Biomedical subjects

R Larrow

Publications and source records attributed to R Larrow.

10 recordsLinked to original sources

PubMed1989

Simultaneous use of Doppler ultrasound and electromagnetic flow probes in fetal flow assessment.

A placental embolization model in the fetal lamb was used to examine the relationship between acute and chronic alternations in placental vascular resistance and changes in flow velocity waveforms as measured by Doppler and electromagnetic flow probes. The peak systolic to end-diastolic (S/D) ratio measured by these techniques was .885 and the correlations between Doppler S/D ratio and placental vascular resistance in the acute and chronic situations were .86 and .339, respectively. This preliminary data suggest that flow velocity waveforms are independent of the method used and that remarkable differences occur in the placental microcirculation during acute and chronic embolization.

Animals↗

PubMed1982

The uterine hemodynamic response to repetitive unilateral vascular embolization in the pregnant ewe.

The longitudinal hemodynamic response of the uterine circulation to pregnancy and to repetitive embolic insult was assessed in 23 singleton ewe pregnancies by means of electromagnetic flow transducers and radionuclide-labeled microspheres. The data indicate that the longitudinal hemodynamic changes observed in the uterine circulation were directly related to the growth rate of the tissue which it supplied. The hemodynamic impact of embolization appears to be secondary to its impact on tissue growth. Embolization simply blunts the normal incremental increases in uterine perfusion and the cross-sectional area of the uterine vascular bed. It alters actual tissue perfusion only within a portion of the cotyledonary circulation. Finally, the data support the presence of functional arterial anastomoses between the two sides of the uterine circulation in this species.

Animals↗

PubMed1981

Fetal metabolic response to experimental placental vascular damage.

The fetal metabolic response to repetitive placental damage, produced by microsphere embolization of the uteroplacental circulation, was examined longitudinally in eight singleton fetal lambs and compared with similar data from seven controls. Significant morphometric fetal growth retardation was associated with an abrupt cessation of the normal increases in oxygen, glucose, and lactate uptake observed in the control animals. However, fetal blood levels and umbilical substrate quotients did not change. At the time of sacrifice, fetal oxidative metabolic rate was reduced significantly. The significance of these findings relative to intact fetal survival is discussed.

Animals↗

PubMed1980

Umbilical blood flow response to embolization of the uterine circulation.

The uterine and umbilical blood flow response to uteroplacental insufficiency, produced by microsphere embolization of the uteroplacental circulation, was examined by means of electromagnetic flow transducers in 12 pregnant ewes. No acute changes were observed in either circulation immediately after embolization of the uterine vasculature. Significant morphometric fetal growth retardation, in terms of weight, length, and ponderal index, was not associated with early changes in fetal pH, PO2, or PCO2. However, the incremental increases in both flows that were observed in control animals did not occur either during or after embolization because of an increase in vascular resistance. During and after embolization the incremental increase in uterine blood flow was blunted or decreased in most, but not all, animals. A rapid, progressive, and persistent decrease in umbilical flow occurred in the growth-retarded group. The significance of these findings relative to intrauterine growth is discussed.

Animals↗

PubMed1980

Physiologic variability and fetal electrocortical activity.

The relationship between fetal electrocortical activity and multiple fetal parameters was examined in chronically instrumented fetal lambs. Consistent small but significant changes in fetal heart rate, mean arterial pressure, umbilical blood flow, and the cerebral uptake of glucose relative to oxygen were observed as fetal electrocortical activity cyclically shifted between high-voltage slow activity and low-voltage fast activity. Cardiovascular parameters were higher and the cerebral uptake of glucose relative to oxygen was lower during high-voltage slow activity than during low-voltage fast activity. The implication of these observations is discussed.

Animals↗

PubMed1971