Maternal perfusion

Dancis J, Lehanka J, Levitz M. Placental transport of riboflavin differential rates of uptake at the maternal and fetal surfaces of the perfused human placenta. Am J Obstet Gynecol 1988 158 204-10. 

It maintains perfusion of the decidua basalis (maternal placenta), presumably by inhibiting the formation of vasoconstrictive prostaglandins and... 

We have tried to circumvent these problems by isolating a cotyledon of the placenta and perfusing its umbilical circulation in situ with blood of known and accurately controlled flow rates and 02 tensions (47). We have also varied maternal arterial Oo tension by administering various concentrations of inspired 02. 

Figure 20. Relation of outflowing (umbilical venous) p02 to the rate of blood flow. Data from five rabbit placentas perfused in situ through an umbilical artery with blood (Hb = 10.7 gram/100 ml) with an average p02 of 10 mm Hg. Maternal arterial p0 averaged 87 mm Hg. The solid curve shows results predicted by a mathematical model using experimental values and assuming a total maternal flow 1 ml/min and diffusing capacity [0.04 ml/(min X mm Hg)].

Role of Various Factors in Placental O2 Transfer. These experiments characterize the dependence of 02 transfer and umbilical venous po2 on maternal arterial p02> fetal placental flow rate, and fetal inflowing po2 on O2 exchange in a single cotyledon of the sheep placenta and on fetal placental flow in the rabbit placenta. Each factor was studied individually while the fetal placental circulation was isolated and perfused in situ. The present findings do not apply for an intact fetus whose blood recirculates between peripheral tissues and the placenta because compensations would tend to maintain 02 transfer equal to fetal 02 consumption in this latter instance. The present data take account of changes in only a single variable. 

In the experiments described here, the maternal and fetal sides of the placenta were perfused simultaneously by an apparatus in which maternal arterial inflow and maternal venous return occur through the base of the placenta, as they do in vivo (20). 

The Perfusion Apparatus. The perfusion apparatus was designed to simulate as closely as possible in vivo physical and physiological conditions pressures, flow patterns, pH, temperature, oxygen pressure, etc. (Appendix I A, IB). The whole apparatus consists of three main parts the artificial uterus which holds the placenta the maternal circulatory loop, simulating the maternal circulation and the fetal circulatory loop, simulating the fetal circulation (Figure 4). 

The Maternal Circulatory Loop. In the arterial circuit, maternal fluid perfusate is propelled from the maternal reservoir by a Bluemle-Holter triple chamber B-3 blood pump through a flowmeter (Gilmont Model J-228) to the arterial opening of the manifold, connected with the 114 arterial tubes. A manometer is connected just before the entrance of the manifold. 

The Oxygenators. Both are disk oxygenators (18). The maternal one is used to oxygenate blood or sometimes to introduce C02 to regulate the maternal pH. The fetal one contains only five disks and is used mostly to introduce C02 into the fetal circulation at the beginning of the perfusion. 

The fetal and maternal flow rates were set at 40-80 ml/min and 450 ml/min, respectively, and an amniotic fluid pressure of 15 mm Hg was maintained over the placenta throughout the experiment. Oxygen tensions were 60-160 mm Hg in the maternal artery and 14-28 mm Hg in the fetal vein. Glucose was added at the beginning of the perfusion to help maintain placental viability. 

Fetal Perfusion. As soon as the saline perfusion is started, there are indications of the adequacy of the fetal perfusion a high fetal pressure at a low fetal flow rate indicates that many capillaries are clotted. In this case, the remaining capillaries rupture and fluid transfers from the fetal to the maternal side at a high rate. Distribution of dye in the fetal circulation was also used to check the completeness of the fetal perfusion. 

Oxygen Transfer—Ot and C02 Response. During the run, a fetal p02 dropping below 14 mm Hg seemed to indicate an inadequate perfusion. If the oxygen supply is eliminated on the maternal side, then resumed, the fetal oxygen tension was observed to successively decrease, then rise to its previous value. At the end of the run, the response of the fetal vessels to oxygen and carbon dioxide was checked to establish the... 

Glucose Transfer and Utilization. The fact that glucose is transferred from the maternal to the fetal side and utilized by the placenta indicates that the placenta is being perfused. 

The average value for all nine runs for a normal maternal glucose concentration of 120 mg % is 1.24 grams glucose/hour/kg. This compares well with the value of 1.35 grams/hour/kg obtained in tissue studies (34) and is further evidence that the placenta is adequately perfused. It also agrees with the 1.25 grams/hour/kg observed by Howard and Krantz (16), but is about twice the rate observed by Krantz et ah (19) in a later study. 

Comparison of various methods led Pientmaki and coworkers (1995) to conclude that the most useful method is to follow the leak from the maternal side to the fetal side. In the histology, typical change in the dual recirculating perfusion system after organ perfusion is tissue edema (Vahiikangas, 1981 Pienimaki et al 1995). However,... 

Picnimaki, P., Haitikainen, A. L., Arvcia, P., Rulanen, T, Herva, R., Pelkonen, O., and Vahakangas, K. (1995). Carbamazepinc and its metabolites in human perfused placenta and in maternal and cord blood. Epilepsia 36,241-248. 

The transfer of zinc across perfused placentas is slow only - 3% of maternal zinc reached the fetal compartment in 2 hours (Beer et al. 1992). The in vitro transfer of zinc between mother and fetus is bidirectional, with binding in the placenta (Beer et al. 1992). It is proposed that zinc uptake in the placenta involves a potassium/zinc transport system (Aslam and McArdle 1992). Newborns may also be exposed to zinc from their mothers by milk transfer of zinc during lactation (Rossowska and Nakamoto 1992). 

Pregnancy causes an increase in maternal blood volume by approximately 50%, reaching a volume of 4-61. The main benefit of this increase is to allow the body to respond to perfusion intake of the low resistance uteroplacental unit in order to handle the blood loss that occurs at delivery [13]. 

Fatty Acids from Human Maternal and Fetal Blood, Perfused Placenta. Chorion Laeve, and Amnion J. Lab. Clin. Med. 70(3) 489-493 (1967) CA 67 98256u... 

In experiments with the perfused guinea pig placenta Kelman (1979) has studied the transfer of heavy metals from the maternal to the embryonic circulation. Using this animal model he was able to demonstrate that the placental transfer for methylmercury was 10-times higher than for anorganic mercury. 

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