Kenneth J. Moise

AMNIOTIC FLUID VOLUME ASSESSMENT: COMPARISON OF ULTRASONOGRAPHIC ESTIMATES VERSUS DIRECT MEASUREMENTS WITH A DYE-DILUTION TECHNIQUE IN HUMAN PREGNANCY

OBJECTIVE The purpose of our study was to compare the accuracy of clinical ultrasonographic techniques of amniotic fluid volume assessment with a dye-dilution technique. STUDY DESIGN We compared amniotic fluid volume as measured by ultrasonographic techniques with a dye-dilution method in 50 women undergoing amniocentesis during the third trimester. Thirteen separate ultrasonographic techniques, including the amniotic fluid index, were evaluated with regression analysis. RESULTS Amniotic fluid volumes as determined by dye-dilution ranged between 129 and 4444 ml. The amniotic fluid index overestimated the actual volume by as much as 88.7% at lower volumes and underestimated the actual volume by as much as 53.9% at higher volumes. CONCLUSIONS Differences in measurement error between the other ultrasonographic methods and the amniotic fluid index did not appear to be sufficient to warrant changes in current clinical practice. A major source of error in ultrasonographic amniotic fluid volume assessment is that one-dimensional measurements are used to estimate the volume of a complex, three-dimensional object.

The oxygen consumption/oxygen delivery curve in severe preeclampsia: Evidence for a fixed oxygen extraction state

OBJECTIVE Increased total body oxygen consumption requirements are usually met by increased oxygen delivery and increased oxygen extraction. In certain conditions (e.g., adult respiratory distress syndrome) the ability to increase oxygen extraction is lost, and any increase in oxygen consumption depends on increased oxygen delivery. The objective of this study was to investigate the oxygen delivery/oxygen consumption relationship in severe preeclampsia. STUDY DESIGN Thirty-two patients with severe preeclampsia (blood pressure > 160/110 mm Hg; 3 to 4+ proteinuria) were monitored with a pulmonary artery catheter. Baseline oxygen consumption and delivery in a group without volume expansion or pharmacologic vasodilatation were compared with those in a group who had received a magnesium sulfate infusion. RESULTS Oxygen consumption, oxygen delivery, arterial-venous-oxygen difference, and the oxygen extraction ratio were low when compared to that for normal 32 to 38 week pregnancy. The oxygen extraction ratio, defined as the ratio of oxygen consumption to oxygen delivery, was abnormally low for pregnancy, especially considering the low oxygen delivery levels in these patients. Oxygen consumption was dependent on oxygen delivery over the entire range of values seen. CONCLUSIONS Severe preeclampsia is associated with an abnormality of tissue oxygen extraction, as evidenced by a low and unresponsive oxygen extraction ratio. Oxygen consumption increases proportionately with increases in oxygen delivery without reaching an oxygen delivery-independent state. Even at high oxygen delivery levels the oxygen consumption in preeclamptic patients is still abnormally low for pregnancy.

A Simple Method to Estimate Volume for Fetal Intravascular Transfusions

We derived a constant termed the transfusion coefficient to simplify the estimation of the fetal intravascular transfusion volume. The product of the estimated fetal weight (g) and 0.02 (transfusion coefficient), estimates the transfusion volume (ml) required to increase the fetal hematocrit by approximately 10 percentage points. Our estimation was comparable to Mandelbrot’s technique and better than Plecas’ method for estimating fetal transfusion volumes. Utilizing the transfusion coefficient to estimate the intravascular transfusion volume for an anemic fetus is simple, rapid and accurate.

Discordant fetal platelet counts in a twin gestation complicated by idiopathic thrombocytopenic purpura

The twin gestation in a patient with idiopathic thrombocytopenic purpura presents a unique problem if vaginal delivery is being considered. Scalp platelet sampling to exclude fetal thrombocytopenia only allows assessment of the presenting fetus. A case is described in which cordocentesis revealed discordant platelet counts in dizygotic twin fetuses.

Fetal membrane patch and biomimetic adhesive coacervates as a sealant for fetoscopic defects

Iatrogenic preterm premature rupture of membranes after fetoscopic procedures affects 10-47% of patients, secondary to the non-healing nature of membranes and the separation of layers during the entry. In this study we developed an in vitro model to mimic the uterine wall-fetal membrane interface using a water column with one end sealed with human fetal membranes and poultry breast, and a defect was created with an 11 French trocar. Further, a fetal membrane patch in conjunction with multiphase adhesive coacervates modeled after the sandcastle worm bioadhesive was tested for sealing of an iatrogenic defect. The sealant withstood an additional traction of 12 g for 30-60 min and turbulence of the water column without leakage of fluid or slippage. The adhesive is non-toxic when in direct contact with human fetal membranes in an organ culture setting. A fetal membrane patch with multiphase adhesive complex coacervates may help to seal the defect and prevent iatrogenic preterm premature rupture of the membranes.

Do abnormal Starling forces cause fetal hydrops in red blood cell alloimmunization

OBJECTIVE The purpose of the current investigation was to ascertain whether derangements in umbilical venous pressure and plasma colloid osmotic pressure are involved in the pathophysiologic condition of immune hydrops fetalis. STUDY DESIGN Umbilical venous pressure (corrected for ambient amniotic fluid pressure) and colloid osmotic pressure were measured during intravascular transfusion. Fetal hydrops was defined as the presence of ascites by ultrasonography. The Mann-Whitney test was used for comparison of groups; a value of p < 0.05 was considered statistically significant. RESULTS Fifteen hydropic fetuses were matched for gestational age with 15 nonhydropic fetuses also undergoing intrauterine transfusion for anemia. On comparison with their nonhydropic counterparts, hydropic fetuses had a statistically lower colloid osmotic pressure. Umbilical venous pressure was higher and the colloid osmotic pressure--umbilical venous pressure gradient was lower in association with fetal hydrops although these differences did not achieve statistical significance. CONCLUSION Mild abnormalities of intravascular Starling forces may play a role in the formation of hydrops in anemic fetuses.

Histologic changes of the fetal membranes after fetoscopic laser surgery for twin-twin transfusion syndrome

Background:Preterm premature rupture of membranes remains a major complication after fetoscopic laser surgery (FLS) for twin-twin transfusion syndrome (TTTS). We studied the histologic changes of fetal membranes post-FLS and investigated a possible impact of amniotic fluid (AF) dilution.Methods:Fetal membranes of 31 pregnancies that underwent FLS for TTTS were investigated histologically at delivery at different sites: trocar site of recipient sac and at distance, donor sac, and inter-twin membrane.Results:The trocar insertion site on the recipient sac showed no signs of histologic hallmarks of healing. Wide-spread alteration in collagen organization and higher apoptotic index in the amnion of the recipient sac which were absent in donor’s and reference membranes. To explain the mechanisms, we analyzed the AF composition of recipient sacs from TTTS pregnancies vs. GA-matched healthy singleton controls and found glucose, protein and lactate dehydrogenase activity were all significantly lower in TTTS sacs consistent with over-dilution of recipient’s AF (~2-fold). In-vitro exposure of healthy amniochorion to analogous dilutional stress conditions recapitulated the histologic changes and induced apoptosis and autophagy.Conclusion:Alteration in structural integrity of the recipient’s amniochorion, possibly in response to dilution stress, along with ineffective repair mechanisms may explain the increased incidence of preterm birth post-FLS.

Correlating Prenatal Imaging Findings of Fetal Ventriculomegaly with the Need for Surgical Intervention in the First 3 Months after Birth

Background/Aims: This study evaluates the predictive value of prenatal imaging measurements regarding the need for cerebrospinal fluid (CSF) diversion for fetal hydrocephalus in the first 3 months after birth. Methods: We retrospectively reviewed a consecutive case series of patients with fetal hydrocephalus from January 2011 to December 2014 (n = 45). Prenatal measurements included head circumference (HC), biparietal diameter (BPD), and lateral ventricle (LV) width. Patients requiring CSF diversion within 12 weeks of birth were compared to those who did not require CSF diversion using the Wilcoxon rank sum test, and receiver-operating characteristic analysis was used to evaluate threshold values. Results: CSF diversion was required within 12 weeks of birth in 30 of 45 patients. Mean LV width (mm) during the entire pregnancy was greater for the surgery group than the nonsurgery group. Neither BPD nor HC showed differences between the groups. A mean LV size ≥15 mm predicted the need for CSF diversion with a sensitivity of 67% and specificity of 73%. Conclusion: LV width is the prenatal imaging measurement that best predicts the need for postnatal CSF diversion.

The Influence of Blood Pressure on Fetal Aortic Distensibility: An Animal Validation Study

Background/Aims: Aortic distension waveforms describe the change in diameter or cross-sectional area over the cardiac cycle. We aimed to validate the association of aortic fractional area change (AFAC) with blood pressure (BP) in a fetal lamb model. Methods: Four pregnant ewes underwent open fetal surgery under general anesthesia at 107-120 gestational days. A 4-Fr catheter was introduced into the fetal femoral artery and vein, or the carotid artery and jugular vein. The thoracic aorta was imaged using real-time ultrasound; AFAC was calculated using offline speckle tracking software. Measurements of invasive BP and AFAC were obtained simultaneously and averaged over 10 cardiac cycles. BP was increased by norepinephrine infusion and the association of aortic distensibility with BP was assessed. Results: Baseline measurements were obtained from 4 lambs, and changes in aortic distensibility with increasing BP were recorded from 3 of them. A positive correlation was found between AFAC and systolic BP (r = 0.692, p = 0.001), diastolic BP (r = 0.647, p = 0.004), mean BP (r = 0.692, p = 0.001), and BP amplitude (r = 0.558, p = 0.016) controlled for heart rate. No association was found between BP and maximum or minimum aortic area. Conclusion: AFAC provides a quantifiable measure of aortic distensibility and correlates with systolic BP, diastolic BP, mean BP, and BP amplitude in a fetal lamb model.