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Biomedical subjects

G Greisen

Publications and source records attributed to G Greisen.

At least 55 records · Page 3Linked to original sources
PubMed1997

Cerebral blood flow and energy metabolism in the newborn.

In normal newborn term and preterm infants CBF is relatively low corresponding to a low metabolic rate for oxygen, whereas cross-brain oxygen extraction is similar to that in adults. This provides for a considerable reserve capacity to deal with decreased CBF or decreased oxygen content in arterial blood. CBF reactivity to CO2 is normal, and the evidence is that pressure-flow autoregulation is present, even in very preterm infants. Absence of autoregulation and CBF-CO2 reactivity has been documented in severely asphyxiated infants, and in preterm infants who went on the develop severe intracranial hemorrhage. A number of methods are available to study CBF and brain metabolism in newborn infants. Several of them involve ionizing radiation, which has limited their use, even though it is unlikely that the associated risks are particularly high. Magnetic resonance spectroscopy has demonstrated a delayed disturbance of energy metabolism following severe asphyxia. Doppler ultrasound has rarely been helpful to obtain quantitative data. Near infrared spectrocopy has now been in use for more than 10 years. It has been slow to fulfill its promise as a continuous monitor of cerebral circulation and of oxygen sufficiency of neurons.

Asphyxia Neonatorum↗
PubMed1996

[Oxygen during delivery and cerebral vasoconstriction in preterm infants].

To determine if the use of oxygen in the delivery room influences subsequent global cerebral blood flow (CBF), 70 infants of gestational age of less than 33 completed weeks were randomly assigned to receive room air (group I) or 80% oxygen (group II) during the initial stabilisation at birth. In group I supplemental oxygen was administered on clinical indications, when required. After being admitted to the neonatal intensive care unit all infants were treated according to our normal practice. At a postnatal age of two hours CBF was measured by xenon clearance. Seventy four per cent of the infants in group I were successfully established without the need for supplemental oxygen. CBF was significantly higher in group I than in group II (CBF median (interquartile range): 15.9 (13.6-21.9) vs 12.2 (10.7-13.8) ml/100 g/minute). Differences in oxygen exposure seemed to be the only explanation for the differences in CBF. No differences in short term outcome were found between the groups.

Cerebrovascular Circulation↗
PubMed1996

Optimising the methodology of calculating the cerebral blood flow of newborn infants from near infra-red spectrophotometry data.

Cerebral blood flow can be measured in neonates by near infra-red spectrophotometry. The tracer is oxyhaemoglobin. The purpose of the study is to compare the test-retest variability of two previously proposed methods (UCH and COP) of analysis, and to investigate the influence of sampling rates, smoothing and integration periods. Under clinical conditions good measurements are often difficult to obtain. Therefore, a second goal is to find ways of determining the quality of individual measurements. 380 cerebral blood flow measurements from 69 infants are analysed. The data set is optimised statistically for the lowest test-retest variability and the following results are obtained. The test-retest variability of measurements at 2 s sampling time data is considerably worse than at 0.5 s sampling time. Smoothing does not change the test retest variability. A 6 s integration period gives higher values and higher test-retest variability than an 8 s integration period. By applying the suggested criteria, a test-retest variability of 17% is achieved, if 50% of the measurements are rejected. The mean cerebral blood flow is 12.2 ml (100 g)-1 min-1 for the UCH method and 9.7 ml [corrected] (100 g)-1 min-1 for the COP method. The test-retest variability of both methods is comparable for 0.5 s sampling time. For 2 s sampling time the method proposed by Skov et al. is significantly better. These test retest variabilities represent maximum values, part of the observed variability may be due to physiological changes of unknown magnitude.

Cerebrovascular Circulation↗
PubMed1996

Growth hormone, insulin-like growth factor I and its binding proteins 1 and 3 in last trimester intrauterine growth retardation with increased pulsatility index in the umbilical artery.

OBJECTIVE: The interrelationships between maternal hormone levels and placental dysfunction in mothers bearing children with intrauterine growth retardation remain unclear. We have examined some endocrinological aspects of intrauterine growth retardation and, in particular, tested whether low levels of GH and IGF-I in maternal serum are associated with direct evidence of placental dysfunction. DESIGN: Prospective, descriptive and comparative. PATIENTS: Women with singleton pregnancies: 48 with a small for gestation fetus (SGA) (estimated fetal weight less than -1.5 standard deviation scores) and 28 with an appropriate for gestation fetus (AGA). MEASUREMENTS: Maternal serum GH, IGF-I, IGFBP-1 and 3 were determined, and fetal weight and umbilical artery pulsatility index (PI) was estimated by ultrasonography and Doppler ultrasound at 33 weeks gestational age. RESULTS: Serum IGF-I was lower in the SGA group (246 vs 297 micrograms/l, P = 0.03) but GH and IGFBP-1 and -3 did not differ between the groups. In the 16 SGA pregnancies with increased PI, IGF-I concentration was low (218 micrograms/l, quartiles 149-265), whereas in the 32 with normal PI, IGF-I was 269 micrograms/l, quartiles 219-382. Serum IGFBP-1 was increased in the high PI group compared to the normal PI group (161 micrograms/l vs 113, P = 0.05). CONCLUSION: Maternal serum IGF-I concentration was lower in small for gestational age pregnancies with increased pulsatility of the umbilical artery blood flow, compared to small for gestational age pregnancies with normal umbilical blood flow, which in turn was close to the IGF-I concentration in appropriate for gestational age pregnancies. Growth hormone concentrations did not differ among the groups.

Female↗
PubMed1996

Changes in EEG, systemic circulation and blood gas parameters following two or six aliquots of porcine surfactant.

Surfactant instillation often causes transient EEG suppression, the cause remaining unknown. To compare the timing of the EEG changes with the timing of the changes in blood gases and systemic circulation we compared two administration modes: 20 preterm infants were randomly assigned to receive the initial dose of surfactant divided into two or six aliquots. Heart rate, blood pressure and transcutaneous blood gases were measured continuously, while left ventricular output was estimated intermittently. No difference in blood gas response was found between the groups, whereas the circulatory changes occurred more gradually with six aliquots. EEG suppression was similar in the two groups and not related to the circulatory or the respiratory changes. Left ventricular output increased in all patients following surfactant instillation. We conclude that the EEG suppression is not directly related to alterations in blood gases or systemic circulation.

Analysis of Variance↗
PubMed1996

Analysis of the risk of brain damage in asphyxiated infants.

The objectives of this study were to analyze the influence of maternal, perinatal and neonatal factors on the neurological sequelae occurring in asphyxiated infants. The clinical records of 79 infants, 35 weeks of gestation or more, treated in the neonatal intensive care unit in whom the principal diagnosis was asphyxia, and who had no major malformation and who survived for more than 24 hours, were analyzed. Analysis of variance was used to compare neurological outcome classified as 1) normal development or mild neurological sequelae, 2) moderate to severe neurological sequelae, and 3) withdrawal of treatment because of signs and symptoms of severe brain damage. The group in whom treatment was withdrawn had lower mean arterial blood pressure on admission, blood glucose and plasma sodium levels than those in the moderate to severe handicap group. The combined group of brain damaged infants, (2 + 3), had lower Apgar scores at five minutes, umbilical cord arterial blood Standardized Base Excess (SBE), lower urinary output, and higher incidence of seizures and higher plasma potassium level than the group with normal development or those with mild handicap. Stepwise multiple logistic regression confirmed these.

Apgar Score↗
PubMed1995

Prediction of birth weight by ultrasound-estimated fetal weight: a comparison between single and repeated estimates.

OBJECTIVES: Ultrasound estimation of fetal weight is used for diagnosing intrauterine growth retardation. The aim of the present study was to assess the accuracy of birth weight prediction by use of a single or repeated estimations of fetal weight in the third trimester. STUDY DESIGN: 1000 pregnant women considered at risk were scheduled to ultrasound estimation of fetal weight, using Warsof's formula, at 28, 31, 34 and 37 weeks of gestation. The 421 pregnancies with term delivery and complete set of ultrasound examinations and 57 pregnancies with preterm delivery with ultrasound examination at 16 and 28 weeks and once more before delivery were included in the present analysis. RESULTS: The accuracy of birth weight prediction improved significantly for every three weeks from 28 to 37 weeks of gestation in the term infants. Prediction based on the average of repeated weight estimates or linear extrapolation from two estimates or extrapolation by a second order polynomium fitted to four estimates did not improve accuracy compared to prediction based on the last estimate before delivery. CONCLUSION: When more than one ultrasound estimation of fetal weight are available, prediction of birth weight in relation to gestational age should be based on the last ultrasound examination only.

Birth Weight↗
PubMed1995

Cerebral blood flow and left ventricular output in spontaneously breathing, newborn preterm infants treated with caffeine or aminophylline.

Aminophylline and caffeine are commonly used for prophylaxis of apnea in premature infants. Previous studies have indicated different effects of the drugs on cerebral circulation. Therefore, we have compared the acute effects of bolus administration of caffeine citrate or aminophylline on left ventricular output, heart rate, blood pressure and global cerebral blood flow. The study group consisted of 33 newborn, spontaneously breathing, preterm infants randomly assigned to receive either aminophylline 5 mg/kg (n = 19) or caffeine citrate 20 mg/kg (n = 14). Two hours after iv drug administration, global cerebral blood flow measured by the Xe-clearance technique was significantly lower after aminophylline than after caffeine (mean (SD)): 13.2 (+2.9/-2.3) versus 17.2 (+7.1/-5.1) ml/100 g/min) (p = 0.01). There were no other statistically significant differences in circulatory or ventilatory parameters between the groups. Further studies are needed to clarify the clinical relevance of these results.

Aminophylline↗
PubMed1995

Quality of life among young adults born with very low birthweights.

Quality of life (QoL) was assessed in 85 young adults, born in 1971-1974 with birthweights < 1500 g (VLBW) and admitted to the neonatal intensive care unit of the State University Hospital in Copenhagen, Denmark. Their QoL was compared to that of 85 subjects with birthweights > 2500 g (NBW) born in the same period at the State University Hospital. The subjects were interviewed by telephone on the basis of the well-defined theories on QoL by Anton Aggernaes. Quality of life was assessed both in objective terms and as judged by the interviewed person. Subjects born with VLBWs and free of handicaps had QoL scores (both objective and subjective) fully comparable with the NBW group. VLBW subjects reporting various physical and mental handicaps had objective as well as subjective QoL scores significantly lower than the NBW group.

Activities of Daily Living↗
PubMed1995

Oxygen at birth and prolonged cerebral vasoconstriction in preterm infants.

To determine if the use of oxygen in the delivery room influences subsequent global cerebral blood flow (CBF), 70 infants of gestational age of less than 33 completed weeks were randomly assigned to receive room air (group I) or 80% oxygen (group II) during the initial stabilisation at birth. In group I supplemental oxygen was administered on clinical indications, when required. After being admitted to the neonatal intensive care unit all infants were treated according to our normal practice. At a postnatal age of 2 hours CBF was measured by xenon clearance. Seventy four per cent of the infants in group I were successfully stabilised without the need for supplemental oxygen. CBF was significantly higher in group I than in group II (CBF median (interquartile range): 15.9 (13.6-21.9) v 12.2 (10.7-13.8) ml/100 g/minute). Differences in oxygen exposure seemed to be the only explanation for the differences in CBF. No differences in short term outcome were found between the groups.

Blood Flow Velocity↗
PubMed1994

Surfactant therapy and nasal continuous positive airway pressure for newborns with respiratory distress syndrome. Danish-Swedish Multicenter Study Group.

BACKGROUND: In southern Scandinavia most babies with respiratory distress syndrome are initially treated with nasal continuous positive airway pressure. We performed a multicenter trial to investigate whether the addition of a single dose of porcine surfactant administered during a short intubation before the occurrence of serious deterioration could reduce the subsequent need for mechanical ventilation. METHODS: We randomly assigned 35 infants with moderate-to-severe respiratory distress syndrome to surfactant therapy (Curosurf, 200 mg per kilogram of body weight) plus nasal continuous positive airway pressure and 33 infants to nasal continuous positive airway pressure alone. The study was not blinded. The indications for mechanical ventilation were a ratio of arterial to alveolar oxygen tension of less than 0.15, severe apneic attacks, or both. RESULTS: Six hours after randomization, when the median age of the babies was 18 hours, the mean ratio of arterial to alveolar oxygen tension was 0.37 in the surfactant-treated babies, as compared with 0.25 in the controls (P < 0.001). The need for subsequent mechanical ventilation was reduced with surfactant therapy (to 43 percent of the surfactant-treated babies as compared with 85 percent of the controls; P = 0.003). When 17 infants with ratios of arterial-to-alveolar oxygen tension of less than 0.15 at randomization were excluded, the need for mechanical ventilation was still significantly reduced in the surfactant-treated group (to 33 percent [9 of 27 babies], as compared with 83 percent [20 of 24 babies] in the control group; (P < 0.001). After 28 days, two of the surfactant-treated babies had died, as compared with five of the control babies. CONCLUSIONS: In babies with moderate-to-severe respiratory distress syndrome treated with nasal continuous positive airway pressure, a single dose of surfactant reduced the need for subsequent mechanical ventilation.

Biological Products↗
PubMed1994

Apparent cerebral cytochrome aa3 reduction during cardiopulmonary bypass in hypoxaemic children with congenital heart disease. A critical analysis of in vivo near-infrared spectrophotometric data.

The purpose of this analysis was critically to examine the changes of cerebral cytochrome oxidase as detected by near-infrared spectrophotometry (NIRS) during induction of cardiopulmonary bypass (CPB) in fourteen children undergoing open heart surgery. Five children were hypoxaemic (arterial oxygen saturation 49%-84%) before the switch to CPB and nine children were not. In the hypoxaemic children, the total cerebral hemoglobin concentration [tHb] decreased rapidly and markedly, reaching a plateau after 2 min. Surprisingly, cytochrome aa3 concentration in its oxygenated form [CytO2] decreased in parallel while the cerebral haemoglobin oxygenation index [HbO2]-[Hb] increased gradually. In the eight normoxaemic children, changes in the NIRS signals were insignificant. When a standard NIRS algorithm was used, the magnitude of the change in [CytO2] was closely associated with the magnitude of the change in [tHb] (p < 0.0001), the time courses of the [CytO2] and [tHb] signals were parallel in 11 of the 14 children and the error of fit in the NIRS multicomponent analysis increased 10- to 100-fold over system noise. A new NIRS algorithm, using wavelength specific optical pathlengths, did not improve the error of fit but produced smaller estimates of [CytO2] changes, which were unrelated to the [tHb] changes. In our opinion the interesting possibility of monitoring cytochrome oxidation by NIRS requires further validation.

Algorithms↗
PubMed1994

Cerebral blood flow and plasma hypoxanthine in relation to surfactant treatment.

We have previously reported reduction in EEG activity in preterm babies after tracheal instillation of Curosurf. To elucidate the cause of EEG depression, we have examined cerebral blood flow (CFB), amplitude-integrated EEG (aEEG), mean arterial blood pressure (MABP) and plasma hypoxanthine (Hx) concentration in a group of preterm babies before and immediately after administration of surfactant. No change occurred in CBF immediately after surfactant treatment despite a significant decrease in MABP. At 60 min after surfactant administration, a significant reduction in CBF occurred (p < 0.05). However, when CBF values were corrected for changes in PaCO2, no reduction in CBF was observed. Mean plasma Hx concentration was 11.6 (SD 7.3) mumol/l before surfactant therapy, which decreased significantly to 8.1 (5.8) mumol/l (p < 0.05) 15-30 min after treatment. No correlations were found between plasma Hx concentration and FiO2, a/A pO2, PaCO2, SaO2, arterial blood pressure, CBF or the degree of EEG depression. This study indicates that EEG depression observed after surfactant instillation is not caused by cerebral ischemia.

Biological Products↗
PubMed1994

Cerebrovascular responses to carbon dioxide as detected by near-infrared spectrophotometry: comparison of three different measures.

Near-infrared spectrophotometry can be used to measure cerebral concentrations of oxyhemoglobin and deoxyhemoglobin. This has been applied to developing methods for quantifying cerebral blood volume (CBV), which is relevant for the investigation of the pathogenesis of brain injury in newborn infants as well as older infants. This study investigates the internal consistency between measurements of CBV using two methods: the oxygen method, which is able to determine absolute values of CBV, and the total Hb method, which can detect changes in CBV only. Cerebral blood flow (CBF) was also measured. Fifteen premature infants were examined. Due to practical problems, in only eight of these was a minimum of two CBF and two CBV values obtained both before and after a change in arterial PCO2 of at least 0.5 kPa. A significant difference between the CBV-CO2 reactivity found by the two methods was demonstrated: 0.89 mL/100 g/kPa (95% confidence interval = 0.63-1.26) for the oxygen method and 0.22 mL/100 g/kPa (95% confidence interval = 0.08-0.36) for the total Hb method. This finding is substantiated by the absolute values of CBV [mean value = 3.7 mL/100 g (SD = 1.1)], CBF [mean value = 11.3 mL/100 g/min (SD = 5.9)], and CBF reactivity [59 +/- 9% (SEM)]. All the values correspond well with previous findings, although the CBV reactivity determined by the oxygen method has not been reported previously. The reason for the discrepancy between the two methods is unclear, but induced changes in the scattering properties of the brain would give rise to errors influencing the total Hb method rather than the oxygen method.

Blood Volume Determination↗
PubMed1994

Tape-recorded EEG and the cerebral function monitor: amplitude-integrated, time-compressed EEG.

Monitoring of spontaneous brain electrical activity (EEG) has three purposes: Detecting sudden loss of background activity as an early sign of brain hypoxia/ischaemia, detection of silent seizures, and helping to diagnose brain damage. Tape-recording allows storage of upto 8 channels of standard EEG for prolonged periods, but some direct readout is necessary for monitoring purposes and review is time consuming. The Cerebral Function Monitoring technique (CFM) provides a 1/500 time-compressed recording of EEG amplitude overall EEG background activity as well as seizures. Lack of knowledge of when and how to intervene, rather than technical problems, puts a limit to the usefulness.

Brain↗
PubMed1994

Weight, length, head circumference, and growth velocity in a longitudinal study of Danish infants.

Two longitudinal studies of infant growth, performed from 1985 to 1988 in the Copenhagen area, have been combined to develop an up-to-date growth reference. Percentile curves were constructed and median growth velocities were calculated for monthly intervals, based on individually estimated growth curves. Compared with references based on data from periods when the prevalence of breast-feeding was low, these data support previous suggestions of a new growth pattern, with higher velocities during the first months and slower velocities during the remaining infancy. The growth of breast-fed infants differs from that of infants not being breast-fed, and special growth references for breast-fed infants have been suggested. We therefore examined growth patterns in the present study according to duration of breast-feeding. At 12 months, infants breast-fed > or = 9 months weighed less (400 g (95% CI: 70 g, 740 g) and were 1.0 cm shorter (0.3 cm, 1.8 cm) than infants breast-fed < 9 months. Part of this difference was already present at six months. Despite this we recommend a single growth reference for Danish infants regardless of mode of feeding. The slower growth in infants breast-fed > or = 9 months, which could be due to differences in composition of weaning foods, should be investigated further.

Body Height↗
PubMed1993

Comparison of the effects of phenobarbitone and morphine administration on EEG activity in preterm babies.

Continuously recorded amplitude-integrated EEG (aEEG) traces of 77 preterm babies were analysed retrospectively, to study the effect of different sedative drugs over a 24-h period. Thirty-seven babies were treated with phenobarbitone, 18 received morphine and 22 babies received no regular sedation. A "burst" was defined as a discharge of integrated amplitude greater than 10 microV and maximum interburst intervals in 10-min epochs over a 2-h period were measured. Maximum interburst was prolonged in babies given either morphine or phenobarbitone for sedation. Administration of a single dose of diazepam for intubation had a marked additive effect on the EEG depression caused by the base sedative and prolonged the effect for 11 to 12 h after drug administration. We conclude that the effect of sedative drugs must therefore be accounted for when interpreting records of quantified EEG for 12 to 24 h after drug administration.

Calcium↗