Uterine Pressure Research Articles

Effects of suprofen and other prostaglandin synthstase inhibitors in a new animal model for myometrial hyperactivity

An in situ model for studying factors related to dysmenorrhea and for evaluating drugs for their inhibitory effects on uterine contractility induced by arachidonic acid and prostaglandins has been developed. Intravenous administration of arachidonic acid and PGF 2α to guinea pigs during the late stage of the estrous cycle, induced dose related uterine contractions and an elevation in uterine basal pressure similar that seen in patients with dysmenorrhea. Pretreatment with prostaglandin synthetase inhibitors inhibited the response to arachidonic acid. The order of relative potency was suprofen (1) > indomethacin (0.65) > naproxen (0.52) > ibuprofen (0.43) > aspirin (0.31). The effectiveness of maximal response for suprofen was significantly greater than that of the other compounds tested. Simultaneous administration of suprofen with PGF 2α also blocked induction of uterine contractions, suggesting the possibility that suprofen also antagonizes PGF 2α receptor binding. Bradykinin also induced uterine constractions, an effect blocked by pretretment with suprofen. Finally, histochemical studies demonstrated stimulation of uterine catecholamine levels (norepinephrine) by arachidonic acid, PGF 2α and bradykinin. These effects were blocked by suprofen. These data suggest that suprofen, an analgesic prostaglandin synthetase inhibitor, may be of use in the clinical tretment of the uterine contractions associated with primary dysmenorrhea.

Aid to diagnosis of foetal bradicardias using the autocorrelation function

Early diagnosis of intense foetal hypoxia, symtoms of which include changes in the foetal heart rate, may constitute a useful tool for the prevention of irreversible damage to the foetus. In the paper three automatic diagnostic methods are described, all based on analysis of the waveform of the autocorrelation function of the sum of signals representing the foetal heart rate and the uterine pressure. The three methods are compared and tested using records taken from a number of patients.

The effects of terbutaline on the acid base balance and circulation of chronically instrumented pregnant sheep.

Terbutaline is considered an effective beta agonist with beta 2 character, for the inhibiton of labor. Its safety was evaluated in twelve infusions of 1,500 micrograms over 30 min, to 8 'steady state' pregnant sheep of 110--134 days of gestation. Experimentation was performed at least 4 days postoperatively. Maternal (n = 12) and fetal (n = 7) arterial blood samples were drawn at 0, 10, 20, 30, 60- and 90 min from the start of the infusion. Uterine blood flow (UBF), blood pressure (BP), and heart rate (HR) were monitored continuously. Maternal pCO2, bicarbonate (HCO-3), and base excess (BE) decreased significantly during the infusion. Maternal pH, pO2, and O2% saturation of the hemoglobin (O2%) remained constant. Maternal hemoglobin (Hb) increased significantly at 10 min. A significant maternal hypotension and tachycardia followed the infusion. UBF decreased by 26% at the end of infusion, recovering by 60 min. Fetal pH, pCO2, Hb, O2%, BP, HR, HCO-3, BE, and CO2 content all remained stable for the duration of the experiment. Fetal arterial pO2 transiently increased at 10 min. No other significant fetal effects were observed.

Effect of nicotine upon uterine blood flow in the pregnant rhesus monkey

Acute effects of nicotine upon the uterine blood flow, blood pressure, maternal and fetal acid-base state, and oxygenation were determined in eight pregnant rhesus monkeys near term. Nicotine was infused intravenously to the mother in a dose of 100 μg/kg of body weight/minute over 20 minutes. The flow rate was measured with the use of the electromagnetic flowmeter. Significant decrease in the uterine arterial blood flow rate, as much as 38% of the control value, was observed during the first 15 minutes of the infusion while aortic pressure increased by 14%. Acidosis and hypoxia resulted in the fetus. Considered together with our previously reported data, the present investigation appears to indicate that the adverse effects of nicotine to the fetus are due to the combined effects of the reduced uterine blood flow and the transmitted nicotine to the fetus.

Postpartum Uterine Pressures with Different Doses of Ketamine

Postpartum Uterine Pressures with Different Doses of Ketamine

Reviews in Perinatal Medicine

are contributors) who cover a number of timely topics in perinatal medicine. For the introductory volume they scarcely could have found two more interesting or informative persons than Drs Lawrence Longo (with Gordon Power) and Abraham Rudolph to author the first two chapters on placental oxygen transfer and cardiac output in the mammalian fetus, respectively. The first volume also considers topics that include fetal pulmonary fluid, onset of breathing, pulmonary transition from fetal life, pulmonary structure during neonatal adaption, continuous transcutaneous oxygen measurements, drugs and anesthetics in the fetus, uterine pres¬ sure, maternal standing during the first stage of labor, betamimetic drugs, fetal heart rate, fetal breath¬ ing, fetal endocrinologie diagnosis, and prenatal genetic diagnosis. The second volume promises to cover a similarly wide group of topics. Most articles are relatively short, usually about 20 pages, although Dr Scarpel¬ li's article is about 68 pages long, Dr Cosmi's is 64, and Dr Carlo Valenti's discourse on genetic diagnosis is about 36 pages. In general, most of the articles are well written and almost all are on a high academic plane. However, here also is one of the problems—the majority of the articles are written for the academic community rather than for the broad community that includes also the practicing physicians. Many contributions tend to be a bit obscure even for the academician. An example of the excellent chap¬ ters that have appeal for all levels of endeavor is Cosmi's article on drugs and anesthetics in fetuses in which the pharmacological characteristics of these drugs are examined at a basic level, while the clinical significances are shown clearly. Also, Dr Eskes deals with uterine pressure at the most basic level, while presenting a beautiful exposition of clinical physi¬ ology of the contracting uterus. An¬ other example is the excellent chapter

Correlations of maternal and fetal endocrine events with uterine pressure changes around parturition in the ewe.

In 4 Clun Forest ewes maternal peripheral plasma concentrations of progesterone were still elevated at the onset of parturient uterine activity. Fetal and maternal plasma concentrations of oestrogen started to rise before parturition and concentrations in maternal plasma were positively correlated with parturient uterine activity (P less than 0.05; r = +0.42). Fetal plasma concentrations of corticosteroids were positively correlated with fetal plasma concentrations of oestrogen (P less than 0.01; r = +0.65), but negatively correlated with maternal peripheral plasma progesterone concentrations (P less than 0.05; r = -0.50). Before parturition plasma concentrations of PGF rose but stayed high only in maternal peripheral plasma. Maternal peripheral plasma concentrations of PGF were positively correlated with uterine activity (P less than 0.05; r = +0.79) and plasma concentrations of oestrogen (P less than 0.05; r = +0.79), but negatively correlated with plasma concentrations of progesterone (P less than 0.01; r = -0.54).

Intrauterine detection of fetal phonocardiosignals

In this paper the application of an open-tip phonocatheter for the detection of fetal phonocardiosignals during parturition is described. The phonocatheter is easily inserted with a conventional polythene guide via the cervical route. The fetal heart sounds are detected by the sound pick-up element located in the catheter tip. Intrauterine pressure is measured simultaneously with the help of a Statham uterine pressure transducer externally connected via the lumen to the open tip of the phonocatheter. Since fetal heart sounds can also be detected before rupture of the membranes, it is possible to measure intrauterine pressure and fetal heart activity simultaneously using only one catheter and without being limited to a particular stage in parturition.

298 METABOLIC CLEARANCE RATE OF OXYTOCIN IN MATERNAL AND FETAL SHEEP

Simultaneous maternal and fetal plasma oxytocin (OXY) concn. (μU/ml) were measured by radioimmunoassay before and during continuous infusion of synthetic OXY to steady state conditions into ewe or fetus (gestational age 124-140 days; at least 5 days post-surgery; estimated fetal wt. 3 kg).Fetal metabolic clearance rates (MCR in ml/kg/min) were calculated to be 18.1 ± 1.1 and 15.0 ± 1.3 at the two infusion rates; maternal MCR were 12.7 ± 2.8 and 13.4 ± 2.3, respectively. Examination of simultaneous fetal and maternal baseline OXY concentrations revealed that fetal levels were significantly higher than maternal: 1.9 ± 0.2 vs 0.7 ± 0.1 (p<.05). Continuous monitoring of uterine pressure revealed that uterine contractions were induced by maternal infusion of 800 μU/kg/min; no uterine contractions were induced by fetal infusion. Conclusions based on these data are: 1) plasma OXY levels exceed maternal levels in fetuses of 124-140 days gestation; 2) transplacental passage of OXY is minimal in both M-F and F-M directions; 3) maternal and fetal MCR of OXY are similar and unrelated to plasma OXY levels.

Effect of prostaglandins on oviduct tone in the domestic hen in vivo

The effect of i.v. injected prostaglandins (PG) F 2 α and E 2 on intraluminal pressure of the different oviductal parts (infundibulum, magnum, isthmus, uterus and vagina) was investigated in the domestic hen. PGF 2 α induced only a pressure rise in all oviduct segments. Administration of PGE 2 resulted in variable changes in oviductal tone: pressure rise in the infundibulum; pressure increase often preceded by a small decrease in the magnum, isthmus and uterus; pressure decrease in the vagina and sometimes in the uterus. Simultaneous i.v. injection of both PG's induced mostly a decrease in vaginal tone. Intraluminal administration of PGF 2 α or E 2 resulted only in an increase in uterine pressure. The observed effects on oviduct tone are discussed and a possible in intervention of both PG's in the mechanism of ovum transport and oviposition in the domestic hen is proposed.

Changes in cervical compliance at parturition independent of uterine activity

A new animal model has been developed to measure intrinsic changes of cervical compliance during spontaneous parturition or exposure to hormonal manipulation. Intermittent measurements of cervical compliance and continuous measurements of uterine and cervical pressure were made during the last month of gestation of nine pregnant ewes. Cervical compliance increased abruptly and dramatically during spontaneous and dexamethasone-induced parturition. Maternal progesterone supplementation at parturition inhibited uterine contractions but not the increase in cervical compliance, demonstrating the independence of the two events. The cervix was found to contract rhythmically and vigorously with a gradual decrease in activity as parturition approached.

Respiratory gases in uterine circulation of pregnant domestic swine as sampled by indwelling catheters

Data dealing with placental respiratory gas exchange are scant for species with an epitheliochorial placenta. None have been obtained from awake, unstressed animals. For this reason 18 pregnant swine were prepared with chronically implanted polyvinyl catheters. Respiratory gases in arterial and uterine venous blood were observed between the 30th day of gestation and term (110 days). There was a statistically significant relationship between uterine venous oxygen partial pressure (Po2 and the day of gestation. The value for Po2, fell from a mean of 70 to 57 Torr. The latter appears to be the highest mean value yet observed in uterine vein of any species at term. pregnancy; chronic preparation Submitted on March 7, 1977

Adrenergic activity of the oviduct of the domestic fowl.

The adrenergic activity of the domestic hen was investigated. Administration of noradrenaline to laying hens at dose levels of 3-5, 7-0, and 14-0 microng/kg produced an increase in the magnal pressure, and a simultaneous decrease in the uterine pressure. Similar doses given to ovariectomized hens caused an inhibition of activity in both segments. Strips of tissues from the vagina and the uterovaginal junction of laying hens were exposed in vitro to noradrenaline at concentrations of 1-5 x 10(-6) and 2.9 x 10(-6) M. The vaginal strips reacted with a sharp increase in tension, while the uterovaginal preparations showed a more gradual and prolonged response. It is suggested that the beta inhibitory activity of the uterus and the alpha excitatory activity of the rest of the oviduct are involved in the regulation of ovum transport.

Effect of ritodrine on uterine activity, heart rate, and blood pressure in the pregnant sheep: Combined use of alpha or beta blockade

Ritodrine hydrochloride was administered parenterally to pregnant ewes during spontaneous or oxytocin-induced uterine activity. The effects of ritodrine on the uterus and cardiovasculature were assessed both with and without simultaneous administration of either alpha or beta blockade. Ritodrine was found to be an effective inhibitor of both spontaneous and induced uterine activity. Ritodrine did cause maternal tachycardia but no significant hypotension. Alpha-adrenergic blockade did not influence the effects of ritodrine. Beta blockade with propranolol reversed the uterine and cardiovascular effects of ritodrine, whereas beta blockade with practolol reversed the cardiovascular effects without interfering with the inhibition of uterine activity produced by ritodrine.

The effect of epidural anesthesia on uterine activity and blood pressure

Because of the unresolved controversy regarding the effect of epidural anesthesia upon uterine contractility, it was decided to study its effect on a small number of patients. Intrauterine and intra-arterial continuous pressure, continuous fetal heart rate, and maternal heart rate recordings were obtained from at least 20 minutes before administration of the epidural anesthetic until complete dilatation in these patients. Nineteen patients were in spontaneous labor, and 18 had labor stimulated with oxytocin, Plain lidocaine, 1 or 1.5 per cent, was used in 12 patients (30 observations), and lidocaine with epinephrine, 1:200,000 was used in 26 patients (51 observations). Uterine contractions were calculated in Montevideo units for 60 minutes following the epidural anesthetic. The changes, if any, were compared in both groups. There was a significant decrease in uterine activity when epinephrine was added to the anesthetic solution, mainly a lessening of intensity. There were comparable decreases in systolic/diastolic blood pressure in both groups and compensatory tachycardia. In one case, severe hypertension was observed following administration of lidocaine epinephrine. It was concluded that the addition of epinephrine to the anesthetic solution predictably produces diminution of uterine activity, and it does not give “cardiovascular support” to the laboring patient.

Relationships between pressure and flow in the umbilical and uterine circulations of the sheep.

We studied the relationship of fetal and maternal vascular pressures to umbilical and uterine blood flow in the unanesthetized ewe and in the sheep fetus in utero by placing electromagnetic flow transducers around both the common umbilical and uterine arteries. Reductions in umbilical arterial pressure or elevations in umbilical venous pressure decreased umbilical blood flow without affecting either the uterine arterial blood flow or other maternal cardiovascular variables which were studied. Elevations in uterine venous pressure or reductions in uterine arterial pressure decreased uterine arterial flow but these interventions had no effect on umbilical blood flow until fetal hypoxemia and bradycardia occurred. When the bradycardia of the fetal hypoxic response was inhibited by atropine, alterations in maternal vascular pressure had no effect on umbilical arterial flow. These data do not support the presence of a "sluice" or "waterfall" effect in the umbilical-placental circulation of the sheep fetus in utero.

Absence of fetal placental waterfall phenomenon in chronically prepared fetal lambs.

An electromagnetic flow sensor was placed on the distal fetal aorta (umbilical flow fraction 78.1 +/- 1.6 SEM, %), an inflatable occluder was tied around the umbilical cord, and catheters were placed in distal branches of an umbilical artery and vein, a uterine vein, and in the amniotic cavity. An inflatalbe occluder was tied around the vagina of some of the ewes. Control values 3 days after surgery were (mean +/- SE): fetal femoral artery pH, 7.37 +/- 0.01; umbilical blood flow, 186 +/- 14 ml-min-1 .kg fetus-1; fetal arterial blood pressure, 39 +/- 3 mmHg; and umbilical venous pressure, 7.4 +/- 1.0 mmHg (above intrauterine pressure). Fetal weight at autopsy was 3.1 +/- 0.3 kg, n = 11. Small increases in umbilical vein pressure caused immediate decreases in placental blood flow without decreases in fetal arterial blood pressure. The relation between venous pressure and umbilical blood flow at constant arterial pressure was that of an inert system, i.e., no evidence of a surrounding pressure (Starling resistor effect or waterfall phenomenon) could be found with increases in venous pressures of 2-40 mmHg. The results were not affected by increases in uterine vein pressure between 2 and 30 mmHg, nor by anesthesia and supine position of the ewe, nor by ganglionic blockade of the fetal ANS. It was concluded that surrounding pressures in the fetal placental circulation could not be demonstrated.

Changes in the cervical blood flow during labour.

The cervical blood flow changes during labour in pregnant women (15 cases) have been studied by local injection of 133Xe into the cervix. The blood flow changes were compared with the external uterine pressure which was measured with a tocograph. During contractions the radioactivity decreased temporarily, but increased again between contractions. The overall decrease was greater in the control group (4 cases) than during spontaneous contractions. The conclusion is, that relative cervical blood circulation is rapidly changed during labour.

Computer monitoring of fetal heart rate and uterine pressure

With the introduction of continuous recording cardiotocographs in the labor room the large quantity of numerical data produced suggested the computer would be of use. In this preliminary study two computers were used: one initially to collect data and later to give comment and advice as the data was collected and the other for in-depth analysis of the previously collected data. On the basis of this new information a new way of analyzing and categorizing labor is suggested and some of the clinical impact so far achieved is described.

Intermittent low-dose administration of prostaglandins intraamniotically in pathological pregnancies: A comparison with oxytocin and ergometrine

The effects of prostaglandin F 2α on uterine contractility were compared with the effects of oxytocin and ergometrine. All patients had an intrauterine death. 5 patients were induced with prostaglandin F 2α, given intraamniotically in low doses, starting with 125 μg. Doses were increased in relation to uterine activity. 5 other patients were induced by intravenous administration of oxytocin and ergometrine. Uterine pressure was monitored by a transabdominal open-tip catheter system. Results were quantitated in tonus (mm Hg), amplitude (mm Hg), frequency (number of contractions per 10 min), Montevideo units, active and total pressure areas per 20 min. Possible biochemical and coagulation changes were controlled before, during and after induction. Changes did not occur. Intermittent increasing small doses of PGF 2α increased uterine activity exponentially. Hypertonia persisting longer than 5 min was seldom seen with oxytocin or with PGF 2α. Ergometrine increased frequency of uterine contractions, without influencing tonus, probably due to a specific effect on the ‘archemyometrium’. The induction-delivery interval was shorter in the PGF 2α group (range: 6–15 h) than in the oxytocin group (range: 7–24 h). In the latter group more inductions were necessary to complete delivery. Using PGF 2α in these small doses did not cause any side effects. With the intraamniotic injections, starting with 125 μg PGF 2α, clinical results are the same as those reported in the literature for high doses.