1
|
Vargas AI, Tarraf SA, Fitzgibbons TP, Bellini C, Amini R. Biomechanical remodeling of the murine descending thoracic aorta during late-gestation pregnancy. Curr Res Physiol 2023; 6:100102. [PMID: 37575979 PMCID: PMC10415834 DOI: 10.1016/j.crphys.2023.100102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 06/29/2023] [Accepted: 07/04/2023] [Indexed: 08/15/2023] Open
Abstract
With the rise in maternal mortality rates and the growing body of epidemiological evidence linking pregnancy history to maternal cardiovascular health, it is essential to comprehend the vascular remodeling that occurs during gestation. The maternal body undergoes significant hemodynamic alterations which are believed to induce structural remodeling of the cardiovascular system. Yet, the effects of pregnancy on vascular structure and function have not been fully elucidated. Such a knowledge gap has limited our understanding of the etiology of pregnancy-induced cardiovascular disease. Towards bridging this gap, we measured the biaxial mechanical response of the murine descending thoracic aorta during a normotensive late-gestation pregnancy. Non-invasive hemodynamic measurements confirmed a 50% increase in cardiac output in the pregnant group, with no changes in peripheral blood pressure. Pregnancy was associated with significant wall thickening ( ∼14%), an increase in luminal diameter ( ∼6%), and material softening in both circumferential and axial directions. This expansive remodeling of the tissue resulted in a reduction in tensile wall stress and intrinsic tissue stiffness. Collectively, our data indicate that an increase in the geometry of the vessel may occur to accommodate for the increase in cardiac output and blood flow that occurs in pregnancy. Similarly, wall thickening accompanied by increased luminal diameter, without a change in blood pressure may be a necessary mechanism to decrease the tensile wall stress, and avoid pathophysiological events following late gestation.
Collapse
Affiliation(s)
- Ana I. Vargas
- Department of Bioengineering, Northeastern University, Boston, MA, 02115, United States
| | - Samar A. Tarraf
- Department of Bioengineering, Northeastern University, Boston, MA, 02115, United States
| | - Timothy P. Fitzgibbons
- Department of Medicine, Division of Cardiovascular Medicine, University of Massachusetts Medical School, Worcester, MA, 01655, United States
| | - Chiara Bellini
- Department of Bioengineering, Northeastern University, Boston, MA, 02115, United States
| | - Rouzbeh Amini
- Department of Bioengineering, Northeastern University, Boston, MA, 02115, United States
- Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA, 02115, United States
| |
Collapse
|
2
|
Li K, Zhang S, Yang L, Jiang H, Chi Z, Wang A, Yang Y, Li X, Hao D, Zhang L, Zheng D. Changes of Arterial Pulse Waveform Characteristics with Gestational Age during Normal Pregnancy. Sci Rep 2018; 8:15571. [PMID: 30349022 PMCID: PMC6197191 DOI: 10.1038/s41598-018-33890-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 10/01/2018] [Indexed: 11/11/2022] Open
Abstract
Arterial pulse waveform analysis has been widely used to reflect physiological changes in the cardiovascular system. This study aimed to comprehensively investigate the changes of waveform characteristics of both photoplethysmographic (PPG) and radial pulses with gestational age during normal pregnancy. PPG and radial pulses were simultaneously recorded from 130 healthy pregnant women at seven gestational time points. After normalizing the arterial pulse waveforms, the abscissa of notch point, the total pulse area and the reflection index were extracted and compared between different measurement points and between the PPG and radial pulses using post-hoc multiple comparisons with Bonferrioni correction. The results showed that the effect of gestational age on all the three waveform characteristics was significant (all p < 0.001) after adjusting for maternal age, heart rate and blood pressures. All the three waveform characteristics demonstrated similar changing trends with gestational age, and they were all significantly different between the measurements from gestational week 12–15 and the others (all p < 0.05, except for the PPG total pulse area between the first and second measurement points). In conclusion, this study has comprehensively quantified similar changes of both PPG and radial pulse waveform characteristics with gestational age.
Collapse
Affiliation(s)
- Kunyan Li
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China.,Department of Medical Science and Public Health, Faculty of Medical Science, Anglia Ruskin University, Chelmsford, CM1 1SQ, UK
| | - Song Zhang
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China
| | - Lin Yang
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China.
| | - Hongqing Jiang
- Haidian Maternal & Child Health Hospital, Beijing, 100026, China
| | - Zhenyu Chi
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China
| | - Anran Wang
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China
| | - Yimin Yang
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China
| | - Xuwen Li
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China
| | - Dongmei Hao
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China
| | - Lei Zhang
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China
| | - Dingchang Zheng
- Department of Medical Science and Public Health, Faculty of Medical Science, Anglia Ruskin University, Chelmsford, CM1 1SQ, UK.
| |
Collapse
|
3
|
Dallmann A, Ince I, Meyer M, Willmann S, Eissing T, Hempel G. Gestation-Specific Changes in the Anatomy and Physiology of Healthy Pregnant Women: An Extended Repository of Model Parameters for Physiologically Based Pharmacokinetic Modeling in Pregnancy. Clin Pharmacokinet 2018; 56:1303-1330. [PMID: 28401479 DOI: 10.1007/s40262-017-0539-z] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND In the past years, several repositories for anatomical and physiological parameters required for physiologically based pharmacokinetic modeling in pregnant women have been published. While providing a good basis, some important aspects can be further detailed. For example, they did not account for the variability associated with parameters or were lacking key parameters necessary for developing more detailed mechanistic pregnancy physiologically based pharmacokinetic models, such as the composition of pregnancy-specific tissues. OBJECTIVES The aim of this meta-analysis was to provide an updated and extended database of anatomical and physiological parameters in healthy pregnant women that also accounts for changes in the variability of a parameter throughout gestation and for the composition of pregnancy-specific tissues. METHODS A systematic literature search was carried out to collect study data on pregnancy-related changes of anatomical and physiological parameters. For each parameter, a set of mathematical functions was fitted to the data and to the standard deviation observed among the data. The best performing functions were selected based on numerical and visual diagnostics as well as based on physiological plausibility. RESULTS The literature search yielded 473 studies, 302 of which met the criteria to be further analyzed and compiled in a database. In total, the database encompassed 7729 data. Although the availability of quantitative data for some parameters remained limited, mathematical functions could be generated for many important parameters. Gaps were filled based on qualitative knowledge and based on physiologically plausible assumptions. CONCLUSION The presented results facilitate the integration of pregnancy-dependent changes in anatomy and physiology into mechanistic population physiologically based pharmacokinetic models. Such models can ultimately provide a valuable tool to investigate the pharmacokinetics during pregnancy in silico and support informed decision making regarding optimal dosing regimens in this vulnerable special population.
Collapse
Affiliation(s)
- André Dallmann
- Department of Pharmaceutical and Medical Chemistry, Clinical Pharmacy, Westfälische Wilhelm-University Münster, Münster, Germany
| | - Ibrahim Ince
- ET-TD-ET Systems Pharmacology CV, Bayer AG, Leverkusen, Germany.
| | - Michaela Meyer
- DD-CS Clinical Pharmacometrics, Bayer AG, Wuppertal, Germany
| | - Stefan Willmann
- DD-CS Clinical Pharmacometrics, Bayer AG, Wuppertal, Germany
| | - Thomas Eissing
- ET-TD-ET Systems Pharmacology CV, Bayer AG, Leverkusen, Germany
| | - Georg Hempel
- Department of Pharmaceutical and Medical Chemistry, Clinical Pharmacy, Westfälische Wilhelm-University Münster, Münster, Germany
| |
Collapse
|
4
|
Robins JB, Woodward M, Lowe G, McCaul P, Cheyne H, Walker JJ. First trimester maternal blood rheology and pregnancy induced hypertension. J OBSTET GYNAECOL 2005; 25:746-50. [PMID: 16368576 DOI: 10.1080/01443610500314637] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
This study evaluates the relationship between the first trimester assessment of maternal rheology and the subsequent development of pregnancy induced hypertension. This is a prospective observational study based in the Glasgow Royal Maternity Hospital, Scotland. From an original population of 744 consecutive antenatal attendees a total of 579 women were booked at less than 14 weeks' gestation. The main study group is a further subset comprising 251 primigravid women booking with a singleton pregnancy without essential hypertension. Previously published data from a group of non-pregnant women of similar age drawn from the same local community was used for external comparison. Blood samples were collected at the booking visit, from which fibrinogen, red cell aggregation, haematocrit and plasma, whole blood, relative and corrected viscosities were recorded. Information was obtained from the case notes in retrospect starting approximately 1 year after the first patients had first been recruited into the trial. The overall outcome of the pregnancies was noted with particular reference to pregnancy induced hypertension (PIH), birth weight, antepartum haemorrhage, pre-term labour, perinatal death, condition at delivery and neonatal complication. Our results show PIH is associated with a significantly raised mean blood viscosity and fibrinogen at time of booking. All significance disappears after adjustment for smoking, diastolic blood pressure and age. Viscosity is, however, only marginally non-significant (p = 0.07). In conclusion, blood rheology, in particular blood viscosity and fibrinogen, may play a predictive role in the development of pregnancy-induced hypertension. When combined with measurement of smoking and diastolic blood pressure at booking, these measurements could be used to calculate a risk score for the development of PIH, allowing targeting of antenatal care. Further data is required.
Collapse
Affiliation(s)
- J B Robins
- Glasgow Royal Maternity Hospital, Scotland, UK.
| | | | | | | | | | | |
Collapse
|
5
|
Boito SME, Struijk PC, Pop GAM, Visser W, Steegers EAP, Wladimiroff JW. The impact of maternal plasma volume expansion and antihypertensive treatment with intravenous dihydralazine on fetal and maternal hemodynamics during pre-eclampsia: a clinical, echo-Doppler and viscometric study. ULTRASOUND IN OBSTETRICS & GYNECOLOGY : THE OFFICIAL JOURNAL OF THE INTERNATIONAL SOCIETY OF ULTRASOUND IN OBSTETRICS AND GYNECOLOGY 2004; 23:327-332. [PMID: 15065180 DOI: 10.1002/uog.1012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
OBJECTIVES To establish the effects of plasma volume expansion (PVE) followed by intravenous dihydralazine (DH) administration on maternal whole blood viscosity (WBV) and hematocrit, uteroplacental and fetoplacental downstream impedance and umbilical venous (UV) volume flow in pre-eclampsia. METHODS In 13 pre-eclamptic women maternal and fetal hemodynamics were established by means of combined measurement of maternal arterial blood pressure (BP), WBV, hematocrit and uterine artery (UtA) resistance index (RI) in addition to umbilical artery (UA) pulsatility index (PI) and UV volume flow obtained from UV vessel area and UV time-averaged flow velocity. In each woman all parameters were measured four times at baseline, after PVE, after DH and 24 h after the start of treatment. RESULTS Maternal diastolic BP, hematocrit and WBV display a significant reduction after PVE. In the fetus UA PI decreases significantly whereas a significant increase in UV cross-sectional area was detected. After maternal DH administration, arterial systolic and diastolic BP and UA PI show a significant decrease compared with the measurements following PVE. At 24 h, only maternal systolic and diastolic BP display a significant further decrease. No significant changes were established for the UtA RI, UV time-averaged velocity and UV volume flow during the entire study period. CONCLUSIONS During pre-eclampsia, maternal PVE followed by DH administration results in a significant reduction in maternal diastolic BP, maternal hematocrit and WBV. Maternal PVE is associated with a significant increase in UV cross-sectional area and a non-significant rise of 11% in UV volume flow. Maternal DH administration does not result in any change in UV cross-sectional area. However, UA PI decreases significantly after both PVE and DH treatment.
Collapse
Affiliation(s)
- S M E Boito
- Department of Obstetrics and Gynaecology, Erasmus Medical Centre, Rotterdam, The Netherlands
| | | | | | | | | | | |
Collapse
|
6
|
Di Naro E, Raio L, Ghezzi F, Franchi M, Romano F, Addario VD. Longitudinal umbilical vein blood flow changes in normal and growth-retarded fetuses. Acta Obstet Gynecol Scand 2002. [DOI: 10.1034/j.1600-0412.2002.810609.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
7
|
Oosterhof H, Wichers G, Fidler V, Aarnoudse JG. Blood viscosity and uterine artery flow velocity waveforms in pregnancy: a longitudinal study. Placenta 1993; 14:555-61. [PMID: 8290495 DOI: 10.1016/s0143-4004(05)80208-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In the course of pregnancy, whole blood viscosity (WBV) decreases, plasma viscosity (PV) increases and uteroplacental resistance to blood flow falls. According to the Hagen-Poiseuille law, viscosity influences resistance to blood flow. To investigate the contribution of these haemorheological changes to the decrease in resistance to blood flow in the uteroplacental circulation, a serial study was performed. Using blood viscosimetry and pulsed Doppler ultrasound recordings of the uterine arteries, 21 women with normal pregnancies were studied every 8 weeks from 12 weeks onwards. Statistical analysis revealed no significant relationship between WBV, PV and pulsatility index of the uterine arteries. It is concluded that the changes in blood viscosities are of minor influence on resistance to blood flow in the uteroplacental circulation throughout normal pregnancy. The vascular changes e.g. the considerable increase of the diameter of the spiral arteries have a much greater impact on resistance to blood flow.
Collapse
Affiliation(s)
- H Oosterhof
- Department of Obstetrics and Gynaecology, University Hospital Groningen, The Netherlands
| | | | | | | |
Collapse
|
8
|
Umapathysivam K, Haskard KA, Meffin E, Jones WR. Correlation of umbilical cord whole blood viscosity and the presence of fetal distress at birth: a mathematical modelling study. Aust N Z J Obstet Gynaecol 1990; 30:71-3. [PMID: 2346456 DOI: 10.1111/j.1479-828x.1990.tb03201.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
This study was designed to investigate the relationship between umbilical cord blood viscosity and clinical parameters such as maternal parity, maternal smoking, mode of delivery, sex of infant and the incidence of fetal distress at birth using mathematical modelling. The results demonstrated vaginal delivery, male infants, infants of primigravidas and low cord whole blood viscosity at a high shear rate were covariables and were associated with an increased incidence of fetal distress and low Apgar scores.
Collapse
Affiliation(s)
- K Umapathysivam
- Department of Obstetrics & Gynaecology, Flinders University of South Australia, Bedford Park
| | | | | | | |
Collapse
|
9
|
Steel SA, Pearce JM, Nash G, Christopher B, Dormandy J, Bland JM. Correlation between Doppler flow velocity waveforms and cord blood viscosity. BRITISH JOURNAL OF OBSTETRICS AND GYNAECOLOGY 1989; 96:1168-72. [PMID: 2686752 DOI: 10.1111/j.1471-0528.1989.tb03192.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The contribution of rheological factors to the impedance of blood flow in the umbilical artery as determined by continuous-wave Doppler ultrasound was investigated. Of the 51 pregnancies recruited, six were complicated by pre-eclampsia, 10 by intrauterine growth retardation, 15 by both pre-eclampsia and fetal growth retardation, and there were 20 controls. A significant correlation was demonstrated between both plasma viscosity and gestational age and the resistance index used to characterize the Doppler waveform. Multiple regression analysis demonstrated that changes in plasma viscosity explained 55% of the variance seen in the resistance index and that this was statistically significant. This finding is, however, unlikely to be of clinical significance as whole blood viscosity had an insignificant effect on the impedance in the umbilical artery. We postulate that vascular factors such as the number and calibre of the placental arterioles are a more important determinant of umbilical artery impedance.
Collapse
Affiliation(s)
- S A Steel
- Department of Obstetrics, St George's Hospital Medical School, London
| | | | | | | | | | | |
Collapse
|
10
|
Beattie RB, Dornan JC. Antenatal screening for intrauterine growth retardation with umbilical artery Doppler ultrasonography. BMJ (CLINICAL RESEARCH ED.) 1989; 298:631-5. [PMID: 2496788 PMCID: PMC1835873 DOI: 10.1136/bmj.298.6674.631] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
To assess the usefulness of continuous wave Doppler ultrasonography as an antenatal screening tool for the detection of intrauterine growth retardation and fetal compromise 2097 singleton pregnancies were studied. Umbilical artery velocity waveforms were obtained at 28, 34, and 38 weeks of gestation, from which the pulsatility index, A/B ratio, and resistance parameter were calculated. No abnormal features or indices of neonatal outcome were adequately predicted. The most sensitive index for being delivered of a growth retarded infant (less than 5th centile birth weight for gestation) was an A/B ratio at 34 weeks (sensitivity 40%, specificity 84%). Other measures that show poor neonatal nutritional state (ponderal index, skinfold thickness, and ratio of mid-arm circumference to head circumference) were even less well predicted. Acute and chronic hypoxia as determined by Apgar score, pH in blood from the cord artery, and packed cell volume correlated poorly with umbilical artery waveform indices, and there was no obvious difference between the indices of those who subsequently required operative or instrumental delivery for fetal distress and those requiring no intervention. There were three unexplained stillbirths in the series, in each of which the fetus had shown waveform patterns that suggested increased peripheral resistance, though the technique did not appear to be useful for predicting the time of subsequent death. Screening for small for dates babies in a three stage programme was of no value regardless of the threshold or index chosen. Obstetricians should resist the temptation to introduce screening with Doppler ultrasonography until its proper role has been determined.
Collapse
Affiliation(s)
- R B Beattie
- Department of Obstetrics and Gynaecology, Queen's University of Belfast
| | | |
Collapse
|
11
|
Steel SA, Pearce JM, Nash G, Christopher B, Dormandy J, Bland JM. Maternal blood viscosity and uteroplacental blood flow velocity waveforms in normal and complicated pregnancies. BRITISH JOURNAL OF OBSTETRICS AND GYNAECOLOGY 1988; 95:747-52. [PMID: 3048372 DOI: 10.1111/j.1471-0528.1988.tb06547.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
According to the Poiseuille-Hagen law, viscosity influences flow resistance. A possible effect of blood viscosity upon the resistance index of the uteroplacental circulation as measured by continuous wave Doppler ultrasound was investigated in 50 pregnant women. It was found that blood viscosity variables explained only about 10% of the variation in the resistance index in all patients, which was not statistically significant. It is suggested, therefore, that the vascular contribution to flow resistance may be more important.
Collapse
Affiliation(s)
- S A Steel
- St. George's Hospital Medical School, London
| | | | | | | | | | | |
Collapse
|
12
|
Huisman A, Aarnoudse JG, Krans M, Huisjes HJ, Fidler V, Zijlstra WG. Red cell aggregation during normal pregnancy. Br J Haematol 1988; 68:121-4. [PMID: 3345288 DOI: 10.1111/j.1365-2141.1988.tb04189.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
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.
Collapse
Affiliation(s)
- A Huisman
- Department of Obstetrics, University of Groningen, The Netherlands
| | | | | | | | | | | |
Collapse
|
13
|
Huisman A, Aarnoudse JG, Heuvelmans JH, Goslinga H, Fidler V, Huisjes HJ, Zijlstra WG. Whole blood viscosity during normal pregnancy. BRITISH JOURNAL OF OBSTETRICS AND GYNAECOLOGY 1987; 94:1143-9. [PMID: 3426986 DOI: 10.1111/j.1471-0528.1987.tb02313.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
In a serial study the changes in whole blood viscosity at different shear rates and its major determinants were determined in 24 healthy women with normal pregnancies. Whole blood viscosity and plasma viscosity were measured with a rotational viscometer. Red cell aggregation was measured by syllectometry. During normal pregnancy we found a decrease in whole blood viscosity at all shear rates until 29 weeks gestation, followed by a smaller increase between 30 and 37 weeks, which was most pronounced at higher shear rates, especially in nulliparae. The changes in whole blood viscosity were to a great extent determined by the changes in haematocrit and plasma viscosity. Haematocrit was more important for whole blood viscosity at lower shear rates, while plasma viscosity had more influence on high shear blood viscosity. The continuous increase in red cell aggregation had no demonstrable influence on low shear blood viscosity as measured in vitro in a rotational viscometer.
Collapse
Affiliation(s)
- A Huisman
- Department of Obstetrics, University of Groningen, The Netherlands
| | | | | | | | | | | | | |
Collapse
|
14
|
Abstract
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.
Collapse
|
15
|
Jouppila P, Kirkinen P, Puukka R. Correlation between umbilical vein blood flow and umbilical blood viscosity in normal and complicated pregnancies. ARCHIVES OF GYNECOLOGY 1986; 237:191-7. [PMID: 3963891 DOI: 10.1007/bf02133781] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Umbilical vein blood flow (UVBF) was studied during the last 24 h before delivery using a combination of real-time and Doppler ultrasonic equipment in 64 normal and pathological pregnancies and the results were correlated with the values of whole blood viscosity taken from the umbilical vein after delivery. UVBF was reduced in the subgroup with chronic fetal distress (n = 14) (P less than 0.001) and the hypertensive pregnancies (n = 17) (P less than 0.05), whereas umbilical blood viscosity was increased only in the subgroup with chronic fetal distress (P less than 0.01) as compared with the normal pregnancies (n = 24). A significant positive correlation was observed between the umbilical blood viscosity and haematocrit values in all the groups of patients. UVBF and blood viscosity had a significant negative correlation in chronic fetal distress (P less than 0.001) and in hypertensive pregnancies (P less than 0.05), but not in normal or diabetic pregnancies (n = 9). Thus haemoconcentration leading to increased fetal blood viscosity may act as an aetiological factor in the reduction of UVBF in developing fetal distress.
Collapse
|