The effect of intravascular blood transfusion on the flow velocity waveform of the portal venous system of the anemic fetus

Fetal cardiac contractility before and after intrauterine transfusion

OBJECTIVE

To evaluate the effect of fetal anemia and intrauterine transfusion on ventricular shortening fraction.

METHODS

The end-diastolic and end-systolic transverse dimensions of the left and right ventricles were obtained using M-mode ultrasonography. The shortening fractions of both ventricles were calculated at three time points: before, immediately after and one day after intrauterine transfusion. The blood volume given at intrauterine transfusion was expressed as a percentage of estimated fetoplacental blood volume.

RESULTS

Complete measurements were obtained from 49 transfusions in 23 fetuses. Intrauterine transfusion was performed at a median gestational age of 31 (range, 19-35) weeks. Median hemoglobin concentration before and after intrauterine transfusion was 7.9 (range, 2.7-13.7) g/dL and 14.3 (range, 12.7-16.1) g/dL, respectively. Both left and right ventricular shortening fractions differed significantly between the three time points. Left ventricular shortening fraction decreased immediately after transfusion in 43 (88%) of the 49 procedures. Right ventricular shortening fraction decreased immediately after transfusion in 42 (86%) of the 49 procedures. At the first intrauterine transfusion, there was only a weak correlation between the decrease in shortening fraction of both ventricles and the transfused volume (left: R(2) = 0.15; P = 0.20/right: R(2) = 0.005; P = 0.81).

CONCLUSION

Transfusion significantly decreases the shortening fraction of both ventricles of the fetal heart. There is, however, little correlation between the decrease in shortening fraction and the volume of red cells given at intrauterine transfusion. Published by John Wiley & Sons, Ltd.

Portal and umbilical venous blood supply to the liver in the human fetus near term

OBJECTIVES

To determine the contribution of the umbilical (UV) and portal (PV) veins to blood supply to the human fetal liver in a low-risk population near term, and to assess the distribution between the left and right lobes.

METHODS

In 91 low-risk pregnancies with normally grown fetuses at 36 weeks of gestation we measured the distribution of blood in the UV and PV to the right and left hepatic lobes using ultrasound imaging and Doppler techniques.

RESULTS

The median (10(th), 90(th) centile) total UV return was 205 (127, 294) mL/min, of which 25% (13, 47%) was shunted through the ductus venosus, 55% (35, 66%) was distributed to the left hepatic lobe, and 20% (11, 30%) was distributed to the right hepatic lobe. While the left lobe was supplied exclusively by the UV, the right lobe received 50% (20, 70%; 37 (16, 65) mL/min) of its venous blood supply from the PV. The total venous blood supply to the liver parenchyma was 185 (114, 277) mL/min; 21% (8, 34%) came from the PV supply to the right lobe and the remainder came from the UV supply to both lobes.

CONCLUSIONS

The venous supply to the left lobe is from nutrient-rich UV blood; for the right lobe, half is from UV blood and half from nutrient-poor PV blood. This watershed between the portal and umbilical venous flows to the fetal liver suggests a corresponding functional dichotomy; this may be modified by hemodynamic influences, with long-term consequences.

Fetal hydrops and hepatosplenomegaly in the second half of pregnancy: a sign of myeloproliferative disorder in fetuses with trisomy 21

OBJECTIVE

To demonstrate the relationship between fetal hydrops and/or hepatosplenomegaly in the second half of pregnancy with a myeloproliferative disorder in fetuses with trisomy 21 or mosaic trisomy 21.

DESIGN

A retrospective case series.

SUBJECTS

Cases were selected from 79 cases of trisomy 21 diagnosed in our prenatal unit between 1993 and 1999.

METHODS

All fetuses had a detailed sonographic anatomic survey and biometry. Doppler of the umbilical and middle cerebral arteries, ductus venosus, inferior vena cava and umbilical vein was performed whenever possible. Two-dimensional echocardiography supplemented by color Doppler flow mapping and spectral pulsed wave Doppler was performed in all cases of fetal hydrops. Fetal karyotyping was obtained by amniocentesis, chorionic villus sampling or fetal blood sampling. In the presence of fetal hydrops a cordocentesis was performed for fetal hematology, biochemistry and TORCH serology. In cases with diagnosis of myeloproliferative disorder, peripheral blast cells were characterized by microscopy, cytochemistry and determination of surface markers. All cases with myeloproliferative disorder were stillborn and subsequently had a postmortem examination performed.

RESULTS

During the study period 79 cases of trisomy 21 were diagnosed. Eleven of these had fetal hydrops. Three of these fetuses presented with hepatosplenomegaly and myeloproliferative disorder in the second and third trimesters. In addition, one fetus with sonographic markers of trisomy 21, where karyotyping was unfortunately unsuccessful, presented with hepatosplenomegaly, hydrops and myeloproliferative disorder. In the four fetuses with hepatosplenomegaly and hydrops, serology was negative for congenital infection. The characteristics of blast cells in the peripheral blood smear revealed a myeloproliferative disorder.

CONCLUSION

Fetal hydrops and/or hepatosplenomegaly in the second half of pregnancy, although suggestive of infectious etiology, may be a sign of myeloproliferative disorder in fetuses with trisomy 21 or mosaic trisomy 21. There is a possibility that a transient myeloproliferative disorder is a more common cause of mid or late-trimester hydrops in cases of trisomy 21 than previously thought. In these hydropic fetuses the prognosis seems to be poor. On the other hand we can speculate that a myeloproliferative disorder and the associated hepatosplenomegaly and/or hydrops may show spontaneous remission or that the transient myeloproliferative disorder may be without any detectable ultrasonographic signs and therefore may be more frequent in utero than realized.

Fetal venous circulation--an update on hemodynamics

The refinements of modern ultrasound techniques permit a renewed examination of old concepts of fetal circulation. The concept of preferential streaming of umbilical blood through the foramen ovale is verified by animal experiments, and ultrasound studies have confirmed that a similar mechanism operates in human fetuses. However, the normalized umbilical flow appears to be less in the human than in fetal sheep, and decreases with advancing gestational age (115 ml min-1 kg-1 at 20 and 64 mL min-1 kg-1 at 40 weeks). Compared to the 50% shunting of umbilical blood through the ductus venosus found in animal experiments, the degree of shunting in the human fetus under physiological conditions is considerably less, 30% at 20 weeks, which decreases to 18% at 32 weeks, suggesting a higher priority of the fetal liver than previously realized. Augmented pulsatility in the precordial veins, ductus venosus, and umbilical vein is an important clinical sign that is poorly understood. Recent fluid dynamic studies show that, apart from the pressure generated in the atria, it is the stiffness of the vessel wall, compliance, and notably, impedance which modify these waves. Particularly the substantial shift in impedance at the ductus venosus-umbilical vein junction causes wave reflection and reduced transmission of waves, the result being diminished or absent pulsation in the umbilical vein.

Assessment of fetal cardiovascular function: ultrasound study of the fetal circulatory compartments

Recent advances in high-resolution ultrasonography combined with color-coded Doppler analysis have enabled a new insight to be gained into fetal physiology and allowed the investigation of small, previously inaccessible fetal vessels under normal and abnormal conditions. In addition, the findings in some cases contradict the accepted fetal pathophysiology derived from animal studies. The aim of the present study is to describe new reports assessing the major compartments of the fetal cardiovascular system (heart, lung, splanchnic and fetal venous circulations) and to discuss the developments in these fields.

A new splenic artery Doppler velocimetric index for prediction of severe fetal anemia associated with Rh alloimmunization

OBJECTIVE

We developed a new Doppler index for the noninvasive prediction of severe fetal anemia by means of Doppler velocimetry of the main splenic artery.

STUDY DESIGN

Doppler velocimetry of the main splenic artery was performed in 85 healthy fetuses and in 22 nonhydropic study case patients (41 measurements) at risk for anemia from Rh sensitization. The deceleration angle between the line describing the average slope during the diastolic phase of the cycle and the vertical axis was measured and expressed in multiples of the median (MoM) for gestational age. Severe anemia was defined as a hemoglobin deficit (mean hemoglobin for gestational age minus measured hemoglobin) >/=5 g/dL. Anemia overall was defined as a hemoglobin deficit >/=2 g/dL.

RESULTS

Mean gestational age at cordocentesis was 28.6 weeks. Severe anemia was noted on 7 occasions (12.6%) and anemia was noted on 21 (51.2%) occasions. There was a significant correlation between deceleration angle and hemoglobin deficit >/=2 g/dL (r = 0.5763, P <.0001) and also with hemoglobin deficit >/=5 g/dL (r = 0.6418, P <.0001). At deceleration angles <0. 90 MoM, a 90.5% sensitivity and a 30% false-positive rate were achieved for anemia detection. At a threshold deceleration angle of <0.60 MoM, the sensitivity for severe anemia was 100%, with an 8.8% false-positive rate.

CONCLUSION

We report a new and sensitive Doppler velocimetric technique for predicting severe anemia. By means of splenic artery velocimetry, all cases of severe anemia could be identified before the development of hydrops, with a >91% reduction in the rate of cordocentesis.