Hannah L. Nathan

Shock index: an effective predictor of outcome in postpartum haemorrhage?

To compare the predictive value of the shock index (SI) with conventional vital signs in postpartum haemorrhage (PPH), and to establish ‘alert’ thresholds for use in low‐resource settings.

An accurate semiautomated oscillometric blood pressure device for use in pregnancy (including pre-eclampsia) in a low-income and middle-income country population: the Microlife 3AS1-2.

ObjectivesTo assess the accuracy of the Microlife 3AS1-2 blood pressure device in pregnancy and pre-eclampsia in a low-resource setting. MethodsProspective validation according to the British Hypertension Society protocol. A total of 45 pregnant women were recruited from Kimberley Hospital (South Africa), of whom 15 had pre-eclampsia. ResultsThe Microlife 3AS1-2 device achieved an overall B/A grade in pregnancy (including pre-eclampsia), passing the British Hypertension Society protocol requirements and achieving the International Organization for Standardization standard with a mean difference and SD of −3.8±7.3 and −1.5±6.2 mmHg for systolic and diastolic pressures, respectively. ConclusionThe Microlife 3AS1-2 device can be recommended for use in pregnancy, including pre-eclampsia. In addition, it fulfils the requirements stipulated by the WHO for an automated blood pressure device suitable for use in a low-resource setting. This makes it the ideal device for antenatal clinics and primary healthcare facilities in low-income and middle-income countries.

Vital Sign Prediction of Adverse Maternal Outcomes in Women with Hypovolemic Shock: The Role of Shock Index.

Objective To determine the optimal vital sign predictor of adverse maternal outcomes in women with hypovolemic shock secondary to obstetric hemorrhage and to develop thresholds for referral/intensive monitoring and need for urgent intervention to inform a vital sign alert device for low-resource settings. Study Design We conducted secondary analyses of a dataset of pregnant/postpartum women with hypovolemic shock in low-resource settings (n = 958). Using receiver-operating curve analysis, we evaluated the predictive ability of pulse, systolic blood pressure, diastolic blood pressure, shock index, mean arterial pressure, and pulse pressure for three adverse maternal outcomes: (1) death, (2) severe maternal outcome (death or severe end organ dysfunction morbidity); and (3) a combined severe maternal and critical interventions outcome comprising death, severe end organ dysfunction morbidity, intensive care admission, blood transfusion ≥ 5 units, or emergency hysterectomy. Two threshold parameters with optimal rule-in and rule-out characteristics were selected based on sensitivities, specificities, and positive and negative predictive values. Results Shock index was consistently among the top two predictors across adverse maternal outcomes. Its discriminatory ability was significantly better than pulse and pulse pressure for maternal death (p<0.05 and p<0.01, respectively), diastolic blood pressure and pulse pressure for severe maternal outcome (p<0.01), and systolic and diastolic blood pressure, mean arterial pressure and pulse pressure for severe maternal outcome and critical interventions (p<0.01). A shock index threshold of ≥ 0.9 maintained high sensitivity (100.0) with clinical practicality, ≥ 1.4 balanced specificity (range 70.0–74.8) with negative predictive value (range 93.2–99.2), and ≥ 1.7 further improved specificity (range 80.7–90.8) without compromising negative predictive value (range 88.8–98.5). Conclusions For women with hypovolemic shock from obstetric hemorrhage, shock index was consistently a strong predictor of all adverse outcomes. In lower-level facilities in low resource settings, we recommend a shock index threshold of ≥ 0.9 indicating need for referral, ≥ 1.4 indicating urgent need for intervention in tertiary facilities and ≥ 1.7 indicating high chance of adverse outcome. The vital sign alert device incorporated values 0.9 and 1.7; however, all thresholds will be prospectively validated and clinical pathways for action appropriate to setting established prior to clinical implementation.

Development of an accurate oscillometric blood pressure device for low resource settings.

ObjectiveTo assess and develop an accurate blood pressure measurement device for use in low resource settings and by untrained staff, according to the World Health Organisation guidelines. MethodsNinety-nine adults were recruited to validate the device according to the International Protocol of the European Society of Hypertension. All participants provided written informed consent. Patients with an arrhythmia or unclear Korotkoff sounds were excluded. Nine sequential same-arm measurements were taken from each participant alternating between the test device and mercury sphygmomanometry. Differences between the test device and observers were evaluated according to the criteria of the International Protocol and the Association for the Advancement of Medical Instrumentation. ResultsThe device failed the first assessment of the oscillometric function and required modification to both the deflation rate and the algorithm to fulfil the International Protocol criteria. It then achieved an acceptable mean difference of −0.7 (4.7) mmHg for systolic and −2.0 (4.6) mmHg for diastolic pressure (oscillometric function) and −1.9 (3.8) mmHg and −0.9 (3.3) mmHg for systolic and diastolic pressures, respectively (auscultatory function). ConclusionThe Microlife 3AS1-2 is a semi-automated upper arm device with features consistent with low resource requirements. We successfully developed this device for accurate blood pressure measurement in adults according to the International Protocol, through adjustment of the deflation rate and algorithm. The accuracy and user-friendly design of this low-cost device makes it a highly valuable monitor in clinical practice, particularly in low resource settings and for use by untrained staff.

Accuracy validation of the Microlife 3AS1-2 blood pressure device in a pregnant population with low blood pressure

ObjectiveTo assess the accuracy of the Microlife 3AS1-2 blood pressure (BP) device in pregnant women with low BP to investigate suitability for hypotensive detection in low-income and middle-income countries. MethodsA prospective observational study was carried out evaluating the Microlife 3AS1-2, a hand-held, upper-arm, semiautomated BP device, according to British Hypertension Society (BHS) protocol methods. Thirty (stable) pregnant women with a clinical systolic BP less than 100 mmHg and/or diastolic BP less than 60 mmHg were recruited from antenatal wards and clinics and their BP was measured by three trained observers at a district-level hospital in South Africa. Accuracy was assessed according to the BHS grading criteria (A/B=pass) and the ANSI/AAMI/ISO standard for mean difference and SD (⩽5±8 mmHg). ResultsThe device achieved an A/A grade according to the BHS grading criteria. The mean difference±SD between the observer and the test device was 0.5±6.2 and 1.3±5.4 mmHg for systolic and diastolic BP, respectively, fulfilling the standard required by the ANSI/AAMI/ISO protocol. All observer differences were within 4 mmHg. ConclusionAccording to the BHS protocol, the Microlife 3AS1-2 BP device is accurate in pregnant women with low BP. The device has been validated previously in pregnancy and pre-eclampsia and also fulfils the criteria of the WHO for use in a low-resource setting. Although unstable women were not included in this validation (for safety and pragmatic reasons), this device could potentially improve the detection of shock secondary to obstetric haemorrhage or sepsis, as well as being used in pre-eclampsia, particularly in low-income and middle-income countries.

Determination of Normal Ranges of Shock Index and Other Haemodynamic Variables in the Immediate Postpartum Period: A Cohort Study

Objective To determine the normal ranges of vital signs, including blood pressure (BP), mean arterial pressure (MAP), heart rate (HR) and shock index (SI) (HR/systolic BP), in the immediate postpartum period to inform the development of robust obstetric early warning scores. Study Design We conducted a secondary analysis of a prospective observational cohort study evaluating vital signs collected within one hour following delivery in women with estimated blood loss (EBL) <500ml (316 women) delivering at a UK tertiary centre over a one-year period. Simple and multiple linear regression were used to explore associations of demographic and obstetric factors with SI. Results Median (90% reference range) was 120 (100–145) for systolic BP, 75 (58–90) for diastolic BP, 90 (73–108) for MAP, 81 (61–102) for HR, and 0.66 (0.52–0.89) for SI. Third stage Syntometrine® administration was associated with a 0.03 decrease in SI (p = 0.035) and epidural use with a 0.05 increase (p = 0.003). No other demographic or obstetric factors were associated with a change in shock index in this cohort. Conclusion This is the first study to determine normal ranges of maternal BP, MAP, HR and SI within one hour of birth, a time of considerable haemodynamic adjustment, with minimal effect of demographic and obstetric factors demonstrated. The lower 90% reference point for systolic BP and upper 90% reference point for HR correspond to triggers used to recognise shock in obstetric practice, as do the upper 90% reference points for systolic and diastolic BP for obstetric hypertensive triggers. The SI upper limit of 0.89 in well postpartum women supports current literature suggesting a threshold of 0.9 as indicating increased risk of adverse outcomes.

Early warning system hypertension thresholds to predict adverse outcomes in pre-eclampsia: A prospective cohort study

Highlights • The CRADLE Vital Signs Alert is designed to risk stratify women with pre-eclampsia.• A yellow or red light corresponds to increased risk of pre-eclampsia complications.• Those who trigger a yellow or red light need escalation of care.

Evaluation of a novel device for the management of high blood pressure and shock in pregnancy in low-resource settings: study protocol for a stepped-wedge cluster-randomised controlled trial (CRADLE-3 trial)

BackgroundObstetric haemorrhage, sepsis and pregnancy hypertension account for more than 50% of maternal deaths worldwide. Early detection and effective management of these conditions relies on vital signs. The Microlife® CRADLE Vital Sign Alert (VSA) is an easy-to-use, accurate device that measures blood pressure and pulse. It incorporates a traffic-light early warning system that alerts all levels of healthcare provider to the need for escalation of care in women with obstetric haemorrhage, sepsis or pregnancy hypertension, thereby aiding early recognition of haemodynamic instability and preventing maternal mortality and morbidity. The aim of the trial was to determine whether implementation of the CRADLE intervention (the Microlife® CRADLE VSA device and CRADLE training package) into routine maternity care in place of existing equipment will reduce a composite outcome of maternal mortality and morbidity in low- and middle-income country populations.MethodsThe CRADLE-3 trial was a stepped-wedge cluster-randomised controlled trial of the CRADLE intervention compared to routine maternity care. Each cluster crossed from routine maternity care to the intervention at 2-monthly intervals over the course of 20 months (April 2016 to November 2017). All women identified as pregnant or within 6 weeks postpartum, presenting for maternity care in cluster catchment areas were eligible to participate. Primary outcome data (composite of maternal death, eclampsia and emergency hysterectomy per 10,000 deliveries) were collected at 10 clusters (Gokak, Belgaum, India; Harare, Zimbabwe; Ndola, Zambia; Lusaka, Zambia; Free Town, Sierra Leone; Mbale, Uganda; Kampala, Uganda; Cap Haitien, Haiti; South West, Malawi; Addis Ababa, Ethiopia). This trial was informed by the Medical Research Council guidance for complex interventions. A process evaluation was undertaken to evaluate implementation in each site and a cost-effectiveness evaluation will be undertaken.DiscussionAll aspects of this protocol have been evaluated in a feasibility study, with subsequent optimisation of the intervention. This trial will demonstrate the potential impact of the CRADLE intervention on reducing maternal mortality and morbidity in low-resource settings. It is anticipated that the relatively low cost of the intervention and ease of integration into existing health systems will be of significant interest to local, national and international health policy-makers.Trial registrationISCRTN41244132. Registered on 2 February 2016.Prospective protocol modifications have been recorded and were communicated to the Ethics Committees and Trials Committees. The adapted Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) Checklist and the SPIRIT Checklist are attached as Additional file 1.

Innovations in vital signs measurement for the detection of hypertension and shock in pregnancy

Approximately 820 women die in pregnancy and childbirth every day worldwide, with 99% of these occurring in low-resource settings. The most common causes of maternal mortality are haemorrhage, sepsis and hypertensive disorders. There are established, effective solutions to these complications, however challenges remain in identifying who is at greatest risk and ensuring that interventions are delivered early when they have the greatest potential to benefit. Measuring vital signs is the first step in identifying women at risk. Overstretched or poorly trained staff and inadequate access to accurate, reliable equipment to measure vital signs can potentially result in delayed treatment initiation. Early warning systems may help alert users to identify patients at risk, especially where novel technologies can improve usability by automating calculations and alerting users to abnormalities. This may be of greatest benefit in under-resourced settings where task-sharing is common and early identification of complications can allow for prioritisation of life-saving interventions. This paper highlights the challenges of accurate vital sign measurement in pregnancy and identifies innovations which may improve detection of pregnancy complications.

Development and evaluation of a novel Vital Signs Alert device for use in pregnancy in low-resource settings

Objectives Haemorrhage, hypertension, sepsis and abortion complications (often from haemorrhage or sepsis) contribute to 60% of all maternal deaths. Each is associated with vital signs (blood pressure (BP) and pulse) abnormalities, and the majority of deaths are preventable through simple and timely intervention. This paper presents the development and evaluation of the CRADLE Vital Signs Alert (VSA), an accurate, low-cost and easy-to-use device measuring BP and pulse with an integrated traffic light early warning system. The VSA was designed to be used by all cadres of healthcare providers for pregnant women in low-resource settings with the aim to prevent avoidable maternal mortality and morbidity. Methods The development and the mixed-methods clinical evaluation of the VSA are described. Results Preliminary fieldwork identified that introduction of BP devices to rural clinics improved antenatal surveillance of BP in pregnant women. The aesthetics of the integrated traffic light system were developed through iterative qualitative evaluation. The traffic lights trigger according to evidence-based vital sign thresholds in hypertension and haemodynamic compromise from haemorrhage and sepsis. The VSA can be reliably used as an auscultatory device, as well as its primary semiautomated function, and is suitable as a self-monitor used by pregnant women. Conclusion The VSA is an accurate device incorporating an evidence-based traffic light early warning system. It is designed to ensure suitability for healthcare providers with limited training and may improve care for women in pregnancy, childbirth and in the postnatal period.