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<140mmHg and diastolic BP<90mmHg, yellow: systolic BP140–159 and/or diastolic BP90–109mmHg (but neither is above the upper threshold), red: systolic BP≥160mmHg and/or diastolic BP≥110mmHg. 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=0.003), magnesium sulfate use (OR 3.40, CI 2.24-5.18, p<0.001) and CCU admission (OR 1.50, CI 1.18-1.91, p<0.001), 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.