Haemorheological studies in the fetus, pregnant and non-pregnant woman

Buchan, Peter Cameron (1980) Haemorheological studies in the fetus, pregnant and non-pregnant woman. MD thesis, University of Glasgow.

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Abstract

The importance of haemorheology in clinical medicine has only recently been widely realised. Haemorheological abnormalities have been found in a variety of pathological conditions but very little has been done in the field of obstetrics and gynaecology either to define normal haemorheological values in the menstrual cycle or in maternal and fetal blood in pregnancy, or to detect haemorheological abnormalities in pathological pregnancy or fetal disease. Haemorheological measurement techniques are constantly in need of evaluation and improvement. The first original work reported in this thesis was the development of the Deer Rheometer for the measurement of plasma and whole blood viscosity. Sample handling and measurement protocols were developed which gave reliable, fast and reproducible measurement of viscosity in biological fluids. In the initial experiments whole blood filtration was used as the method for measurement of erythrocyte deformability, but factors other than erythrocyte deformability were found to influence the rate of filtration. These factors were identified and eliminated or reduced to a minimum so that a highly sensitive filtration technique for the measurement of erythrocyte deformability was developed. Having established these two new methodologies and adding standard methods for the measurement of haematocrit and plasma fibrinogen, the normal levels of haemorheological parameters were measured in serial study throughout the menstrual cycle and normal pregnancy and in healthy full term and preterm fetuses. The cyclical variation in haemorheological parameters seen in the spontaneous menstrual cycle was abolished by ovulation suppression with ethinyloestradiol 30 mug and norgestrel 250 mug and the absolute level of each parameter was altered in such a way as would predispose to thrombosis. The effects of maternal cigarette smoking on maternal and fetal haemorheology were investigated in serial study. Cigarette smoking caused a reduction in maternal erythrocyte deformability throughout pregnancy, but did not affect other haemorheological factors. In contrast, the fetal blood exhibited an increased haematocrit and whole blood viscosity and reduced erythrocyte deformability. These changes in fetal haemorheology were associated with a significant reduction in birth weight in cigarette smokers and hyperviscosity causing impaired perfusion of the placental villi may be responsible for this fetal growth retardation. Pre-eclampsia resulted in elevation of maternal haematocrit, plasma fibrinogen, plasma and whole blood viscosity and reduction in erythrocyte deformability. In fetal blood the haematocrit and whole blood viscosity were elevated but plasma fibrinogen and viscosity and erythrocyte deformability were not altered. In the mother pre-eclampsia is characterised by acute hyperviscosity state associated with hypovolaemia and this could lead both to impaired placental perfusion and eventually to disseminated intravascular coagulation. Essential hypertension of mild or moderate degree had little effect on either maternal or fetal haemorheology and this was in keeping with the good fetal outcome in the cases studied. Both during labour and in the immediate neonatal period the infant is liable to anoxic acidosis. A series of in vitro and in vivo experiments investigated the effects of hypoxic acidosis on fetal erythrocyte deformability, Fetal erythrocytes mere particularly sensitive to the effects of hypoxic acidosis and a hypothesis was developed to show ways in which haemorheological factors might contribute to the pathogenesis of anoxic intracranial haemorrhage. The last chapter dealt with the importance of haemorheological factors in the pathogenesis of neonatal hyperbilirubinaemia following induction of labour. A prospective clinical study showed that oxytocin used in the induction of labour caused a decrease in erythrocyte deformability due to osmotic swelling and resulted in increased haemolysis with consequent hyperbilirubinaemia. Gupivicaine, used in epidural anaesthesia, was shown in in vitro studies to reduce erythrocyte deformability, but prostaglandin E2, used in the induction of labour, had a variable and clinically insignificant effect on fetal cells. The work reported in this thesis is largely new and obviously confirmatory work must follow. Haemorheological therapy is already being used in pre-eclampsia and with a better understanding of normal and pathological haemorheology in both mother and fetus a wider application of haemorheological therapies will follow.

Item Type: Thesis (MD)
Qualification Level: Doctoral
Additional Information: Adviser: J S Scott
Keywords: Medicine
Date of Award: 1980
Depositing User: Enlighten Team
Unique ID: glathesis:1980-73905
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56
URI: http://theses.gla.ac.uk/id/eprint/73905

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