R. Lewander

Uteroplacental Blood Flow in Pre-Eclampsia Measurements with Indium-113M and a Computer-Linked Gamma Camera

Uteroplacental blood flow was measured with a computer-linked gamma camera after intravenous injection of 1 mCi indium-113m. Results of the measurements from 32 pre-eclamptic pregnancies and 37 normal controls are compared. The uteroplacental blood flow was measured as an index calculated from the rise time and maximum activity of the isotope accumulation curve. The uteroplacental blood flow was reduced with 50% in pre-eclampsia. In severe pre-eclampsia it was more compromised than in mild pre-eclampsia. A diminished uteroplacental blood flow was found in pre-eclampsia even in the absence of intrauterine growth retardation. The maternal placental circulation in the supine position was reduced with one third compared to that in the left lateral recumbent position.

Uteroplacental blood flow index in intrauterine growth retardation of fetal or maternal origin

Summary. Uteroplacental blood flow index was determined in 30 women with intrauterine growth retardation (IUGR group) and in 26 women without fetal growth retardation (control group) during the last trimester of pregnancy. After 1 mCi (37 MBq) of indium‐113m chloride had been injected intravenously the radiation was registered by a computer‐linked scintillation camera positioned above the placenta during 10 s‐intervals for 240 s. From the isotope accumulation curve a Uteroplacental blood flow index could be calculated for each patient. The median blood flow index in the IUGR group was less than half of that in the control group. In the IUGR group the index was as low in the six women who gave birth to infants with congenital malformations as in the other 24 women in whom fetal growth retardation was due to maternal factors.

Comparison of Uteroplacental Blood Flow in Normal and in Intrauterine Growth-Retarded Pregnancy

Uteroplacental blood flow was studied with a noninvasive method using indium-113m and a computer-linked gammacamera. The blood flow was determined from the ratio of the maximum and the rise time of the isotope accumulation curve of the placenta. Eight pregnancies with intrauterine growth retardation (IUGR) were compared with 11 normal pregnancies. In the IUGR group the mean placental blood flow was only 1/4 of corresponding mean values of the normal group. The difference was highly significant (p less than 0.01).

Acute effect of an antihypertensive drug, labetalol, on uteroplacental blood flow

Summary. The effect of a new antihypertensive drug, labetalol, on uteroplacental blood flow was determined in eight pre‐eclamptic women. After injection of 0.5 mCi of 113mIn the radioactivity in the placenta was recorded by a gamma camera linked to a computer and the placental blood‐flow index was calculated from the ratio between the maximum radioactivity of the isotope‐accumulation curve and the rise time of the curve. Labetalol, a combined α‐ and β‐adrenoceptor antagonist was given intravenously and after 30 min a second uteroplacental blood‐flow index was calculated. There was a significant mean decrease of blood pressure from 147/98 to 128/83 mmHg, but no change in uteroplacental blood‐flow index, so that uteroplacental vascular resistance tended to decrease.

Acute Effect of Dihydralazine on Uteroplacental Blood Flow in Hypertension during Pregnancy

The uteroplacental blood flow was measured in 12 women with hypertension during pregnancy before and after intravenous injection of dihydralazine. After intravenous administration of 18.5 MBq (0.5 mCi) 113mIn, the gamma radiation emanating from the placenta was recorded with a computer-linked gamma camera during 10-second intervals for 240 s. From time-activity analysis of the isotope curve a uteroplacental blood flow index could be calculated. 30 min after the intravenous injection of dihydralazine, 18.5 MBq 113mIn were again administered, and a second uteroplacental blood flow index was calculated. After dihydralazine administration there was a significant reduction of mean blood pressure (p less than 0.01) and an increase of mean maternal heart rate (p less than 0.01). There was no significant change in uteroplacental blood flow or in uteroplacental vascular resistance.

Labetalol for the Treatment of Hypertension in Pregnancy: Pharmakokinetics and effects on the uteroplacental blood flow

Abstract. Plasma levels of labetalol were measured in 7 hypertensive pregnant women who were given 200 mg three times daily orally. The plasma concentrations were usually lower than those reported in the non‐pregnant state at a comparative dose. In 5 women the ratio between fetal and maternal plasma labetalol concentrations could be calculated at parturition. The median value of this quotient was about 50%. The effect of labetalol 1 mg/kg body weight intravenously was registered with functional placental scintigraphy. Fifteen women participated. A computer‐linked gamma camera above the uterus registered the radioactivity in the placental region after two intravenous bolus injections of 18.5 MBq indium‐113m chloride. From the radioactivity uptake curves, uteroplacental blood flow indices could be calculated before and 30 minutes after the labetalol injection. Despite a significant reduction in maternal blood pressure, no change in uteroplacental blood flow index was found. This could indicate that the vascular resistance in the maternal placental circulation was reduced by labetalol.

Uteroplacental Blood Flow in Pregnancy Hypertension after the Administration of a Beta-Adrenoceptor Blocker, Pindolol

The effect of a beta-adrenoceptor blocker, pindolol, on uteroplacental blood flow was determined in 10 women with pregnancy hypertension using an isotope technique giving a very low radiation dose. 0.5 mCi 113mIn was injected intravenously before and 30 min after 10 mg pindolol was given orally. After the administrations of 113mIn serial scintigrams were recorded for 240 s by a gamma camera on line with a computer, and the placenta was outlined for time-activity analysis of the isotope accumulation curves. From these curves a relative measure of the uteroplacental blood flow could be determined. Pindolol induced a significant fall in mean arterial pressure but there was no reduction of uteroplacental blood flow index.

The Effect of Beta-Receptor-Stimulating Agents on the Utero-Placental Blood Flow

Abstract. The influence of salbutamol, a beta‐2‐receptor‐stimulating agent, on the blood flow through the uteroplacental unit was evaluated in the human. Serial placenta scintigrams were analysed quantitatively, after injection of 0.5 mCi Indium‐ 113m, by means of a gamma‐camera connected on line to a computer. The examinations were performed in the third trimester of pregnancy. No sedation was used. Uterine contractions were not present. Salbutamol caused an increase in activity over the placental region, corresponding to a 15% increase in blood volume. The rise time of the initial phase of isotope accumulation (calculated from 5 to 95% of final activity) was prolonged by 100% during salbutamol infusion. As the rise time is proportional to the volume/flow ratio of blood in the uteroplacental region, our data indicate that salbutamol infusion causes a decrease in blood flow in the absence of uterine contractions.

Does a Blood Pressure Reduction After Dihydralazine, Labetalol Or Pindolol Affect the Human Maternal Placental Circulation?

The maternal placental blood flow was studied in 37 pregnant women in the last trimester of pregnancy. Thirty women had pregnancy induced hypertension defined as a blood pressure of 140/90 mm Hg or more. 0.5 mCi indium-113m was injected intravenously and the radioactivity was registered in a scintillation camera positioned above the placenta. The images obtained were stored in a computer connected on-line to the gamma camera. After computerized summation of the images the placenta could be encircled. The radioactivity in the placental region was plotted as a function of time. From the time-activity curve a uteroplacental blood flow index could be calculated. This index is a semi-quantitative measure of the maternal placental blood flow. After the first blood flow measurement an anti-hypertensive drug was given and a second blood flow measuremnt was performed 30 minues later. When dihydralazine was injected intravenously it was found that the change in uteroplacental blood flow index was correlated to the ...

Utero-Placental Blood Flow and the Effect of β2-Adrenoceptor Stimulating Drugs

Abstract. The immediate effect of a β2‐adrenoceptor stimulating drug, salbutamol, on utero‐placental blood flow in the last trimester of pregnancy was evaluated in 16 women without uterine contractions, using a method applying 113‐m Indium and a computer‐linked gamma camera. Serial scintigrams over the placental site showed a 15 per cent increase in activity during a short salbutamol infusion, denoting an augmented blood pool in the intervillous space. At the end of a 25–30 min salbutamol infusion, a mean prolongation of the rise time of the isotope accumulation curve by 100 per cent could be calculated. A utero‐placental blood flow index derived from the ratio of the maximum activity and the rise time of the accumulation curve above the placenta showed a decrease ranging from 18 to 50 per cent. It is conceivable that this initial decrease would disappear during continued infusion, as has been shown to occur in the pregnant sheep model.