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R van Mastrigt

Publications and source records attributed to R van Mastrigt.

At least 37 records · Page 2Linked to original sources
PubMed2001

Computerized assessment of detrusor instability in patients treated with sacral neuromodulation.

PURPOSE: We previously described an automatic procedure for diagnosing and grading detrusor instability using a cystometric study. In our current study we applied a modified version of the program in patients with urge incontinence treated with sacral neuromodulation to test its capacity to detect changes after therapeutic intervention and understand the mode of action of neuromodulation. MATERIALS AND METHODS: We analyzed cystometric studies before and after neuromodulation in 26 consecutive patients, including 22 women and 4 men, and evaluated parameter changes. We also assessed the relationship of instability parameters at baseline with symptomatic results, which were derived from voiding-incontinence diaries, in female patients to identify urodynamic prognosticators of success. RESULTS: The automatic procedure correctly diagnosed stability and instability in our patients in 51 of the 52 measurements considered. Neuromodulation had an average suppressive effect on the amplitude of unstable contractions. At baseline the amplitude of the maximum unstable contraction and mean active pressure during unstable episodes were significantly less in the 7 women who achieved stability than in the 15 who did not. However, no urodynamic parameters were identified that predicted the symptomatic outcome of treatment. CONCLUSIONS: Our algorithm accurately diagnoses and grades detrusor instability, and provides parameters with predictive value in regard to the probability that a bladder may or may not become stable with neuromodulation. However, the symptomatic result of this treatment option seems to depend on noncystometric factors.

Algorithms↗
PubMed2001

The variable outflow resistance catheter: a new method to measure bladder pressure noninvasively.

PURPOSE: In a previous study an external condom catheter was used to measure noninvasively bladder pressure during interruption of the flow rate. The pressure increase in the condom sometimes caused a sphincter contraction that made bladder pressure measurement unreliable. Therefore, we developed a new variable outflow resistance catheter to measure noninvasively bladder pressure without interrupting the flow rate. MATERIALS AND METHODS: The new catheter consists of an incontinence condom connected to a set of various outflow tubes and a pressure transducer. A remotely controlled pneumatic valve was fitted over each tube to interrupt flow through it. We measured isovolumetric pressure, maximum flow rate, and pressure and flow rates at various outflow resistances in 9 healthy male volunteers. RESULTS: We derived a mathematical equation to estimate isovolumetric pressure from the pressure and flow rate values measured at various outflow resistances. The difference in the estimated and truly measured mean isovolumetric pressures plus or minus standard deviation was 0 +/- 6 cm. water. CONCLUSIONS: The new variable outflow resistance catheter may be used to measure isovolumetric bladder pressure noninvasively without interrupting the flow rate. It has been previously shown that a combination of this pressure and a separately measured maximum flow rate may be used to diagnose bladder outlet obstruction noninvasively.

Catheterization↗
PubMed2001

Supramaximal stimuli do not evoke a maximal contraction in urinary bladder smooth muscle fibers.

BACKGROUND: Smooth muscle fibers can be stimulated with an electrical field, high potassium or carbachol. We studied the effect of combined, supramaximal stimulation on the isometric force and the maximum shortening velocity of the pig urinary bladder. MATERIALS AND METHODS: After determining the dose response curve of each stimulation type, we stimulated 8 fibers with cumulative addition of supramaximal stimuli. RESULTS: The isometric force elicited with either potassium, carbachol or electrical field stimulation alone was the same for each stimulus. After addition of a second or third different supramaximal stimulus, the force further increased to a value that was on average 40% higher. CONCLUSIONS: Carbachol, high potassium or electrical field stimulation work through different stimulation pathways. Maximum stimulation with one of the stimuli does not result in a maximum isometric force development and maximum shortening velocity.

Animals↗
PubMed2001

Intracellular electrical activity in human urinary bladder smooth muscle: the effect of high sucrose medium.

INTRODUCTION: The primary key to pharmacotherapy of bladder instability is in the excitation-contraction coupling of detrusor smooth muscle cells. To study this process, simultaneous recordings of mechanical and electrical activity are required. However, recording of mechanical activity induces movement, which may affect the quality of intracellular recordings. MATERIALS AND METHODS: We therefore compared the electrical activity of human detrusor smooth muscle cells in normal Krebs' solution and in a hypertonic solution, which immobilizes the tissue, enabling us to study the effect of movement on the membrane potential. Carbachol and KCl were applied to induce contractions. RESULTS: Sucrose in the medium made the tissue rigid and abolished its movement, while the electrical response was not affected. When compared with recordings in normal Krebs' solution, the average resting membrane potential was not altered. However, the membrane potential was more stable, with far less spike-shaped potentials. The spike-shaped potential amplitude was larger, while the duration was decreased. CONCLUSIONS: Impairing the ability of tissue movement resulted in changes in the electrophysiological properties of detrusor smooth muscle cells. The results suggest that stretch has an effect on L-type Ca2+ channels.

Action Potentials↗
PubMed2001

Measurement of urinary flow rate using ultrasound in young boys and infants.

PURPOSE: We present a technique for measuring urinary flow rates with ultrasound in male infants and children. MATERIALS AND METHODS: Urinary flow rate was measured simultaneously by an ultrasound probe placed around the base of the penis and by a funnel with a rotating disk at the bottom in 30 boys with a mean age of 6.7 years (range 4.5 to 10.5), and by ultrasound in 8 infants with a mean age of 10 months (range 1 to 28). Voided volume was measured with a graded cylinder or calculated from the weight change of diapers in infants. Ultrasound and rotating disk maximum flow rates were calculated. The ultrasound signal was calibrated by comparing the collected voided volume to the area under the curve for that void. The volume calculated from the rotating disk flow rate curve was also compared with the collected volume. RESULTS: Both methods yielded similar flow curves. However, ultrasound maximum flow rate significantly exceeded rotating disk maximum flow rate (13 +/- 6 ml. per second, range 5 to 22 versus 10 +/- 4 ml. per second, range 4 to 21, t test p <0.001). The underestimation of the flow rate by the rotating disk method may have been due to adherence of urine to the funnel wall. Rotating disk maximum flow rate was lower and voided volume was underestimated by up to 50% (average 15 +/- 2%) in 21 cases. Ultrasound maximum flow rate averaged 6 +/- 3 ml. per second (range 3 to 11.6 [oldest infant]) in the 8 infants. CONCLUSIONS: Urinary flow rates can be measured accurately using ultrasound in boys who produce small volumes and/or who are not toilet trained and also in infants. In future studies ultrasound will be applied to subsets of male infants with bladder dysfunction.

Child↗
PubMed2000

Simultaneous recording of mechanical and intracellular electrical activity in guinea-pig urinary bladder smooth muscle: a comparison with human detrusor contraction.

OBJECTIVES: To study the relationship between the electrical and mechanical activity of guinea-pig detrusor muscle and compare this with the results obtained in human tissue. The guinea pig is the most used model to study the electrical basis of human bladder contraction. METHODS: We simultaneously recorded the mechanical and intracellular electrical activity in muscle strips. To study the effect of tissue movement on the membrane potential, the medium was made hypertonic with sucrose. Carbachol and KCl were applied to the bath to induce contractions. RESULTS: Carbachol resulted in a force response without a consistent change in the membrane electrical activity. KCl induced depolarization of the membrane associated with force development. Sucrose in the medium greatly impaired the ability to contract, without affecting the electrical activity. Compared with recordings in normal Krebs' solution, the resting membrane potential was not altered. In both media, spike-shaped potentials with variable amplitudes and shapes were recorded. These events were minimally affected by sucrose. CONCLUSIONS: In contrast to the response to KCl, the overall mechanical response of guinea-pig detrusor strips to muscarinic receptor stimulation did not correlate with the electrical activity of a single cell. Sucrose had only a minimal effect on the electrical activity, demonstrating that the electrical responses we measured were not affected by movement. Our intracellular recordings in guinea-pig tissue differed from the results obtained by other groups, but show great resemblance with those we recorded in human urinary bladder smooth muscle strips.

Animals↗
PubMed2000

The role of intracellular and extracellular calcium in mechanical and intracellular electrical activity of human urinary bladder smooth muscle.

We studied the role of extracellular and intracellular Ca2+ in human detrusor smooth muscle contraction. Simultaneous recordings of mechanical and intracellular electrical activity were made in three different Ca2+ concentrations: normal Krebs' solution (100%), 10% of the standard Ca2+ concentration and a solution in which Ca2+ was omitted from the medium (0%). Spontaneous contractions and KCl or CCh induced contractions were studied. Ryanodine and caffeine were used to manipulate the intracellular Ca2+ stores. The present results show that only a very small amount of Ca2+ in the extracellular space is sufficient to support spontaneous and induced contractions. Spike-shaped potentials and long lasting depolarisations were recorded in all three solutions. However, the prevalence of long lasting depolarisations increased when the extracellular Ca2+ concentration was reduced. The amplitude of the spike-shaped potentials and long lasting depolarisations appeared to be negatively affected by diminishing the extracellular Ca2+ concentration. Additionally, the duration of the long lasting depolarisations was reduced in 0% Ca2+. The contraction upon KCl stimulation was primarily depending on the extracellular Ca2+. Upon muscarinic receptor stimulation, a combined activation of Ca2+ mobilisation from intracellular and extracellular stores may occur; the ratio of contribution of these two sources changes in accordance with the requirements of the conditions.

Acetylcholine↗
PubMed2000

Factors causing differences in voiding parameters between conventional and ambulatory urodynamics.

Voiding parameter values measured with ambulatory urodynamic monitoring (AM) are generally found to be different from those measured with conventional cystometry (CMG). The reason for this is unclear, but might be related to differences in the voided volume. To verify this hypothesis, we compared voidings from female patients at an initial bladder volume that was close to the modal volume (that is, the volume most often voided by the patient as derived from frequency/volume charts) with voidings at maximum cystometric capacity during a routine video urodynamic examination. A first group of 35 patients voided at the modal volume before they did at capacity. The order was reversed in a second group of 12 patients. The dependence of the voiding parameters on the voided volume and the order of the measurements were examined. It was found that the maximum flow rate depended significantly on the voided volume, but the associated detrusor pressure did not. Urethral resistance and bladder contraction strength were not volume dependent either. It was concluded that the differences between AM and CMG cannot be explained from possible differences in the voided volume.

Female↗
PubMed2000

Changes in bladder contractility and compliance due to urethral obstruction: a longitudinal followup of guinea pigs.

PURPOSE: We established the longitudinal changes in bladder contractility and compliance as a result of urethral obstruction using a guinea pig model. MATERIALS AND METHODS: Obstruction was induced in guinea pigs by a silver ring around the urethra. Urodynamic studies were performed longitudinally in individual animals. Bladder contractility and compliance were calculated from the measured bladder pressure and urine flow rate. RESULTS: Bladder contractility developed in distinct phases. It reached a maximum 200% increase after an average of 3.25 weeks concomitant with an almost 2-fold increase in urethral resistance, remained 150% to 200% increased during weeks 4 to 7 and then decreased to starting levels again, while urethral resistance remained almost 2-fold increased. Bladder compliance decreased by 80% during the first 3 weeks and continued to decrease to 5% of its original value after 10 to 11 weeks. CONCLUSIONS: Our data indicate that as a result of obstruction bladder function passes through a specific sequence of stages, including first a compensatory increase in contractility, then a stabilization phase and finally a decompensation state. In contrast bladder compliance shows a continuous decrease. The data suggest that for assessing how far a bladder has deteriorated due to obstruction a combination of functional and structural data may be warranted.

Animals↗
PubMed1999

Non-invasive measurement of bladder pressure using an external catheter.

Previous studies showed that, on the basis of a combination of maximum flow rate and isovolumetric bladder pressure, objectively diagnosing infravesical obstruction is possible. In this study, we validated a newly developed external catheter to measure non-invasively this pressure, which avoids the risk of damaging or infecting the urethral and bladder wall as occurs with invasive urodynamics. To evaluate the external catheter, we simultaneously recorded the internal bladder pressure signal (measured invasively) and the external pressure signal (measured non-invasively) in 40 non-obstructed and obstructed patients. Additionally, we tested whether the external pressure depended on bladder volume in five healthy volunteers. The simultaneously measured internal bladder pressure and external pressure showed good agreement in the non-obstructed patients. There was less agreement in the obstructed group. Nevertheless, the external pressure in these patients was significantly higher than in the non-obstructed patients. The maximum external pressure depended significantly on the bladder volume in all volunteers. We concluded that isovolumetric bladder pressure can be measured non-invasively with the external catheter. In non-obstructed patients, this pressure accurately represents the internal bladder pressure. We think that it is possible to distinguish between obstructed patients and patients with a weak detrusor by combining the non-invasively measured isovolumetric bladder pressure with a separately measured maximum flow rate. Neurourol. Urodynam. 18:455-475, 1999.

Catheterization↗
PubMed1999

The cognitive and behavioural effects of clobazam and standard monotherapy are comparable. Canadian Study Group for Childhood Epilepsy.

PURPOSE: To compare the cognitive and behavioural effects of clobazam versus standard monotherapy in the treatment of childhood epilepsy. METHODS: A randomized, double-blind, prospective design was carried out at three Canadian pediatric epilepsy centres. This study was part of a larger multi-centre study on the efficacy of clobazam. Children with newly diagnosed epilepsy were assigned randomly to receive clobazam or carbamazepine. Children who had failed previous treatment with carbamazepine were assigned randomly to clobazam or phenytoin. Children who had failed on any other antiepileptic drug were assigned randomly to receive clobazam or carbamazepine. In a subset of patients neuropsychological assessments were carried out at 6 weeks and 12 months after initiation of medication. Intelligence, memory, attention, psychomotor speed, and impulsivity were assessed. RESULTS: There were no differences between the clobazam and standard monotherapy groups on any of the neuropsychological measures obtained at 6 weeks or 12 months. There was no evidence for a deterioration in performance for those children who remained on clobazam for the entire 12-month study period. CONCLUSION: The cognitive and behavioural effects of clobazam appear to be similar to those of standard monotherapy.

Adolescent↗
PubMed1999

Intracellular recording of spontaneous electrical activity in human urinary bladder smooth muscle strips.

We studied the spontaneous electrical activity of human urinary bladder smooth muscle strips, with the eventual aim of uncovering the mechanism underlying the clinical syndrome of the unstable bladder. Intracellular microelectrodes were used to record the membrane potentials of detrusor cells in muscle bundles originating from biopsy samples. Spontaneous spike-shaped potential fluctuations were analysed automatically. The membrane potential at the start of the potential change (V(start)), amplitude, duration at 10% of the amplitude (d(10%)), and upstroke velocity (DeltaV/Deltat) were estimated and statistically analysed. The mean resting membrane potential of the detrusor strip cells was -42 mV (SD: 9 mV). Different types of spontaneous activity could be recorded. On successive impalements within one preparation, the type of activity varied from one single spike-shaped potential to extensive bursts and was not correlated to the resting membrane potential. There was a large variation in size and shape of the spike-shaped potentials between the biopsy samples and even within one cell. The results provide the first description of spontaneous electrical activity in human detrusor smooth muscle strips. This activity is asynchronous, which could aid to maintain a low pressure in the bladder. Most likely, this spontaneous detrusor activity is myogenic in origin.

Action Potentials↗
PubMed1999

Threshold for efferent bladder nerve firing in the rat.

In this study, the mechanism involved in the initiation of voiding was investigated. Bladder pressure and bladder and urethral nerve activity were recorded in the anesthetized rat. Bladder nerve activity was resolved into afferent and efferent activity by means of a theoretical model. The beginning of an active bladder contraction was defined as the onset of bladder efferent firing at a certain time (t0). From t0 onward, bladder efferent activity increased linearly during deltat seconds (rise time) to a maximum. The pressure at t0 was 1.0 +/- 0.4 kPa, the afferent nerve activity at t0 was 2.0 +/- 0.6 microV (53 +/- 15% of maximum total nerve activity), and deltat was 11 +/- 13 s. Between contractions the afferent activity at t0 was never exceeded. Urethral afferent nerve activity started at bladder pressures of 2.1 +/- 1.1 kPa. Therefore, we concluded that urethral afferent nerve activity does not play a role in the initiation of bladder contractions; voiding contractions presumably are initiated by bladder afferent nerve activity exceeding a certain threshold.

Animals↗
PubMed1999

Repeat noninvasive bladder pressure measurements with an external catheter.

PURPOSE: Previously it has been shown that an objective diagnosis of infravesical obstruction can be made by combining the maximum flow rate and isovolumetric bladder pressure. We evaluate a noninvasive method to measure isovolumetric bladder pressure to help develop a noninvasive modality for diagnosing obstruction. MATERIALS AND METHODS: An external catheter consisting of an incontinence condom, tube and pressure transducer was used. Flow rate through the catheter was remotely interrupted to measure the bladder pressure in the condom. Two series of measurements were done in 11 healthy male volunteers. In the first series we determined whether voiding was affected after flow rate interruption. In the second series we analyzed repeat pressure measurements of 1 voiding to determine whether maximum isovolumetric pressure depended on bladder volume. RESULTS: Flow rate was unaffected after interruption for pressure measurement. Repeat measurements of isovolumetric bladder pressure demonstrated that the pressure depended significantly on bladder volume. Average maximum isovolumetric pressure was 12.2 kPa. at a bladder volume of 251 ml. CONCLUSIONS: As no inhibition of voiding was noted after a single pressure measurement, repeat noninvasive measurements can be made on voiding. With repeat measurements the dependence of isovolumetric bladder pressure on bladder volume can be considered to obtain a reliable estimate of pressure as a basis for a noninvasive diagnosis of obstruction.

Adult↗
PubMed1999

ORCA: the versatile CPR.

The introduction of computer-based patient records (CPRs) that fully replace paper records proves especially difficult in specialized care, despite the potential advantages of CPRs for patient care and research. Improved data legibility, availability, sharing of records, and decision support may directly benefit patient care. Barriers to the introduction of CPR applications at institutions may be caused by lack of infrastructure, or by financial or organizational issues. To have clinicians interactively enter data at the point of care is still a big challenge. This paper presents an overview of ORCA (Open Record of CAre): a generic CPR, designed for integration with existing systems, presentation of multi-media patient data, and the collection of structured data, directly by clinicians. ORCA can easily be tailored to the needs of a variety of medical specialists without the need for changes to its data model, functionality, or interface. The paper describes the essence of the architecture of ORCA and the user benefits with emphasis on the support of structured data entry.

Medical Records Systems, Computerized↗
PubMed1998

Diagnosis and grading of detrusor instability using a computerized algorithm.

PURPOSE: Detrusor instability and hyperreflexia are characterized by involuntary detrusor contractions in the filling phase of the voiding cycle. The diagnosis is made when urodynamic evaluation reveals such contractions. To compare patients and evaluate treatment a method is needed to quantify the degree of instability. We developed an instability parameter based on the area under the curve of involuntary detrusor contractions on conventional filling cystometry. MATERIALS AND METHODS: We developed an automatic method to calculate the area under the curve of involuntary detrusor contractions in conventional filling cystometry. Logistic regression was used to construct decision rules to differentiate stable from unstable bladders. These rules, derived from a group of 100 children, were applied to a second group of 77 who were independently assessed by 3 urodynamics experts. RESULTS: Typically 88% of the second group were correctly classified as stable or unstable by the automatic procedure. In the unstable subgroup there was poor correlation between the calculated instability parameter and the instability score assigned by the experts. Most likely this difference occurred because the experts based their opinion mainly on the amplitude of the highest unstable contraction and the percentage of filling time that instability was found. CONCLUSIONS: The proposed method of automatically grading detrusor instability based on the area under detrusor contractions differs from the intuitive method used by experts. Since no standard is available, it cannot be concluded which method is better. Our proposed method is objective and it results in a single physical value.

Algorithms↗
PubMed1998

Neurophysiological modeling of voiding in rats: urethral nerve response to urethral pressure and flow.

In male urethan-anesthetized rats, activity was measured in nerves that run over the proximal urethra. The urethral nerve response to stepwise urethral perfusion could be described by a four-parameter model (fit error < 6%). At the onset of perfusion, the urethra was closed and the pressure increased with the infused volume. The nerve activity (NA) increased linearly with this inserted volume to a maximum (NAmax), which was proportional to the instantaneous pressure. The duration of this first episode (delta t) was inversely proportional to the perfusion rate. After infusion of a fixed volume, the urethra opened and the NA decreased with a time constant phi -1 (approximately 1.8 s) to an elevated level (NAlevel). NAlevel was linearly related to the steady-state pressure. Accordingly, sensors in the urethra are sensitive to pressure rather than to the perfusion rate. The parameters NAmax, NAlevel, and delta t showed very good reproducibility (SD approximately 19% of mean). The measured activity was most likely afferent and conducted to the major pelvic ganglion.

Animals↗