Search PubMed⌕ Search

Biomedical subjects

E H Hon

Publications and source records attributed to E H Hon.

At least 19 recordsLinked to original sources
PubMed1992

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.

Adult↗
PubMed1991

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.

Birth Weight↗
PubMed1987

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.

Blood Pressure Determination↗
PubMed1985

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.

Electrocardiography↗
PubMed1979

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.

Anesthesia, Obstetrical↗
PubMed1979

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.

Apgar Score↗
PubMed1979

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.

Animals↗
PubMed1978

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.

Analgesics, Opioid↗
PubMed1978

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.

Anesthesia, Obstetrical↗
PubMed1977

Heart-rate variability in brain-damaged adults.

To test whether or not the characteristics of the adult heart-rate reflect the condition of the central nervous system (as they seem to do in the fetus), ten patients with neurological deficits of acute onset were studied. No patients had received drugs and none was hypoxic. The findings indicate that the normal cyclic changes in heart-rate are reduced in the presence of severe brain damage. Variability decreases rapidly if intracranial pressure rises, and the rate of return of variability reflects the subsequent state of neuronal function, even when intracranial pressure has been restored to normal. In this limited setting, then, it appears that heart-rate variability may reflect the functional state of the central nervous system.

Adolescent↗
PubMed1977

A study of the relationship between Goodwin's high-risk score and fetal outcome.

Correlation between Goodwin's high-risk score and Apgar score was studied in 266 pregnancies managed with the use of the information from clinical monitoring. The correlation coefficients between Goodwin's score and Apgar scores were -0.3178 for one-minute Apgar scores and -0.2668 for five-minute Apgar scores. Both are significant at the level of p less than 0.001. When the patients were divided into two groups by Goodwin's score, fetuses of the group with the higher score (greater than or equal to 4) were significantly more acidotic than those of the group with the lower score. Therefore, Goodwin's high-risk scoring system is simple and useful in the selection of potential risk patients.

Adult↗
PubMed1977

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.

Acid-Base Equilibrium↗
PubMed1976

Quantitation of uterine activity in 100 primiparous patients.

An on-line technique for quantitating uterine activity by measuring the total area under the intrauterine pressure curve was utilized during the labor of 100 primiparous patients. Uterine activity was measured in uterine activity units (1 UAU=1 Torr minute). UAU's were calculated for each patient in both cumulative and noncumulative fashions. The rate of uterine activity (UAU per unit of time) increased as labor progressed, yet the total UAU's expended at each centimeter of dilatation progressively decreased with advancing dilatation. Thus, the rate of cervical dilatation increased faster than could be accounted for by the increase in uterine activity. The implication being that the efficiency of uterine contractions increases with advancing labor. It no longer appears reasonable to refer to labor in terms of elapsed time. Information regarding the "pattern of cervical dilatation" and uterine activity appears to be much more meaningful to the evaluation of progress in labor. Quantitation of uterine activity may provide useful information for the ongoing management of labor. Quantitation of UA does provide a means of evaluating the effects of specific events such as medication, anesthesia, and manipulation on UA.

Adolescent↗
PubMed1976

Effects of ritodrine hydrochloride on uterine activity and the cardiovascular system in toxemic patients.

The effects of ritodrine hydrochloride were evaluated in 25 toxemic patients in active labor utilizing continuous electronic monitoring of fetal and maternal cardiovascular systems and uterine activity. Fetal scalp blood and free flowing maternal antecubital venous blood was obtained for pH, Po2, Pco2, base deficit and blood glucose determinations prior to and immediately following the study period. The initial ritodrine dose was 50 mug/min for 15 minutes. The dose was increased by 50 mug/min each 15 minutes until there was a clinically apparent reduction in uterine activity. Once this was accomplished, the infusion was maintained for 30 minutes. There was a consistent increase in the maternal heart rate (MHR) and a significant rise in fetal heart rate (FHR) late in the infusion and in the postinfusion period. There was a widening of the maternal pulse pressure mainly due to a reduction in diastolic pressure with little change in the mean blood pressure. Maternal and fetal pH decreased and base deficit increased during the study although the PO2 and PCO2 remained unchanged. Maternal and fetal blood glucose rose significantly following ritodrine infusion.

Blood Glucose↗
PubMed1976

The effect of drugs on uterine activity.

Uterine activity was measured for a 30-minute preinjection period and a 30-minute postinjection period for six drugs commonly used in labor. Uterine activity was quantitated by measuring the area below the uterine pressure curve with an on-line technic utilizing a voltage control oscillator. Uterine activity readings were obtained every 2.5 minutes and reported in uterine activity units (UAU). Unmedicated labor demonstrated a relatively static increase in UAU per unit of time in labor. On comparing total UAU before and after injection, only magnesium sulfate was noted to cause a decrease in total UAU. Utilizing 10-minute summations of UAU, the pre- and postinjection periods were compared to the calculated expected UAU for the 30 minutes following the preinjection period (assuming no drug had been used). For each of the other drugs, the positive slope of the calculated expected UAU shifted to a negative slope of the actual observed UAU following drug administration.

Adolescent↗