The role of the erythrocyte in the outcome of pregnancy with preeclampsia

Abstract

The objective of this study was to analyze the relationships of osmotic and mechanical stability of erythrocytes with anthropometric, biochemical, hematologic and hemodynamic variables in pregnant women with preeclampsia (PE). The studied population consisted of 20 normotensive patients and 16 patients with PE. Patients with PE presented worse gestational outcome, greater hematologic impairment, erythrocytes osmotically more stable in vitro, but in conditions of isotonicity with the in vivo medium, in addition to hyperflow in orbital territory, when compared to normotensive patients. The correlation analysis between anthropometric, hematologic and hemodynamic variables in patients with PE indicated that erythrocytes with lower volumes and lower levels of hemoglobin favor the occurrence of a better gestational outcome, because they are more stable and because they are associated with a decrease in the hemodynamic changes present in the disease. This should mean that the tendency to microcytosis, probably due to a mechanism of compensatory mechanical selection, is a desirable characteristic in the disease.

Fig 1. Typical curve of hyposmotic lysis of erythrocytes, with definition of the osmotic stability variables A_mim, A_max, H₀, H₅₀, H_100, and dX.

Fig 2. Typical curve obtained in the kinetics of erythrocyte mechanical lysis, with definition of the kinetic variables t_1/2 and A_mmax.

Fig 3. Doppler velocimetry of the ophthalmic artery of a pregnant woman with preeclampsia.

The Y axis represents the flow velocity (cm/s) and the X axis represents time (seconds). A rapid increase in velocity, with formation of the peak systolic velocity (PSV), is followed by a rapid fall and a new velocity rise, with the formation of the second systolic peak (P2), followed by the aortic notch, which closes the systolic cycle. The subsequent rise of velocity constitutes the diastolic phase of the pulse wave velocity (PWV), which ends with the end-diastolic velocity (EDV). In severe preeclampsia there is an increase in the amplitude of P2, characterizing the presence of a hump.

Fig 4. Values of ρ coefficients for significant (p<0.05) Spearman correlations between some pairs of variables in pregnant women with preeclampsia.

Red and blue shading were used for positive and negative correlations, respectively. Abbreviations: MCV, mean corpuscular volume; MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular hemoglobin concentration; VLDL-C, very low density lipoprotein cholesterol; PSV, peak systolic velocity; P2, second peak of systolic velocity; PR, peak ratio; A_min, absorbance at 540 nm associated with residual lysis of the erythrocytes population; dX, variation in the concentration of NaCl responsible for total hemolysis; H_50, saline concentration capable of promoting 50% hemolysis; A_mmax, absorbance at 540 nm associated with the mechanical lysis of the whole population of RBC.