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T Kiserud

Publications and source records attributed to T Kiserud.

At least 55 records · Page 3Linked to original sources
PubMed1998

Postnatal closure of ductus venosus in preterm infants < or = 32 weeks. An ultrasonographic study.

AIM: To assess ultrasonographically the flow pattern and the time of postnatal closure of ductus venosus in preterm infants < or = 32 weeks. METHODS: Thirty-three preterm infants < or = 32 weeks were studied within the first 1 to 5 days of life and followed every second day with ultrasound until no flow was detected either through the ductus venosus or the ductus arteriosus. RESULTS: The ductus venosus was closed in only 9% by day 3, in 40% by day 8 and 88% by day 18. All were closed by day 37. This is significantly later than in healthy term neonates. Closure of the ductus venosus was not significantly correlated with closure of ductus arteriosus. CONCLUSION: The ductus venosus shows a delayed closure in preterm infants, with no significant correlation to the closure of the ductus arteriosus or the condition of the infant. We speculate that immaturity of the ductus venosus and possibly increased levels of dilating prostaglandins leads to a delayed obliteration of the vessel. An open ductus venosus represents a portocaval shunt and may have metabolical and pharmacological consequences.

Aging↗
PubMed1998

Ductus venosus agenesis prevents transmission of central venous pulsations to the umbilical vein in fetal sheep.

Velocity pulsations in the umbilical vein are widely used as a marker for congestive heart failure in the fetus. It has been suggested that the atrial pressure waves are transmitted to the umbilical vein mainly through the ductus venosus. In a case of ductus venosus agenesis in a fetal sheep of 110 days' gestation, we recorded pressures in the inferior vena cava and umbilical vein simultaneously with Doppler velocimetry in the medial hepatic vein and umbilical vein, under general anesthesia. During fetal respiratory acidosis (pH 7.01) and varying degrees of umbilical clamping, we did not observe the typical pulsations in the umbilical vein (deflections of the maximum velocity during atrial contraction) in spite of varying degrees of reversed flow in the hepatic vein (5-16%). The systolic-diastolic pressure amplitude in the inferior vena cava was 5.5-6.4 mmHg, sometimes reaching 9.19-11.03 mmHg. Varying degrees of reversed portocaval pressure gradient during atrial contraction (1.40-9.51 mmHg), periods of reversed portocaval pressure gradient throughout the entire cardiac cycle, tachycardia (240 beats/min) or bradycardia (99 beats/min) also did not produce the type of pulsation in the umbilical vein that reflects augmented atrial contractions. The results support the hypothesis that the ductus venosus is essential for the transmission of atrial pressure waves to the umbilical vein.

Animals↗
PubMed1998

How repeat measurements affect the mean diameter of the umbilical vein and the ductus venosus.

Blood flow measurement in the fetus is susceptible to substantial error. Increased numbers of measurements can improve the precision. To quantify this, we assessed how the number of ultrasound measurements affected the calculation of individual mean diameters of fetal veins. A study of the umbilical vein (UV) and ductus venosus (DV) was carried out in 167 pregnancies in a clinical setting. The UV diameter was measured 2-13 times in 163 participants and the DV for the same number of times in 158. A one-way analysis of variance gave mean within-subject SD of 0.23 mm for the UV (diameter 2.0-8.0 mm) and 0.17 mm for the DV (diameter 0.3-2.3 mm). The 95% limit for the within-subject mean diameter calculated from two, four, six and ten measurements of the UV were 0.31, 0.22, 0.18 and 0.14 mm, respectively. For the DV the corresponding results were 0.23, 0.16, 0.13 and 0.10 mm. The study shows how increasing the number of measurements to calculate a mean diameter substantially improves the precision of vascular cross-section assessment. The limitation of the method is expressed in the exponential increase in numbers needed to achieve further improvement.

Analysis of Variance↗
PubMed1998

Simulation of pressure drop and energy dissipation for blood flow in a human fetal bifurcation.

The pressure drop from the umbilical vein to the heart plays a vital part in human fetal circulation. The bulk of the pressure drop is believed to take place at the inlet of the ductus venosus, a short narrow branch of the umbilical vein. In this study a generalized Bernoulli formulation was deduced to estimate this pressure drop. The model contains an energy dissipation term and flow-scaled velocities and pressures. The flow-scaled variables are related to their corresponding spatial mean velocities and pressures by certain shape factors. Further, based on physiological measurements, we established a simplified, rigid-walled, three-dimensional computational model of the umbilical vein and ductus venosus bifurcation for stationary flow conditions. Simulations were carried out for Reynolds numbers and umbilical vein curvature ratios in their respective physiological ranges. The shape factors in the Bernoulli formulation were then estimated for our computational models. They showed no significant Reynolds number or curvature ratio dependency. Further, the energy dissipation in our models was estimated to constitute 24 to 31 percent of the pressure drop, depending on the Reynolds number and the curvature ratio. The energy dissipation should therefore be taken into account in pressure drop estimates.

Bias↗
PubMed1997

Umbilical flow distribution to the liver and the ductus venosus: an in vitro investigation of the fluid dynamic mechanisms in the fetal sheep.

OBJECTIVES: The study aimed to determine whether an inherent difference in vascular resistance between the liver and the ductus venosus influences the distribution of umbilical blood to the two sections of the circulation. STUDY DESIGN: Flow was measured in vitro in six fetal sheep liver preparations, perfused at varying pressures with saline solution or with blood of hematocrit 25% to 26% or 41% to 42%, with an occluded or open ductus venosus, at a temperature of 19 degrees C to 21 degrees C with likely absence of local control mechanisms. RESULTS: There was a linear relationship between pressure and flow through the liver, except at very low pressures when the linearity was broken. A closing pressure of 1 to 4 mm Hg was noted, lowest with saline solution and highest with hematocrit 42%. An open ductus venosus reduced overall resistance and brought down the closing pressure to <1 mm Hg. This also occurred during perfusion with high hematocrit. Thus at low pressures a proportionally greater fraction of umbilical flow was directed through the ductus venosus. CONCLUSIONS: The different physical properties of the portal vasculature and of the ductus venosus, pressure and viscosity, have a substantial impact on distribution of umbilical flow to the two parts of the circulation. Reduced umbilical venous pressure and increased hematocrit favor an increased fraction of flow through the ductus venosus.

Animals↗
PubMed1997

Echogenic material in the fetal gallbladder and fetal disease.

The presence of echogenic material within the gallbladder is probably a rare finding in the fetus, and the list of predisposing factors known for postnatal life seems not to be applicable to prenatal diagnosis. In the present study 1656 obstetric scans were performed on referrals to the Unit of Fetal Medicine. No echogenic gallbladder contents were found before 28 weeks. In the subgroup of 523 fetuses who were examined during gestational weeks 28-42, six fetuses were found to have echogenic material in the gallbladder. The echogenicities were found in patients who had the following: extra-amniotic hematoma with intrauterine growth retardation and oligohydramnios, tetralogy of Fallot, trisomy 21 with atrioventricular septal defect and transient ascites, early abnormally distended fetal gallbladder, chromosomal aberration (translocation 10; 11) with bilateral clubfoot, and gastroschisis. Echogenic densities had disappeared at ultrasound scans performed during early postnatal life in four cases, were absent at five weeks in one case, and still present as calculi 8 months after birth in one case. Although no causative conclusions can be drawn from the report, these conditions are suggested as possible predisposing factors for the presence of echogenic material in the fetal gallbladder.

Adult↗
PubMed1997

Ultrasonographic study of ductus venosus in healthy neonates.

AIM: To assess ultrasonographically the flow pattern and the time of postnatal closure of ductus venosus related to the other fetal shunts. METHODS: Fifty healthy, term neonates were studied from day 1 up to day 18 using a VingMed CFM 800A ultrasound scanner. RESULTS: Ductus arteriosus was closed in 94% of the infants before day 3. Ductus venosus, however, was closed in only 12% at the same time, in 76% before day 7, and in all infants before day 18. A closed ductus venosus or ductus arteriosus did not show signs of reopening. Pulsed and colour Doppler flow could be detected across the foramen ovale in all infants during the sequential investigation. At day 1, when the pulmonary vascular resistance was still high, a reversed Doppler flow velocity signal was seen in ductus venosus in 10 infants (20%) and a bidirectional flow in ductus arteriosus in 26 (52%). Closure of the ductus venosus was not significantly correlated with closure of the ductus arteriosus nor related to sex nor weight loss. CONCLUSIONS: The time of closure of the ductus venosus evaluated by ultrasonography is much later than that of the ductus arteriosus. The flow pattern in ductus venosus reflects the portocaval pressure gradient and the pressure on the right side of the heart and in the pulmonary arteries. Both the flow pattern in the ductus venosus as well as that in the ductus arteriosus may be an indication of compromised neonatal haemodynamics.

Ductus Arteriosus↗
PubMed1996

Lack of evidence of permanent engraftment after in utero fetal stem cell transplantation in congenital hemoglobinopathies.

The use of fetal hematopoietic stem cells for in utero transplantation to create permanent hematochimerism represents a new concept in fetal therapy. In one fetus with alpha-thalassemia, one with sickle cell anemia, and one with beta-thalassemia, we have transplanted fetal liver cells obtained from legal abortions in gestational weeks 6-11. The fetus with alpha-thalassemia was transplanted twice during pregnancy, in the 15th (20.4 x 10(8) cells/kg) and in the 31st weeks of gestation (1.2 x 10(8) cells/kg), and is now two years of age. One fetus with sickle cell anemia received its transplant in the 13th week of gestation (16.7 x 10(8) cells/kg), and is now one year old. The fetus with beta-thalassemia was transplanted in 18th week (8.6 x 10(8) cells/kg), and is now three months old. Engraftment was evaluated by chromosomal analysis (sex chromosomes), red cell phenotyping, HLA class I and II typing, and PCR (polymerase chain reaction) for Y chromosome-specific sequences and DNA polymorphisms in cord and peripheral blood. The children with alpha- and beta-thalassemia underwent bone marrow aspirations at 3 and 7 months of age, respectively. In neither of these cases were we able to detect convincing evidence of stem cell engraftment. Thus, the administration of fetal stem cells to fetal recipients after the 12th week of gestation did not result in permanent hematochimerism. It remains to be determined whether the engraftment process can be promoted by earlier transplantations and/or higher cell doses.

Adult↗
PubMed1996

Evaluation of a risk of malignancy index based on serum CA125, ultrasound findings and menopausal status in the pre-operative diagnosis of pelvic masses.

OBJECTIVE: To evaluate the ability of a risk of malignancy index (RMI), based on a serum CA125 level, ultrasound findings and menopausal status, to discriminate a benign from a malignant pelvic mass and to discriminate early stage (Figo Stage I) from Stages II, III and IV of ovarian cancer. DESIGN: A prospective study. SETTING: Department of Gynaecology, Trondheim University Hospital, Trondheim, Norway. PARTICIPANTS: One hundred and seventy-three women, 30 years or older, consecutively admitted between February 1992 and February 1994 for primary laparotomy of a pelvic mass. MAIN OUTCOME MEASURES: The sensitivity, specificity and positive predictive value of serum CA125 level, ultrasound findings and menopausal status, separately and combined into the RMI, to diagnose ovarian cancer. RESULTS: The RMI was more accurate than any individual criterion in diagnosing cancer. Using a RMI cut-off level of 200 to indicate malignancy, the RMI derived from this dataset gave a sensitivity of 80%, specificity of 92% and positive predictive value of 83%. Applying RMI criteria developed by others, the following test performance was found: sensitivity 71%, specificity 96% and positive predictive value 89%. For the Stages II, III and IV of ovarian cancer the sensitivity increased to approximately 90% without any substantial loss in specificity. CONCLUSIONS: The risk of malignancy index is able to correctly discriminate between malignant and benign pelvic masses. It is a scoring system which can be introduced easily into clinical practice to facilitate the selection of patients for primary surgery at an oncological unit.

Adult↗
PubMed1995

[Preoperative identification of malignancy among women with a pelvic mass. Evaluation of a risk index based on ultrasound findings. CA 125 in serum and menopausal status].

A risk of malignancy index (RMI) based on vaginal ultrasound, the tumour marker CA 125 level in serum, and menopausal status was calculated in 134 consecutive patients with a pelvic mass. 41 patients harboured a malignancy, while in 93 the condition was benign. The specificity according to the presence of a malignancy was 95% using the risk of malignancy index, compared with 78% when ultrasound was used alone, and 78% when CA 125 was used alone. The corresponding sensitivities were 73, 71 and 83% respectively. The majority of patients with a false negative index score had early stage ovarian cancer. Only one of the 21 patients with advanced ovarian cancer had a score below the limit of 200. The use of the risk malignancy index is a convenient method for pre-operative identification of cases of advanced ovarian cancer.

Adult↗
PubMed1995

Early development of the hindbrain: a longitudinal ultrasound study from 7 to 12 weeks of gestation.

Twenty-nine healthy pregnant women were examined by transvaginal ultrasound to evaluate embryonic development in vivo between 7 and 12 weeks of gestation. The rhombencephalon with its fourth ventricle, the cerebellum and the choroid plexuses of the fourth ventricle were identified and measured. The cavity of the rhombencephalon, the future fourth ventricle, was always visible from 7 weeks, initially lying superiorly in the head of the embryo. The cerebellum and the choroid plexuses of the fourth ventricle became distinguishable during week 8. The volume of the rhombencephalic cavity was estimated. The shape and size of these rhombencephalic structures, their position in relation to each other and their relation to other brain structures changed specifically during the embryonic and early fetal period. This sonoembryological development corresponded to the descriptions in classical embryological literature.

Adult↗
PubMed1995

Three-dimensional imaging of the brain cavities in human embryos.

A system for high-resolution three-dimensional imaging of small structures has been developed, based on the Vingmed CFM-800 annular array sector scanner with a 7.5-MHz transducer attached to a PC-based TomTec Echo-Scan unit. A stepper motor rotates the transducer 180 degrees and the complete three-dimensional scan consists of 132 two-dimensional images, video-grabbed and scan-converted into a regular volumetric data set by the TomTec unit. Three normal pregnancies with embryos of gestational age 7, 9 and 10 weeks received a transvaginal examination with special attention to the embryonic/fetal brain. In all three cases, it was possible to obtain high-resolution images of the brain cavities. At 7 weeks, both hemispheres and their connection to the third ventricle were delineated. The isthmus rhombencephali could be visualized. At 9 weeks, the continuous development of the brain cavities could be followed and at 11 weeks the dominating size of the hemispheres could be depicted. It is concluded that present ultrasound technology has reached a stage where structures of only a few millimeters can be imaged in vivo in three-dimensions with a quality that resembles the plaster figures used in embryonic laboratories. The method can become an important tool in future embryological research and also in the detection of early developmental disorders of the embryo.

Brain↗
PubMed1995

Early development of the abdominal wall, stomach and heart from 7 to 12 weeks of gestation: a longitudinal ultrasound study.

The purpose of this ultrasound study was to describe longitudinally the normal embryonic development in vivo. Twenty-nine healthy pregnant women were examined five times each with transvaginal ultrasound between 7 and 12 weeks of gestation measured from the last menstrual period. Structures such as the midgut herniation into the umbilical cord, the stomach and the heart were recognized and measured. It was possible to identify the physiological midgut herniation during weeks 7-8. It was always present from 8.5 to 10.5 weeks. At 12 completed weeks, the gut was retracted into the abdominal cavity for all the fetuses. We visualized the stomach in nine embryos (31%) during week 8, in 22 embryos (76%) before 10 weeks, and in all fetuses before 11 weeks. The heart rate increased rapidly to a mean of 175 beats per minute (bpm) at the beginning of week 9. Thereafter it decreased slowly to a mean of 166 bpm at 12 weeks. The mean heart diameter was 22% of the crown-rump length at 7 weeks, 17% at 9 weeks and only 13% at 12 weeks.

Abdominal Muscles↗
PubMed1995

Prenatal diagnosis of osteogenesis imperfecta.

The lethal perinatal types (II A-C) of osteogenesis imperfecta are reported to occur in approximately 1:55000 births. We here present three cases in three unrelated families, diagnosed by antenatal ultrasound within one year. A reliable diagnosis of the lethal perinatal type of osteogenesis imperfecta can be made by ultrasound examination during the second trimester, by identification of fractures of the long bones. The compression of the fetal head by the ultrasound probe and the low echogeneity of the cranium, should raise the suspicion of skeletal dysplasia, but is not diagnostic for osteogenesis imperfecta. The diagnosis is confirmed by postmortem examination including radiography and biochemical studies of cultivated fibroblasts from the fetus. Although rare, this lethal condition should be recognized when an ultrasound examination is performed, to prevent unnecessary obstetric intervention. In families with a previously affected fetus, prenatal diagnosis by first trimester transvaginal ultrasound investigation or chorionic villus sampling should be discussed.

Adult↗
PubMed1994

Early development of the forebrain and midbrain: a longitudinal ultrasound study from 7 to 12 weeks of gestation.

The purpose of this longitudinal study was to describe embryonic development in vivo. Twenty-nine healthy pregnant women were examined five times with transvaginal ultrasound between 7 and 12 weeks of gestation. Brain structures such as the hemispheres, the choroid plexus of the lateral ventricles, the diencephalon, and the mesencephalon were identified and, if possible, measured. It was possible to identify the cavities of the hemispheres, the diencephalon and the mesencephalon during week 7. The choroid plexus of the lateral ventricles became visible during week 8. The growth of the length, width and height of the hemispheres and the choroid plexus of the lateral ventricles was curvilinear, that of the mesencephalon and diencephalon was linear except for the width of the diencephalon. The width of the diencephalon, the future third ventricle, was 1.1 mm during week 7. It decreased to 0.8 mm at 12 weeks. Apart from the rhombencephalon, the cavity of the diencephalon was the large dominating brain structure during embryonic development. In early fetal life the cerebral hemispheres took over this dominance. The study was in full agreement with descriptions in the embryological literature, both concerning the anatomical features and their chronological formation.

Journal Article↗
PubMed1994

Ductus venosus blood velocity and the umbilical circulation in the seriously growth-retarded fetus.

Based on the assumption that the ductus venosus is regulator of oxygenated blood in the fetus, the present study investigated the blood flow velocity of the ductus venosus in relation to the umbilical circulation in the that seriously growth-retarded fetus. The study group of 38 fetuses (gestational week 17-39) had no chromosomal aberrations or structural malformations and had an ultrasonographic biometry of < 2.5th centile and birth weight of <or= 2.5th centile. Of the 38 fetuses seven died in utero and four died postnatally. The ultrasonographic examination included pulsed Doppler measurement of the umbilical artery pulsatility index (PI), the umbilical vein dimension and blood flow velocity, and the peak and maximum blood flow velocities of the ductus venosus. The majority of fetuses had a raised PI in the umbilical artery (26/38) and reduced blood flow in the umbilical vein (25/33). Despite such changes in the umbilical circulation, a normal peak velocity in the ductus venosus was maintained in all fetuses. During the atrial contraction, however, 13 fetuses had reduced or reversed blood velocity in the ductus venosus. Reduced ductus venosus velocity during atrial contraction seemed to be a serious finding linked to raised PI and absent or reversed end-diastolic flow in the umbilical artery, and umbilical vein pulsation. The results support the assumption that the blood flow of the ductus venosus is a preferential bloodstream in the human fetus that is maintained within normal ranges as long as possible during placental hemodynamic compromise.

Journal Article↗
PubMed1994

Estimation of the pressure gradient across the fetal ductus venosus based on Doppler velocimetry.

In the fetus, the umbilical vein is directly linked to the inferior vena cava by the narrow ductus venosus. Thus, the ductus venosus blood velocity probably reflects the pressure gradient between the umbilical vein and the central venous system. In a longitudinal study that included 29 normal fetuses, pulsed Doppler velocimetry was carried out in the umbilical vein and the ductus venosus during the last half of the pregnancy. By applying the Bernoulli equation, we estimated the pressure gradient across the ductus venosus to vary between 0-3 mm Hg during the heart cycle; it remained within those ranges during gestational weeks 18-40. During fetal inspiratory movement, pressure gradients up to 22 mm Hg were estimated. The estimated ductus venosus pressure gradient seems to be within ranges compatible with known umbilical venous pressures, and may provide a new opportunity to understand central venous hemodynamics and respiratory force in the fetus once methodological limitations are controlled.

Blood Flow Velocity↗