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Biomedical subjects

G Greisen

Publications and source records attributed to G Greisen.

At least 91 records · Page 5Linked to original sources
PubMed1990

Vasoparalysis associated with brain damage in asphyxiated term infants.

The relationship of cerebral blood flow to acute changes in arterial carbon dioxide and mean arterial blood pressure (MABP) was determined during the first day of life in 19 severely asphyxiated term infants supported by mechanical ventilation. For comparison, 12 infants without perinatal asphyxia were also investigated. Global cerebral blood flow (CBF infinity) was determined by xenon 133 clearance two or three times within approximately 2 hours. During the cerebral blood flow measurement, the amplitude-integrated electroencephalogram and visual-evoked potential were recorded. Changes in arterial carbon dioxide pressure followed adjustments of the ventilator settings, whereas MABP fluctuated spontaneously. Arterial oxygen pressure and blood glucose concentration were in the normal range. Five of the asphyxiated infants had isoelectric electroencephalograms and died subsequently with severe brain damage. They had a high CBF infinity (mean 30.6 ml/100 gm/min) and abolished carbon dioxide and MABP reactivity. Lower CBF infinity (mean 14.7 ml/100 gm/min) and abolished MABP reactivity were found in another five asphyxiated infants with burst-suppression electroencephalograms in whom computed tomographic or clinical signs of brain lesions developed. The carbon dioxide reactivity was preserved in these infants. In the remaining nine asphyxiated infants without signs of central nervous system abnormality, carbon dioxide and MABP reactivity were preserved, as was also the case in the control group. We conclude that abolished autoregulation is associated with cerebral damage in asphyxiated infants and that the combination of isoelectric electroencephalograms and cerebral hyperperfusion is an early indicator of very severe brain damage.

Asphyxia Neonatorum↗
PubMed1990

Redistribution of cerebral activity during childhood.

Data on the functional development of brain structures in early childhood are scarce. Cognition changes markedly from pre-school age to school age, and we thought it of interest to examine the level of functional activity of selected brain regions. Nine preschool children were studied and compared with eight school children and eighteen adults. Xe133 emission tomography was used for determination of regional cerebral blood flow (rCBF). It was demonstrated that activity in the striatal regions is low in early childhood. In school age the proportion of flow to these regions is increased by about 11-14 per cent (difference between medians). Perfusion of the occipital lobes decreased with age when studied with open eyes and closed eyes, possibly reflecting loss of synapses and decreased plasticity.

Adolescent↗
PubMed1990

Carbon dioxide-related changes in cerebral blood volume and cerebral blood flow in mechanically ventilated preterm neonates: comparison of near infrared spectrophotometry and 133Xenon clearance.

Carbon dioxide-induced changes in near infrared spectrophotometry recordings were compared with changes in cerebral blood flow estimated by 133Xenon clearance (global cerebral blood flow (infinity)) at serial measurements in 24 mechanically ventilated preterm infants (mean gestational age 30.2 wk). In all infants, three measurements were taken at different arterial carbon dioxide tension levels (mean 4.4 kPa, range 2.1-7.8) obtained by adjustment of the ventilator settings. Mean arterial blood pressure changed spontaneously, whereas arterial oxygen tension was kept within normal range. At all wavelengths (904, 845, 805, and 775 nm), the OD increased at higher arterial carbon dioxide tension levels, indicating cerebral vasodilation. This conclusion was supported by conversion of the data to changes in oxygenated and deoxygenated Hb concentration. A parallel increase in cerebral blood volume index and global cerebral blood flow (infinity) was found (p less than 0.0001). The oxygenation level of cytochrome aa3 increased with increases in oxygen delivery (p less than 0.0001). This observation, however, may have been artifactual due to cross-talk between the oxidized cytochrome aa3 and the oxygenated Hb signals, as these signals were closely interrelated in the present experimental design. We suggest that near infrared spectrophotometry may be used for estimation of the cerebral blood volume index/cerebral blood flow-CO2 reactivity within a wide range of arterial carbon dioxide tension. Knowledge of the light path length would put this estimation on a quantitative basis.

Birth Weight↗
PubMed1990

Status at four years of age in 280 children weighing 2,300 g or less at birth.

To assess the functional ability in low birth weight children at age 4-5, 114 survivors with very low birth weight (VLBW) less than or equal to 1,500 g, 166 survivors with birth weight 1,501-2,300g (LBW), and 115 comparison children with normal birth weight (NBW) were enrolled in a follow-up study. Twenty-four (21%) VLBW and 11 (6.6%) LBW-children had major clinical abnormalities compared to 1 (0.9%) of the NBW children. Twenty-two percent of the VLBW-children were below the 3rd-centile for height and weight. Fewer VLBW than LBW-children were neurologically and ophthalmologically normal. Even after exclusion of the handicapped children, the LBW as well as the VLBW children scored significantly lower than the NBW children in the McCarthy Scales of Children's Abilities, most markedly in the motor and perceptual performance scales. A simple test using grooved pegs clearly demonstrated the poor visual-motor integration in VLBW and LBW children. A marked difference between the NBW and the two LBW groups was seen in a qualitative evaluation of motor performance. Only 5% of VLBW children scored at or above the median for the NBW in all of three fields: general cognitive, motor performance, and pegboard, as opposed to 11% of LBW and 18% of NBW children. Neither sex, age corrected for prematurity, nor psycho-social background factors explained the differences between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Child, Preschool↗
PubMed1989

[Perinatal growth. A practical perinatal growth curve].

A linear perinatal growth curve, covering the period from 28 weeks gestation to 18 weeks after term birth is presented. The curve was first presented 15 years ago, and is now supported by Danish data, both cross-sectional and longitudinal. It may be used for classification of birth weight in relation to gestational age and at the same time for monitoring of postnatal growth, regardless of gestational age at birth. Limitations of empirical curves are pointed out. The postnatal growth potential of preterm infants is stressed.

Denmark↗
PubMed1989

[Choice of treatment in very premature deliveries. A nation-wide questionnaire study].

The principles for treatment of very premature deliveries in obstetric, surgical and paediatric departments were investigated by means of a questionnaire. This contained fictitious case histories about transfer in cases of threatened delivery, caesarean section in cases of interuterine asphyxia, resuscitation after delivery, transfer to a paediatric department and employment of respirators in cases of increasing respiratory difficulty following deliveries after 24, 26 and 28 full weeks of pregnancy. Replies were obtained from 26 out of 29 maternity departments, 28 out of 33 surgical departments with more than 100 deliveries in 1985, and 18 out of 18 paediatric departments. In all of the situations, considerable restraint was expressed as regard the most premature deliveries. For example, only two obstetric departments, two surgical and four paediatric departments stated that they would, as a rule, attempt resuscitation after deliveries at gestational ages of 24 weeks. For deliveries at 26 weeks, the figures were 18, 12 and 12, respectively. A certain tendency was observed for less restraint in 1985 as compared with 1979. Tendencies to centralize the very premature deliveries were greater in East Denmark than in West Denmark where respirator treatment was more frequently employed for the smallest infants.

Denmark↗
PubMed1989

Heterogeneity of cerebral vasoreactivity in preterm infants supported by mechanical ventilation.

The reaction of cerebral blood flow to acute changes in arterial carbon dioxide pressure (PaCO2) and mean arterial blood pressure was determined in 57 preterm infants supported by mechanical ventilation (mean gestational age 30.1 weeks) during the first 48 hours of life. All infants had normal brain sonograms at the time of the investigation. In each infant, global cerebral blood flow was determined by xenon-133 clearance two to five times within a few hours at different levels of PaCO2. Changes in PaCO2 followed adjustments of the ventilator settings. Arterial oxygen pressure was intended to be kept constant, and mean arterial blood pressure fluctuated spontaneously between measurements. The data were analyzed by stepwise multiple regression, with changes in global cerebral blood flow, PaCO2, mean arterial blood pressure, and postnatal age or intracranial hemorrhage used as variables. In infants with persistently normal brain sonograms, the global cerebral blood flow-carbon dioxide reactivity was markedly lower during the first day of life (mean 11.2% to 11.8%/kPa PaCO2) compared with the second day of life (mean 32.6/kPa PaCO2), and pressure-flow autoregulation was preserved. Similarly, global cerebral blood flow-carbon dioxide reactivity and pressure-flow autoregulation were present in infants in whom mild intracranial hemorrhage developed after the study. In contrast, global cerebral blood flow reactivity to changes in PaCO2 and mean arterial blood pressure was absent in infants in whom ultrasonographic signs of severe intracranial hemorrhage subsequently developed. These infants also had about 20% lower global cerebral blood flow before hemorrhage, in comparison with infants whose sonograms were normal, a finding that suggests functional disturbances of cerebral blood flow regulation. Several perinatal factors were tested, but only birth after abruptio placentae was related to subsequent periventricular hemorrhage (p = 0.037).

Age Factors↗
PubMed1989

Low CBF, discontinuous EEG activity, and periventricular brain injury in ill, preterm neonates.

Cerebral blood flow was measured by intravenous 133Xe clearance one to four times during the first 48 h of life in 20 infants, born after 27 to 33 weeks of gestation, who were under mechanical ventilation and being monitored by amplitude integrated EEG, resulting in 36 sets of simultaneous CBF and EEG measurements. Mean CBF infinity, a measure of global flow to white as well as grey matter, was 10.0 ml/100 g/min +/- 3.5 SD. Definite EEG activity was seen with CBF infinity values as low as 5 ml/100 g/min. CBF infinity was related to the level of EEG activity, discontinuous EEG activity being associated with low CBF infinity (p = 0.014). It was not possible to determine if this relation indicated the presence of marginal ischaemia or primary inhibition of electrical activity resulting in decreased CBF, two infants developing periventricular leucomalacia, however, and one who developed intraparenchymatous hemorrhage were among the seven with CBF infinity values of less than or equal to 8 ml/100 g/min (p = 0.031). This suggests that ischaemia of periventricular white matter may have been present concurrently with cortical electrical activity.

Brain Diseases↗
PubMed1989

Effect of PaCO2 and haemoglobin concentration on day to day variation of CBF in preterm neonates.

The CBF was measured on the first three days of life in 22 mechanically ventilated, preterm neonates (mean gestational age 29.5 weeks) with simultaneous recordings of arterial carbon dioxide tension (PaCO2), arterial oxygen tension (PaO2), haemoglobin concentration (Hgb), haemoglobin oxygen saturation and mean arterial blood pressure (MABP). CBF infinity tended to increase slightly with age. The intra-individual variation of CBF infinity was positively related to changes in PaCO2 (p = 0.0004) and inversely related to changes in Hgb (p = 0.029). Neither PaO2 nor MABP achieved a significant relation to changes in CBF infinity. Thus, the mean CBF infinity -CO2 reactivity was calculated to 22.1% per kPa whereas CBF infinity increased by a mean of 11.9% per mM decrease of Hgb thereby providing a constant oxygen delivery to the brain. It is concluded that PaCO2 and Hgb have the expected effect on CBF infinity in preterm neonates even during respiratory distress shortly after birth.

Age Factors↗
PubMed1989

Perinatal growth retardation in preterm infants.

Perinatal and 4-year follow-up data were analysed for 137 children born after 26 to 35 weeks of gestation. All were free of severe prenatal or neonatal illness and of major handicaps. Infants who were light-for-gestation at birth were approximately 0.6 SDS smaller at 4 years than the appropriate-for-gestation infants as regards height, weight, and head circumference (p less than 0.005). The McCarthy general cognitive score was reduced (p = 0.03). Motor scores, standardised for cognitive function, were also reduced (p = 0.02) indicating that motor--perhaps cerebellar--function is particularly vulnerable to perinatal growth retardation.

Birth Weight↗
PubMed1989

Fetal abdominal circumference rather than fetal femur length/abdominal circumference ratio predicts fetal malnutrition in high risk pregnancies.

The aim of this study was to compare the ability of abdominal circumference (AC) and fetal femur length/abdominal circumference ratio (FFL/AC) measured by ultrasound within a period of 2 weeks before birth to predict low birth weight percentile and neonatal signs related to fetal malnutrition. From longitudinal ultrasound measurements in 35 normal pregnancies reference data of AC and FFL was obtained. FFL/AC ratio was constant from 21 weeks until term (mean 20.9, SD 1.2) (figure 1). In 350 risk pregnancies AC standard deviation score (AC-SDS) correlated far better than FFL/AC ratio with the deviation of birth weight from normal (figure 3). Furthermore AC-SDS correlated better with ponderal index (PI) and skinfold thickness (ST) than did FFL/AC ratio. Using cut-off levels on AC-SDS and FFL/AC ratio, which selected about 30% of the population, the sensitivity of AC-SDS in predicting the infant being LGA was 81.8% versus 42.9% using FFL/AC ratio (table II). The prediction of the infant being SGA was not improved when the change in AC-SDS or FFL/AC over the last 6-8 weeks of pregnancy was considered. We conclude that AC-SDS correlates well with birth weight deviation and predicts the infant being SGA with a precision equal to the best results reported in the literature, and that FFL/AC ratio is unreliable even when GA is not known because of a high false positive rate.

Abdomen↗
PubMed1988

Early growth delay in diabetic pregnancy: relation to psychomotor development at age 4.

Ninety nine consecutive insulin dependent and 101 non-diabetic pregnant women were examined by ultrasonograph to assess early fetal growth. In 42 of the diabetic mothers and three of the non-diabetic mothers the scan showed early intrauterine growth delay. At 4-5 years of age all children available for study were evaluated by the Denver developmental screening test. Only 23 of the 34 children of diabetic mothers with early intrauterine growth delay had normal test scores compared with 46 of the 50 children of diabetic mothers with normal intrauterine growth. The children failed in personal-social development, gross motor development, and particularly in language and speech development. Children of diabetic mothers with normal early fetal growth had scores very similar to those of the children of non-diabetic mothers, of whom 76 of the 86 tested had normal scores. This study suggests that children with a history of growth delay in early diabetic pregnancy should be screened for possible developmental impairment.

Adult↗
PubMed1988

Indomethacin and cerebral blood flow in premature infants treated for patent ductus arteriosus.

Central blood flow (CBF) was estimated by an intravenous 133-xenon technique in six preterm infants before and after administration of indomethacin for closure of patent ductus arteriosus. CBF fell in all infants (range 12%-40%), the mean fall was 24% (P less than 0.005). Though none of the infants showed signs of impaired cerebral function during or following the injections, the results do not indicate whether or not the use of indomethacin is a potential hazard.

Cerebrovascular Circulation↗
PubMed1988

Intravenous 133Xe clearance in preterm neonates with respiratory distress. Internal validation of CBF infinity as a measure of global cerebral blood flow.

An intravenous 133Xe clearance technique is described, giving very low values of global cerebral blood flow (CBF infinity) in mechanically ventilated, preterm infants. External monitoring of the chest is used to estimate the arterial input function to the brain, with a modified correction to allow for increased recirculation due to right-to-left shunting. The results compared well in 10 studies in seven infants, where CBF infinity could also be calculated from direct simultaneous blood sampling from the right radial artery (7.9 ml/100 g/min +/- 2.5 SD vs. 8.4 +/- 3.6, p less than 0.05). In 25 studies in 12 infants the results compared well with those calculated from simultaneous 133Xe concentrations in expired air. Fifteen-minute clearance data gave better precision than 8-min data. The modified chest curve correction was partly effective in a case of extreme right-to-left shunting.

Cerebrovascular Circulation↗
PubMed1988

Compensatory increase of CBF in preterm infants during hypoglycaemia.

Cerebral blood flow (CBF00) was investigated in 24 preterm infants (mean 30.8 weeks of gestational age) by use of intravenous 133-Xe clearance technique while screening simultaneously for low blood glucose after birth (mean 3 hours). CBF was significantly increased in 10 infants with blood glucose lower than 1.7 mmol/l compared to normoglycaemic infants and tended to decrease rapidly after treatment. Nine of the 10 hypoglycaemic infants were monitored for cerebral function. Well defined visual evoked cortical potentials were elicitable in all and the aEEG was not less active during the hypoglycaemic episode. Therefore, it is suggested that compensatory increase of CBF may have supported the cerebral metabolism during uncomplicated hypoglycaemia.

Blood Gas Monitoring, Transcutaneous↗
PubMed1988

Poor reversibility of EEG abnormality in hypotensive, preterm neonates.

Twenty-four infants, 32 weeks of gestation or less, were studied with continuous recording of amplitude integrated electroencephalogram (aEEG) and repeated Doppler ultrasound determination of the mean blood flow velocity in the internal carotid artery (cMFV). The recording was started after the initiation of mechanical ventilation for respiratory distress. Of twelve infants receiving blood or albumin transfusion to expand the intravascular volume and in whom adequate data were available, both mean arterial blood pressure and cMFV increased in eight, and cMFV but not blood pressure in further two. In the present circumstances we consider the cMFV increases to represent true increases in cerebral blood flow. aEEG burst rate increased distinctly in five of the twelve infants during or immediately following transfusion, but did only approach the level of the four non-transfused infants after several hours, indicating a dysfunction of neural tissue not readily reversible by improved blood flow.

Blood Flow Velocity↗