Erythrocyte aggregation during normal pregnancy

Investigating the blood rheology in the first trimester pregnancies with high risk for preeclampsia

BACKGROUND

Pregnancy is a dynamic process associated with changes in vascular and rheological resistance. Maternal maladaptation to these changes is the leading cause of pregnancy complications such as preeclampsia.

OBJECTIVE

This study aimed to assess the hemorheological alterations in pregnancies with a high risk for preeclampsia in the first trimester.

METHODS

Ninety-two pregnant women were allocated into the high preeclampsia risk group (37 cases) and control groups (55 cases). Plasma and whole blood viscosity and red blood cell morphodynamic properties, including deformability and aggregation were assessed by Brookfield viscometer and laser-assisted optical rotational cell analyzer (LORRCA) at 11-14 gestational weeks.

RESULTS

Whole blood viscosity was significantly higher in the high-risk group at all shear rates. Plasma viscosity and hematologic factors showed no differences between the groups. Hematocrit levels positively correlated with high blood viscosity only in the high-risk group. There were no significant changes in the other deformability and aggregation parameters.

CONCLUSIONS

Changes in the whole blood viscosity of pregnant women with high preeclampsia risk refer to impaired microcirculation beginning from the early weeks of gestation. We suggest that the whole blood viscosity is consistent with the preeclampsia risk assessment in the first trimester, and its measurement might be promising for identifying high-preeclampsia-risk pregnancies.

Natural killer cells and their activation status in normal pregnancy

Increased peripheral blood-activated NK cell counts are associated with increased risk of miscarriage and failed in vitro fertilization treatment. However, assessment of activated peripheral NK cells in normal and pathological pregnancies beyond implantation and early miscarriage has not been described. Total CD69 expressing NK cells counts were measured by flow cytometry in healthy women with singleton pregnancies, including 45 at 11⁺⁶–13⁺⁶ weeks' gestation, 46 at 20⁺⁰–22⁺⁴ weeks, and 42 at 31⁺⁶–33⁺⁵ weeks. The number of peripheral blood NK cells decreased, whereas the percentage of activated CD69 expressing NK cells increased from the first to the third trimester of pregnancy. This study shows the course of peripheral blood NK cells and activated CD69 expressing NK cells in uncomplicated nulliparous singleton pregnancies. This is a first step in understanding their implication in pathological pregnancies.

The effect of betamethasone administration to pregnant women on maternal serum indicators of infection

OBJECTIVE

To study the effect of betamethasone therapy on maternal white blood cell count, C-reactive protein and erythrocyte sedimentation rate in women at high risk for preterm delivery.

STUDY DESIGN

We included women at gestational age of 24 to 34 weeks who were treated by betamethasone for enhancement of fetal lung maturity, because of imminent preterm labor with intact membranes. Blood tests for white blood cell and differential count, C-reactive protein and erythrocyte sedimentation rate were drawn before betamethasone injection, 2 hours after, and then every 24 hours for three days.

RESULTS

105 women were included. The mean white blood cell count increased by 33% on day one, and returned to baseline level three days after the first injection of betamethasone. A significant rise in neutrophil count, and drop in lymphocyte count was noted as early as two hours after the first injection and lasted for two days. Mean C-reactive protein and erythrocyte sedimentation rate levels were not changed significantly by betamethasone treatment.

CONCLUSIONS

Antenatal betamethasone therapy causes a transient increase in maternal leukocyte count but has no effect on serum C-reactive protein and erythrocyte sedimentation rate. This information is relevant for preterm pregnant women who are at high risk for chorioamnionitis.

Lower limb vein enlargement and spontaneous blood flow echogenicity are normal sonographic findings during pregnancy

PURPOSE

We studied pregnancy-induced changes in lower limb venous function.

METHODS

We used plethysmography and sonography to assess the changes in venous wall distensibility, saphenous vein diameters, and spontaneous blood flow echogenicity in the common femoral veins in 190 consecutive women during and after uncomplicated pregnancies (total of 409 examinations).

RESULTS

The percentage of women with clinical symptoms and signs of venous insufficiency increased significantly during pregnancy. The mean diameters of the great and small saphenous veins also increased significantly, while occlusive venous plethysmography showed a decrease in parameters indicating vein distensibility. Spontaneous blood flow echogenicity in the common femoral veins was clearly visible or marked in 6% of cases during the first trimester of pregnancy, 63% during the second trimester, and 96% during the third trimester, versus 6% after delivery (p < 0.0001). The mean hematocrit decreased and the mean fibrinogen concentration increased during pregnancy.

CONCLUSIONS

The increase in lower limb venous pressure seen during pregnancy leads to venous overdistention and worsens blood stasis. Decreased venous flow velocity and rheological alterations result in increased red cell aggregation, giving rise to spontaneous blood flow echogenicity. Spontaneous blood flow echogenicity is therefore a normal finding during pregnancy and should not be mistaken for venous thrombosis.

Review article: The management of inflammatory bowel disease during pregnancy

The management of inflammatory bowel disease during pregnancy is a particular challenge because adequate disease control before and during gestation is essential for both maternal and foetal health. As a practical problem this situation arises frequently, because a quarter of patients conceive after the diagnosis of their disease. Many of the clinical, biochemical, radiological and endoscopic investigations that are used to monitor and assess disease activity are difficult to use and interpret during pregnancy. Furthermore, patients and clinicians often have concerns about the safety of medical and surgical treatments for the foetus. This review is designed for the practising clinician, to guide the management of patients with inflammatory bowel disease before and during pregnancy. The literature is at times conflicting and data on some issues are scanty, therefore recommendations are based on the balance of evidence including, if necessary, extrapolation from other conditions.

Nifedipine treatment in preeclampsia reverts the increased erythrocyte aggregation to normal

OBJECTIVES

Our objectives were to assess erythrocyte aggregation in hypertensive pregnancy and to evaluate the effect of the antihypertensive treatment on it.

STUDY DESIGN

The mean entity of erythrocyte aggregation was determined by an automatic aggregometer in 57 pregnant women: 20 normotensive, seven chronically hypertensive, 10 chronically hypertensive with superimposed preeclampsia, and 20 with preeclampsia. Ten of the latter were subsequently treated by 40 mg/day oral nifedipine; the other 10 by 400 mg/day oral labetalol, to keep diastolic blood pressure < 90 mm Hg. Also, patients with superimposed preeclampsia were treated with 40 mg/day oral nifedipine.

RESULTS

Erythrocyte aggregation was increased in all the hypertensive pregnant patients compared with the normotensive pregnant controls, regardless of both the onset (chronic or pregnancy-induced) of hypertension and the status of plasma macromolecules. Antihypertensive treatment with labetalol significantly reduced the aggregability of erythrocytes, whereas treatment with nifedipine reverted it to normal.

CONCLUSIONS

Increased erythrocyte aggregation may be due to either conformational changes of the membrane occurring during hypertension or a redistribution of the ionic charges on the two surfaces of the membrane. The effect of nifedipine by restoring the ionic charges may be due to this latter event.

Hemorheologic abnormalities in patients with human immunodeficiency virus infection and ophthalmic microvasculopathy

The severity of conjunctival microvascular changes and the presence of cotton-wool spots were compared to factors that may affect blood flow (hematocrit level, red cell aggregation, fibrinogen level, plasma viscosity, circulating immune complexes, and quantitative immunoglobulin levels) in 22 human immunodeficiency virus-infected individuals. The severity of conjunctival disease was associated with increased zeta sedimentation ratios (a measure of red cell aggregation) and fibrinogen levels. The presence of cotton-wool spots was also associated with higher fibrinogen levels. Plasma viscosity and quantitative IgG levels were above normal levels in most patients, although a relationship to disease severity was not established. Altered blood flow may contribute to vascular damage and ocular ischemic lesions in patients with human immunodeficiency virus infection.

Red cell aggregation during normal pregnancy

Red cell aggregation (RCA) is responsible for the increase in whole blood viscosity at lower shear rates. RCA depends on the concentrations of red cells and plasma proteins with a high molecular weight and a large and asymmetrical spatial structure such as fibrinogen, immunoglobulin M and alpha 2-macroglobulin. During normal pregnancy, changes occur in all these concentrations. In a prospective study these changes and their influence on the resulting RCA were investigated in 24 healthy women with normal pregnancies. RCA was determined by light reflection measurement (syllectometry). RCA considerably increased during normal pregnancy in spite of the physiological haemodilution. The aggregation half time, used as a measure for RCA, decreased from an average non-pregnant value of 5.6 s to 3.3 s at 37 weeks. Multiple regression analysis showed that the increase in RCA could be mainly attributed to the raised fibrinogen concentration. However, at 37 weeks other factors, in addition to fibrinogen, contribute significantly to the increase in RCA.

Blood rheology and pregnancy

Pregnancy is a hypervolaemic situation with early expanded plasma volume, a high cardiac output and a decrease in the vascular and rheological resistance. The increase in plasma volume correlates better with fetal size than maternal size. The hypervolaemic and vasodilated state that accompanies normal pregnancy results in a high flow in the uterine arteries. In contrast, patients with PIH (pregnancy-induced hypertension) or placental insufficiency may have a contracted plasma volume secondary to diffuse vasoconstriction. In spite of the intense vasospasm and hypovolaemia, pre-eclampsia has generally a cardiac output which may be equal, higher or lower compared with non-eclamptic pregnancy. Hypovolaemia is reflected in a higher haematocrit than normal. In the case of a hypovolaemic state, haemoconcentration is associated with high red cell aggregation. In fetal distress and severe PIH, the rheological status (haemoconcentration and elevated red cell aggregation) has a high predictive value for perinatal complications. In patients with severe PIH, erythrocyte filtration is impaired. The increased leukocyte count in patients with PIH may occlude small vessels and could be a factor impairing intervillous blood flow. The increased erythrocyte rigidity may result from a re-distribution of cellular calcium metabolism (Blaustein concept). We conclude that there is an optimal haematocrit during pregnancy between 30% and 38%. The presence of a high haematocrit and in addition elevated red cell aggregation should alert the physician to an increased risk of fetal compromise.

Changes in blood rheology in patients with stable angina pectoris as a result of coronary artery disease

We investigated several rheologic variables in 17 patients (11 men, six women, mean age = 52.1 +/- 9.8 years) with chronic stable angina. None took any medication except for sublingual nitroglycerin for 2 weeks before the study, and all had angiographically proven coronary artery disease with no history of myocardial infarction. Rheologic measurements included hematocrit, whole blood and plasma viscosity (750 and 1500 sec-1), degree of red cell aggregation via the zeta sedimentation ratio, and the extent and rate of red cell aggregation after stasis (Myrenne aggregometer). Compared with normal control donors, salient observations in the patients as a group included: a small (6%) but significant increase in hematocrit, a significant elevation in plasma viscosity (9%), significant increases in whole blood viscosity at both shear rates (14% and 16%), significant increases in the degree (12%), the extent (41%), and the rate (28% faster time constant) of red cell aggregation, an elevated alpha 2 level (15% increase) and a significantly increased fibrinogen concentration (25% increase), both of which correlated with the enhanced red cell aggregation. Rheologic abnormalities were evident when patients with disease in either one vessel or two to three vessels were compared with controls, but differences between these subgroups of patients were not significant. We conclude that patients with angina have rheologic abnormalities that are compatible with disturbed blood flow and an enhanced tendency for coronary arterial thrombosis.