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Biomedical subjects

A H Shennan

Publications and source records attributed to A H Shennan.

At least 19 recordsLinked to original sources
PubMed2006

Can aneroid sphygmomanometers be used at altitude?

Mercury-independent devices are increasingly being used in clinical practice as mercury will soon be removed from clinical use as a result of environmental, health and safety concerns. The aim of this study was to evaluate the accuracy of a portable aneroid device in an adult population at high altitude by following the part of the protocol of the British Hypertension Society regarding comparison between device and observer. We examined 10 subjects in Cerro de Pasco, Peru, which is situated 4370 m above sea level. The aneroid device was initially calibrated at both high altitude and at sea level to ensure optimal function. Validation of the device was undertaken at high altitude by connecting it in parallel to two mercury sphygmomanometers. Eleven sequential same-arm measurements were taken from each subject by two trained observers, alternating between mercury sphygmomanometry and the aneroid device. Simultaneous mercury readings were also recorded for additional analysis. During calibration, all 60 comparisons between the aneroid and mercury sphygmomanometers were within 3 mm Hg both at sea level and at high altitude. At validation, the device achieved an A grade for both systolic and diastolic pressures and also fulfilled the requirements of the Association for the Advancement of Medical Instrumentation. The mean and standard deviation for systolic and diastolic pressures, respectively, were -1.32 (4.3) mm Hg and 3.7 (4.7) mm Hg in sequential analysis and -0.7 (2.6) mm Hg and -3.3 (2.7) mm Hg in simultaneous analysis. We conclude that the Riester-Exacta portable aneroid device can be recommended for use in an adult population at high altitude.

Adult↗
PubMed2006

Vitamin C and vitamin E in pregnant women at risk for pre-eclampsia (VIP trial): randomised placebo-controlled trial.

BACKGROUND: Oxidative stress could play a part in pre-eclampsia, and there is some evidence to suggest that vitamin C and vitamin E supplements could reduce the risk of the disorder. Our aim was to investigate the potential benefit of these antioxidants in a cohort of women with a range of clinical risk factors. METHODS: We did a randomised, placebo-controlled trial to which we enrolled 2410 women identified as at increased risk of pre-eclampsia from 25 hospitals. We assigned the women 1000 mg vitamin C and 400 IU vitamin E (RRR alpha tocopherol; n=1199) or matched placebo (n=1205) daily from the second trimester of pregnancy until delivery. Our primary endpoint was pre-eclampsia, and our main secondary endpoints were low birthweight (<2.5 kg) and small size for gestational age (<5th customised birthweight centile). Analyses were by intention to treat. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN 62368611 . FINDINGS: Of 2404 patients treated, we analysed 2395 (99.6%). The incidence of pre-eclampsia was similar in treatment placebo groups (15% [n=181] vs 16% [n=187], RR 0.97 [95% CI 0.80-1.17]). More low birthweight babies were born to women who took antioxidants than to controls (28% [n=387] vs 24% [n=335], 1.15 [1.02-1.30]), but small size for gestational age did not differ between groups (21% [n=294] vs 19% [n=259], 1.12 [0.96-1.31]). INTERPRETATION: Concomitant supplementation with vitamin C and vitamin E does not prevent pre-eclampsia in women at risk, but does increase the rate of babies born with a low birthweight. As such, use of these high-dose antioxidants is not justified in pregnancy.

Adult↗
PubMed2006

Vaginal delivery can be considered in monochorionic diamniotic twins.

The outcomes of 60 sets of monochorionic diamniotic (MCDA) twins were compared with 218 sets of dichorionic diamniotic (DCDA) twins. The caesarean section rates for MCDA were similar to those for DCDA twins (56.6 versus 53.6%, P > 0.1). Although the number of babies with 5-minute Apgar score of <7 was significantly higher for vaginally delivered MCDA twins compared with that of DCDA twins (12 versus 3.5%, P < 0.001), the umbilical artery pH of <7.2 was similar (20 versus 13%, P > 0.05). Admission to neonatal intensive care unit (NICU) and neonatal mortality were also similar in both groups. Delivery by caesarean section was associated with increased admission to the NICU and neonatal mortality for MCDA twins when compared with vaginal delivery group. From this retrospective cohort study, we can conclude that vaginal delivery for MCDA twins appeared to be a reasonable management option when similar selection criteria for vaginal delivery of DCDA twins were applied.

Adult↗
PubMed2005

An accurate automated blood pressure device for use in pregnancy and pre-eclampsia: the Microlife 3BTO-A.

OBJECTIVE: To assess the accuracy of an automated blood pressure device (Microlife 3BTO-A) in pregnancy and pre-eclampsia according to the British Hypertension Society (BHS) protocol. DESIGN: Prospective observational study. SETTING: Antenatal ward and clinics at Guy's and St Thomas' Hospital, London, UK. POPULATION: One hundred and five pregnant women including 35 women with non-proteinuric hypertension and 35 with pre-eclampsia. METHODS: Two trained observers took nine sequential same-arm measurements from each woman. Measurements alternated between a mercury sphygmomanometer and the device. MAIN OUTCOME MEASURES: Grading criteria of the BHS protocol (A/B grade = pass; C/D grade = fail). RESULTS: The device passed the BHS protocol by achieving an A/B grade. It also achieved criteria of the Association for the Advancement of Medical Instrumentation for systolic and diastolic pressures respectively, in normotensive [-0.5 (5.7) mmHg; -0.07 (7.7) mmHg], non-proteinuric hypertensive [-3.3 (6.9) mmHg; -2.4 (6.6) mmHg] and pre-eclamptic pregnancy [-4.1 (6.4) mmHg; -1.3 (7.9) mmHg]. CONCLUSION: The Microlife 3BTO-A can be recommended for use in a pregnant population, including pre-eclampsia, according to the BHS protocol.

Adult↗
PubMed2003

A randomised controlled trial of fluid pre-loading before low dose epidural analgesia for labour.

Preloading with fluid is recommended before regional block in labour. Low dose epidurals may produce less haemodynamic disturbance than traditional stronger solutions of local anaesthetics. Our aim was to compare the incidence of hypotension in normal labouring women who received a low dose epidural (0.1% bupivacaine 15 mL with fentanyl 2 microg microg.mL(-1)) with and without an i.v. crystalloid preload. Women with normal labours were randomised to the intervention group: no i.v. crystalloid preload (n = 85) and the control group: 7 mL mL.kg(-1) i.v. crystalloid solution before epidural injection (n = 83). Mean arterial pressure was recorded every 5 min for 30 min. There was no difference between the groups in mean decrease in mean arterial pressure and similar proportions of women showed falls in mean arterial pressure of 20% or greater (13% vs. 11%, risk ratio 1.2, 95% CI 0.54 to 2.8, P = 0.6). Blinded analysis by independent obstetricians revealed no differences in the fetal heart rate abnormalities (20% vs. 15%, risk ratio 1.3, 95% CI 0.67 to 2.7). A scientifically valid conclusion whether preloading is useful cannot be drawn from this study. This study suggests that about 350 participants in each group would be necessary to exclude a type 2 error in a future study.

Clinical Trial↗
PubMed2003

Validation of the Welch Allyn 'Vital Signs' blood pressure measurement device in pregnancy and pre-eclampsia.

OBJECTIVE: To establish the accuracy the Welch Allyn 'Vital Signs' blood pressure monitor in pregnancy and pre-eclampsia according to a modified British Hypertension Society protocol. DESIGN: Prospective observational study. SETTING: Maternity Unit/Obstetric Ward, Guy's and St Thomas' Hospital, London, UK. POPULATION: Forty-three pregnant women of whom 12 had pre-eclampsia. METHODS: Nine sequential same-arm measurements were taken from each woman by two trained observers, alternating between a mercury sphygmomanometer and the device. The last seven readings were analysed according to the British Hypertension Society protocol. The accuracy of the device was determined using the grading scale indicated by the British Hypertension Society protocol (grade A/B = pass, grade C/D = fail). MAIN OUTCOME MEASURES: Grading criteria of the British Hypertension Society Protocol. RESULTS: The Welch Allyn 'Vital Signs' monitor achieved a grade A for both systolic and diastolic pressures in pregnant women who did not have pre-eclampsia. In those women with pre-eclampsia, it achieved a grade D and B for systolic and diastolic pressures, respectively. The mean differences between the observers and the device in women without pre-eclampsia were -2.6 (6.4) and -1.5 (7.2) mmHg for systolic and diastolic pressures [and in pre-eclamptic women -7.8 (6.3) and -5.5 (6.5)mmHg]. It therefore fulfils criteria set by the Association for the Advancement of Medical Instrumentation (mean <5 mmHg and standard deviation <8 mmHg) in pregnancy, but not in pre-eclampsia. CONCLUSION: This is the first automated device suitable for robust clinical use that can be recommended for use in pregnancy. However, it should be borne in mind that-similar to other devices--it significantly under--recorded readings obtained in pre-eclamptic women.

Blood Pressure↗
PubMed2002

Upright versus recumbent position in the second stage of labour in women with combined spinal-epidural analgesia.

Neuraxial blockade is widely used for pain relief in labour. This form of analgesia may be associated with an increase in instrumental delivery rates due to dystocia. 'Traditional' epidurals cause motor blockade and hence immobility. Using a low dose anaesthetic-opioid combination with either epidural or combined spinal-epidural, selective sensory blockade can be achieved, allowing mobility as well as pain relief. In this study, we randomised women with combined spinal-epidural analgesia either to mobilise (upright group n = 25) or to remain recumbent (n = 41) in the second stage of labour. We found women in the upright group had significantly shorter total second stage, (132 vs 109 min,P = 0.019) particularly during the pushing phase (73 vs 51 min, P = 0.011). Although there were fewer instrumental deliveries in the upright group, this was not statistically significant. Women who were randomised to the upright group, did actually mobilise. We conclude that mobilisation in the second stage of labour is possible, and may reduce the length of the second stage.

Clinical Trial↗
PubMed2002

Obstetric cholestasis, outcome with active management: a series of 70 cases.

OBJECTIVE: To determine the nature and outcome of obstetric cholestasis in a United Kingdom population. DESIGN: Prospective analysis of clinical outcome in women diagnosed with obstetric cholestasis that is actively managed. SETTING: Antenatal population of three London hospitals between August 1999 and April 2001. POPULATION: Seventy women with obstetric cholestasis defined as abnormal liver function (one or more abnormality in gamma-glutamyl transpeptidase, alanine amino-transferase, aspartate amino-transferase and total bile acids) in a pregnant woman with pruritus, in the absence of other pathology. METHODS: All women were interviewed weekly regarding their symptoms. All were actively managed according to a standardised protocol, which included early delivery before 38 weeks. Obstetric outcome was recorded. RESULTS: Seventy women of mean age 30 (6) years delivered 73 infants. The median gestation at onset of pruritus was 30 (range 4-39) weeks and at diagnosis of obstetric cholestasis was 33.7 (range 21-40.7) weeks. Asian women were more likely to be diagnosed with obstetric cholestasis. Pruritus was usually severe and generalised, and commonly worst on the palms and/or soles of the feet. There were no stillbirths or perinatal deaths. Twenty-five women required caesarean section (36%); only four (16%) were for fetal distress. Twelve women (17%) delivered before 37 weeks, of which eight (67%) were iatrogenic. Ten (14%) infants required admission to the special care baby unit of which four (40%) were ventilated. CONCLUSIONS: Policies of active management result in increased intervention and associated complications. This must be balanced against possible reductions in perinatal mortality.

Adolescent↗
PubMed2001

Validation of the Welch Allyn 'Vital Signs' oscillometric blood pressure monitor.

This study has determined the accuracy of the Welch Allyn 'Vital Signs' blood pressure (BP) monitoring device in an adult population, according to the criteria of the British Hypertension Society (British Hypertension Society, 1993). Validation was also classified by the American 'Association for the Advancement of Medical Instrumentation' (AAMI). The Welch Allyn 'Vital Signs' monitor achieved a BHS grade A for both systolic and diastolic BP. It also met the criteria for the AAMI protocol. The mean differences between trained observers using a mercury sphygmomanometer and the device were -1 +/- 5 mm Hg for systolic BP and -3 +/- 4 mm Hg for diastolic BP. The Welch Allyn 'Vital Signs' monitor can be recommended for clinical use in the adult population. This is one of the first oscillometric monitors designed for routine use in a hospital environment that has been found to provide an accurate assessment of BP by accepted validation procedures.

Adult↗
PubMed2001

Pruritus may precede abnormal liver function tests in pregnant women with obstetric cholestasis: a longitudinal analysis.

Obstetric cholestasis is a liver disorder unique to pregnancy, which typically presents with pruritus. However, pruritus is common in pregnancy and the diagnosis of obstetric cholestasis is confirmed by finding abnormal liver function. We report 10 cases in which pruritus occurred before any abnormality in liver function tests (including total serum bile acids) and discuss the implications of this for clinical practice.

Adult↗
PubMed2000

Reliable urine analysis in the management of hypertensive pregnancies.

OBJECTIVE: To determine the intra- and inter-observer precision of the Clinitek 50 automated urinalysis system. SETTING: A teaching hospital. METHODS: Urine samples were tested by seven operators with Multistix 8SG reagent strips, in duplicate and in replicates of five by the same operators, and by groups of four operators on the same samples. Precision was assessed using true urine samples and Chek-Stix control strips. RESULTS: All 32 samples tested in duplicate and in replicates of five agreed to within one colour block by between 99.4 and 100% for all eight analytes. Seven samples tested by four different operators also gave 100% agreement to within one colour block for nearly all analytes. All operators found the Clinitek 50 system to be quick and easy to use. CONCLUSION: The Clinitek 50 automated urinalysis device demonstrates high intra- and inter-observer precision for duplicate, multiple replicate and multiuser testing with consistent performance. There is potential to improve antenatal care by introducing this technology into hospital or home-based care.

Female↗
PubMed2000

A comparison of hemodynamic data derived by pulmonary artery flotation catheter and the esophageal Doppler monitor in preeclampsia.

OBJECTIVE: This study was undertaken to compare hemodynamic data derived with the esophageal Doppler monitor against those obtained with a pulmonary artery flotation catheter in women with complicated preeclampsia. STUDY DESIGN: Seventeen women with severe preeclampsia who had a pulmonary artery flotation catheter placed for clinical indications also had an esophageal Doppler monitor inserted. Hemodynamic data were recorded on 2 occasions separated by several hours with both the pulmonary artery flotation catheter and the esophageal Doppler monitor simultaneously. RESULTS: The esophageal Doppler monitor underestimated cardiac output by 36% +/- 14% (mean +/- SD). The esophageal Doppler monitor accurately estimated cardiac output in 3 women >40 years old, whereas in the remaining women (all <35 years old) the esophageal Doppler monitor underestimated cardiac output by 38% +/- 11%. The esophageal Doppler monitor accurately reflected changes in cardiac output with time when compared with the pulmonary artery flotation catheter. CONCLUSION: In women with preeclampsia the esophageal Doppler monitor consistently underestimated cardiac output by approximately 40%. It is not known whether the apparent increase in accuracy among the women >40 years old arose by chance or reflected a real improvement in performance. The esophageal Doppler monitor accurately reflected the direction and magnitude of the changes in cardiac output with time.

Adult↗
PubMed2000

A validation of the Mobil O Graph (version 12) ambulatory blood pressure monitor.

OBJECTIVE: To assess the clinical accuracy of the Mobil O Graph (version 12) ambulatory blood pressure monitor in an adult population. METHODS: The accuracy of the device was assessed by predefined criteria (British Hypertension Society, BHS) in 85 subjects recruited from the patients and staff in a teaching hospital. A series of same-arm sequential blood pressure measurements were taken: first two observers taking simultaneous mercury readings, followed by a reading with the Mobil O Graph ambulatory monitor. A total of seven readings were taken from each subject in the sitting position. The data were then analysed according to the BHS protocol and the criteria of the Association for the Advancement of Medical Instrumentation (AAMI). RESULTS: The Mobil O Graph ambulatory monitor fulfilled the criteria of the BHS protocol, achieving a grade B for systolic blood pressure (SBP) and a grade A for diastolic blood pressure (DBP). The mean differences were -2+/-8 mmHg for SBP and -2+/-7 mmHg for DBP. The device therefore also passed the AAMI standard (the mean to be within 5+/-8 mmHg). CONCLUSION: The Mobil O Graph ambulatory monitor performed in a satisfactory manner according to the BHS and the AAMI criteria and can therefore be recommended for clinical use in the general population.

Adolescent↗