Microcirculatory and Tissue and Cerebral Oxygenation in Preeclampsia and Normal Pregnancy: An Observation Study

Overview

Preeclampsia is a disease of pregnancy affecting 3% to 8% of all pregnancies and is a major cause of maternal and perinatal morbidity and mortality. Characterized by alter placentation with subsequent release of inflammatory mediators leading to a generalized endothelial dysfunction. It is now accepted that endothelial dysfunction heralds the clinical manifestations of preeclampsia. The side-stream darkfield (SDF) microscopy device emits a 550 nm green light with a depth region of interest of 500 um. Green light is absorbed by the erythrocytes and appears black. SDF is a well-known non-invasive tool that can study the microcirculatory changes. It was used before in many situations especially in sepsis and septic shock patients. Near-infra-red spectroscopy (NIRS) device, measures the absorbance of near-infra-red (NIR) light by tissues perfused with oxygenated blood, and is capable of measuring changes in parenchymal volume tissues. It was used before in many situations (including pregnant patients) to reflect the tissue oxygenations. The investigators are planning to use the SDF and NIRS tools to study the microcirculatory change in preeclamptic subjects and normal pregnant subjects. If these two devices are able to determine any changes this should stand as a baseline for future studies in this field.

Study procedures: * Consented at the time of enrollment in the study, which will be at hospital admission for delivery. * Demographic data, medical history, obstetrical history, prenatal history and delivery information will be obtained from medical records and the subject * Proteinuria, Placental weight, BMI, Birth weight and gender, mother smoker or not, clinical parameter of preeclampsia, and severity of preeclampsia, uterine artery Doppler results will be collected from medical records . * SDF and NIRS application will be done once. Measurements: Sidestream dark field (SDF) The side-stream darkfield camera ( CytoCam) will be put under the subjects tongue for 5-10 minutes. Multiple pictures of the small blood vessels will be taken. Two fields will be selected that included at least 2 arterioles and 2 venules. Arterioles will be identified as high-flow vessels in which the direction of flow is from larger diameter vessels to smaller diameter vessels, while the reverse will be true for venules. Furthermore, arterioles will be distinguished from venules by the difference in erythrocyte flow velocity, which is substantially higher in arterioles than in venules. At least 2 arterioles and 2 venules will be taken from each captured image sequence to measure the blood vessel diameter. The diameter of blood vessels will be determined using image processing software specifically designed for analysis of the microcirculation. The diameter of microvessels will be determined by drawing a perpendicular line from one side of the luminal vessel wall to the other at 3 separate locations. The functional capillary index (FCD) and the microvascular flow index (MFI) will be calculated as well. The FCD is defined as the total length of perfused capillaries per mm2. The MFI is used to describe the different flow velocities in venules in each observation field. This is a reproducible and validated index based on a semi-quantitative scoring (0=no flow, 1=intermittent flow, 2=sludging flow, 3=continuous flow and 4=high flow) of flow patterns in large (\>50 μm), medium (25-50 μm) and small (10-25 μm, including capillaries) venules. Intermittent flow is characterized by a discontinuous flow pattern of erythrocytes during systolic heart contraction, which halts (or even reverses) during the diastolic phase. In sludging flow, individual erythrocytes have different low continuous velocities and they can be easily distinguished from each other. Continuous flow is characterized by an uninterrupted, uniform laminar flow pattern of erythrocytes that still just can be distinguished from each other. With high flow, the velocity of erythrocytes has exceeded the capture rate of the camera and therefore individual erythrocytes cannot be traced anymore and appear as a black column of cells. CytoCam product is registered by the FDA with number D186803 Class1 exempt. This product is intended to be used for visualization of micro-circulation in tissue in orifices of the human body which may be non-invasively accessed and cutaneous surfaces. Near-infra-red spectroscopy (NIRS) Artinis PortaLite with OxySoft softwear Artinis systems has developed a customizable NIRS device that measures tissue oxygenation saturation (StO2) of both muscle and brain tissue. This device can be customized in terms of emitter wavelength (5 are available, all in the NIR range) and configuration (2 emitters each @ 30, 35, and 40 mm from the detector). Critically, unlike most other commercially available NIRS devices for clinical care, the Artinis device allows exportation of the actual absorbance waveforms @ 15 Hz sampling rate. Thus, the Artinis PortaLite with OxySoft softwear will be used for research only, not for clinical care. The NIRS probe will be applied to one of the patient's thenar muscle and over the patient forehead and tissue oxygenation (TOI) will be recorded for 5 minutes.