Maternal Pulse Rate Research Articles

Blood pressure changes during labour and whilst ambulating with combined spinal epidural analgesia

To determine the influence of combined spinal epidural analgesia with fentanyl and low dose bupivacaine on maternal blood pressure and pulse rate in labour. Also, to evaluate the maternal cardiovascular response to mobilising with this form of analgesia in labour. Finally, to define the changes that occur in blood pressure and pulse rate during the second stage of labour and immediately postpartum when using combined spinal epidural analgesia. A prospective observational study. Blood pressure and pulse measurements were made at least every 10 minutes, using the SpaceLabs 90207 ambulatory blood pressure monitor, on 62 women in labour with combined spinal epidural analgesia. A significant fall in systolic blood pressure (> 20%) occurred in eight women (12%), all within 30 minutes of the spinal injection. Fifty-two women subsequently received an epidural dose (mean interval 90 minutes after spinal) and none of these women had a fall in systolic blood pressure of greater than 20%. No women had symptoms related to hypotension. Thirty-five women ambulated for more than 10 minutes on 65 occasions. Average blood pressure remained unchanged while ambulating (126/79 versus 126/79), but pulse rate was significantly increased (85 to 90, P < or = 0.001). The mean blood pressure in the second stage of labour (n = 41) did not rise with pushing (134/83 versus 134/83), but the pulse rate increased significantly (94 to 108, P < or = 0.001). Blood pressure remained unchanged immediately postpartum (n = 33) (134/83 versus 134/81) following ergometrine administration. The combined spinal epidural analgesia will only result in significant falls in systolic blood pressure within 30 minutes of the spinal injection. No further important changes in blood pressure occur when mobilising or with epidural top-ups. The combined spinal epidural analgesia may modify the normal compensatory mechanisms of blood pressure control, but does not cause significant maternal hypotension once the spinal injection has been given.

The impact of alpha-adrenergic stimulation on umbilical blood flow.

This study evaluated the effects of intranasal phenylephrine, an alpha-adrenergic agonist used for respiratory congestion, on uteroplacental blood flow. Twelve subjects were recruited from the Women's Clinic. Inclusion criteria were age greater than 18 years, singleton gestation, absence of medical illness and gestational age of 22-38 weeks. Phenylephrine (0.2 ml of 1% aq. solution) was applied to each nostril. Maternal blood pressure and pulse, umbilical artery velocimetry, and fetal heart rate were recorded prior to drug administration and at 5, 15, 30, 45 and 60 min after administration. There were no significant changes in maternal pulse, blood pressure or fetal heart rate. All subjects had normal baseline umbilical artery Doppler systolic/diastolic ratios. Eleven of 12 subjects demonstrated an elevation of the systolic/diastolic ratio consistent with vasoconstriction following administration. This elevation reached statistical significance at 30 min. Significant individual variation existed with regards to timing of maximal excursion of the systolic/diastolic ratio. The mean maximal change of the systolic/diastolic ratio was 1.57 +/- 1.25 (p < 0.001) ranging from -0.53 to 4.11. The use of over-the-counter alpha-adrenergic agents may result in decreased umbilical artery flow velocities. In high-risk pregnancies these medications may be contraindicated.

Maternal and fetal haemodynamics in hypertensive pregnancies during maternal treatment with intravenous hydralazine or labetalol

Intravenous treatment with 10 mg of hydralazine or 100 mg of labetalol was randomly allocated to 30 hypertensive pregnant women. Umbilical artery flow velocity waveforms were recorded using a pulsed Doppler duplex scanner (ATL Mk V) and umbilical artery pulsatility index (PI) and fetal heart rate (FHR) were derived from these recordings. Maternal blood pressure decreased significantly after both drugs. Maternal pulse rate increased after hydralazine but did not change significantly after labetalol. FHR did not change significantly after hydralazine but decreased after labetalol. PI decreased after hydralazine and increased after labetalol--most fetuses showed little change but a few in each group showed large changes in PI, as did two of five additional patients studied. We attributed the decrease in PI in some fetuses after hydralazine to vasodilation, and the increase in PI in some fetuses after labetalol to vasoconstriction in the fetoplacental circulation, suggesting that fetal beta-blockade may occur after maternal treatment with labetalol.

The Effects of Epidural Anesthesia on the Doppler Velocimetry of Umbilical and Uterine Arteries in Normal Term Labor

To study the possible effects of epidural anesthesia on the Doppler velocimetry of the fetal umbilical and maternal uterine arteries, 15 normal term parturients were examined during active labor. Each Doppler study, conducted over 90 minutes after a 500-mL intravenous volume pre-load, was divided into three phases: 30 minutes of pre-anesthetic control, 30 minutes during epidural catheter placement and dosing, and 30 minutes after establishing effective regional blockade. During each phase, maternal blood pressure and pulse were monitored every 5 minutes, and continuous-wave Doppler recordings of the umbilical and uterine arteries were made at three separate intervals. Epidural placement and dosage techniques were similar for all patients; 0.25% bupivacaine solution was used and sensory levels of T6 obtained. The mean maternal systolic and diastolic blood pressures and pulse rate declined significantly, but no woman experienced hypotension. Mean systolic/diastolic ratios and pulsatility indices of the umbilical and uterine arteries did not change significantly during the study. We conclude that effective epidural anesthesia does not have a significant impact on Doppler flow characteristics of either the maternal or fetal umbilical vasculature, despite lowered maternal blood pressure and pulse rate.

Blood pressure measured telemetrically from home throughout pregnancy

Sixty-eight healthy pregnant women measured their blood pressure at home for 1 day every 4 weeks from 14 weeks' gestation until delivery. Blood pressure measurements were made with the Cambridge blood pressure telemetry system, which was composed of a Dinamap 1846 monitor linked to and controlled by a dedicated microprocessor which communicated transtelephonically with a hospital-based microcomputer. On each measurement day each woman measured her blood pressure five times: on first rising and then at 10 AM, 2 PM, 6 PM and 10 PM. At each measurement session the blood pressure was automatically taken 10 times at 1-minute intervals. A total of 23,790 individual blood pressure measurements were analyzed. Systolic, diastolic, and mean arterial blood pressures were lowest at 18 weeks' gestation, rising slowly thereafter at a rate of 0.4 mm Hg systolic and 0.2 mm Hg diastolic per week. The maternal pulse rate also increased steadily after 18 weeks at a rate of 0.25 beats/min per week. There was a strong correlation between the blood pressures at 18, 26, and 38 weeks. All blood pressure parameters were significantly lower on first rising than at other times of the day, although the differences were small: 5 mm Hg for systolic, 4 mm Hg for mean arterial, and 3 mm Hg for diastolic blood pressure. After 10 AM, however, there was no significant daytime variation in any blood pressure parameter, indicating that for most purposes the time of day at which pressure measurements are made is unimportant.

Activation of the renin-angiotensin system during ritodrine treatment in preterm labor

Plasma renin activity, active renin concentrations, and total renin concentrations were measured serially in 15 women in preterm labor treated with ritodrine. All three parameters showed rapid increases during treatment that depended on ritodrine doses and paralleled changes in maternal pulse rate. The slope of the correlation between plasma renin activity and active renin concentrations suggested an increase in both active renin and renin substrate during ritodrine treatment. In contrast, levels of inactive renin remained unchanged for several hours during ritodrine infusion, showing only a late and much smaller response than that of either total or active renin concentrations. Thus ritodrine treatment results in further activation of an already activated renin-angiotensin system in pregnancy. This activation relates to an increase in both renin enzyme and its substrate. It may be responsible for the disturbance in water balance and the risk of pulmonary edema associated with beta-sympathomimetic drug treatment in preterm labor.

Failure of exogenous prostacyclin to change placental and fetal blood flow in preeclampsia

Seven patients with acute preeclampsia ans six with superimposed preeclampsia were infused intravenously with incremental doses of prostacyclin (up to 8 ng/min/kg during 80 minutes). Prostacyclin infusion was accompanied by significant decreases in maternal blood pressure and consistent rises in maternal plasma or urinary 6-keto-prostaglandin F1α, but it caused no changes in maternal or fetal pulse rate or uterine contractility. Moreover, prostacyclin did not change the placental and umbilical blood flow, which were measured before and at the end of infusion. All women experienced facial flushing and two complained of headache during infusion. There was no difference in prostacyclin effects between women with acute or superimposed preeclampsia. These results may be taken as evidence that intravenous prostacyclin is not a specific therapy to increase placental or umbilical blood flow in preeclampsia.

Uptake of halothane by the foetal lamb in utero.

The uptake of halothane by the normal foetus in utero was determined, using the pregnant ewe as an experimental animal model. Six pregnant ewes of 125–135 days gestation were surgically prepared under general anaesthesia. Potyvinyl catheters were placed in the maternal femoral artery and vein and in the foetal femoral artery and vein and the axillary artery. Each animal was allowed to recover for 24–36 hours prior to study. On the day of the experiment a tracheostomy was performed and after a control period, the ewe was anesthetized with 1.5 per cent halothane in oxygen. During each study, maternal and foetal blood pressure were continuously recorded. Simultaneous maternal and foetal arterial halothane concentrations were measured to construct an uptake curve for the foetus. During the study, foetal mean arterial blood pressure fell significantly (27per cent). There were no significant changes in foetal or maternal pulse rate or acidbase status. Halothane appeared in the foetal blood by two minutes but foetal halothane levels remained significantly lower than maternal for 24 minutes. We conclude that halothane crosses the placenta rapidly and produces a decrease in foetal blood pressure but no change in foetal oxygenation or acid-base status.

Insulin-induced hypoglycemia in pregnant diabetics. Maternal and fetal cardiovascular reactions.

Insulin (0.1 IU/kg bw) was injected intravenously in 9 pregnant diabetics in the last trimester of pregnancy. Maternal levels of blood glucose, estriol, human placental lactogen, blood pressure and pulse rate were measured and fetal heart rate (FHR) recorded. During hypoglycemia maternal blood pressure remained unchanged but maternal pulse rate tended to increase. Plasma levels of estriol and HPL remained unchanged. In 6 of the 9 patients there was a decrease in FHR variability during the hypoglycemic period. FHR variability increased after normalization of maternal blood glucose levels. The decrease in FHR variability could be a direct effect of glucopenia on the fetal heart.

Dopamine influence on human uterine activity at term pregnancy.

The influence of dopamine on uterine activity was studied by external tocography in women at the end of a normal pregnancy. In those who were not in labour dopamine infusion (2 micrograms min-1 kg-1 body weight) induced regular uterine contractions and with higher doses the response increased. For women in spontaneous labour, dopamine at a dose of 4 micrograms min-1 kg-1 caused a significant increase in the frequency of contraction, but in women receiving an oxytocin infusion, no further stimulation was seen. Dopamine did not have any noticeable effect on fetal heart rate, maternal pulse rate or blood pressure and no other general effects were observed.

Atenolol in the treatment of pregnancy-induced hypertension.

1 The pharmacological properties of atenolol suggest its possible usefulness in pregnancy-induced hypertension. The pharmacokinetics of atenolol in the pregnant woman, concentrations in cord blood, and its effects on maternal blood pressure and the foetus, are evaluated. 2 We studied 13 pregnant women with hypertension, most of them uncontrolled on methyldopa. Whole blood concentrations and urinary excretion of the drug were measured over 24 h following a 100 mg dose. Effects on maternal blood pressure, pulse rate and foetal heart rate and cardiotocograph were compared for the 4 days before treatment and the first 4 days of treatment. The birth weights and Apgar scores of the babies were recorded. 2 The pharmacokinetics of atenolol (plasma half-life of about 8 h) in pregnant women do not differ from the findings in the non-pregnant. The levels of atenolol in the cord blood were confirmed as approximately equal to those in the maternal blood. 4 In the ten women in whom blood pressure was assessed a small significant fall in blood pressure was observed. 5 A 5% mean fall in foetal heart rate resulted but in one case was a rate below 120 beats/min recorded. There was no evidence of depression of the stress response of the foetal heart. Apgar scores 5 min post partum were satisfactory. 6 Atenolol appears to be safe for use in hypertensive pregnancies. Its effectiveness as an antihypertensive agent in pregnancy requires further controlled evaluation.

Swimming and physical fitness during pregnancy

The influence of aerobic swin conditioning on levels of maternal physical fitness and the influence of each swim bout on selected maternal and fetal circulatory parameters were investigated. Thirteen women who met criteria for a low-risk homogeneous sample were randomly assigned to either an experimental ( n = 7) or a control ( n = 6) group. Experimental subjects participated in ten weeks of a swim conditioning program, while control subjects maintained their normal activities (to exclude aerobic conditioning). Fitness levels for all subjects were determined from respiratory gas analysis during graded exercise testing on a treadmill prior to and following the swim conditioning program. Testing indicated that experimental subjects were able to maintain their initial fitness levels over the twelve weeks of increasing gestation, while control subjects were not able to do so. These findings suggest the effectiveness of the swim conditioning program in countering a potential decrease in fitness levels. Importantly, maternal blood pressure, pulse, and fetal heart rate response remained within clinically normal limits during swim conditioning for experimental subjects, and during treadmill testing for all subjects.

Fetal breathing movements and maternal exercise.

Earlier statements that fetal breathing movements (FBM) are sensitive to changes in the fetal homeostasis prompted the study of the effect of maternal exercise on FBM and fetal heart rate. Forty women in the last trimester of gestation were subjected to a work load (80 W) for 5 min on a bed ergometer cycle; in 30 of them FBM were recorded by A-mode ultrasound, and in 10, the fetal heart rate was monitored by continuous ultrasound. Maternal blood pressure, pulse rate, blood pH and pCO2, and transcutaneous pO2 were also followed. The FBM showed a transient marked increase in incidence immediately after the end of the exercise. No changes in basal level or in baseline variability of the fetal heart rate were found in the recovery period after work. Some possible causes of the observed FBM alterations are discussed. The findings imply that, after this particular form of stress, FBM are a more sensitive indicator of the physiological state of the fetus than the fetal heart rate.

Uterine and cardiovascular effects of aminophylline

Aminophylline (250 mg., over five minutes) was infused intravenously to 10 patients with oxytocin-induced contractions. The uterine activity decreased to 87 per cent because of the effect on contraction intensity; contraction frequency was unaffected. The maximum maternal pulse rate increased to 33 beats per minute. Blood pressure was unaffected. The fetal heart rate and beat-to-beat variability increased. An increased dosage of aminophylline produced unacceptably high maternal tachycardia. Comparing the results to those produced by the β-sympathomimetic drugs in the same experimental model, it is concluded that aminophylline exhibits poor uterine selectivity with an unfavorable cardiovascular/tocolytic ratio.

OBSERVATIONS OF FETAL BREATHING MOVEMENTS TRANSMITTED THROUGH MATERNAL ABDOMINAL WALL

Abstract One hundred women during the second half of pregnancy were observed, and fetal breathing movements were seen transmitted through the maternal abdominal wall in thirty-four. These movements were more often present in multi-gravidae towards term. The origin of the movements was checked by comparing traces of maternal abdominal-wall movements with ultrasound A scans of the fetal chest: the frequencies were similar, and different from the maternal pulse-rate.

OBSERVATIONS OF FETAL BREATHING MOVEMENTS TRANSMITTED THROUGH MATERNAL ABDOMINAL WALL

One hundred women during the second half of pregnancy were observed, and fetal breathing movements were seen transmitted through the maternal abdominal wall in thirty-four. These movements were more often present in multi-gravidæ towards term. The origin of the movements was checked by comparing traces of maternal abdominal-wall movements with ultrasound A scans of the fetal chest: the frequencies were similar, and different from the maternal pulse-rate.

The mechanism of action of exogenous ATP for the treatment of fetal hypoxia during delivery.

SummaryChanges in uterine blood flow, the fetal heart rate, maternal pulse rate and blood pressure were recorded in healthy pregnant women before and after intramuscular ATP administration. The authors postulate that the temporary increase in uterine blood flow following ATP administration and depending on the duration of the pregnancy might be connected with the vasodilatator effect of ATP, which might also explain its beneficial effect in fetal hypoxia.