The location of chronic pregnancy hypertension on the vasoconstriction-volume spectrum: working hypothesis.

OBJECTIVE: The purpose of this study was to examine whether volume loading is a factor in chronic pregnancy hypertension. STUDY DESIGN: Five patients with chronic hypertension performed home self-monitoring daily with a noninvasive pressure transducer from a fingertip. Determinants of mean arterial pressure were computed from the pressure data and a concurrent electrocardiogram. For this study blood pressure and rapid ejection time, which is an empiric indicator of arterial compliance, were evaluated during antihypertensive therapy. Data were transmitted by facsimile to the hospital. RESULTS: One patient with hypertension who was admitted to the study at 10 weeks' gestation became normotensive with a diuretic (furosemide) alone. Medication was discontinued at 23 weeks' gestation. This patient remained normotensive until delivery at 41 weeks' gestation. Blood pressure was controlled with furosemide combined with nifedipine and labetolol in the other 4 cases. Three patients were studied with concurrent blood pressure and rapid ejection time measurements made before and after antihypertensive medication. All 3 showed decreases in these measurements with medication. CONCLUSION: Both volume excess and vasoconstriction should be considered in the pathogenesis of chronic pregnancy hypertension.

Hemodynamic concomitants of glycemia in diabetes mellitus: working hypothesis.

This report illustrates a working hypothesis that proposes a simple-to-use, noninvasive hemodynamic system to provide myocardial contractility and arterial compliance patterns that may be clinically useful adjuncts to insulin and glycemic measurements in diabetes mellitus. This proposition is based on the concept that biochemical cellular milieu may only obliquely predict cellular function, whereas in the biophysical domain, it may be more clearly delineated.

Working hypothesis relative to the hemodynamics of menstruation and pregnancy.

A working hypothesis relative to detailed hemodynamic changes that occur during menstruation and pregnancy theorizes that the marked biophysical similarities existing between the postovulatory phase of the menstrual cycle and the latter half of pregnancy are endocrine based. The data are acquired with apparatus that records cutaneous pressure pulses and the maternal electrocardiogram, which together provide the basis for deriving the determinants of mean arterial pressure.

Hemodynamic patterns in preterm and term labor: working hypothesis.

This report describes hemodynamic patterns recorded from patients who had spontaneous abortion, preterm, and term labor. A working hypothesis theorizes that specific patterns observed in these situations can be identified and correlated with those present in the preovulatory and postovulatory phases of the menstrual cycle and thereby provide a clue to endocrine imbalances that may occur during pregnancy and play a role in the pathophysiology of these complications.

Apparatus for home monitoring of pregnant hypertensive patients.

A simple, convenient to use apparatus suitable for patient self-monitoring is described and illustrated with graphs of mean arterial pressure determinants which provide clinically useful hemodynamic details unobtainable with cuff blood pressure measurements. A bathroom scale and a forearm cuff blood pressure system completes the home monitoring apparatus.

R-pulse wave timing in cardiovascular monitoring: further observations.

Pulse wave arrival times measured from the peak of the R-wave of the electrocardiogram to the onset of a peripheral pulse wave were recorded with a miniature pressure transducer in a group of 72 hypertensive pregnant women, of whom 19 were receiving sympatholytic antihypertensive medication and 53 were not. The mean (+/- SD) pulse wave arrival time of the hypertensive pregnant group was 204 +/- 15 milliseconds, which was significantly shorter than that measured in a group of 49 uncomplicated normotensive pregnant subjects (222 +/- 16 milliseconds) (P less than .001). The mean pulse wave arrival times were shortest in the subset of pregnant hypertensive patients not on sympatholytic medication (201 +/- 13 milliseconds) as compared with patients on such medication (212 +/- 18 milliseconds) (P less than .01). These observations suggest that patients with pregnancy hypertension have much shorter pulse wave arrival times than normotensive pregnant women. Further studies are needed to determine the potential usefulness of this cardiovascular index for evaluation of hypertensive states during pregnancy.

Peripheral pulse pressure patterns in pregnancy hypertension.

Maternal heart rate and pulse pressure patterns were examined in 30 hypertensive pregnant women using noninvasive methodology described previously. "Narrow" and "wide" pulse patterns were identified. Narrow cutaneous pulse pressure patterns, which are thought to be caused by vasoconstriction, were associated with lower birth weight infants (1870 +/- 983 versus 3225 +/- 838 g; P less than .001) and earlier deliveries (34.2 +/- 5.2 versus 37.9 +/- 2.8 weeks; P less than .05). The data suggest that these adjunctive maternal cardiovascular-system evaluation techniques may be useful in identifying patients at risk of adverse perinatal outcome by detecting vasospasm of the peripheral microcirculation.

Noninvasive blood pressure patterns.

The apparatus described in this report provides a noninvasive, nonocclusive technique for continuously measuring cutaneous blood pressure changes over extended periods of time. The data are acquired with miniature pressure transducers mechanically coupled to the cutaneous tissue overlying the thumb and wrist. The cutaneous blood pressure patterns obtained with this apparatus indicate that the stress of uterine contractions causes readily identifiable blood pressure pattern changes. Preliminary results suggest that data obtained with this instrumentation is more complete than that obtainable with intermittent occlusive blood pressure measuring systems currently in use.

Limitations of autocorrelation in fetal heart rate monitoring.

Fetal heart rate monitors that use autocorrelation of the ultrasonic fetal signal usually produce a cleaner fetal heart rate record than that obtainable with conventional ultrasonic fetal monitors. However, since the autocorrelation function will emphasize any periodic signal originating from the fetus or the mother, in clinical situations the resultant fetal heart rate tracing may contain spurious data. To illustrate the limitations of the autocorrelation technique in fetal monitoring, we compared the autocorrelated ultrasound fetal heart rate records from 23 patients in active labor with the simultaneously recorded direct scalp fetal electrocardiogram tracings. The results indicate that every hour of recording contained, on the average, five instances in which data were missing (range, 0 to 13), four in which data were added (range, 0 to 23), and seven instances in which data were absent for greater than 1 minute (range, 0 to 26). The potential problem of misinterpretation of autocorrelated fetal heart rate data is discussed.

Heart rate variability in diabetes: relationship to age and duration of the disease.

Heart rate variability (HRV) during deep breathing was studied with a neonatal heart monitor in 143 control subjects and 218 patients with diabetes (102 with IDDM and 116 with NIDDM). In the control group HRV decreased after age 20 by 4-5 beats per decade (from 29.7 +/- 5.8 beats at age 20-29 to 11.8 +/- 5.4 beats at age 60+). In all age groups HRV in IDDM was lower than in the controls, and both age and duration of diabetes played a role in the decrease of HRV (from 21.5 +/- 5.3 beats at age 20-29 to 6.3 +/- 5.4 at age 60+). In NIDDM aging seemed to play a less important role, and the influence of the duration of the disease was not statistically significant. In both groups of patients the frequency of HRV below the 2.5th percentile was 82% in those with symptoms and/or signs of autonomic neuropathy, 64% in patients with peripheral neuropathy only, and 36% in those who had no obvious signs or symptoms of neuropathy. Interindividual variability was pronounced, and age and duration of the disease together accounted for only 36% of the observed differences between IDDM and the controls. Determination of HRV with a standard neonatal heart monitor presents an easy, simple, and nonstressful test of cardiac autonomic neuropathy. The norms of the test are age related.

The cutaneous R-pulse interval: its application as a clinical measure of neonatal cardiovascular function.

The time interval from the onset of the R wave of the ECG to the onset of the cutaneous capillary pulse wave, i.e., cutaneous R-pulse interval or RPIc, was evaluated in 21 full-term and 22 preterm infants as a measure of cardiovascular function. RPIc showed a significant linear relationship with birth weight (r = .58, p less than .001) and gestational age (r = .62, p less than .001) for healthy infants. At similar gestational ages, the sick infants showed a significant prolongation of RPIc when compared to their healthy counterparts (mean prolongation 18.5 msec, p less than .01). The infusion of calcium gluconate, an inotropic agent, consistently and significantly shortened the RPIc from its preinfusion value (p less than .01). In 7 infants, simultaneous measurement of intra-aortic R-pulse interval accompanied parallel changes in RPIc. These preliminary observations suggest that continuous monitoring of RPIc may provide a reliable noninvasive measure of neonatal cardiovascular function.

Changes in the lecithin:sphingomyelin ratio during labor and the associated fetal heart rate patterns.

Serial samples of amniotic fluid were taken from 38 patients in spontaneous labor and the lecithin:sphingomyelin (L:S) ratios were estimated. The fetal heart rate (FHR) pattern for each patient was analyzed, and the baseline rate, long-term variability, and periodic changes wee determined. It was found that changes in the L:S ratios were significantly correlated with the duration of labor and FHR long-term variability. Very low L:S ratios were observed in some patients whose infants did not subsequently develop respiratory distress syndrome. This raises the possibility that during labor the amniotic fluid is no longer representative of lung fluid, perhaps because of reduced tracheal fluid efflux, a process which may operate when the fetus is under stress.

R--pulse wave timing: a technique for continuous cardiovascular monitoring in obstetrics--preliminary report.

A simple, noninvasive technique for continuous cardiovascular monitoring in obstetrics using R--pulse wave timing is described. This preliminary study suggests that different maternal heart rate/R pulse patterns are found in different clinical circumstances. A significant decrease in the R pulse interval occurred in the third trimester in both normal and diabetic women in the left lateral position when compared to the supine position. The R pulse intervals were all prolonged in the standing position in both gravid and nongravid women. During labor R pulse interval usually shortened during uterine contraction. Prolongation of R pulse interval was observed during thiopental injection, hypotension, and excessive bleeding at cesarean section. Exercise testing in healthy male subjects suggested that the change in R pulse interval becomes constant when the oxygen consumption rate reaches a plateau at 100% maximal work load. Further extensive clinical study appears worthwhile since it may add another dimension to cardiovascular monitoring and give an early indication of cardiovascular reserve.

Electromechanical intervals of the fetal cardiac cycle.

The measurement of electromechanical intervals of the fetal cardiac cycle may be useful in the evaluation of cardiac status, since they are based upon sound physiological principles. Studies of EMIs in the human fetus are currently in their infancy and clinical evaluation of their usefulness awaits the development of adequate data acquisition, reduction and analysis techniques.

Fetal heart rate variability: an approach to automated assessment.

Three hundred seventy-five hours of fetal heart rate (FHR) data derived from the direct fetal electrocardiogram (ECG) were studied. This data had been stored on magnetic tape from 83 intrapartum patients. By means of a computerized technique, the FHR variability was assessed quantitatively. The degree of variability was then related to: (1) state of labor, (2) fetal scalp pH values, and (3) the 1-minute Apgar score. FHR variability was computed from differences between consecutive R-R intervals measured from the R wave of each fetal ECG. A trend of increasing variability was seen with advancing labor, defined by either time prior to delivery or cervical dilatation, but values were not statistically significant. Significantly less FHR variability was encountered when fetal scalp pH values below 7.20 were compared to higher values. FHR variability assessed during the 20 minutes immediately preceding delivery was significantly lower in infants with 1-minute Apgar scores less than 7. Machine assessment of FHR variability thus could be correlated with fetal condition as determined by scalp pH and neonatal outcome determined by Apgar score.

The effects of paracervical block on uterine activity and beat-to-beat variability of the fetal heart rate.

Paracervical block analgesia with the use of lidocaine hydrochloride provoked little change in uterine activity. The general trend in uterine activity was an increase, although there was considerable variation in individual response. Beat-to-beat variability in the fetal heart rate increased following the block. The increase in variability began almost immediately, with the greatest increase occurring at a time when one would expect maximum maternal and fetal lidocaine levels. It is proposed that this increase in fetal heart rate variability is an early sign of post-paracervical block hypoxemia and/or hypoxia.

The effect of drugs on fetal heart rate variability.

Baseline FHR variability has been quantitated into the mathematical indices of differential index (short-term variability) and interval index (long-term variability). Normal values have been determined. The effect that drugs used during labor have on FHR baseline variability has been evaluated. A clinically meaningful change in variability has been observed following low-dose administration of Demerol, morphine, Nisentil, Phenergan, and Vistaril. A statistically significant increase in variability has been observed following administration of magnesium sulfate.

Intrapartum fetal cardiac arrest. A preliminary observation.

In 13 patients, episodes of transient fetal cardiac arrest were observed in a group of 594 extensively monitored labors during a given 3-year period. The number of episodes per patient ranged from one to six, with a maximal duration of cardiac arrest (R-R interval) being 5.2 seconds. All of the patients responded to changing maternal position or termination of pregnancy except 1. This patient received Atropine as a premedication for cesarean section. The parasympatholytic properties of Atropine minimized the severity of cardiac arrest. The effect of cardiac arrest on fetuses is not clearly shown in these preliminary observations. The prompt elimination of cardiac arrest is thought to be imperative in reducing perinatal loss. Cardiac arrest is though to be an extensive form of severe variable deceleration. The hypothesis is made that these fetuses had an unbalanced autonomic nervous system and/or an overwhelming vagal tone. If these signs are detected early by fetal monitoring, attention should be paid to the possibility of cardiac arrest.