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Biomedical subjects

A W Halligan

Publications and source records attributed to A W Halligan.

At least 19 recordsLinked to original sources
PubMed2001

Analysis of ambulatory blood pressure monitor data using a hierarchical model incorporating restricted cubic splines and heterogeneous within-subject variances.

Hypertensive disorders of pregnancy are associated with significant maternal and foetal morbidity. Measurement of blood pressure remains the standard way of identifying individuals at risk. There is growing interest in the use of ambulatory blood pressure monitors (ABPM), which can record an individual's blood pressure many times over a 24-hour period. From a clinical perspective interest lies in the shape of the blood pressure profile over a 24-hour period and any differences in the profile between groups. We propose a two-level hierarchical linear model incorporating all ABPM data into a single model. We contrast a classical approach with a Bayesian approach using the results of a study of 206 pregnant women who were asked to wear an ABPM for 24 hours after referral to an obstetric day unit with high blood pressure. As the main interest lies in the shape of the profile, we use restricted cubic splines to model the mean profiles. The use of restricted cubic splines provides a flexible way to model the mean profiles and to make comparisons between groups. From examining the data and the fit of the model it is apparent that there were heterogeneous within-subject variances in that some women tend to have more variable blood pressure than others. Within the Bayesian framework it is relatively easy to incorporate a random effect to model the between-subject variation in the within-subject variances. Although there is substantial heterogeneity in the within-subject variances, allowing for this in the model has surprisingly little impact on the estimates of the mean profiles or their confidence/credible intervals. We thus demonstrate a powerful method for analysis of ABPM data and also demonstrate how heterogeneous within-subject variances can be modelled from a Bayesian perspective.

Bayes Theorem↗
PubMed2001

Leucocyte intracellular pH and Na+/H+ exchanger isoform-1 activity in postpartum women with pre-eclampsia.

OBJECTIVE: To investigate leucocyte Na+/H+ exchanger isoform 1 activity in postpartum pre-eclamptics. DESIGN: Exchanger isoform-1 activity and intracellular resting pH were established in leucocytes isolated from two study groups. SAMPLE: Leucocytes isolated from 10 women who had had pre-eclamptic pregnancies more than five months postpartum, and from 10 age-matched normotensive women who were more than five months postpartum. SETTING: Hypertension Clinic, Antenatal Assessment Area, Leicester Royal Infirmary. METHODS: A well validated technique involving flurometry using a pH sensitive dye (BCECF-AM) was performed to determine exchanger isoform-1 activity and intracellular pH. Determination of exchanger isoform-1 protein abundance was performed by western blotting. Exchanger isoform-3 protein abundance was examined to rule out the possibility of activity due to this particular isoform. RESULTS: Intracellular pH was significantly lower in the postpartum pre-eclamptic group (7.11 +/- 0.02), compared with the postpartum normotensive controls (7.33 +/- 0.04; P < 0.001). Exchanger isoform-1 efflux rate (in mmol/L/minute) was significantly higher in the postpartum pre-eclamptic group (35.91 +/- 3.1), compared with the postpartum normotensives (23.94 +/- 2.0; P = 0.005). Exchanger isoform-1 protein density was established to be similar among the two subject groups. No exchanger isoform-3 protein was identified by western blotting. CONCLUSION: Our results suggest that elevated exchanger isoform-1 activity is an important finding in women who have suffered from pre-eclampsia. This increased activity is not due to an increase in exchanger isoform-1 protein abundance or the presence of exchanger isoform-3.

Adult↗
PubMed2001

Quantitative and qualitative assessment of women's experience of a one-stop menstrual clinic in comparison with traditional gynaecology clinics.

OBJECTIVE: A quantitative and qualitative evaluation of the views of patients attending two types of clinics for menstrual disorders. METHODS: Semi-structured qualitative interview and quantitative questionnaire. SETTING: Five traditional general gynaecology clinics and a one-stop menstrual clinic, where investigations are performed and results given to patients on the same day. PARTICIPANTS: Two hundred and thirty-nine women (126 from the gynaecology clinic and 113 from the menstrual clinic) were recruited into the quantitative study; 18 and 26 patients from the gynaecology and the menstrual clinic, respectively, were interviewed for the qualitative study. MAIN OUTCOME MEASURES: Women's views about their care and progress towards resolution of their problem. RESULTS: Following the initial consultation, 106 (84%) of the gynaecology clinic, and 98 (87%) of the menstrual clinic patients completed the first part of the questionnaire. Of those, 75 (71%) and 79 (81%) patients from the two types of clinic, respectively, completed a follow up questionnaire one year later. There were statistically significant differences in all the components of the first part of the questionnaire (information, continuity, waiting, organisation, and limbo) in favour of the one-stop menstrual clinic. After one year, there was a statistically significant difference in one of the components, patient centeredness, but not in overall process co-ordination. The interviews showed that patients attending the menstrual clinic appreciated getting the results of their investigations on the same day. They also found the organisation of the one-stop menstrual clinic more closely suited to their needs and as a result were more likely to feel they were making progress. CONCLUSION: Women were consistently more positive about their experience in the one-stop clinic. One-stop clinics organised to meet the needs of patients might be appropriate for other clinical conditions. The combination of quantitative and qualitative methods is an effective method of assessing patients' views of health services.

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

Birth weight and 24-hour ambulatory blood pressure in nonproteinuric hypertensive pregnancy.

OBJECTIVE: The aim of this study was to examine the relationship between maternal ambulatory blood pressure monitor measurements during pregnancy and birth weight in a population of women considered to have hypertension according to conventional antenatal clinic measurement. STUDY DESIGN: A prospective observational study was carried out within the obstetric departments of Leicester Royal Infirmary and Queen Charlotte's Hospital. A total of 237 women were found to have hypertension (blood pressure >/=140/90 mm Hg) without significant proteinuria during examination in the antenatal assessment area. Sequential-day unit blood pressure recordings and a 24-hour automated ambulatory blood pressure recording were performed, and the results were compared with the principal outcome measure of birth weight. RESULTS: A significant inverse association (gradient, -13.5; 95% confidence interval -23.4 to -3.6) was found between daytime ambulatory diastolic blood pressure measurement and birth weight. An increase of 5 mm Hg in daytime mean diastolic blood pressure was associated with a fall in birth weight of 68.5 g. This association remained after adjustment for potential confounders that included maternal age, maternal weight, smoking status, ethnicity, and gestational age at delivery. No such association was found between obstetric day unit assessment of blood pressure and birth weight. CONCLUSION: There is a significant association between blood pressure and birth weight in nonproteinuric hypertensive pregnancies. The best predictor of this association is the daytime mean ambulatory diastolic blood pressure measurement. This is further evidence that maternal blood pressure may be an important confounding and potentially genetic variable in the association between birth weight and subsequent adult hypertension.

Adult↗
PubMed2000

Changes in baroreceptor sensitivity for heart rate during normotensive pregnancy and the puerperium.

Normal pregnancy is associated with marked changes in cardiovascular haemodynamics, which in part may be due to changes in autonomic control mechanisms. Baroreflex sensitivity for heart rate (BRS) was calculated in the supine and standing positions using power spectral analysis of pulse interval (PI) and systolic blood pressure (SBP) in 16 normotensive pregnant women and 10 normotensive non-pregnant controls. The pregnant women were studied on three occasions during their pregnancy (early, mid- and late gestation) and once during the puerperium. Supine total SBP variability increased between early and late pregnancy by 79% [95% confidence intervals (CI) 30%, 145%; P<0. 001], and supine high-frequency PI variability decreased by 75% (CI 51%, 88%; P<0.001). Supine BRS fell by 50% (P<0.001), with values returning to early-pregnancy levels in the puerperium, which were similar to those recorded in the control group. Standing SBP variability and BRS values were unchanged during pregnancy and post partum. The low/high frequency ratio of PI variability, taken as a surrogate measure of sympathovagal balance, increased by 137% (CI 42%, 296%; P<0.01) in the supine but not the standing position from early to late pregnancy. This was due to a decrease in high-frequency variability rather than to an increase in low-frequency variability, suggesting that these changes may have been due to vagal withdrawal rather than increased sympathetic activity. Normotensive pregnancy is associated with a marked decrease in supine BRS, although the exact mechanisms for these changes remain unclear. Further studies are required to define whether changes in BRS and sympathovagal tone in early pregnancy can be used to predict the onset of pregnancy-induced hypertension.

Adolescent↗
PubMed1999

Comparison of auscultatory and oscillometric automated blood pressure monitors in the setting of preeclampsia.

OBJECTIVE: The aim of this study was to compare the accuracy of 2 automated blood pressure monitors against mercury sphygmomanometry and intra-arterial blood pressure determination in women with preeclampsia. STUDY DESIGN: The auscultatory and oscillometric monitors were compared with mercury sphygmomanometry according to the British Hypertension Society protocol and criteria of the Association for the Advancement of Medical Instrumentation in a group of 30 women with proteinuric preeclampsia. In addition both monitors were compared with intra-arterial blood pressure measurements in a group of 6 women with severe preeclampsia. The mean (+/- SD) of the differences was calculated and a paired t test was used to compare values obtained with each monitor with intra-arterial measurements. RESULTS: Compared with mercury sphygmomanometry the auscultatory QuietTrak monitor markedly underestimated systolic and diastolic blood pressure by 13 +/- 15 mm Hg. The oscillometric SpaceLabs 90207 monitor also underestimated systolic pressure by 10 +/- 10 mm Hg and diastolic pressure by 8 +/- 7 mm Hg. According to the British Hypertension Society grading criteria both monitors achieved the lowest grade (D) for recording systolic and diastolic pressure. The 2 monitors also did not meet the accuracy criteria stipulated by the Association for the Advancement of Medical Instrumentation. Compared with intra-arterial readings the SpaceLabs monitor significantly underestimated systolic and mean arterial pressures (by 19 and 7 mm Hg, respectively, P <. 01). The QuietTrak monitor significantly underestimated systolic, diastolic, and mean arterial pressures (by 25 mm Hg, P <.05, 18 mm Hg, P <.01, and 20 mm Hg, P <.01, respectively). CONCLUSION: Neither monitor can be recommended for clinical use in women with proteinuric preeclampsia.

Auscultation↗
PubMed1999

Measuring blood pressure in normal and hypertensive pregnancy.

The measurement of blood pressure is an integral part of antenatal care. Mercury sphygmomanometry is the gold standard for the determination of indirect blood pressure and has been used in pregnancy from the time blood pressure was first associated with adverse obstetric outcome. However, there is good evidence that current practice using mercury sphygmomanometry is far from perfect. This article will describe the history of blood pressure determination, why blood pressure is important in pregnancy and the problems associated with sphygmomanometry. It will discuss the advantages and disadvantages associated with alternative methods of blood pressure determination in pregnancy. Automated equipment should always be compared with mercury sphygmomanometry following a recognized protocol, such as that published by the British Hypertension Society, before its accuracy can be assumed in clinical practice. There is now good evidence that the accuracy of these devices deteriorates in women who develop pre-eclampsia. Home monitors have the potential to improve surveillance and to reduce in-patient monitoring.

Blood Pressure↗
PubMed1999

Has pelvimetry a role in current obstetric practice?

Radiological pelvimetry is still requested in some centres before planned vaginal delivery for breech presentation or following a previous caesarean section. In a retrospective review of the utilisation of pelvimetry in 167 cases in our department, 103 (62%) and 64 (38%) had pelvimetry in the postnatal and antenatal periods respectively. Antero-posterior inlet and outlet diameters were inadequate in 19.2% and 16.2% respectively. Of those who had postnatal pelvimetry, only 36 (35%) returned to our unit for further confinement and the caesarean section rate in this group was 75%. The main indications for antenatal pelvimetry were breech presentation (28), previous caesarean section (23) and anticipated cephalopelvic disproportion (13). The caesarean section rates in these groups were 82%, 70% and 45% respectively. However, the emergency caesarean section rate in the breech presentation group was 28%. Nine patients (32%) of those who had breech presentation and delivered by elective caesarean section had normal pelvic measurements. Pelvimetry should only be performed if its results will influence the mode of delivery. Pelvimetry may be useful in selecting fetuses with breech presentation for vaginal delivery or elective caesarean section. However it would increase the likelihood of caesarean section in cephalic presentation.

Journal Article↗
PubMed1999

The role of observer error in antenatal dipstick proteinuria analysis.

OBJECTIVE: To determine the role of inter-observer error and the influence of training upon dipstick urine analysis. DESIGN: A two phase observational and training study. METHODS: Five standard solutions of serum albumin were used to test the accuracy of midwives and nursing auxiliaries involved in dipstick urine analysis at a maternity hospital. The standard solutions were chosen such that they should have resulted in negative (n = 2) and positive (n = 3) dipstick test results, respectively. SETTING: A teaching maternity hospital and academic department of obstetrics and gynaecology. PARTICIPANTS: Twenty midwives, 20 nursing auxiliaries and nine laboratory technicians. RESULTS: For the two nonproteinuric solutions, a higher false positive rate was observed for nursing auxiliaries (40% and 55%), compared with midwives (5% and 30%) (P = 0.020 and P = 0.20, respectively). Before training, laboratory technicians recorded high false positive rates (67% and 89%), but after training these were reduced to 0% and 22% (P = 0.25 and P = 0.023, respectively). Both nursing auxiliaries and midwives recorded false negative rates of between 10% and 45% for the three proteinuric solutions. CONCLUSIONS: Observer error may be reduced by assigning midwives to urine dipstick analysis or by the implementation of directed training. Classification of pre-eclampsia or other hypertensive diseases of pregnancy on the basis of the presence and degree of proteinuria should be confirmed with a 24-hour quantitative protein collection.

False Negative Reactions↗
PubMed1999

The relative accuracy of sequential same-arm and simultaneous opposite-arm measurements for the intra-arterial validation of blood pressure monitors.

OBJECTIVE: To compare the results of simultaneous opposite-arm and sequential same-arm intra-arterial validation of automated blood pressure monitors. DESIGN: Intra-arterial blood pressure measurements were compared with blood pressure measurements obtained using conventional sphygmomanometry and two automated blood pressure monitors (the Dinamap XL and the SpaceLabs Scout) using a methodology based on the protocol published by the Association for the Advancement of Medical Instrumentation (AAMI) for the intra-arterial validation of automated monitors. METHODS: Thirteen women with radial arterial lines were recruited from the obstetric intensive care unit at Groote Schuur Hospital, Cape Town. For each woman, intra-arterial blood pressure measurements were compared with those obtained by mercury sphygmomanometry and by using the two automated blood pressure monitors with both a sequential same-arm protocol and a simultaneous opposite-arm protocol. The mean and SD of the differences was calculated for each protocol and the results were compared using Student s t test. RESULTS: The differences between the 'means of the differences' for these two protocols never differed by more than 2 mmHg. For individuals the differences between data obtained using the two methodologies were up to 32 mmHg for mercury sphygmomanometry and 18 mmHg for the automated monitors. The differences between the SD of the differences were all less than 3 mmHg except for that of systolic blood pressure obtained by mercury sphygmomanometry, which was 7 mmHg CONCLUSIONS: The results of this study show that a sequential same-arm and a simultaneous opposite-arm comparison of intra-arterial and indirect blood pressure measurements yield similar results.

Arteries↗
PubMed1998

Automated, ambulatory, or conventional blood pressure measurement in pregnancy: which is the better predictor of severe hypertension?

OBJECTIVES: Our purpose was to investigate the benefit, if any, of automated blood pressure monitoring over obstetric day unit conventional blood pressure measurement in the assessment of hypertensive pregnancies. STUDY DESIGN: A prospective, observational study was carried out in two large teaching hospitals. Three hundred and forty-eight women with a confirmed clinic blood pressure of at least 140/90 mm Hg were recruited. Conventional blood pressure measurements (< or =5) were obtained on the day unit and simultaneously an ambulatory blood pressure monitor was applied for 24 hours. The predictive ability of day unit assessment (blood pressure > 140/90 mm Hg) and automated blood pressure monitoring (blood pressure > 130/85 mm Hg) was compared. Principal outcome measures included the occurrence of severe hypertension (> 160/110 mm Hg) and proteinuria (> 500 mg or 2+) within (a) 2 weeks and (b) the remainder of the pregnancy. Thompson's method was used to compare sensitivity and specificity of the day unit blood pressure and automated blood pressure monitoring. RESULTS: Three hundred and forty-eight women were recruited to the study. The comparison between automated blood pressure monitoring and conventional blood pressure measurement for both sensitivity and specificity for systolic and diastolic blood pressure revealed increased sensitivity and decreased specificity with automated blood pressure monitoring for all principal outcomes except development of proteinuria for systolic blood pressure. Sensitivity for the outcomes was increased with automated blood pressure monitoring by between 14% and 27% for systolic blood pressure and between 7% and 39% for diastolic blood pressure, with the greatest improvement seen for the development of severe hypertension within 2 weeks of assessment. CONCLUSIONS: In the assessment of hypertensive pregnancies, automated blood pressure measurement was a significantly better predictor (compared with conventional day unit assessment) for the development of severe hypertension within 2 weeks of assessment for both systolic and diastolic blood pressure.

Adult↗
PubMed1997

Differing responses in blood pressure over 24 hours in normotensive women receiving oral or transdermal estrogen replacement therapy.

OBJECTIVE: To examine the effects of oral and transdermal estrogen replacement therapy (ERT) on ambulatory 24-hour blood pressure (BP) recordings. METHODS: In a nonrandomized, prospective study, 90 normotensive, oophorectomized women, ages 30-59 years, underwent ambulatory 24-hour BP measurements at study entry and after 3 and 6 months of either oral (n = 50) or transdermal (n = 40) ERT. RESULTS: In the women receiving transdermal estrogen, we observed a change in mean nighttime systolic BP of -4.2 mmHg (95% confidence interval [CI] -7.7, -0.7; P = .039) after 6 months, treatment. There was a change in mean daytime diastolic BP after 3 months (-3.3 mmHg; 95% CI -5.5, -0.9; P = .016) and 6 months (-4 mmHg; 95% CI-6.8, -1.2; P = .014), and in mean nighttime diastolic BP after 3 months (-3.8 mmHg; 95% CI -6.6, -0.9; P = .027) and 6 months (-4.4 mmHg; 95% CI -7.1, -1.7; P = .005). No significant BP changes were observed in the women taking oral estrogen. Although the statistical power to detect a change of 4 mmHg at the 5% significance level was 90% for diastolic BP, it was weaker for systolic BP (63%) in this group. However, in more than one-third of the women receiving either treatment, a statistically significant increase in BP was observed. CONCLUSIONS: Transdermal ERT was associated with a reduction in mean ambulatory BP, whereas oral treatment did not alter BP. Although the overall effect of estrogen was to lower BP, individual responses were variable, and BP increased in more than one-third of the women on either treatment. Therefore, long-term monitoring of ambulatory measurements may be required.

Administration, Cutaneous↗
PubMed1997

Automated blood pressure measurement as a predictor of proteinuric pre-eclampsia.

OBJECTIVES: To investigate the relation between antenatal clinic, obstetric day unit and 24-hour ambulatory blood pressure measurements and 24-hour proteinuria levels in hypertensive pregnancies. DESIGN: An observational study. PARTICIPANTS: Forty-eight women presenting with new hypertension after 20 weeks of gestation. RESULTS: The closest relation was found between ambulatory blood pressure measurements and 24-hour proteinuria levels. No significant relation was found between the conventional diastolic blood pressure threshold of 90 mmHg and 24-hour proteinuria levels. CONCLUSIONS: Ambulatory blood pressure measurement gives better information about disease status in pre-eclampsia as assessed by proteinuria than does conventional sphygmomanometry.

Adolescent↗