Biomedical subjects

J A Low

Publications and source records attributed to J A Low.

At least 55 records · Page 3Linked to original sources

PubMed1993

Vibroacoustic-induced fetal movement: two stimuli and two methods of scoring.

OBJECTIVE: To determine whether the fetal movement response elicited by vibroacoustic stimulation depends upon the vibrator and the method used to judge movement. METHODS: Two methods of obtaining elicited fetal movement responses--maternal perceptions and ultrasound scan observations--were compared using two different vibroacoustic stimuli in 16 low-risk term pregnancies. RESULTS: Analyses of response over trials showed that the percentage of agreement between ultrasound scan observations and maternal perceptions varied (52-96%) across stimuli. The mothers perceived 64% less movement when vibrator 1 was used and 14% less movement response with vibrator 2. Analyses of average movement scores across subjects showed similar results. Vibrator 1 elicited significantly fewer maternal perceptions of fetal movement compared with ultrasound scan observation (an average of 0.8/3 compared with 2.3/3 movements per subject, respectively). For vibrator 2, there were no differences in average movement scores obtained by maternal perception and ultrasound scan observation (an average of 2.4/3 versus 2.8/3, respectively). CONCLUSION: The stimulus used in vibroacoustic stimulation testing influences the reliability of maternal movement perceptions as compared with ultrasound scan observations.

Acoustic Stimulation↗

PubMed1993

Middle cerebral artery blood flow velocity in the newborn following delivery.

Ninety-five normally grown term and preterm newborns were examined to determine the means and prediction limits of cerebral blood flow velocity following delivery and to examine the relationship of systemic blood pressure to cerebral blood flow velocity. Doppler blood flow velocity was observed during the four days following delivery. Continuous measures of blood pressure and heart rate were recorded concurrently. Mean peak systolic and end diastolic blood flow velocity immediately following delivery was 43.2 and 9.3 cm/sec for term newborn, and 31.8 and 3.3 cm/sec for preterm newborn. During the 24 h following delivery there was no change of peak systolic blood flow velocity but a two to three fold increase of end diastolic blood flow velocity in the term and preterm newborn. The reference limits for peak systolic and end diastolic blood flow velocity provide criteria to define abnormal increases and decreases of blood flow velocity. During the 24 h following delivery, increasing diastolic blood pressure was associated with increasing end diastolic blood flow velocity independent of birth weight and time following delivery. Also there was a significant correlation between systemic pressure pulsatile index and middle cerebral artery blood flow velocity pulsatile index. Thus systemic blood pressure pulsatility must be recognized as distinct from other intracerebral influences on cerebral blood flow velocity regulation in the newborn.

Blood Flow Velocity↗

PubMed1993

Relationship of fetal asphyxia to neuropathology and deficits in children.

Neuropathological studies suggest that the majority of the fetal asphyxial complications resulting in brain damage in either preterm or term fetus occur before the onset of labor. Anoxia because of the rapid sequence of events will usually result in death of the fetus. Hypoxia of 1-3 h duration may account for brain damage and deficits in children who survive. The threshold for brain damage is a severe acidosis with a pH < 7.0 in conjunction with systemic hypotension. The prevalence of antepartum fetal asphyxia and the frequency of deficits in such children have not been established. The prevalence of intrapartum fetal asphyxia determined biochemically is 2%. The majority of these children develop normally because of fetal cardiovascular compensatory mechanisms which protect the brain. However, beyond the threshold of asphyxia in either the preterm or term fetus, neuropathology may develop leading to deficits in some children.

Animals↗

PubMed1992

Association of intrauterine fetal growth retardation and learning deficits at age 9 to 11 years.

OBJECTIVE: We examined the association of fetal and newborn complications, socioeconomic status, and home environment with learning deficits as assessed between 9 and 11 years of age. STUDY DESIGN: A total of 218 high-risk newborns have been assessed at 1, 4, and 9 to 11 years of age. Fetal and newborn complications included 77 newborns with growth retardation. Socioeconomic variables included parental occupation and education. Outcome measures at 9 to 11 years included the Woodcock Reading Mastery Test and the Wide Range Achievement Test. Motor and cognitive development was assessed by a neurologic examination, the Bruininks-Oseretsky Test of Motor Proficiency, and the Wechsler Intelligence Scale for Children. Behavior was assessed with the Achenbach Child Behavior Check List and Connor's Teacher Rating Scale. RESULTS: Learning deficits were identified in 77 of the 218 children (35%). Children with learning deficits had lower full-scale IQ scores and behavioral problems of inattention and anxiety. Both fetal growth retardation and the father's occupation score were independently associated with these learning deficits. CONCLUSION: Fetal growth retardation, socioeconomic status, and behavioral characteristics of inattention and anxiety are associated with less favourable academic achievement at 9 to 11 years of age.

Child↗

PubMed1992

The clinical diagnosis of asphyxia responsible for brain damage in the human fetus.

OBJECTIVE: Our objective was to review the clinical findings in infants who died in the perinatal period with brain damage attributable to asphyxia. STUDY DESIGN: The neuropathologic findings in 208 perinatal deaths have been reviewed. Thirty cases (22 fetal, eight newborn) had evidence of white matter or neuronal necrosis due to asphyxia. The clinical course of the pregnancy in 22 cases with brain damage attributable to fetal asphyxia were examined. RESULTS: The diagnosis of asphyxia was confounded by several factors: (1) asphyxia may occur at any time in the last half of pregnancy, (2) 50% of the antepartum asphyxia occurred when the pregnancy had no risk factors, (3) periodic fetal assessment in the complicated preterm pregnancies failed to identify the asphyxial episodes in the remaining cases of antepartum asphyxia, and (4) indicators of fetal asphyxia in the cases of intrapartum fetal asphyxia were obtained after the central nervous system injury had occurred. CONCLUSION: These findings highlight the difficulty in the diagnosis of fetal asphyxia at a stage that could permit intervention to prevent brain damage.

Adult↗

PubMed1992

Maturation of human fetal responses to vibroacoustic stimulation.

Maturation of human fetal response to vibroacoustic stimulation was examined in 60 fetuses from 23 to 36 weeks gestational age. Subjects received vibroacoustic or no-stimulus control trials (randomly assigned) while fetal heart rate (FHR) was recorded and movement was observed on real-time ultrasound scan. Initially, at 26-28 weeks, a small FHR deceleration response occurred; subsequently, FHR acceleration responses occurred. From 29 weeks, 83%-100% of subjects responded with an FHR acceleration > or = 10 BPM on the first vibrator trial and accelerations were observed on 83%-92% of all vibrator trials. From 26 to 36 weeks the percentage of fetuses responding with movement on the first vibrator trial increased from 58% to 100%; on all vibrator trials responses increased from 53% to 94%. It was concluded that maturation of human fetal response to vibroacoustic stimulation begins at about 26 weeks gestation, increases steadily over a 6-week period, and reaches maturity at about 32 weeks.

Acoustic Stimulation↗

PubMed1992

Hypotension and hypoxemia in the preterm newborn during the four days following delivery identify infants at risk of echosonographically demonstrable cerebral lesions.

This prospective study of 130 preterm newborns at less than 34 weeks gestational age has examined the predictive value of abnormalities in continuously recorded newborn blood pressure, heart rate, and oxygen tension during the 4 d following delivery for echosonographically demonstrable cerebral lesions (EDCL) identified in the infant by six months corrected age. EDCL consisting of intraventricular hemorrhage, ventriculomegaly, or hyperechoic parenchymal lesions in the brain were identified in 44 preterm newborns (34%). The incidence of EDCL in preterm newborns with no hypotension or hypoxemia was 13%. The incidence of EDCL was significantly increased in preterm newborns with either hypotension or hypoxemia. The probability of EDCL exceeded 50% when the total exposure to either hypotension or hypoxemia during the 4 d exceeded 50 mmHg-hours, or when newborn hypotension and hypoxemia occurred concurrently. No relationship to hypertension, bradycardia, or tachycardia was detected. These findings indicate that hypotension and hypoxemia in the preterm newborn during the 4 d following delivery are useful risk markers of EDCL.

Brain Diseases↗

PubMed1992

Mortality and morbidity after intrapartum asphyxia in the preterm fetus.

This matched cohort study examined the significance of intrapartum fetal asphyxia determined biochemically in the preterm newborn in regard to outcome during the first year. Thirty preterm newborns with metabolic acidosis at delivery were compared with 60 preterm newborns, matched for birth weight, with normal blood gas measures. Deaths during the first year were reviewed. Assessment of the surviving children at 1 year corrected age included neurologic examination, Bayley scales, and Uzgiris and Hunt scale to define motor and cognitive development. Seven asphyxiated infants (23%) died during the first year compared with two nonasphyxiated infants (3%), a statistically significant difference (P less than .006). Among the surviving children, the incidence of minor motor and/or cognitive deficits was the same in the two groups. The incidence of major motor and/or cognitive deficits in the group with asphyxia (eight of 30) was significantly greater than in the control group (eight of 60) (P less than .03). These results indicate that intrapartum fetal asphyxia in the preterm newborn is a contributing factor to the mortality and morbidity observed in these children.

Asphyxia Neonatorum↗

PubMed1991

The current status of maternal and fetal blood flow velocimetry.

Significant progress has been achieved in regard to normative data for uteroplacental and fetal blood flow velocity and the factors which may affect these observations. Associations have been demonstrated between abnormal indices of maternal and fetal blood flow velocity and pregnancy-induced hypertension, fetal growth retardation, fetal blood gas measures, and intrapartum clinical fetal distress. However, in general, the predictive power is modest and no evidence has yet been provided to indicate that these measures can be used as a screening test in the general obstetric population. Continuing research is highly desirable. At the present time, the use of Doppler assessment of blood flow in pregnancy should be limited to the investigational setting.

Apgar Score↗

PubMed1991

Blood pressure and heart rate of the preterm newborn following delivery.

Thirty-five preterm newborns were studied to determine the mean blood pressure and heart rate of preterm newborns less than 1500 gm and greater than or equal to 1500 gm at birth. Systemic blood pressure increased and heart rate decreased with increasing maturity at birth. Both systemic blood pressure and heart rate increased during the four days following delivery. The 95% prediction limits of stable preterm newborns less than 1500 gm and greater than or equal to 1500 gm at birth are useful criteria to define hypertension and hypotension, as well as tachycardia and bradycardia.

Aging↗

PubMed1991

Maternal and ultrasound measurements of elicited fetal movements: a methodologic consideration.

Two methods of evaluating fetal movement responses elicited by vibroacoustic stimulation--maternal perceptions and ultrasound scan observations--were compared in 58 low-risk and 35 high-risk pregnancies from 23-36 weeks' gestation. Maternal perception of vibrator-elicited fetal movement was poor compared with ultrasound scan observation. Regardless of gestational age or risk status, the mothers perceived 27-75% fewer movements than observed with ultrasound scan. In addition, maternal movement perceptions on vibrator versus no-stimulus control trials were not reliable until 29-32 weeks' gestation, with the percentage of movement responses increasing across gestation from 11 to 48%. In contrast, ultrasound scan observations of movement were reliable on vibrator compared with no-stimulus control trials from 26 weeks, with the percentage of movement responses increasing from 22% at 23-25 weeks to 94% at 35-36 weeks. We conclude that maternal perceptions of fetal movements cannot be substituted for ultrasound scan observations for accurate assessment of fetal movements during vibroacoustic stimulation testing.

Adult↗

PubMed1990

Intrapartum asphyxia in the preterm fetus less than 2000 gm.

The incidence of intrapartum asphyxia in the preterm fetus less than 2000 gm (6%) is greater than that in the mature fetus (2%). Severe antepartum hemorrhage is the only clinical marker predictive of asphyxia in the preterm fetus. Marked deceleration patterns and particularly late decelerations may be of predictive value for asphyxia. However, many intrapartum asphyxial episodes are not identified on the basis of clinical observations. Consistent diagnosis of intrapartum asphyxia in the preterm fetus requires routine umbilical cord blood gas and acid-base assessment at delivery.

Asphyxia Neonatorum↗

PubMed1990

The association of intrapartum asphyxia in the mature fetus with newborn behavior.

A matched cohort study of mature newborns with biochemically determined intrapartum fetal asphyxia and mature newborns with normal blood gas and acid-base assessments at delivery were studied to demonstrate the effect of fetal asphyxia on newborn behavior as expressed by the Brazelton newborn behavioral assessment scale. The newborn behavioral assessment scale was administered 3 days after delivery and again 2 weeks after delivery. The Lester newborn behavioral assessment scale summary scores for the group with asphyxia were of the same order as those in the control group. This was also true of the group of newborns with asphyxia with the more severe metabolic acidosis and those with low Apgar scores. These findings support the contention that many newborns who have undergone an intrapartum asphyxial insult will not have evidence of central nervous system injury and that the threshold of central nervous system injury is at the severe end of the spectrum of asphyxia as expressed by a metabolic acidosis.

Age Factors↗

PubMed1990

The association of fetal and newborn metabolic acidosis with severe periventricular leukomalacia in the preterm newborn.

One hundred twenty preterm newborns less than 34 weeks' gestational age have been studied prospectively to determine the frequency of fetal and newborn metabolic acidosis and to examine the relationship of metabolic acidosis to periventricular leukomalacia as demonstrated by serial newborn ultrasonographic examinations. Fetal metabolic acidosis, based on an umbilical artery buffer base less than 34 mmol/L at delivery, occurred in three cases (2%), one of which had evidence of periventricular leukomalacia. Newborn metabolic acidosis that is based on a buffer base less than 34 mmol/L during the 4 days after delivery occurred in 12 cases (10%), five of which had evidence of periventricular leukomalacia. There is a significant relationship between the degree and duration of newborn metabolic acidosis and the occurrence of periventricular leukomalacia. This study indicates that systemic metabolic acidosis is an important pathophysiologic marker of periventricular leukomalacia. Intrapartum fetal asphyxia with metabolic acidosis, although an infrequent occurrence in the preterm newborn, may account for a few cases of periventricular leukomalacia, while the more common newborn metabolic acidosis, when of sufficient degree and duration, carries a high risk of periventricular leukomalacia.

Acidosis↗

PubMed1990

Maturation of responses elicited by a vibroacoustic stimulus in a group of high-risk fetuses.

The study was designed to characterize the changes in fetal heart rate (FHR) and movement responses in a group of high-risk fetuses to address the question of differential responding as a function of risk status. The study included 36 women admitted to hospital with threatened preterm labour (e.g., contractions, bleeding, premature rupture of membranes) with singleton pregnancies between 23 and 34:6 weeks gestational age. Each fetus received three vibration and three no-stimulus control trials, intermixed and randomly presented. Vibration trials consisted of a 2.5-second (s) application of the tip of a battery-powered, hand-held commercial vibrator to the maternal abdomen over the site of the fetal head while the FHR was recorded continuously and movements were scored from a cross section of the infant's abdomen viewed with a real-time ultrasound scanner. FHR within 20 s and movements within 5 s of trial onset were scored blind as to vibration or control trial. Repeated measures ANOVA demonstrated that fetuses responded to vibration with FHR accelerations from 29 weeks and movements from 26 weeks. Although movements increased with increasing gestational age, the mean peak FHR acceleration showed no significant increase from 29 to 32 weeks. From 29 weeks, the latency to response was 5 s and the peak of the acceleration occurred at about 10 to 12 s. At 26-28 weeks, a small but reliable cardiac deceleration occurred at about 5 s after stimulus onset. These preliminary findings suggest a maturation of fetal sensitivity to vibroacoustic stimulation which is similar for groups of low-risk and high-risk fetuses. However, the variability in outcome--from preterm newborn death to "healthy" term delivery--in the high-risk group suggests that the sample may be heterogeneous.

Acoustic Stimulation↗

PubMed1989

Temporal relationships of neuropathologic conditions caused by perinatal asphyxia.

The neuropathologic conditions in 120 perinatal deaths attributed to fetal or newborn asphyxia were examined. Central nervous system necrosis was present in 16 of these deaths. The approximate time of asphyxial insult was established by determining the duration of the process, based on the findings of neuronal necrosis, macrophage response, or an astrocyte response, in conjunction with clinical data. The time of the asphyxial insult for the 16 perinatal deaths was as follows: antepartum fetal asphyxia, two cases; antepartum-intrapartum fetal asphyxia, five cases; intrapartum fetal asphyxia, four cases; and neonatal asphyxia, five cases. These observations indicate that an asphyxial insult may occur in the antepartum period, in the prodromal period of preterm labor, in the intrapartum period, and in the neonatal period. Five to ten percent of the asphyxial insults in each reproductive time period were initially sublethal, allowing necrosis of the brain of the fetus or newborn to develop.

Asphyxia Neonatorum↗

PubMed1989

Human fetal responses to sound as a function of stimulus intensity.

The effect of stimulus intensity on fetal heart rate (FHR) acceleration and body movement responses was evaluated in term fetuses in a two-stage study. During the first stage (N = 30), a pink noise played at 110 or 105 dB elicited a greater mean peak FHR acceleration than when played at 100 dB. Movement scores indicated that the 110-dB noise elicited more movements than the 105-dB noise which, in turn, elicited more than the 100-dB noise. The FHR acceleration and movement responses elicited on 100-dB sound trials could not be differentiated from spontaneous activity on no-sound control trials. During the second stage (N = 93), the 110-dB pink noise elicited a mean peak FHR acceleration of 14 beats per minute on the first stimulus presentation, replicating the findings of the first stage. Furthermore, the percentage of 110-dB stimulus/control trials in which there was an FHR acceleration greater than ten beats per minute (stage 1: 57%/10%; stage 2: 58%/24%) and movement response (stage 1: 50%/7%; stage 2: 52%/7%) was virtually identical in the two stages. We conclude that fetal response varies as a function of stimulus intensity and that the threshold for response to an air-borne pink noise is between 100-105 dB. These findings have implications for stimulus selection and control procedures in acoustic stimulation testing.

Acoustic Stimulation↗

PubMed1989

The unstable urethra in the female.

The clinical and urodynamic characteristics of 54 women with unstable urethras (falls of urethral pressures of at least 20 cm H2O) were compared with those of 171 patients with stable urethras. The unstable-urethra patients were younger and presented with an increased incidence of marked urgency and a lower incidence of genuine stress incontinence. The average urethral pressure fall was preceded by a 6-cm increase in maximum urethral pressure. The mean (+/- SD) fall of urethral pressure was 30 +/- 12 cm H2O and the average duration of the event was 8 seconds. The level of the urethral pressure fall was not influenced by bladder volume but correlated positively with higher maximum urethral pressures. The present findings suggest that the unstable urethra plays a limited role in genuine stress incontinence but may be linked with the unstable detrusor.

Adult↗