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H N Whitfield

Publications and source records attributed to H N Whitfield.

At least 37 records · Page 2Linked to original sources
PubMed1996

Use of image enhancement during lithotripsy.

Renal excursion during breathing is inevitable and is a cause of poor localization during extracorporeal shock-wave lithotripsy (SWL), which in theory might lead to poor treatment results. Eighty-one patients underwent lithotripsy treatment with and without the use of an image enhancement system designed for use with the Dornier MPL9000 lithotripter. This device contains a memory incorporated into a separate differential grayscale monitor, which allows the stone image to be stored. Shockwave release is enabled only when this image corresponds to the real-time image on the lithotripter ultrasound monitor. No improvement in success rates was found using this system, although upper-pole stones appeared to be fragmented more successfully. Overall, the results were favorable in both groups after a single treatment. Further work is needed to establish whether image enhancement is capable of improving the success rates and reducing the side effects of lithotripsy by better targeting.

Adult↗
PubMed1994

Post-irradiation bladder dysfunction: muscle strip findings.

Strips of rat detrusor muscle were studied in an organ bath 6 months after X-irradiation at doses of 15 and 25 Gy; cystometric studies in these animals had shown a persistent and significant reduction in compliance. The organ bath study demonstrated an increase in the purinergic sensitivity of irradiated detrusor muscle as compared with control. This was significant: p < 0.0145 for the 25 Gy dose group (n = 8) and p < 0.0456 for the 15 Gy group (n = 8) at an alpha,beta-methylene-ATP concentration of 10(-4) M (Mann-Whitney U-Test). There was no difference in sensitivity to cholinergic or noradrenergic stimulation, or to electrical stimulation of the transmural nerves. The finding of purinergic hypersensitivity in irradiated muscle, coupled with ultrastructural evidence of a neural injury, raises the interesting possibility that a denervation supersensitivity phenomenon may contribute to the pathophysiology of post-irradiation bladder dysfunction.

Animals↗
PubMed1994

Magnetic resonance imaging of urinary calculi.

Accurate prediction of the response of an individual patient to lithotripsy remains impossible. Certain factors such as the chemical composition, size, and position of the calculus are known to be important in determining the success rate. This paper reports the use of magnetic resonance imaging (MRI) to evaluate 141 urinary calculi in vitro. A wide range of signals for each chemical type of calculus was found on each of the three imaging sequences used (T1-weighted, T2-weighted, and proton density). None of the chemical groups examined showed a typical MRI profile allowing it to be distinguished from the other groups. Analysis of variance showed a statistical difference between signals for apatite and struvite on the T1-weighted sequence, and between struvite and uric acid on the proton density sequence (both, P < 0.05). These results show for the first time that MRI is capable of distinguishing between different chemical types of stones. This is particularly important for the comparison of struvite and apatite which appear to be similar in conventional investigations but have quite different hardness values. Further work is in progress correlating the results of this study with stone microhardness and extracorporeal shockwave lithotripsy fragility tests to determine whether MRI accurately predicts the success of lithotripsy.

Humans↗
PubMed1994

Does lithotripsy cause hearing loss?

OBJECTIVE: To determine whether lithotripsy with the Dornier MPL9000 has any significant effect on the hearing of either patients or operators, as determined by pure tone audiometry. PATIENTS AND METHODS: Twenty patients had audiometry prior to a single exposure to lithotripsy and one hour after treatment. Staff were monitored on a 3 monthly basis. RESULTS: No evidence was found to suggest that single or repeated exposure to the noise emitted by this Dornier lithotripter was associated with any hearing loss. CONCLUSIONS: These results suggest that the risk to the hearing of patients exposed to lithotripter noise is negligible. Cochlear damage resulting from excessive noise depends on both the intensity of the sound and the duration of exposure. The acoustic properties of the building housing the machine may also be important and can significantly influence the intensity of the sound at the ear. At marginal levels it may be years before the deficit reaches a level that can be detected by subjective audiometry. In addition, susceptibility to noise induced hearing loss is difficult to predict. Although these results suggest that there is minimal risk to the hearing of staff members exposed to lithotripter noise, the authors recommend that staff exposed to repeated lithotripter noise over long periods undergo regular audiometric assessment (including a preemployment baseline assessment) to identify evidence of noise induced auditory trauma, and that protective equipment be worn by staff members to reduce the possibility of long-term damage.

Audiometry↗
PubMed1994

Choosing the correct pain relief for extracorporeal lithotripsy.

OBJECTIVES: To determine the best choice of analgesic for patients undergoing lithotripsy, and to attempt to identify factors which might predict which patients are most likely to find the procedure painful. PATIENTS AND METHODS: Sixty patients with stones in the pelvicalyceal system of the kidney were randomized prospectively to undergo lithotripsy with the Dornier MPL9000 lithotripter (Dormier Medical Systems, Marietta, GA, USA) after receiving either diclofenac 100 mg per rectum (n = 30) or pethidine 50 mg intravenously (n = 30) for analgesia. The patients completed a detailed questionnaire prior to treatment, and the level of pain perceived during lithotripsy was monitored using visual analogue scales (VASs). Arterial oxygen saturation (SaO2) was monitored before analgesia was given, throughout the treatment and for 30 min after cessation of treatment. RESULTS: The VASs were available for 56 patients and the results of pulse oximetry for 51 patients. Although a higher kilovoltage was recorded in the group who received pethidine this difference was not significant. Patients who received diclofenac or pethidine alone, showed a non-significant fall of SaO2 30 minutes after the end of treatment, although the largest fall in SaO2 observed with pethidine was 10%. Patients who received diclofenac and pethidine similarly showed a non-significant fall in SaO2. Four patients received intravenous benzodiazepines in addition to pethidine, and in this group there was a dramatic fall in SaO2 which persisted more than 30 min after the end of treatment (P < 0.0027). Diclofenac provided effective analgesia for most of the patients who underwent lithotripsy. Overall 11 patients (18%) required additional analgesia. Diclofenac or pethidine alone, in the doses used in this study, did not cause a significant drop in SaO2 during ESWL. The only response found to be of value in predicting a painful experience was fear of the dentist. CONCLUSIONS: This study shows that modern lithotripsy, in addition to being safe and effective, can be performed as an out-patient procedure using simple non-opiate analgesics. The need for stronger analgesia and/or sedation should be tailored to the needs of the individual patient, although it remains difficult to predict which patients will require such measures.

Adult↗
PubMed1993

Mechanical testing of urinary calculi.

The ability to predict how easily a stone will break in response to extracorporeal and intracorporeal lithotripsy would be advantageous for the urologist. In a study of fragments from 52 urinary calculi, in vitro microhardness results were found to increase for the series struvite to brushite. Ultrasound velocity measurements performed on 35 intact urinary stones showed a similar trend. This suggests that ultrasound velocity may be a useful indicator of stone strength and one which could be used in vitro to assist the planning of stone treatment.

Elasticity↗
PubMed1993

Management of complex renal calculi.

The treatment of small renal pelvic and ureteric calculi can be performed with relative safety and efficacy using lithotripsy or an endourological method. There remains however, a proportion of stones that are resistant to these methods because of their anatomical position, physical composition or sheer size. To these stones must be applied a treatment strategy using the variety of techniques to their maximum advantage. This article aims to review the accumulated experience on the management of these more complex urinary calculi.

Calcium Phosphates↗
PubMed1993

Post-irradiation bladder dysfunction: development of a rat model.

The aim of this research was to establish a small animal model for the functional and morphological study of post-irradiation bladder dysfunction. Young adult female Wistar rats were X-irradiated with single doses of 10, 15, 20 or 25 Gy. Filling cystometry was performed to assess changes in reservoir function: the volume infused to produce a rise in intravesical pressure of 5 cmH2O was calculated as an index of compliance. A biphasic reduction in this index was noted in animals receiving 15-25 Gy; the first reduction developed at about 4 weeks, and the second started at 3-4 months and persisted at 6 months. Bladder tissue was taken at this time (6 months post-irradiation) for morphological study. Histological examination demonstrated an increased mast cell density in the irradiated bladders, but was otherwise non-specific; fibrosis was discernible in only half of the 18 animals studied. Electron microscopy showed focal degeneration of smooth muscle cells, and in some areas there was selective degeneration of unmyelinated axon profiles. The biphasic reduction in the compliance index is consistent with the timing of the symptoms of the acute and late irradiation reactions reported by radiotherapy patients. Changes in axon profiles and mast cell density may be of functional significance.

Animals↗
PubMed1993

Choosing a powerful lithotriptor.

Clinicians have no yardstick to help them choose the most efficient lithotriptor. Their leading priority is a system allowing complete disintegration of the stone with the minimum number of shocks and a low re-treatment rate. One of the prerequisites of this system is a powerful shock wave generator. "Power" is as yet ill defined in lithotripsy. Therefore clinicians' choice depends upon other factors. Acoustic output measurements were recorded on 3 commercial lithotriptors representing the 3 main shock wave generating systems. These were the Dornier MPL 9000 (standard and X-155 electrodes), the Siemens (Lithostar, Lithostar Plus and System C) and the Wolf Piezolith 2300. The shock wave measurements were correlated to the capability of the lithotriptors to disintegrate standard stone models in vitro. Two factors were identified. The pulse intensity integral in the focus and the size of the focal zone proved to be the most important factors to assess and compare the efficacy or "power" of different lithotriptors. Together they can help clinicians to identify and choose the most efficient shock wave generating systems.

Acoustics↗
PubMed1993

Predicting the outcome of radical radiotherapy for invasive bladder cancer.

The correlation between T stage, histological grade, the presence of squamous metaplasia, and nuclear morphometry scores and response to radiotherapy and survival was investigated in 60 patients with muscle invasive transitional cell carcinomas of the bladder. Patients with T2 tumours showed a complete response significantly more often than those with T3 lesions. Multivariate analysis showed that T stage and initial response to radiotherapy were very strong predictors of survival though they were not independent variables. Histological grade, the presence of squamous metaplasia, and nuclear morphometry scores were not found to have any predictive value.

Aged↗
PubMed1992

Radiation protection in percutaneous renal surgery.

Two British centres have published the radiation doses received during percutaneous nephrolithotomy (PCNL). Their results were disparate. This study was performed to establish the likely exposure of the eyes and fingers of an experienced urological surgeon who creates the track into the kidney and also performs the endoscopic operation. In addition, some radioprotective gloves were evaluated. Provided that specific precautions, including a judicious use of screening, are taken, the current dose limits are unlikely to be exceeded. However, a 30% reduction in the dose limits is probable. Wearing routine radiation badges under a lead apron is an inadequate method of monitoring exposure: urologists should press for more active assistance from radiation protection officers in the monitoring of procedures in theatre and the use of ultrasound should be encouraged.

Gloves, Surgical↗
PubMed1992

Potential use of tissue adhesive in urinary tract surgery.

The search for a tissue adhesive which obviates the need for suture materials in the apposition of wound edges is not new. The early adhesive products lacked the required safety and efficacy. Experimental use of a new fibrin adhesive has shown that it may have potential use where inflammatory reaction to the suture material is undesirable or water-tight sealing of the anastomosis is required.

Animals↗
PubMed1992

The development of synthetic polymers that resist encrustation on exposure to urine.

The consequences of long-term exposure of synthetic materials to urine have prevented the development of alloplastic replacement of diseased or damaged parts of the urinary tract. Similarly, urethral and ureteric catheters require regular replacement if the complications of encrustation and blockage are to be avoided. The mechanism of encrustation is not understood completely and thus it is unclear why certain materials appear better able to resist encrustation. This study has involved the development of a new encrustation model to provide a reproducible and quantitative assessment of the susceptibility of polymers to encrustation. This model will allow beneficial characteristics of co-polymer design to be recognised, with the aim of finding new materials that are tolerant of exposure to urine. Results of co-polymers examined show that the incorporation of fluorine-containing components confers significant resistance to the formation of encrustation. It is suggested that the physico-chemical properties of polymer surfaces may be important determinants of resistance to encrustation.

Calcium↗