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Biomedical subjects

R Yates

Publications and source records attributed to R Yates.

At least 19 recordsLinked to original sources
PubMed2001

Rapid and radical amniodrainage in the treatment of severe twin-twin transfusion syndrome.

We have evaluated the role of a rapid and radical method of amniodrainage in the treatment of severe twin-twin transfusion. The outcome of 15 patients with severe twin-twin transfusion for which a amniodrainage was performed by means of a vacuum bottle system was compared with the outcome of 15 patients with a similar condition, matched for gestational age at the time of the initial procedure and drained using a standard procedure. In the study group the amniodrainage ended when no amniotic fluid could be aspirated, whereas the women in the standard group were drained with a syringe system and the fluid was removed until the deepest amniotic fluid pool was <8 cm. At the initial procedure, the mean volume of amniotic fluid drained was significantly (p<0.05) higher (3252 vs 2153 ml) and the length of the procedure significantly (p<0.001) shorter (21 vs 41 min) in the study group than in the standard group. The mean post-procedure amniotic fluid index was significantly (p<0.001) smaller (2.9 vs 7.7 cm) after radical amniodrainage than after the standard amniodrainage. The mean number of procedures was significantly (p<0.001) lower (1.5 vs 5.6) in the study group compared to the standard group. In the study group the mean placental thickness increased significantly (p<0.001) from 9 mm before the procedure to 49 mm after, and the overall perinatal survival rate was 80% and the proportion of pregnancies with at least one survivor was 93%. The present data indicate that early, rapid and radical amniodrainage is an effective and low-cost therapy for severe twin-twin transfusion syndrome. Compared to the standard amniodrainage technique it also appears to reduce the need for multiple procedures.

Amnion↗
PubMed2001

An early bone tool industry from the Middle Stone Age at Blombos Cave, South Africa: implications for the origins of modern human behaviour, symbolism and language.

Twenty-eight bone tools were recovered in situ from ca. 70 ka year old Middle Stone Age levels at Blombos Cave between 1992 and 2000. These tools are securely provenienced and are the largest collection to come from a single African Middle Stone Age site. Detailed analyses show that tool production methods follow a sequence of deliberate technical choices starting with blank production, the use of various shaping methods and the final finishing of the artefact to produce "awls" and "projectile points". Tool production processes in the Middle Stone Age at Blombos Cave conform to generally accepted descriptions of "formal" techniques of bone tool manufacture. Comparisons with similar bone tools from the Later Stone Age at Blombos Cave, other Cape sites and ethnographic collections show that although shaping methods are different, the planning and execution of bone tool manufacture in the Middle Stone Age is consistent with that in the late Holocene. The bone tool collection from Blombos Cave is remarkable because bone tools are rarely found in African Middle or Later Stone Age sites before ca. 25 ka. Scarcity of early bone tools is cited as one strand of evidence supporting models for nonmodern behaviour linked to a lack of modern technological or cognitive capacity before ca. 50 ka. Bone artefacts are a regular feature in European sites after ca. 40 ka, are closely associated with the arrival of anatomically modern humans and are a key behavioural marker of the Upper Palaeolithic "symbolic explosion" linked to the evolution of modern behaviour. Taken together with recent finds from Klasies River, Katanda and other African Middle Stone Age sites the Blombos Cave evidence for formal bone working, deliberate engraving on ochre, production of finely made bifacial points and sophisticated subsistence strategies is turning the tide in favour of models positing behavioural modernity in Africa at a time far earlier than previously accepted.

Anthropology, Physical↗
PubMed2001

Online motion-gated dynamic three-dimensional echocardiography in the fetus--preliminary results.

The aim of this study was to visualise the fetal heart in dynamic three dimensions (4-D) during an ultrasound (US) scan (online), rather than after (offline). With special pairing and sequential setting to minimise interference between two scanners, umbilical arterial Doppler waveforms (UADWs) from one scanner were used as an online motion gating source to trigger simultaneous 3-D cardiac structural data acquisition by another. Of 25 data sets from 10 fetuses, 18 were acquired in 15 to 30 s per set with > or = 50% Doppler waveforms efficiently converted to triggering signals. Of 15 valid 4-D data sets, 10 were reconstructed in 2 to 20 min, compared to over 2 h previously reported (mainly for offline gating). Fine structures (including chordae tendinae and trabecular muscles) were depicted in six sets. The main problems in degrading 4-D images were extensive shadowing (6) from bony structures during rigid mechanical scanning, and random motion artefacts (6) from prolonged setting-up time with a complex combination of several systems. Integration of these systems is, therefore, recommended.

Artifacts↗
PubMed2001

The erosive effects of some mouthrinses on enamel. A study in situ.

BACKGROUND: There are both anecdotal clinical and laboratory experimental data suggesting that low pH mouthrinses cause dental erosion. This evidence is particularly relevant to acidified sodium chlorite (ASC) formulations since they have plaque inhibitory properties comparable to chlorhexidine but without the well known local side effects. AIM: Studies in situ and in vitro were planned to measure enamel erosion by low pH mouthrinses. The study in situ measured enamel erosion by ASC, essential oil and hexetidine mouthrinses over 15-day study periods. The study was a 5 treatment, single blind cross over design involving 15 healthy subjects using orange juice, as a drink, and water, as a rinse, as positive and negative controls respectively. 2 enamel specimens from unerupted human third molar teeth were placed in the palatal area of upper removable acrylic appliances which were worn from 9 a.m. to 5 p.m., Monday to Friday for 3 weeks. Rinses were used 2x daily and 250 ml volumes of orange juice were imbibed 4x daily. Enamel loss was determined by profilometry on days 5, 10 and 15. The study in vitro involved immersing specimens in the 4 test solutions together with a reduced acid ASC formulation for a period of 4 h under constant stirring; Enamel loss was measured by profilometry every hour. RESULTS: Enamel loss was in situ progressive over time with the 3 rinses and orange juice but negligible with water. ASC produced similar erosion to orange juice and significantly more than the two proprietary rinses and water. The essential oil and hexetidine rinses produced similar erosion and significantly more than water. Enamel loss in vitro was progressive over time, and the order from low to high erosion was reduced acid ASC, ASC, Essential oil, and hexetidine mouthrinses and orange juice. CONCLUSION: Based on the study in situ, it is recommended that low pH mouthrinses should not be considered for long term or continuous use and never as pre-brushing rinses. In view of the plaque inhibitory efficacy of ASC, short- to medium-term applications similar to those of chlorhexidine would be envisaged.

Adult↗
PubMed2001

Pharmacokinetics and tolerability of the orally active selective epidermal growth factor receptor tyrosine kinase inhibitor ZD1839 in healthy volunteers.

OBJECTIVE: To investigate the pharmacokinetics and tolerability of ZD1839 (Iressa), an orally active selective epidermal growth factor receptor-tyrosine kinase inhibitor, in healthy volunteers. DESIGN: Two randomised, double-blind, placebo-controlled, parallel-group studies of pharmacokinetics and tolerability, followed by a nonblind, randomised, 2-period crossover study to assess the effect of food on bioavailability. SETTING: Two centres in the UK. STUDY PARTICIPANTS: Healthy male volunteers aged between 18 and 62 years. INTERVENTIONS: The first study investigated the pharmacokinetics and tolerability of ascending single oral doses of ZD1839 (1 to 75mg). The second study investigated the pharmacokinetics and tolerability of multiple doses of ZD1839 (100mg once daily for 3 days). The third study investigated the effect of food on the bioavailability of a single 50mg dose of ZD1839. OUTCOME MEASURES AND RESULTS: Peak plasma drug concentrations (Cmax) of ZD 1839 occurred between 3 and 7 hours after administration. Cmax and area under the concentration-time curve (AUC) were dose-proportional from 10 to 100mg. The terminal elimination half-life (t1/2beta) was 28 hours (range 12 to 51 hours). Cmax was reduced by 34% and AUC by 14% by ingestion of food; t1/2beta was not affected. Urinary recovery of ZD1839 was <0.5%, indicating that this was not a major route of elimination. The pharmacokinetics of ZD1839 during administration of multiple doses could be predicted from day 1 values. There were no serious adverse events or withdrawals, and the frequency of adverse events was similar that with placebo. CONCLUSIONS: These data support the further clinical investigation of ZD 1839. The elimination half-life suggests that once daily oral administration is appropriate.

Adolescent↗
PubMed2000

Scientific, ethical, and logistical considerations in introducing a new operation: a retrospective cohort study from paediatric cardiac surgery.

OBJECTIVE: To review the initial impact on mortality of infants with congenital heart disease of a new surgical technique that is now taken for granted. DESIGN: Retrospective cohort study. SETTING: A tertiary paediatric cardiology centre. SUBJECTS: 325 consecutive neonates with simple transposition of the great arteries admitted before, during, and after the preferred management changed from the Senning operation to the arterial switch (1978-98); and 100 consecutive neonates requiring a different neonatal open heart operation that did not change in that period. MAIN OUTCOME MEASURES: Mortality before and early after operation reconstructed sequentially as the series evolved and retrospectively once the series was complete; actuarial survival associated with the different treatment strategies. RESULTS: For both the transposition and the comparison group, early mortality in 1998 was lower than in 1978. During that period, however, there was a phase temporally related to the adoption of the switch operation in which early mortality for transposition increased. Actuarial survival of recent patients with "intention to treat" with arterial switch is superior to those with intention to treat with the Senning operation, as predicted when the switch operation was first adopted. CONCLUSIONS: A period of increased hazard for individual patients may occur when a specialist community, a particular unit, and an individual surgeon are all learning a new technique concurrently. Obtaining informed consent during this time of uncertainty is helped by clarity about the objectives of treatment and availability of relevant local and international data.

Child↗
PubMed2000

Transposition of the great arteries, ventricular septal defect and diaphragmatic hernia in a fetus: the role of prenatal diagnosis in helping to predict postnatal survival.

Congenital heart disease and congenital diaphragmatic hernia are frequently associated. The combination of these lesions is predictive of poor postnatal survival. The identification of both lesions during prenatal life may facilitate improved survival in carefully selected cases. We present a case of left-sided diaphragmatic hernia with transposition of the great arteries and a ventricular septal defect (VSD) that survived following repair of both defects within the first six weeks of life.

Adult↗
PubMed2000

Effects of the aromatase inhibitor anastrozole on serum oestrogens in Japanese and Caucasian women.

PURPOSE: Substantial differences in plasma oestrogen disposition have been reported between Japanese and Caucasian women, but there are currently few data available on the relative endocrinological effects of aromatase inhibitors in these two groups. Hence, the effects of the nonsteroidal aromatase inhibitor anastrozole on serum oestrogen concentrations were compared in 24 healthy postmenopausal Japanese women and 24 healthy postmenopausal Caucasian women. METHODS: Anastrozole, 1 mg/day, was given once daily for 16 days. Serum oestradiol and oestrone sulphate levels were measured on three consecutive days beginning 2 days before the first dose, and on a further three consecutive days beginning on the penultimate day of dosing. Trough concentrations of anastrozole (measured 24 h after dosing) were also determined during the same periods. RESULTS: There were no substantial differences in plasma oestrogen concentrations between the Japanese and Caucasian women at baseline. On average, anastrozole suppressed serum oestradiol and oestrone sulphate levels by approximately 87% and 93%, respectively, for both Japanese and Caucasian women, and minimum plasma anastrozole concentrations at steady-state (anastrozole C(min)) were also similar in both groups. Statistical analysis of serum oestradiol and serum oestrone sulphate levels, and plasma anastrozole C(min) showed that there were no statistically significant differences between the Japanese and Caucasian women. CONCLUSION: Neither the pharmacodynamic effects of anastrozole on serum oestrogens nor the pharmacokinetics of anastrozole differ between postmenopausal Japanese and Caucasian women. Hence, these findings suggest that the therapeutic benefits of anastrozole in Caucasians will be predictive of the drug's effect in Japanese women and support the use of anastrozole in postmenopausal Japanese women with breast cancer.

Aged↗
PubMed2000

Calculating blood flow from Doppler measurements in the systemic-to-pulmonary artery shunt after the Norwood operation: a method based on computational fluid dynamics.

Hypoplastic left heart syndrome is currently the most lethal cardiac malformation of the newborn infant. Survival following a Norwood operation depends on the balance between systemic and pulmonary blood flow, which is highly dependent on the fluid dynamics through the interposition shunt between the two circulations. We used computational fluid dynamic (CFD) models to determine the velocity profile in a systemic-to-pulmonary artery shunt and suggested a simplified method of calculating the blood flow in the shunt based on Doppler measurements. CFD models of systemic-to-pulmonary shunts based on the finite element method were studied. The size of the shunt has been varied from 3 to 5 mm. Velocity profiles at proximal and distal positions were evaluated and correlations between maximum and mean spatial velocity were found. Twenty-one Doppler measurements in the proximal and distal part of the shunt were obtained from six patients with hypoplastic left heart syndrome. Combining Doppler velocities and CFD velocity profiles, blood flow rate in the shunt was calculated. Flow rate evaluated from aortic Doppler and oxygen saturation measurements were performed for comparison. Results showed that proximal shunt Doppler velocities were always greater than the correspondent distal ones (ratio equal to 1.15 +/- 0.11). CFD models showed a similar behaviour (ratio equal to 1.21 +/- 0.03). CFD models gave a V(mean)/V(max) ratio of 0. 480 at the proximal junction and of 0.579 at the distal one. The agreement between the flow evaluated in the proximal and distal areas of the shunt was good (0.576 +/- 0.150 vs. 0.610 +/- 0.166 l/min). Comparison of these data with saturation data and aortic Doppler measurements correlate less well (0.593 +/- 0.156 vs. 1.023 +/- 0.493 l/min). A formula easily to quantify shunt flow rate is proposed. This could be used to evaluate the effects of different therapeutic and pharmacological manoeuvres in this unique circulation.

Anastomosis, Surgical↗
PubMed2000

Dilated cardiomyopathy in dystrophic epidermolysis bullosa.

BACKGROUND: Dystrophic epidermolysis bullosa (DEB) is an uncommon genetic disorder of the skin and mucosae. In 1996, we reported the occurrence of lethal dilated cardiomyopathy (DCM) in two affected children. METHODS: In the past seven years we have routinely screened patients with severe DEB who have been under the care of this hospital by yearly clinical review, echocardiography, and quantification of plasma selenium and carnitine concentrations, as deficiency of these micronutrients is known to be associated with the development of DCM. RESULTS: Six of 61 children have developed DCM over the seven year period of this study, four of whom have not been previously reported, and three of whom have since died. We compared the concentrations of selenium and free and total carnitine in the children who developed DCM to concentrations in those with severe DEB who did not. The concentrations of free and total carnitine when first measured were significantly lower in the children with DCM, but the selenium concentrations were not. CONCLUSIONS: We now believe that DCM is a not infrequent complication of severe recessive DEB, and may be related in part to carnitine concentrations, though the exact mechanism remains unclear. We therefore recommend that patients with this condition should undergo regular cardiac review including echocardiography.

Biomarkers↗
PubMed2000

Mitral valve replacement in children: mortality, morbidity, and haemodynamic status up to medium term follow up.

OBJECTIVE: To investigate the outcome of mechanical mitral valve replacement in children after up to 11 years of follow up. DESIGN: Retrospective analysis of case records. Operative survivors underwent echocardiographic studies to define current haemodynamic status and prosthetic valve function. SETTING: Tertiary referral centre. PATIENTS: All 54 children who underwent mitral valve replacement between January 1987 and December 1997. RESULTS: 30 day mortality was 20.3% and was associated with small valve size and supra-annular position. The actuarial freedom from the following events at five years (70% confidence interval (CI)) was: death, including 30 day mortality and transplantation, 68% (70% CI 62% to 75%); bleeding, 89% (70% CI 84% to 94%); non-structural valve dysfunction and reoperation, 92% (70% CI 87% to 97%). The incidence of endocarditis and thromboembolism was low and there was no structural valve failure. Event-free survival was 52% (70% CI 45% to 60%). Low weight, young age, and small valve size increased the chance of death or reoperation. On echocardiography, left ventricular dilatation and wall motion abnormalities were often observed. A high mean gradient over the prosthesis was associated with small valve size but not with length of follow up. CONCLUSIONS: With the use of mechanical prostheses for mitral valve replacement in children, the problem of structural valve failure is no longer an issue. However, the procedure is still associated with a high complication rate, both at surgery and during follow up, and should therefore be reserved for patients in whom valve repair is not technically feasible.

Adolescent↗
PubMed2000

Quality of life in children following mitral valve replacement.

OBJECTIVE: To measure the health related quality of life (QoL) following mitral valve replacement in childhood. DESIGN: Cross sectional study. SETTING: Tertiary referral centre. METHODS: 19 patients, median age (range) 14.4 (9.7-25.4) years, were studied at a median of 7.6 (0.5-11.2) years after their most recent mitral valve replacement. General health status was measured using age specific validated questionnaires. Ten children aged between 9-15 years completed the child health related quality of life questionnaire, and for nine older patients the UK version of the short form 36 was used. Specific questions were added to the existing questionnaires to study the effect of long term anticoagulation treatment. RESULTS: All patients in the younger age group reported impaired QoL. Five rated their QoL within the range of children with chronic physical disabilities, and in the remaining five it was worse. In the older age group, all but two patients perceived their QoL as normal or near normal compared with a reference population matched for sex and age. Having regular blood tests had a negative effect on QoL in three young children, and one older patient reported impaired QoL related to taking daily warfarin tablets. CONCLUSIONS: In this small group, the effect of mitral valve replacement on QoL appears to be age specific, with more impairment in younger children. Long term anticoagulation treatment is well tolerated in most patients.

Adolescent↗
PubMed1999

Comparison of long-term outcomes of atrial repair of simple transposition with implications for a late arterial switch strategy.

BACKGROUND: We report the single-institution, long-term results of 358 patients with simple transposition of the great arteries surviving >30 days after a Mustard (n=226, 1965 to 1980) or Senning (n=132, 1978 to 1992) procedure. METHODS AND RESULTS: Outcome measures included late death, reintervention, ECG and ambulatory ECG rhythm, new arrhythmia, and functional status. Average follow-up was 13.4 (range 0.32 to 17.9) years for the Senning group and 11.7 (range 0.04 to 23.9) years for the Mustard group. The Senning group had a better survival rate at 5, 10, and 15 years (95% versus 86%, 94% versus 82%, and 94% versus 77%, respectively). In both groups, the majority of late deaths were sudden, without preceding ventricular dysfunction. Survival and survival free of reintervention were significantly better in the Senning group (relative risk [RR] 0.34, P=0.06 versus RR 0.39, P=0.027). Loss of sinus rhythm was comparable and unrelated to death. After era correction, the incidence of atrial flutter was similar and strongly associated with late death in both groups. Clinical systemic ventricular failure was uncommon, and at last follow-up, 92% of the Senning group and 89% of the Mustard group were in New York Heart Association class I. In a model exploring the implications of elective arterial switch conversion, this would only be beneficial if the hazard late after switch was markedly reduced and/or the hazard after the Senning procedure increased with time. CONCLUSIONS: Late outcomes after the Senning procedure are superior to those after the Mustard procedure. Both groups had late sudden deaths that were not associated with clinical systemic ventricular failure. Good functional status after the Senning procedure suggests that a strategy of elective switch conversion cannot be justified for patients with isolated transposition.

Cardiac Surgical Procedures↗
PubMed1999

Persistent pulmonary hypertension of the term neonate: a strategy for management.

UNLABELLED: The management of 32 consecutive term infants referred with persistent pulmonary hypertension of the newborn were reviewed. Despite indices suggesting severe cardiorespiratory failure with a median alveolar-arterial oxygen gradient of 591 torr (inter-quartile range 432-618) and oxygenation index of 31 (18-44), all but one patient responded to conventional treatment with inhaled nitric oxide and high frequency oscillatory ventilation. CONCLUSION: Patients should be referred early to centres where maximal conventional support can be offered before consideration for extracorporeal membrane oxygenation.

Administration, Inhalation↗
PubMed1999

Common arterial trunk associated with double aortic arch.

The combination of common arterial trunk associated with double aortic arch is very rare. We are aware of only four cases ever reported in English literature. We add two cases of this entity and comment on the morphological aspects, the clinical impact of the combined lesions, and their diagnostic and therapeutic implications.

Aorta, Thoracic↗