A Prospective Randomized Study of Automated versus Mercury Blood Pressure Recordings in Hypertensive Pregnancy (PRAM Study)

The assessment of blood pressure in pregnant women: pitfalls and novel approaches

Accurate assessment of blood pressure is fundamental to the provision of safe obstetrical care. It is simple, cost effective, and life-saving. Treatments for preeclampsia, including antihypertensive drugs, magnesium sulfate, and delivery, are available in many settings. However, the instigation of appropriate treatment relies on prompt and accurate recognition of hypertension. There are a number of different techniques for blood pressure assessment, including the auscultatory method, automated oscillometric devices, home blood pressure monitoring, ambulatory monitoring, and invasive monitoring. The auscultatory method with a mercury sphygmomanometer and the use of Korotkoff sounds was previously recommended as the gold standard technique. Mercury sphygmomanometers have been withdrawn owing to safety concerns and replaced with aneroid devices, but these are particularly prone to calibration errors and regular calibration is imperative to ensure accuracy. Automated oscillometric devices are straightforward to use, but the physiological changes in healthy pregnancy and pathologic changes in preeclampsia may affect the accuracy of a device and monitors must be validated. Validation protocols classify pregnant women as a "special population," and protocols must include 15 women in each category of normotensive pregnancy, hypertensive pregnancy, and preeclampsia. In addition to a scarcity of devices validated for pregnancy and preeclampsia, other pitfalls that cause inaccuracy include the lack of training and poor technique. Blood pressure assessment can be affected by maternal position, inappropriate cuff size, conversation, caffeine, smoking, and irregular heart rate. For home blood pressure monitoring, appropriate instruction should be given on how to use the device. The classification of hypertension and hypertensive disorders of pregnancy has recently been revised. These are classified as preeclampsia, transient gestational hypertension, gestational hypertension, white-coat hypertension, masked hypertension, chronic hypertension, and chronic hypertension with superimposed preeclampsia. Blood pressure varies across gestation and by ethnicity, but gestation-specific thresholds have not been adopted. Hypertension is defined as a sustained systolic blood pressure of ≥140 mm Hg or a sustained diastolic blood pressure of ≥90 mm Hg. In some guidelines, the threshold of diagnosis depends on the setting in which blood pressure measurement is taken, with a threshold of 140/90 mm Hg in a healthcare setting, 135/85 mm Hg at home, or a 24-hour average blood pressure on ambulatory monitoring of >126/76 mm Hg. Some differences exist among organizations with respect to the criteria for the diagnosis of preeclampsia and the correct threshold for intervention and target blood pressure once treatment has been instigated. Home blood pressure monitoring is currently a focus for research. Novel technologies, including early warning devices (such as the CRADLE Vital Signs Alert device) and telemedicine, may provide strategies that prompt earlier recognition of abnormal blood pressure and therefore improve management. The purpose of this review is to provide an update on methods to assess blood pressure in pregnancy and appropriate technique to optimize accuracy. The importance of accurate blood pressure assessment is emphasized with a discussion of preeclampsia prediction and treatment of severe hypertension. Classification of hypertensive disorders and thresholds for treatment will be discussed, including novel developments in the field.

Setting and techniques for monitoring blood pressure during pregnancy

BACKGROUND

Regular blood pressure (BP) measurement is crucial for the diagnosis and management of hypertensive disorders in pregnancy, such as pre-eclampsia. BP can be measured in various settings, such as conventional clinics or self-measurement at home, and with different techniques, such as using auscultatory or automated BP devices. It is important to understand the impact of different settings and techniques of BP measurement on important outcomes for pregnant women.

OBJECTIVES

To assess the effects of setting and technique of BP measurement for diagnosing hypertensive disorders in pregnancy on subsequent maternal and perinatal outcomes, women's quality of life, or use of health service resources.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) on 22 April 2020, and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) involving pregnant women, using validated BP devices in different settings or using different techniques.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data, assessed risk of bias, and used the GRADE approach to assess the certainty of the evidence.

MAIN RESULTS

Of the 21 identified studies, we included three, and excluded 11; seven were ongoing. Of the three included RCTs (536,607 women), one was a cluster-RCT, with a substantially higher number of participants (536,233 deliveries) than the other two trials, but did not provide data for most of our outcomes. We generally judged the included studies at low risk of bias, however, the certainty of the evidence was low, due to indirectness and imprecision. Meta-analysis was not possible because each study investigated a different comparison. None of the included studies reported our primary outcome of systolic BP greater than or equal to 150 mmHg. None of the studies reported any of these important secondary outcomes: antenatal hospital admissions, neonatal unit length of stay, or neonatal endotracheal intubation and use of mechanical ventilation. Setting of BP measurement: self-measurement versus conventional clinic measurement (one study, 154 women) There were no maternal deaths in either the self-monitoring group or the usual care group. The study did not report perinatal mortality. Self-monitoring may lead to slightly more diagnoses of pre-eclampsia compared with usual care (risk ratio (RR) 1.49, 95% confidence interval (CI) 0.87 to 2.54; 154 women; 1 study; low-certainty evidence) but the wide 95% CI is consistent with possible benefit and possible harm. Self-monitoring may have little to no effect on the likelihood of induction of labour compared with usual care (RR 1.09, 95% CI 0.82 to 1.45; 154 women; 1 study; low-certainty evidence). We are uncertain if self-monitoring BP has any effect on maternal admission to intensive care (RR 1.54, 95% CI 0.06 to 37.25; 154 women; 1 study; low-certainty evidence), stillbirth (RR 2.57, 95% CI 0.13 to 52.63; 154 women; 1 study; low-certainty evidence), neonatal death (RR 1.54, 95% CI 0.06 to 37.25; 154 women; 1 study; low-certainty evidence) or preterm birth (RR 1.15, 95% CI 0.37 to 3.55; 154 women; 1 study; low-certainty evidence), compared with usual care because the certainty of evidence is low and the 95% CI is consistent with appreciable harms and appreciable benefits. Self-monitoring may lead to slightly more neonatal unit admissions compared with usual care (RR 1.53, 95% CI 0.65 to 3.62; 154 women; 1 study; low-certainty evidence) but the wide 95% CI includes the possibility of slightly fewer admissions with self-monitoring. Technique of BP measurement: Korotkoff phase IV (K4, muffling sound) versus Korotkoff phase V (K5, disappearance of sound) to represent diastolic BP (one study, 220 women) There were no maternal deaths in either the K4 or K5 group. There may be little to no difference in the diagnosis of pre-eclampsia between using K4 or K5 for diastolic BP (RR 1.16; 95% CI 0.89 to 1.49; 1 study; 220 women; low-certainty evidence), since the wide 95% CI includes the possibility of more diagnoses with K4. We are uncertain if there is a difference in perinatal mortality between the groups because the quality of evidence is low and the 95% CI is consistent with appreciable harm and appreciable benefit (RR 1.14, 95% CI 0.16 to 7.92; 1 study, 220 women; low-certainty evidence). The trial did not report data on maternal admission to intensive care, induction of labour, stillbirth, neonatal death, preterm birth, or neonatal unit admissions. Technique of BP measurement: CRADLE intervention (CRADLE device, a semi-automated BP monitor with additional features, and an education package) versus usual care (one study, 536,233 deliveries) There may be little to no difference between the use of the CRADLE device and usual care in the number of maternal deaths (adjusted RR 0.80, 95% CI 0.30 to 2.11; 536,233 women; 1 study; low-certainty evidence), but the 95% CI is consistent with appreciable harm and appreciable benefit. The trial did not report pre-eclampsia, induction of labour, perinatal mortality, preterm birth, or neonatal unit admissions. Maternal admission to intensive care and perinatal outcomes (stillbirths and neonatal deaths) were only collected for a small proportion of the women, identified by an outcome not by baseline characteristics, thereby breaking the random allocation. Therefore, any differences between the groups could not be attributed to the intervention, and we did not extract data for these outcomes.

AUTHORS' CONCLUSIONS

The benefit, if any, of self-monitoring BP in hypertensive pregnancies remains uncertain, as the evidence is limited to one feasibility study. Current practice of using K5 to measure diastolic BP is supported for women with pregnancy hypertension. The benefit, if any, of using the CRADLE device to measure BP in pregnancy remains uncertain, due to the limitations and instability of the trial study design.

Can we predict and prevent emergency department visits for postpartum hypertensive complications in patients with hypertensive disorders in pregnancy?

Background: Hypertensive disorders of pregnancy are major causes of maternal mortality and morbidity, and postpartum hypertensive complications have significant implications on maternal health and public health care system. Antepartum community care programs for hypertension are in place at major centers of Canada, however, such a program for postpartum are usually lacking, and could be a cost-effective solution to reduce postpartum hypertensive complications.Objectives: To assess the proportion of women who present to the emergency department (ED) or outpatient clinics for postpartum hypertensive (PPHTN) complications up to 6 weeks postpartum, among pregnancies complicated by antenatal hypertensive disorders in Calgary, Canada. Secondary objectives were to identify risk factors for PPHTN complications, and to perform a cost-benefit analysis to support postpartum community care program (PCCP) as a way to decrease ED and clinic visits for PPHTN complications, and thus has a favorable economic impact on the public health care system.Study design: Retrospective cohort study using administrative databases, followed by chart review of ED visits to confirm diagnoses and estimate cost of visits and admissions. The participants were women followed by the Calgary Antenatal Community Care Program (ACCP) for hypertensive disorders, from 2014 to 2015, inclusive. The primary outcome was ED or clinic visit associated with an outpatient database record of hypertensive disorder diagnosis, within 42 days postpartum.Results: Among 319 deliveries included in the study, 30 women (9.4, 95%CI: 6.2-12.6%) visited ED or clinics for PPHTN. We identified multiple antihypertensive medication uses and abnormal postpartum gestational hypertension labs as risk factors for ED visit among these women. We estimate a CAD$152 per antenatal hypertensive patient cost benefit for PCCP.Conclusion: The proposed PCCP appears to have an economic benefit to health care system with a decrease in ED and clinic visits. Further studies with greater sample size could strengthen the findings in this study.

Awaiting blood pressure stabilization in ambulatory pregnant women: is 5 minutes sufficient?

OBJECTIVE

Current recommendations for timing of blood pressure measurement in ambulatory pregnant women vary and are based on studies in the nonpregnant population. The objective of this study was to determine if there is a difference in systolic blood pressure (SBP) and diastolic blood pressure (DBP) between minute-5 and minute-10.

METHODS

A prospective study was conducted at our prenatal care clinics. Participants had their blood pressure measured upon sitting and every 5 minutes for 15 minutes. Initial SBP and DBP were compared to measurements at each time point. Additionally, the SBP and DBP at minute-5 were compared to minute-10. All statistical tests were two-sided.

RESULTS

Data from 400 patients were analyzed. Of these, 34.0% were in the first, 30.7% were in the second trimester, and 35.2% were in the third trimester. In each trimester, there was a significant difference in the SBP and DBP at minute-5 compared to minute-0. At minute-10 compared to minute-5, there was no further drop for all trimesters, except for a small drop in DBP in the second trimester (-1.3 ± 6.0, p = 0.012).

CONCLUSION

In an ambulatory setting, 5 minutes after sitting appears to be an appropriate time point to measure blood pressure in pregnancy.

Blood pressure profile in pregnancy: The impact of its duration on results and patients' well-being

BACKGROUND

A blood pressure profile (BPP) is often used to diagnose and manage hypertension in pregnancy. However, there is no consensus on the number and interval of blood pressure (BP) readings required.

AIMS

To ascertain whether BP readings at 15-min interval over one hour yields clinically equivalent results to readings at 60-min interval over three hours.

MATERIALS AND METHODS

Eighty unique women were recruited to this prospective study. Automated BP machines were used to take readings at 15-min interval over one hour and at 60-min interval over three hours. The mean systolic and diastolic BPs obtained using each regimen were calculated and compared. Women also completed a questionnaire to evaluate the psychosocial and financial impact of a prolonged outpatient investigation.

RESULTS

BP readings from 67 patients were included for analysis. Clinical equivalence was assessed using the British Hypertension Society (BHS) validation criteria for comparing nonmercury devices to the gold-standard calibrated mercury device. Mean SBP readings for 54% (36/67), 90% (60/67) and 97% (65/67) and mean DBP readings for 73% (49/67), 94% (63/67) and 100% (67/67) were within 5, 10 and 15 mmHg agreement across the two time regimens which achieved grade B and grade A validation, respectively. A BPP was costly and stressful for women and affected their ability to attend work and look after other children.

CONCLUSIONS

A BPP performed over one hour compared to over three hours yields clinically equivalent results, yet has psychosocial and financial advantages.

SOMANZ guidelines for the management of hypertensive disorders of pregnancy 2014

This guideline is an evidence based, practical clinical approach to the management of Hypertensive Disorders of Pregnancy. Since the previous SOMANZ guideline published in 2008, there has been significant international progress towards harmonisation of definitions in relation to both the diagnosis and management of preeclampsia and gestational hypertension. This reflects increasing knowledge of the pathophysiology of these conditions, as well as their clinical manifestations. In addition, the guideline includes the management of chronic hypertension in pregnancy, an approach to screening, advice regarding prevention of hypertensive disorders of pregnancy, and discussion of recurrence risks and long term risk to maternal health. The literature reviewed included the previous SOMANZ Hypertensive Disorders of Pregnancy guideline from 2008 and its reference list, plus all other published National and International Guidelines on this subject. Medline, Cochrane Database of Systematic Reviews (CDSR), Cochrane Central Registry of Controlled Trials (CCRCT), National Institute for Health and Care Excellence (NICE) Evidence Search, and Database of Abstracts and Reviews of Effects (DARE) were searched for literature published between January 2007 and March, 2014.

Measuring blood pressure in pregnancy and postpartum: assessing the reliability of automated measuring devices

OBJECTIVE

To determine the reliability of automated blood pressure (BP) measuring devices in hypertensive pregnancies.

METHODS

Three sequential measurements were taken using mercury sphygmomanometry and an automated device in pregnant hypertensive women (n = 89).

RESULTS

Systolic BP (SBP) was higher with the automated device (mean difference 2.5 mmHg, 95% CI: 1.9-3.2 mmHg), whereas diastolic BP (DBP) was higher with the mercury sphygmomanometer (mean difference 2.0 mmHg, 95% CI: 1.5-2.6 mmHg). Within-patient variability for the automated device was: SBP 4.8 mmHg (95% CI: 4.6-5.2 mmHg), DBP 3.4 mmHg (95% CI: 3.1-3.7 mmHg); and for mercury sphygmomanometry: SBP 3.7 mmHg (95% CI: 3.5-4.0 mmHg), DBP 3.0 mmHg (95% CI: 2.8-3.3 mmHg).

CONCLUSION

Outpatient automated BP measurement agrees well with mercury sphygmomanometry in hypertensive pregnancies.