PREDICTION OF FLUID RESPONSIVENESS WITH PASSIVE LEG RISING IN PREGNANT PATIENTS WITH SEVERE PREECLAMPSIA

INTRODUCTION The clinical manifestations of preeclampsia (PE) are the consequence of endothelial dysfunction. [1, 2] Different hemodynamic patterns have been described, which includes: high vascular resistance, cardiac output (CO) alterations, relative hypovolemia, and increased risk for pulmonary oedema, [3-6] which has been recognised as the most common final cause of death in women with complications of hypertension7. The risk of pulmonary oedema in preeclampsia is caused by different pathophysiological changes that follow the disease. It can be classified as increase preload caused by iatrogenic resuscitation and resolving puerperal oedema. Cardiac causes such as the presence of a myopathic ventricle, diastolic dysfunction, valvular heart disease, increased afterload caused by severe hypertension and increased vascular resistance, and other factors such as reduced oncotic pressure increased capillary permeability or a combination of all.

A cornerstone of treatment to correct the potential hypovolemia in preeclampsia is intravascular volume optimization, which usually is performed as a fluid challenge, [8-9] However, the increased risk of pulmonary oedema has made us understand the need to use dynamic hemodynamic parameters for fluid responsiveness to guide optimal intravascular volume optimization in this group of patients.

Monitoring fluid therapy upon clinical observation or the estimation of filling pressures using clinical markers such as blood pressure, pulse rate and urinary output as an endpoint of euvolemia may be inaccurate in women with severe preeclampsia. In critically ill settings the resolution of severe hypovolaemia is accompanied by rising blood pressure, falling of pulse rate and increasing the urinary output. However, in preeclamptic women, oliguria may develop because of intrinsic renal disease and may not respond to plasma volume expansion with an increase of urinary output. [20] Tachycardia commonly complicates severe preeclampsia, and a persistently rapid pulse rate may not be a reliable indication of intravascular volume depletion, especially when the systolic blood pressure is within reasonable limits.

In the intensive care unit, patients with spontaneous ventilation, an increase of stroke volume during passive leg raising (PLR) predicts fluid responsiveness. [10-13] However, during pregnancy, the validity of PLR has been questioned, secondary to the known anatomical changes that occur from the compression of the inferior vena cava (IVC) by the gravid uterus and the presence of increased abdominal pressure. [14-16] However recently Brun20 published the first study that showed that PLR accurately predicts fluid responsiveness in the setting of Severe Preeclampsia.

Thoracic bioreactance technology, [17] which is based on the analysis of thoracic voltage amplitude changes in response to a high-frequency injected current, and has the potential to be a useful noninvasive clinical tool for monitoring hemodynamics in pregnant women. However, the prediction of fluid responsiveness in these patients, secondary to anatomical and physiological changes associated with pregnancy has not been established.

The objective of this protocol is to evaluate if PLR test can predict fluid responsiveness in pregnant patients with severe preeclampsia.

MATERIALS AND METHODS The study is approved by the Institutional Review Board. Both ethic and research committee approved the protocol with registers number DI/17/112/03/039. Patients will be informed and signed consent before participation. Patients are going to be prospectively assessed, and consecutive measurements will be performed in an obstetric ICU of Mexico´s General Hospital Dr Eduardo Liceaga from December 2016 to July 2017. A sample was calculated for known variance P .01. Measurements for blood pressure and heart rate are made using bioreactance (NICOMTM Panamedical Mexico City, Mexico) technology.[18] The monitor will be placed at bedside, to monitor Systolic Arterial Pressure (SAP) and Diastolic Arterial Pressure (DAP), Stroke Volume (SV), Stroke Volume Index (IVS), Cardiac Output (CO) and Cardiac Index (CI).18 Because hemodynamic values may vary within a respiratory cycle,[17] an average of 10 consecutive cardiac cycles, over at least one respiratory cycle, was used for measurements of SAP, DAP, MAP, SV, and ISV.

Moreover, we use the best dynamic index report under those 10 minutes. A PLR manoeuvre was performed for 3 minutes. The manoeuvre involved elevating the patient's legs and placing them on an inflatable leg wedge providing an angle of 45 degrees while in the supine position. Next, a 250 crystalloid /colloid (Hartmann + albumin 25%) bolus was given recording the same hemodynamic parameters to observe changes in dynamic measurements to compare both results and classified them as responder and non-responder. No determination or Central Venous Pressure or surrogate was made because of the accumulative evidence of the failure of this methods to detect changes in intravascular volume status. A change of 12% after PLR and bolus was used to consider a patient responder[20]. Finally, we used the values for ISV because it would be the better parameter (without the influence of heart rate and independent of the body area).

STATISTICAL ANALYSIS Using SPSS 23 statistics Descriptive data analysis of patients will be performed for this purpose, a multivariable database will be constructed, and descriptive statistical analyses made. To evaluate the distribution between variables a Pearson chi-square test will be used. Mean standard deviation (SD) values, and analysis of proportion with the aim of knowing the probabilistic intersections. The area under the curve, sensitivity, specificity, negative predictive and positive predictive value will be calculated for 12 for ISV.