Fetal cerebral, circulatory, and metabolic responses during heart rate decelerations with umbilical cord compression

OBJECTIVE

The purpose of this study was to determine the cerebral, circulatory, and metabolic responses of the ovine fetus near term to umbilical cord compression with variable-type fetal heart rate decelerations.

STUDY DESIGN

Nine fetal sheep, at 0.9 of gestation, were studied before, during, and after umbilical cord occlusion for 1-minute and again after repetitive 1-minute cord occlusions every 5 minutes for 1 hour, with resultant fetal heart rate decelerations of approximately 90 beats/min. Brachiocephalic arterial and sagittal venous blood was analyzed for oxygen content, blood gases and pH, glucose, and lactate. Cerebral and upper body blood flow was measured with the microsphere technique.

RESULTS

Umbilical cord occlusion with moderate to severe variable-type fetal heart rate deceleration resulted in an immediate drop in arterial PO2 by approximately 7 torr, an increase in PCO2 by approximately 9 torr, and a small but significant increase in lactate levels. Cerebral oxidative metabolism was well maintained but required an increase in fractional oxygen extraction because the variable change in cerebral blood flow was insufficient to maintain oxygen delivery. A redistribution of upper body blood flow was evident, with that to the bran and heart variably maintained or increased whereas that to muscle tissue was markedly decreased. Repetitive umbilical cord occlusion over 1 hour resulted in a significant drop in fetal arterial pH, with the acidemia mixed as PCO2 increased approximately 6 torr, whereas lactate levels increased almost fourfold.

CONCLUSION

Although cerebral oxidative metabolism appears to be well maintained during moderate to severe variable-type fetal heart rate decelerations with umbilical cord occlusion, the need to increase fractional oxygen extraction and the redistribution of blood flow from carcass tissues may contribute to an accumulation of lactic acid both within the brain and systemically when such an insult occurs repeatedly.

Effects of long-term hypoxemia on pituitary-adrenal function in fetal sheep

To test the hypothesis that long-term hypoxemia causes premature activation of the fetal pituitary-adrenal function, we embolized the fetal side of the placenta in pregnant sheep and examined the changes in concentrations of immunoreactive adrenocorticotropic hormone (irACTH), cortisol, and prostaglandin E2 (PGE2) in fetal plasma, and levels and localization of proopiomelanocortin (POMC) mRNA in the pars distalis and the pars intermedia of the fetal pituitary. Twelve fetal sheep were studied (6 embolized and 6 control) for 21 days between 0.74 and 0.88 of gestation. Daily injections of nonradiolabeled microspheres were given into the fetal abdominal aorta to decrease fetal arterial oxygen content by 40-50% of the preembolization values. In the embolized group, concentrations of irACTH, PGE2, and cortisol in fetal plasma increased gradually and were significantly (P < 0.05) elevated above those of controls after day 10, day 16, and day 20, respectively. POMC mRNA levels in the pars distalis of the fetal pituitary were not different from those of controls but were significantly reduced in the pars intermedia (P < 0.05). We conclude that levels of POMC mRNA in the pars distalis are unchanged during long-term hypoxemia possibly because of negative feedback effects of elevated cortisol on the pituitary gland. During long-term fetal hypoxemia, there is a differential regulation of POMC mRNA expression in the pars distalis and pars intermedia.

Diurnal changes in lumbar intervertebral distance, measured using ultrasound

STUDY DESIGN

This study measured the distances between the tips of the transverse processes of adjacent lumbar vertebrae (L1-L4) in the same subjects after 1 day of normal activities and again the next morning.

OBJECTIVES

To determine the feasibility of directly measuring the lumbar intervertebral distance using ultrasound and to determine the magnitude of the diurnal change in the intervertebral distance.

SUMMARY OF BACKGROUND DATA

A diurnal variation in height results from, in part, a decrease in height of the intervertebral discs with loading of the spine during the day. Previous estimates of the diurnal changes in disc height have used radiologic, stereophotographic, and magnetic resonance imaging techniques. No previous study has used ultrasound imaging.

METHODS

Ultrasound was used to measure the distance between the tips of adjacent lumbar vertebral transverse processes. Measurements were made on six occasions in each of seven subjects after 6:00 PM in the evening and again the following morning before rising.

RESULTS

The distance between the tips of adjacent transverse processes could be measured, within an individual, with a reproducibility of better than +/- 7.5% coefficient of variation. Reproducibility of the measurement of the total distance between L1 and L4 was better than +/- 4%. The intervertebral distances between L1 and L4 were significantly greater in the morning than in the evening. The average diurnal change in the total intervertebral distance L1-L4 was 5.3 mm.

CONCLUSIONS

The study confirms the feasibility of using ultrasound to directly measure changes in the distances between the lumbar vertebrae.

Fetal placental embolization in the late-gestation ovine fetus: alterations in umbilical blood flow and fetal heart rate patterns

OBJECTIVE

Our goal was to determine the effect of chronic and acute umbilical-placental embolization on placental hemodynamic and fetal heart rate patterns in relation to fetal oxygenation in the near-term ovine fetus.

STUDY DESIGN

Daily fetal placental embolization was performed during 10 days in 9 sheep fetuses until fetal arterial oxygen content decreased by approximately 30%. Nine control fetuses received saline solution. Mean and pulsatile umbilical blood flow, perfusion pressure, placental vascular resistance, fundamental impedance, pressure pulsatility index, and umbilical artery resistance index corrected to a fetal heart rate of 160 beats/min were measured. On day 10 both groups were acutely embolized until fetal arterial pH decreased to approximately 7.00. Fetal heart rate was measured with the Sonicaid System 8000 (Oxford Sonicaid, Oxford, United Kingdom).

RESULTS

Chronic fetal placental embolization was associated with a progressive reduction in umbilical blood flow (p < 0.00001) and fetal arterial oxygen content (p < 0.001) whereas fetal heart rate patterns remained unaltered. A chronic increase in umbilical artery resistance index corrected to a fetal heart rate of 160 beats/min could be entirely explained only if the changes in umbilical artery pressure pulsatility index and the fundamental impedance were taken into account, in addition to the changes observed in placental vascular resistance. During acute embolization leading to a 50% reduction in umbilical blood flow (p < 0.0002) and a three times increase in placental vascular resistance (p < 0.0001), the most consistent change in fetal heart rate patterns related to progressive metabolic acidosis was an 84% decrease in absolute acceleration frequency (p < 0.0001) whereas short-term fetal heart rate variability remained unaltered.

CONCLUSION

Changes in umbilical artery resistance index induced by chronic umbilical-placental embolization resulting in fetal hypoxemia occurred before any changes in fetal heart rate patterns were detectable. A decrease in the absolute acceleration frequency was the only component of fetal heart rate patterns related to progressive metabolic acidosis in the near-term ovine fetus.

Translabial ultrasonography and placenta previa: does measurement of the os-placenta distance predict outcome?

The aim of this study was to assess the value of the measurement of os-placenta distance by translabial ultrasonography in the evaluation of placenta previa. This method was used in 40 women with suspected placenta previa to measure the distance between the placenta and internal cervical os. Sonographic diagnoses were compared to placental location determined at delivery. Translabial ultrasonography proved superior to the transabdominal route in both diagnosis and exclusion of placenta previa. Measurement of the os-placenta distance can be used as an adjunct to clinical assessment to predict the likelihood of safe vaginal delivery in cases of suspected placenta previa.

Increased fetal plasma prostaglandin E2 concentrations during fetal placental embolization in pregnant sheep

OBJECTIVE

The purpose of this study was to examine the effect of chronic fetal placental embolization on fetal plasma prostaglandin E2 concentrations.

STUDY DESIGN

Fourteen pregnant sheep were studied (seven embolized and seven controls) for 10 days between 0.84 and 0.91 of gestation. Daily injections of nonradioactive microspheres were made to decrease fetal arterial oxygen content by 30% to 35% of preembolization values.

RESULTS

In response to repeated embolization, fetal plasma prostaglandin E2 concentrations increased significantly on day 1, declined to near control levels on days 2 to 6, but were significantly elevated again after day 7. Maternal prostaglandin E2 levels remained unchanged throughout the study. Fetal plasma prostaglandin E2 levels increased significantly with decreasing fetal oxygenation when fetal arterial oxygen content was < 2.0 mmol/L.

CONCLUSION

We conclude that there is increased production of prostaglandin E2 by the placenta during progressive fetal hypoxemia induced by fetal placental embolization. We speculate that the progressive increase in prostaglandin E2 may be an important hormonal adaptive mechanism to maintain fetal homeostasis during the development of placental insufficiency.

Lol p I-specific IgE and IgG synthesis by peripheral blood mononuclear cells from atopic subjects in SCID mice

BACKGROUND

The development of an animal model representative of the in vivo situation of human atopic diseases is always of interest for a better understanding of IgE production and regulation. Along these lines, mice with severe combined immunodeficiency (SCID mice) engrafted with lymphocytes from atopic subjects might be a suitable model for such studies.

OBJECTIVE

This study aims to analyze the production of Lol p I-specific IgE and IgG antibodies in SCID mice after transplantation of human peripheral blood mononuclear cells from atopic patients sensitive to grass pollens and from nonatopic donors.

METHODS

Peripheral blood mononuclear cells were transplanted into SCID mice, which were then challenged with Lol p I, and antibody responses (IgG and IgE) were analyzed over a 6-week period.

RESULTS

Total IgG antibody was measured in each mouse serum after transplantation. Also, most mice (regardless of whether donors were atopic) that were challenged with Lol p I produced specific IgG antibody. Total IgE antibody production was observed only in mice grafted with cells from atopic patients. Lol p I-specific IgE antibodies were also produced after immunization with Lol p I. Although IgG antibody/response tended to plateau, the IgE antibody response increased until it peaked and declined thereafter. Interferon-gamma was detected in sera from mice producing IgE antibody, which supports a possible role of interferon-gamma in the decrease of IgE response.

CONCLUSION

This study suggests that the SCID mouse model could represent an interesting approach to studying specific, total IgG and IgE antibody production, and ultimately their regulation.

Alterations in fetal and placental deoxyribonucleic acid synthesis rates after chronic fetal placental embolization

OBJECTIVE

Fetal growth and development are closely related to normal placental growth and function. We performed a study to determine the effect of a 10-day period of fetal hypoxemia induced by umbilical-placental hypoperfusion on tissue deoxyribonucleic acid synthesis rates in the 0.84 to 0.91 of gestation ovine fetus and placenta.

STUDY DESIGN

Daily fetal placental embolization was performed in four chronically catheterized sheep fetuses until fetal arterial oxygen content decreased by approximately 30% compared with preembolization values. Five control fetuses received vehicle only. On experimental day 10, the deoxyribonucleic acid synthesis rate was determined by injecting tritiated thymidine (1 mCi/kg) intravenously approximately 8 hours before the end of the study.

RESULTS

Fetal arterial oxygen decreased from 3.2 +/- 0.1 (SEM) mmol/L preembolization to 2.2 +/- 0.2 mmol/L on day 10 (p < 0.001) and remained unchanged in controls. On day 10 deoxyribonucleic acid synthesis rates were significantly reduced in embolized fetuses compared with controls, by 38% in cotyledons (83.0 +/- 15.1 vs 133.7 +/- 9.9 disintegrations/min/micrograms deoxyribonucleic acid, p < 0.05), 28% in the left ventricular wall (36.8 +/- 3.7 vs 51.0 +/- 4.7 disintegrations/min/micrograms deoxyribonucleic acid, p < 0.05), and 45% in the quadriceps muscle (15.4 +/- 4.0 vs 28.1 +/- 3.0 disintegrations/min/micrograms deoxyribonucleic acid, p < 0.05). Tritiated thymidine autoradiography demonstrated that cotyledonary deoxyribonucleic acid synthesis occurred exclusively in the fetal trophoblasts cells.

CONCLUSION

We concluded that a reduction in cotyledonary, quadriceps muscle, and left ventricular myocardium deoxyribonucleic acid synthesis rates are the earliest adaptive mechanisms of fetal growth associated with development of umbilical-placental insufficiency. We speculate that alteration in the myocardial deoxyribonucleic acid synthesis rate could be a major contributing factor in the deterioration of fetal myocardial function associated with increased placental vascular resistance.

Cardioprotection and thrombolysis by anistreplase in anesthetized dogs

Anistreplase is a thrombolytic agent comprising a complex of streptokinase, lys-plasminogen, and a p-anisoyl group, which temporarily protects the catalytic center of the enzyme complex. Streptokinase was previously shown to reduce infarct size (IS) in dogs with a fibrin-rich clot in the left anterior descending coronary artery (LAD) without necessarily producing reperfusion. Therefore, we hypothesized that IS in this model would be reduced by anistreplase. In addition, we studied the effect of tissue-type plasminogen activator (t-PA) on IS, testing our hypothesis in anesthetized dogs in which thrombin (100 U) and calcium (50 microliters, 0.05 M) were sequentially injected into the LAD to form a thrombus, anistreplase [0.01, 0.05, or 0.10 U/kg intravenous (i.v.) bolus], t-PA (0.1, 0.5, 2, or 8 micrograms/kg/min infusion for 60 min) or vehicle (VEH) was administered 55 min later. Anistreplase (0.05 or 0.10 U/kg) significantly (p < 0.05) reduced clot weight (VEH 22 +/- 3 mg; anistreplase 0.05 U/kg, 13 +/- 4 mg; anistreplase 0.10 U/kg, 0.7 +/- 0.6 mg), increased incidence of reperfusion (VEH 0%; anistreplase 0.05 U/kg, 42%; anistreplase 0.10 U/kg, 100%) and reduced IS (VEH 23 +/- 3%; anistreplase, 0.05 U/kg, 14 +/- 2%; anistreplase 0.10 U/kg, 15 +/- 2%). t-PA reduced thrombin weight (VEH 26 +/- 3 mg; 2 micrograms/kg/min t-PA 12 +/- 4; 8 micrograms/kg/min t-PA 2 +/- 2 mg) and increased incidence of reperfusion (VEH 0%; 2 micrograms/kg/min 75%; 8 micrograms/kg/min 100%), but IS was not altered (VEH 19 +/- 3%; 0.1 microgram/kg/min 18 +/- 3%; 0.5 microgram/kg/min 23 +/- 2%; 2 micrograms/kg/min 16 +/- 5%; 8 micrograms/kg/min: 19 +/- 3%).(ABSTRACT TRUNCATED AT 250 WORDS)

A flat decelerative fetal heart rate tracing with normal fetal heart rate variability

We report two cases for which computer interpretation of nonstress test indicated a flat decelerative trace in spite of normal fetal heart rate variability. Fetal behavioral state in the first case and signal loss in the second case were possibly responsible for this computerized interpretation of the tracings in the absence of fetal distress.

[Risk of pregnancy complications associated with residency]

OBJECTIVE

To determine, through a review of published articles, whether a higher prevalence of pregnancy complications is associated with residency in medicine.

DATA SOURCES

Articles published between January 1980 and December 1992 found through a MEDLINE search using the MeSH terms "pregnancy complications" and "internship and residency" and through a review of the bibliographies of articles found.

STUDY SELECTION

Of the 17 articles found, 6 contained data on the prevalence of pregnancy complications in residents.

DATA EXTRACTION

The methodologic quality of the studies was evaluated systematically with the use of a grid. Data on the prevalence of the six most common pregnancy complications were retained.

DATA SYNTHESIS

Four of the six articles had methodologic weaknesses (missing or inappropriate control groups, poorly controlled historical bias). The best study showed a higher prevalence of premature labour, pre-eclampsia and voluntary abortion in the residents than in the control subjects.

CONCLUSIONS

It is difficult to draw definitive conclusions from a single study that met the criteria for methodologic quality. More and better-controlled studies involving larger numbers of subjects are needed.

Fetal endocrine responses to chronic placental embolization in the late-gestation ovine fetus

OBJECTIVE

The purpose of this study was to examine the effect of chronic fetal placental embolization on the fetal corticotropin, cortisol, and catecholamines concentrations and on myometrial contractility pattern.

STUDY DESIGN

Fourteen fetal sheep were studied (seven embolized, seven controls) for 10 days between 0.84 and 0.91 of gestation. Daily injections of nonradioactive microspheres were performed to decrease fetal arterial oxygen content by 30% to 35% of the preembolization value. Umbilical artery Doppler flow velocity waveforms were measured daily.

RESULTS

Chronic fetal placental embolization produced progressive fetal hypoxemia (p < 0.001) with changes in umbilical artery Doppler flow velocity waveforms indicative of a 25% increase in placental vascular resistance (p < 0.01). In response to chronic fetal hypoxemia there was a progressive increase in baseline fetal plasma norepinephrine concentration (p < 0.001). There was a transient fourfold to fivefold increase in baseline fetal plasma cortisol levels concomitant with a significant decrease in baseline immunoreactive corticotropin between days 7 and 9 of embolization (both p < 0.05), with a return to control values by day 10. There was a 57% increase in myometrial contracture frequency in the embolized group when compared with controls (p = 0.001).

CONCLUSIONS

During repetitive chronic placental damage that led to fetal hypoxemia, the fetal endocrine environment changed with time in a direction that would prevent the onset of premature activation of the hypothalamic-pituitary-adrenal axis and premature delivery.

Waldenström hypergammaglobulinemic purpura and pregnancy

BACKGROUND

Waldenström hypergammaglobulinemic purpura is characterized by hypergammaglobulinemia, recurring purpura, and an elevated erythrocyte sedimentation rate. It is a rare disease and, to our knowledge, there have been no previous reports of its presence during pregnancy. We report a patient with this disease whose pregnancy was complicated by severe fetal growth restriction (FGR) and acute fetal distress.

CASE

A 24-year-old primigravid woman with a history of Waldenström hypergammaglobulinemic purpura and renal insufficiency developed FGR at 32 weeks' gestation. Cesarean delivery was performed at 33.5 weeks because of acute fetal distress, and a 1305-g male infant was delivered. Neonatal outcome was successful. No deterioration of the woman's medical condition occurred during or after her pregnancy.

CONCLUSION

Successful pregnancy outcome is possible in women with Waldenström hypergammaglobulinemic purpura. In view of the risk of FGR, close monitoring of fetal growth and well-being is recommended in women with this condition.