A Comparison of BNP Levels Using the Nexfin Device in Healthy Pregnant and Preeclamptic Women

Hypertensive disorders of pregnancy including preeclampsia are the leading cause of pregnancy related mortality in the United States. Timely and appropriate management of hypertensive disorders of pregnancy is critical to prevent complications such as kidney failure, HELLP syndrome, disseminated intravascular coagulation, placental abruption, intrauterine fetal demise, intracranial bleed, coma and death. (HELLP syndrome is a group of symptoms that occur inpregnant women who have: H -- hemolysis (the breakdown of red blood cells); EL -- elevated liver enzymes; LP -- low platelet count.) Hypertensive disorders of pregnancy include gestational hypertension (HTN), chronic HTN, preeclampsia and preexisting HTN with superimposed preeclampsia.

Hypertensive disorders may also lead to significant maternal and/or fetal morbidity. Based on the severity of the disease process and gestational age of the fetus, decision needs to be made whether to proceed with immediate delivery or continue expectant management. Meanwhile, maintenance of optimal blood pressure, blood volume, and cardiac output are recommended to preserve placental perfusion and to prevent unfavorable maternal and/or fetal outcomes.

Previous studies have demonstrated blood flow differences in pregnancies complicated by preeclampsia vs. healthy pregnant women evidenced by decreased arterial compliance, increased systemic vascular resistance and after load, and changes in blood volume and cardiac output. Additionally, various serum markers have been tried to identify women with preeclampsia. B-Type natriuretic peptide (BNP) has been consistently shown to be elevated in preeclampsia, and serves as a marker of heart function and intra vascular volume status.

Continuous hemodynamic monitoring may play a crucial role in timely management of these patients with severe disease due to the dynamic nature of the disease process. Existing methods are not preferred in pregnancy due to their invasive nature, and there is lack of validated non-invasive means to provide real time information on various hemodynamic parameters including cardiac output in these critically ill pregnant women.

Among new cardiac monitoring devices, the Nexfin device (BMEYE, Amsterdam, Netherlands) has recently been introduced. Nexfin device is a device approved by the Food and Drug Administration (FDA) as a non-invasive reliable method of continuous measuring arterial blood pressure in pregnant women. However there are no preliminary data on preeclamptic patients using this device. The standard of care is to use a sphygmomanometer for blood pressure monitoring. Additionally there are no studies comparing the hemodynamics of healthy and preeclamptic women using Nexfin device. Nexfin is thought to be superior over other available non-invasive methods as it is a safe and a considerably accurate method. Nexfin provides continuous blood pressure, heart rate, cardiac output, stroke volume, systemic vascular resistance and left ventricular contractility indices.

The study aims to determine if the non-invasive Nexfin device can be used to reliably distinguish hemodynamics in preeclamptic vs. healthy pregnant women with singleton pregnancies along with use of BNP levels. Investigators aim to recruit 33 healthy controls and 33 subjects diagnosed with preeclampsia (mild and severe). Subject's systolic and diastolic blood pressures will be measured using both the Nexfin device and a standard sphygmomanometer (blood pressure meter). Additionally hemodynamic measure such as: heart rate, cardiac output, stroke volume, systemic vascular resistance, and left ventricular contractility will be recorded using the Nexfin device. Investigators will perform a blood draw to measure BNP levels as an additional assessment of the hemodynamic changes in the two groups.