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Biomedical subjects

N J Parr

Publications and source records attributed to N J Parr.

At least 37 records · Page 2Linked to original sources
PubMed1992

Gastric pressure response to low dose dopamine infusion in normal man.

The gastric pressure response to distension was measured during intravenous infusion of dopamine at a rate of 2 mug min(-1)kg(-1) over 2h 50min in 5 normal volunteers to determine whether dopamine at this dose potentiated gastric adaptive relaxation, leading to a fall in gastric pressure and thus a potential delay in gastric emptying. This would be of obvious importance in patients being given dopamine at this dose to support renal function and at the same time being fed by nasogastric tube. The pressure response decreased during the first hour in all five subjects (p < 0.01). In 2 it recovered during the third hour to pre-infusion values, but in 2 it remained diminished; in 1 subject the results were equivocal. Circulating dopamine, noradrenaline and adrenaline concentrations all increased during dopamine (p < 0.05), but compared with control there was no difference in plasma free fatty acids, glycerol, cortisol or glucose concentrations. Dopamine at 2 mug min(-1) kg(-1) produced a transient fall in gastric pressure in all subjects, and a persistent fall in some. The changes in gastric pressures were seen at infusion rates that produced no metabolic or inotropic effects.

Journal Article↗
PubMed1992

Mechanisms responsible for diminished fragmentation of ureteral calculi: an experimental and clinical study.

We molded 24 synthetic stones (mean weight 680 mg., range 641 to 715) from a commercial mixture of gypsum, silica, cellulose and polyvinyl acetate. Each stone was subjected to 400 shocks on a Wolf 2300 Piezolith and groups of 6 stones were treated in 4 different modes. Mean amounts fragmented were 243 +/- 18 mg. in a free environment, 62 +/- 18 mg. confined loosely in a latex tube, 22 +/- 8 mg. impacted in the tube and 30 +/- 8 mg. impacted alongside a 7F stent. During a 30-month period 118 patients received in situ extracorporeal shock wave lithotripsy for ureteral calculi using the same lithotriptor. The mean stone burden was 11.4 mm. (range 4 to 29). Success was greater for patients with calculi 10 mm. or less than for those with stones greater than 10 mm. (71% versus 51%, p less than 0.05), despite the former group receiving less shocks (5,404 versus 7,491). The influence of size was then excluded by studying the number of shocks delivered per mm. of calculus. Patients receiving 500 to 699 shocks per mm. showed a higher success rate than those receiving a smaller number of shocks per mm. Treatment with a greater number of shocks per mm. did not improve success rate. The experimental study demonstrated that confinement and impaction significantly diminish the rate of fragmentation of calculi. However, the clinical study suggested that there may be an optimum number of shocks per mm. that should be delivered. Treatment beyond this point fails to improve results. The 28% failure rate even in those receiving the highest number of shocks per mm. suggests that large, impacted calculi are unsuitable for treatment with in situ shock wave lithotripsy on this machine.

Adolescent↗
PubMed1992

J-wire facilitates retrograde manipulation of ureteric calculi prior to extracorporeal shock wave lithotripsy.

During a 13-month period, 55 patients underwent attempted retrograde manipulation for ureteric lying above the pelvic brim. The mean stone burden was 11 mm (range 5-21); 41 stones (75%) were primary ureteric calculi and 14 (25%) were fragments resulting from extracorporeal shock wave lithotripsy to renal calculi. The method of retrograde manipulation was recorded prospectively. Retrograde flushing through an 8F angiography catheter with a mixture of saline and lignocaine gel was successful in 27 patients (49%). The insertion of a J-wire through the angiocath allowed for successful manipulation in a further 17 patients (31%). Retrograde manipulation was impossible in 11 patients (20%). There were 4 complications (7%), none attributable to the use of a J-wire.

Adolescent↗
PubMed1991

Robust electromagnetic probe for the monitoring of lithotriptor output.

The ability to measure the powers and pressures generated by extracorporeal lithotriptors is important for both patient safety and treatment planning. Regular measurements of output have been impossible in the past because there have been no instruments available that could withstand prolonged or repeated exposure to lithotriptor fields. The literature contains reports of various devices that have been used to make measurements of lithotriptor output, and these are briefly described here. The authors report the use of a new electromagnetic probe as a robust monitoring device. It has been tested by comparison with a PVdF coplanar membrane hydrophone, by comparison with the results of disintegrating a series of synthetic stones and by impact measurements. The electromagnetic probe has also been used to monitor the output of a piezoelectric extracorporeal lithotriptor over a 12-month period. Fluctuations in pulse energy of up to 350% were observed.

Electromagnetic Phenomena↗
PubMed1991

The impact of extracorporeal piezoelectric lithotripsy on the management of ureteric calculi: an audit.

The presentation and management of 153 patients with ureteric calculi requiring active treatment over a 12-month period were reviewed; 74% of patients had primary ureteric calculi and 26% had ureteric calculi composed of fragments resulting from extracorporeal piezoelectric shockwave lithotripsy (EPL) to renal calculi; 32 patients (21%) had more than 1 calculus or a steinstrasse. The primary procedures included were in situ EPL (n = 54), push-bang (44), retrograde ureteroscopy (40), Dormia basket extraction (6), push-pull (1), antegrade ureteroscopy (1) and combinations of these (7). The success of the primary procedure could not be predicted from stone size, site or duration in the ureter, but upper tract dilatation was significantly less (p less than 0.01) in the successful group. The overall success rate for complete stone extraction was 97%, but 54 patients (35%) required more than 1 procedure to achieve this. In situ EPL and push-bang, as either primary or secondary procedures, were successful in treating 79 patients (52%); 2 patients required ureterolithotomy (1.3%). The overall complication rate was 18%. Since EPL is only successful in treating approximately half of ureteric calculi, a range of other treatments should be available to maintain a low rate of open surgery.

Adolescent↗
PubMed1991

Does further extracorporeal lithotripsy promote clearance of small residual fragments?

Small persistent fragments (less than or equal to 4 mm) following extracorporeal shock wave lithotripsy have been termed clinically insignificant residual fragments (CIRF), but their presence may be associated with an increased rate of development of recurrent symptomatic renal calculi. We have adopted a policy of further extracorporeal piezoelectric shock wave lithotripsy (EPL) for patients with CIRF in an attempt to promote complete clearance. A series of 22 patients with a mean initial stone burden of 16 mm (range 7-48) developed CIRF after a median of 2 EPL treatment sessions (range 1-9). CIRF were in the lower calices (n = 20), middle calices (n = 1) and upper calices (n = 1). These calices were normal (n = 6), slightly dilated (n = 9), moderately dilated (n = 2) or grossly dilated (n = 5). After 6 to 14 months, patients underwent a further session of EPL. One month later, 3 patients with normal calices showed a considerable reduction in CIRF, but all other patients showed no change. When CIRF form in normal calices a further session of EPL may promote clearance. However, when calices containing CIRF are significantly dilated, further EPL is of no value.

Adult↗
PubMed1990

Lithotripsy for calculi in caliceal diverticula?

There is continuing debate about the optimum management of patients with calculi in caliceal diverticula. Extracorporeal piezoelectric lithotripsy (EPL) has the advantage of being non-invasive, whereas endourological management can treat the underlying anatomical problem. A total of 20 patients with calculi in caliceal diverticula were treated with EPL. Twelve of 16 patients with symptoms (75%) were rendered symptom-free but only 5 (25%) became stone-free. This information should be of value in counselling patients before selecting the appropriate treatment.

Adult↗
PubMed1989

Transurethral resection of the prostate and bladder tumour without withdrawal of warfarin therapy.

Twelve resections of prostate and 1 extensive bladder tumour were performed in patients on long-term anticoagulation without withdrawal of warfarin therapy. The mean preoperative prothrombin index was 2.3. Four patients required blood transfusion. There were no major complications. The effects of surgery and infusion of fresh frozen plasma (FFP) on the level of anticoagulation were monitored. FFP reduced the prothrombin index by 0.25/unit. Transurethral resection can be carried out safely by an experienced urologist on patients anticoagulated with warfarin, reducing the risk of serious thromboembolic complications associated with withdrawal of anticoagulation.

Aged↗
PubMed1989

Intermittent omental torsion--an unusual cause of recurrent abdominal pain?

A case of haemoperitoneum arising from an omental haematoma is described. Histology suggests that this resulted from an omental torsion. The omentum, however, was not torted at the time of laparotomy. Furthermore, there was a history of similar episodes of pain over the previous eighteen months. This suggests that spontaneous derotation of an omental torsion may occur, and may be an unusual cause of recurrent abdominal pain.

Abdomen↗
PubMed1988

Relationship between gastric emptying of liquid and postvagotomy diarrhoea.

Gastric emptying of liquid was studied in 10 normal volunteers and in 27 patients previously treated with truncal vagotomy and drainage. Thirteen of the twenty-seven patients complained of persistent postvagotomy diarrhoea. For each study 300 ml 15 per cent dextrose, labelled with 99mTc-diethylene triamine penta-acetic acid (DTPA), was ingested at a standard rate by subjects who sat facing a gamma camera. Imaging proceeded for 30 min. Gastric area activity curves were corrected for emptying of the test meal during ingestion, and for movement using a new image alignment technique. Gastric emptying at 15 min was 10 +/- 2.6 per cent (mean +/- s.e.m.) in healthy volunteers, 48 +/- 7.3 per cent in patients without diarrhoea, and 84 +/- 2.3 per cent in those with diarrhoea (P less than 0.001, ANOVA). Gastric emptying from 15 min onwards was slower than normal in both patient groups (P less than 0.001). These results show that initial gastric emptying is rapid following truncal vagotomy and drainage, and this change is greater in patients with postvagotomy diarrhoea. No patient with diarrhoea had normal initial gastric emptying.

Adult↗
PubMed1988

Intragastric bile does not perturb gastric emptying of liquids in humans.

Gastric stasis and duodenogastric reflux have each been implicated in the pathogenesis of various upper gastrointestinal disorders. However, the relationship between intragastric bile and gastric emptying has not been explored. In each of nine healthy volunteers (seven men and two women, ages 22-47 years), gastric emptying of 300 ml 10% dextrose labeled with [99mTc]DTPA was measured twice using gamma camera imaging. During one study, 20 min after ingestion of the test meal, 525 mg of freeze-dried, sterilized human T-tube bile dissolved in 20 ml water was introduced into the stomach via a previously sited fine-bore nasogastric tube. Intragastric bile salt concentrations were calculated to be within the range 1.7-2.9 mM. In control studies, 20 ml of water alone was similarly introduced. Emptying at 20 min was comparable for both groups of studies (38 +/- 3% vs 39 +/- 4%; mean values +/- SEM). For each individual study, emptying from 20 to 60 min was well represented by a single exponential function (r = 0.81-0.99). Half-emptying times for curves fitted over this period were similar in the two groups (bile: T1/2 = 18.8 +/- 2.6 min; control T1/2 = 18.8 +/- 1.9 min). These results indicate that intragastric bile, in concentrations similar to those found in patients with gastric ulcer, has no effect on gastric emptying of dextrose in normal subjects.

Adult↗
PubMed1988

Endometriosis and the gut.

Six patients with endometriosis involving the intestine are described and illustrate the variety of symptoms which may occur in this condition, many of which are frequently associated with the more common gastrointestinal illnesses. A correct preoperative diagnosis based on history, clinical examination, radiology, and endoscopy may be difficult to make, and when first discovered at laparotomy endometriosis can easily be mistaken for other inflammatory, or neoplastic processes. A histological diagnosis should always be made before definitive treatment.

Adult↗
PubMed1988

Mechanisms governing the biphasic pattern of gastric emptying after truncal vagotomy and pyloroplasty.

The pattern of gastric emptying after truncal vagotomy and drainage is usually biphasic. An early rapid phase is followed by a characteristically abrupt transition to slow emptying. The mechanisms responsible for this pattern were studied in six dogs with truncal vagotomy and pyloroplasty, fitted with a proximal duodenal cannula. Gastric emptying was measured using gamma camera imaging of a radiolabelled 15% dextrose test meal. Sixty one hour studies were done using five designs. (1) With the cannula closed gastric emptying was initially rapid, followed by stasis (emptying at 15 min - 32% (5.3), 60 min - 34% (4.8); mean (SE)). (2) With the cannula open emptying was very rapid (15 min - 76% (4.2) p less than 0.001, 60 min - 88% (2.6) p less than 0.001 ANOVA). (3) Distal duodenal instillation of isotonic saline, at a rate equivalent to gastric emptying with the cannula closed, did not retard this rapid emptying (15 min - 78% (10.6), 60 min - 90% (5.4)). (4) With duodenal instillation of 15% dextrose, gastric emptying remained faster than in studies without diversion (15 min - 50% (7.0) NS, 60 min - 65% (6.8) p less than 0.01), but was slower than during diversion alone (p less than 0.05). (5) Finally, duodenal instillation of 15% dextrose before administration of the test meal produced slower initial emptying without subsequent stasis (15 min - 24% (4.5), 60 min - 47% (10.6)), although the amounts emptied were not significantly different from those with the cannula closed. These results indicate that after truncal vagotomy and pyloroplasty small bowel resistances play a significant role in controlling gastric emptying. Osmoreceptor responses persist after truncal vagotomy, but sympathetic inhibitory responses to small bowel distension are not involved in the regulatory process.

Animals↗
PubMed1988

Abnormal pattern of gastric emptying of liquid in chronic duodenal ulcer.

Gastric emptying was measured in 12 patients with chronic duodenal ulceration and compared with the results from 10 healthy volunteers. The test meal of 300 ml 15% dextrose, labelled with 99mTc-DTPA, was ingested in increments over 6 min. Gamma camera imaging proceeded over 30 min, with a 1-min frame time. A direct correction was applied for the fraction emptying into the small bowel during the ingestion period. Gastric emptying at 6 min was significantly greater in the group with duodenal ulcer (14.4 +/- 2.7% vs. 4.2 +/- 0.9%: mean +/- SEM, p less than 0.01). From this time onwards there were no significant differences in the rates of gastric emptying. These results suggest that chronic duodenal ulcer is associated with an abnormal pattern of gastric emptying of liquid, characterised by an initial rapid phase.

Adult↗