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

Objectives: To evaluate the association between blood pressure (BP) measurements and adverse outcomes in women with pre-eclampsia. Study design: A prospective cohort study of women with pre-eclampsia admitted to three South African tertiary facilities. BP was measured using the CRADLE Vital Signs Alert (VSA), incorporated with a traffic light early warning system; green: systolic BP < 140 mmHg and diastolic BP < 90 mmHg, yellow: systolic BP 140-159 and/or diastolic BP 90-109 mmHg (but neither is above the upper threshold), red: systolic BP >= 160 mmHg and/or diastolic BP >= 110 mmHg. Main outcome measures: Maternal: death, eclampsia, stroke, kidney injury; process measures: magnesium sulfate use, Critical Care Unit (CCU) admission; perinatal: stillbirth, neonatal death, preterm delivery. Results: Of 1547 women with pre-eclampsia (including 42 twin pregnancies), 33.0% of women triggered a red light on admission and 78.6% at their highest BP. Severe hypertension and adverse outcomes were common across yellow and red categories. Comparing admission red to yellow lights, there was a significant increase in kidney injury (OR 1.74, CI 1.31-2.33, trend test p =. 003), magnesium sulfate use (OR 3.40, CI 2.24-5.18, p < .001) and CCU admission (OR 1.50, CI 1.18-1.91, p < .001), but not for maternal death, eclampsia, extended perinatal death or preterm delivery. Conclusion: The CRADLE VSA, with integrated traffic light early warning system, can identify women who are hypertensive, at increased risk of severe pre-eclampsia complications and in need of escalation of care. Women who triggered a red light were at increased risk of kidney injury, magnesium sulfate use and CCU admission.