effects of sacral (S3) nerve stimulation in patients using a new surgical approach for sacral neuromodulator implantation. Modification of the implantation method with sacral laminectomy and bilateral electrode placement led to distinct improvement of stimulation, positioning and dislocation. We developed tailored laminectomy for bilateral neuromodulator electrode implantation to minimize surgical trauma. MATERIALS AND METHODS: Tailored laminectomy was performed in 6 patients with urge incontinence and 3 with a hypocontractile detrusor. After making a 10 cm. longitudinal skin incision we exposed the spinous processes of S2 and S3. Instead of complete 2-level laminectomy, only 2 oval laminectomy holes were made with a high speed ball drill. An electrode fixation hole was drilled at the edge of the laminectomy window and the wire was fixed with nonabsorbable suture material. RESULTS: In patients with idiopathic urge incontinence (followup 12.5 months, range 7 to 18) the number of leaks decreased from 7.2 to 0 daily and functional bladder capacity increased from 298 to 352 ml. In patients with a hypocontractile detrusor (followup 10.5 months, range 6 to 20) detrusor pressure increased during voiding from 12 to 34 cm. water and post-void residual decreased from 350 to 58 ml. Average surgery time was 2 hours 15 minutes. In 1 case a seroma developed near the impulse generator. CONCLUSIONS: Tailored laminectomy is a fast, minimally invasive and reliable technique for neuromodulator implantation.

Adult↗
PubMed1999

Sacral anterior root stimulation and cryotechnique: A new option for selective urethral sphincter block and reversible deafferentation in the future?

A possible application of cryotechnique might be a selective block of nerve fiber activity during sacral anterior root stimulation to achieve selective block of urethral sphincter and reversible deafferentation. In 13 foxhounds, electrical stimulation of sacral anterior roots S2 was performed while the accompanying spinal nerves were simultaneously cooled down from +25 degrees C in a stepwise fashion until a block of urethral sphincter activity was observed. The effects of cold block on the urethral sphincter and bladder were monitored by urodynamic investigation. In 2 additional dogs sacral posterior roots S2 were cooled down to +3 degrees C while accompanying anterior and posterior roots were stimulated distal to the cryothermode. Compound action potentials (APs) were registered proximal to the cryothermode before, during and after cooling and recovery time of cold blocked nerves was evaluated. Complete cold block of the urethral sphincter during spinal nerve cooling was achieved in all cases. Block temperature averaged +12 degrees C. Detrusor pressure was a mean 5,2 cm water. Recovery time was on average 5 min. The cold block was always reversible. In both dogs of the second series the compound action potentials disappeared nearly completely at +3 degrees C. Three min after the end of the cooling period the appearance of the compound action potentials was back to normal. In this study, cryotechnique proved to be effective for selective and reversible block of nerve fibers during sacral anterior root stimulation. In functional electrical stimulation this technique may lead to an improvement of quality of life in para- or tetraplegic patients resulting in optimization of voiding, standing, walking and grasping and does so without the necessity of surgical dorsal root rhizotomy.

Action Potentials↗
PubMed1999

Effects of acute urinary bladder overdistension on bladder response during sacral neurostimulation.

OBJECTIVE: Urinary retention and micturition disorders after overdistension are clinically well-known complications of subvesical obstruction. We attempted to evaluate whether bladder overdistension influences bladder response and whether overdistension supports detrusor decompensation. METHODS: Following lumbal laminectomy in 9 male foxhounds, the sacral anterior roots S2 and S3 were placed into a modified Brindley electrode for reproducible and controlled detrusor activation. The bladder was filled in stages of 50 ml from 0 to 700 ml, corresponding to an overdistension. At each volume, the bladder response during sacral anterior root stimulation was registered. After overdistension, the bladder was refilled stepwise from 0 to 300 ml and stimulated. RESULTS: In all dogs, the bladder response was influenced by the intravesical volume. The maximum pressure (mean 69.1 cm H(2)O) was observed at mean volume of 100 ml. During overdistension, a significant reduction in bladder response of more than 80% was seen. After overdistension, a significant reduction in intravesical pressure of 19.0% was observed. In 2 cases, reduction in bladder response was more than 50% after a single overdistension. CONCLUSIONS: We conclude that motoric bladder function is influenced during and after overdistension. A single bladder overdistension can support acute and long-lasting detrusor decompensation. In order to protect motoric bladder function, bladder overdistension must be prevented.

Animals↗
PubMed1999

Extradural cold block for selective neurostimulation of the bladder: development of a new technique.

PURPOSE: Cryotechnique for selective block of the urethral sphincter and simultaneous activation of the bladder was developed to achieve physiological micturition during sacral anterior root stimulation (SARS). MATERIALS AND METHODS: In ten foxhounds SARS of S2 was carried out while extradurally both spinal nerves S2 were cooled down from positive 25C in a stepwise fashion until a sphincter block was observed. Subsequently, SARS of S2 was performed while the pudendal nerves were cooled down from + 15C. The effects of spinal and pudendal nerve cold block on the urethral sphincter and bladder during SARS and the recovery time were monitored by urodynamic investigation. RESULTS: A complete cold block of the urethral sphincter during spinal nerve cooling was achieved in all cases. During pudendal nerve cooling, the sphincter was completely blocked in two, and incompletely blocked in four dogs. Cold block temperature of the spinal nerves averaged +11.7C and of the pudendal nerves +6.2C. During SARS and spinal nerve cooling, an increase in intravesical pressure up to 13 cm. water was recognized, and recovery time was on average 6.6 minutes. Intravesical pressure remained unchanged during pudendal nerve cooling, with recovery time being less than 1 minute. The cold block was always reversible. CONCLUSIONS: Cryotechnique is an excellent method for selective and reversible block of the urethral sphincter during SARS to avoid detrusor-sphincter-dyssynergia. The application of cryotechnique in functional electrical stimulation leads to an improvement of quality of life in para- or tetraplegic patients because of selective nerve stimulation with optimization of micturition, standing, walking and grasping and does so without the necessity of surgical dorsal root rhizotomy.

Animals↗
PubMed1998

Smooth muscle electromyography of the urinary bladder.

To elucidate smooth muscle activity of the urinary bladder, we utilized an optimized animal model and a specially developed, computer-aided data acquisition and analysis system for bioelectrical signals. Twenty-five Wistar rats were pharmacologically paralyzed and artificially respirated. The urinary bladder was exposed by a suprapubic midabdominal incision, and both ureters were ligated to prevent physiological filling of the bladder. The bladder was initially emptied by slight manual pressure and was then filled via a transurethral catheter in 0.1-ml steps to a maximum of 0.45 ml with physiological saline. A custom-made, gold-plated needle electrode was tangentially guided by a micromanipulator to the smooth muscle of the bladder dome, and the recordings commenced. Furthermore, smooth muscle EMG recordings of the bladder were performed after pharmaco-stimulation of the detrusor with carbachol. Initial results demonstrate that, with the animal model presented here, it is possible to record reproducible and almost artifact-free smooth muscle activity from the urinary bladder. All experiments displayed a stochastic distribution of similar electrical events, increasing in appearance and amplitude with increased bladder volume and after pharmacostimulation with carbachol. Two-dimensional power spectrum analysis revealed a main signal frequency below 1 Hz.

Animals↗
PubMed1998

Highlights on the latest developments in neurourology - diagnostic technology.

Improved appreciation of detrusor malfunction within the complex pathology of lower urinary tract syndrome has led to increased interest in detrusor muscle disorders and possible detrusor myopathies. The rapid development of alternative methods and new pharmacological agents for the treatment of lower urinary tract dysfunction initiate subtle differential diagnosis of the underlying pathology. Research activities related to bladder physiology, neurophysiology and neuropharmacology have increased in the last 10 years. Primarily a purely basic scientific field, neurourology now commences to become a clinically highly significant and useful research domain. This article offers insight into the latest developments in the diagnostic techniques of this exciting field. One of these is smooth muscle EMG of the urinary bladder that aims at distinguishing between signal pattern changes and subsequent evaluation of the different functional and electrophysiological states of smooth muscle cells in various pathologies or in pharmacological tests during urodynamic investigation. A second innovative method in geriatric patients is the measurement of the sensory input to the brain due to bladder distention. The reported techniques are two new examples of lower urinary tract evaluation that contribute to knowledge on the physiology and pathophysiology of the urinary bladder.

Clinical Laboratory Techniques↗