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Biomedical subjects

A Hrbek

Publications and source records attributed to A Hrbek.

At least 19 recordsLinked to original sources
PubMed2002

Follow-up into young adulthood after cardiopulmonary resuscitation in term and near-term newborn infants. I. Educational achievements and social adjustment.

AIM: Long-term sequelae after perinatal asphyxia have generally been assessed at preschool or school age. The aim of the study was to confirm the hypothesis that there could be impairment of cognitive and memory functions that does not become apparent until education and adult life impose special demands. METHODS: Seventy-one term or near-term newborns in need of cardiopulmonary resuscitation because of presumed perinatal asphyxia were investigated with evoked EEG potentials during the first week of life and were investigated at a follow-up clinic until 18 mo of age. At that time 12 subjects showed signs of neuro-developmental impairment. The remaining 59 were considered healthy. They were contacted at young adult age and given a questionnaire containing questions about type of education, need for extra support at school, present activity/employment, living conditions, spare-time activities and self-estimation of health. RESULTS: Thirty-five control subjects were approached at the same time. From the group that was resuscitated at birth, 53 questionnaires were returned and 30 from the control group. Although the resuscitated subjects had signs of both encephalopathy and pathologic evoked responses during their neonatal period, the questionnaire revealed that they had coped with school equally as well as their peers, that the rate of entering university studies was the same and that living conditions were similar between the groups. CONCLUSION: These individuals who were resuscitated at birth and who demonstrated various degrees of neonatal encephalopathy suffered either brain injury that could be diagnosed at 18 mo of age or managed as well as their non-resuscitated peers in terms of educational achievement and social adjustment at young adult age.

Asphyxia Neonatorum↗
PubMed1987

Postasphyxial cerebral survival in newborn sheep after treatment with oxygen free radical scavengers and a calcium antagonist.

Acute, severe intrapartum asphyxia was mimicked by tying the umbilical cord in the exteriorized fetal sheep. After a standard time period cardiopulmonary resuscitation was instituted. In the treatment group (n = 14) the lambs were given a composition of scavengers of oxygen-derived free radicals and a calcium channel blocker. The control group of lambs (n = 12) was given placebo. The trial was blind and randomized. Hemodynamic and neurophysiological variables were measured from 30 min before asphyxia to 2 h postresuscitation. Mean arterial blood pressure, sagittal sinus venous pressure, heart rate, and cardiac output did not differ between the two groups although dramatic changes took place during asphyxia and resuscitation. Cerebral blood flow measured by 133-Xe washout method increased in both groups immediately after resuscitation. The treated animals retained an augmented cerebral blood flow during the 2 h postresuscitation while the control animals lost the increase of cerebral blood flow. The treated lambs recovered their somatosensory evoked potentials partially or completely in eight of 14 cases while the same figures for the control lambs were one of 12 cases. Immediately after resuscitation the cerebral reactions recovered to some extent in both groups but during the following 2 h the cerebral cortical function deteriorated in the control group but improved in the treated lambs. It is concluded that part of the brain damage in connection with acute, severe asphyxia may be inflicted by oxygen-derived free radicals released during the reoxygenation phase after resuscitation and that oxygen-derived free radical scavengers and calcium channel blockers may find a place in cardiopulmonary resuscitation.

Animals↗
PubMed1986

Fetal cerebral, cardiovascular and metabolic reactions to intermittent occlusion of ovine maternal placental blood flow.

In 10 mature, acutely exteriorized fetal sheep cardiovascular, cerebral and metabolic reactions were followed during intermittent occlusions of maternal placenta blood flow. The response was analysed from blood pressure, heart rate, myocardial contractility, combined cardiac output, ST waveform analysis of the fetal ECG, and from the evoked EEG response. The metabolic response was judged from blood gases, pH, lactate and circulating catecholamines. Basal values were within the range seen in the 'chronic' fetal lamb preparation. During moderate asphyxia, achieved by 10 1 min occlusions separated by 2 min periods of free maternal aorta blood flow, cardiovascular performance was increased with a substantial catecholamine surge but minor effects on cerebral and metabolic functions. During the marked asphyxia, achieved by five 2 min occlusions, marked metabolic changes occurred together with abolition of cerebral function. Forty-five minutes after asphyxia, 9/10 of the fetuses had regained cerebral, metabolic and cardiovascular functions.

Animals↗
PubMed1984

Does glucose administration affect the cerebral response to fetal asphyxia?

This study was designed to test whether the fetal brain has an increased resistance towards asphyxia at high levels of blood-glucose, compared with low levels. 35 fetal sheep were exteriorized and investigated under general anesthesia. Cerebral blood flow (CBF) was estimated with the 133Xenon-washout method. Cerebral uptake of oxygen, glucose, and lactate was measured. Somatosensory evoked potentials (SEP) were recorded. The fetuses were subjected to controlled asphyxia by ventilating the ewes with gas mixtures low in oxygen. The blood sugar levels of the fetuses were varied over a four-fold range. During normal oxygenation of the fetus variations in the blood glucose concentration induced considerable changes in the cerebral glucose uptake, whereas CBF and oxygen uptake were unaffected. During asphyxia, hyperglycemia was associated with rapid development of acidosis and reduction in cerebral oxygen consumption together with deterioration of the neurophysiological characteristics of the brain. Far from being beneficial during asphyxia, fetal hyperglycemia appeared to reduce the tolerance of the fetal brain towards asphyxia. This report together with other evidence provides support for the view that extra glucose might be disadvantageous for the asphyxiated fetus.

Animals↗
PubMed1984

Maternal beta-adrenoceptor blockade reduces fetal tolerance to asphyxia. A study in pregnant sheep.

Maternal and fetal beta 1-adrenoceptor blockade was induced in sheep by infusing i.v. 11 pregnant ewes with metoprolol in doses producing maternal plasma concentrations of metoprolol comparable to those obtained in clinical use. Ten other ewes and their fetuses served as controls. Under acute anaesthesia the fetus was exteriorized and subjected to two levels of controlled asphyxia by intermittent, complete obstruction of the maternal placental blood flow. Fetal haemodynamic reactions were assessed by measuring fetal heart rate, cardiac contractility, cardiac output and cerebral blood flow. The metabolic reactions were evaluated from blood gases, pH, lactate and hypoxanthine concentrations, while the electrophysiological status of the brain was evaluated from the somatosensory evoked EEG potentials (SEP). Already during the period of moderate asphyxia the beta-blocked fetuses demonstrated a blunted haemodynamic response, in comparison with the control fetuses, resulting in an accelerating lactic acidosis, signs of a breakdown of intra-cellular energy-rich phosphates and an impaired cerebral function. During the period of severe asphyxia, both groups of fetuses exhibited signs of extensive cerebral deterioration. During the ensuing recovery phase, 80% of the control fetuses regained their brain function, as assessed by SEP, whereas this was true for only 30% of the beta 1-blocked fetuses. It is concluded that the ovine fetus relies heavily on greatly increased sympatho-adrenal activity to adapt itself to asphyxia and that blockade of the fetal beta 1-adrenoreceptors by maternal medication is a hazard to the potentially asphyctic fetus.

Adrenergic beta-Antagonists↗
PubMed1982

Cerebral arterio-venous difference for hypoxanthine and lactate during graded asphyxia in the fetal lamb.

Hypoxanthine (HX) and lactate are degradation products from energy-rich intracellular substrates (ATP and glycogen), and their concentration will increase during anaerobic conditions, such as fetal asphyxia. In this study the accumulation of the two metabolites in blood during asphyxia was studied in 7 acutely exteriorized fetal lambs. The arterio-venous difference of HX and lactate over the brain was related to the function of the fetal brain as reflected by the somato-sensory evoked electroencephalogram potentials (SEP). Increased concentrations of HX in plasma and lactate in blood occurred simultaneously with deterioration of the SEP and the 3 variables correlate highly significantly. During normoxia, a net cerebral influx was found for HX, which in combination with severe asphyxia gradually changed to a net efflux. A linear correlation was found between the cerebral arterio-venous differences of HX and the impairment of the SEP. No such correlation existed for lactate. The results suggest, that the fetal brain has a high threshold for degrading its energy-rich intracellular purines.

Animals↗
PubMed1982

Clinical application of evoked EEG responses in infants. III: congenital hypothyroidism.

Previous studies have shown a close relationship between maturation of the central nervous system and development of evoked EEG responses. In this study, 13 infants with congenital hyperthyroidism were examined between the ages of one week and 17 weeks in an attempt to evaluate the degree of developmental retardation and the influence of hormonal treatment. It was found that visual evoked responses were abnormal in 12 of the patients, the most common abnormality being an immature abnormal response pattern. Latency was increased significantly in 10 of the 11 patients who were diagnosed before the age of six months, but was normal in the remaining two who were diagnosed later. A significant reduction of photic driving occurred in only two patients; it was the sole abnormality in one of them. Both the response pattern and latency became normal during treatment. The authors conclude that recording visual evoked responses is a simple and useful method of evaluating cerebral function in congenital hypothyroidism, both before and during treatment.

Brain↗
PubMed1979

Effects on the child of alcohol abuse during pregnancy. Retrospective and prospective studies.

Retrospective and prospective investigations of children to alcoholic women gave an incidence of fetal alcohol lesion of one per 300 deliveries of whom half had the complete fetal alcohol syndrome. Perinatal and infant mortalities were increased seven to tenfold and low birth weight (less than or equal to 2 500 g), preterm deliveries (less than 37 weeks) and smallness for gestational age (less than -2 S.D.) were increased eightfold, threefold and twelvefold, respectively. Small size at birth correlated with reduced mental performance later in life, 58% had IQ below 85 and 19% below 70.8% had cerebral palsy. The incidence of cerebral palsy associated with maternal inebriety was 1/5 000 deliveries, i.e. every sixth case of cerebral palsy. Tracing of alcoholic women during pregnancy and treatment gave favourable effect on intrauterine growth when sobriety could be induced early in pregnancy but could not protect from functional brain disturbance measured by neurological performance and be evoked response electroencephalography. Damage to the fetus by alcohol is now the largest known health hazard by a noxious agent that is preventable.

Alcoholism↗
PubMed1977

Clinical application of evoked electroencephalographic responses in newborn infants. I: Perinatal asphyxia.

Evoked electroencephalographic responses are useful for the study of cerebral maturation in full-term and pre-term newborn infants. In an attempt to achieve wider clinical application, 57 newborn infants with differing degrees of perinatal asphyxia were examined. Altogether 154 examinations were performed. In all of them photostimulation was used, and in 72 investigations somatosensory evoked responses were also recorded. The following results were obtained: (1) Visual evoked responses were affected in 85 per cent of the cases. Somatosensory evoked responses were affected less often - in 65 per cent of the newborn babies examined. The incidence and degree of deviations were related to the degree of asphyxia. (2) The most characteristic features of the evoked responses in asphyxiated infants were abnormal response patterns, increase of latency and poor photic driving. (3) On the basis of all alterations observed, a scoring system was developed which enabled quantitative evaluation. The evoked response risk-score correlated well with the degree of asphyxia. (4) Repeated observations were important: a permanently high risk-score at repeated investigations was a serious prognostic sign.

Asphyxia Neonatorum↗
PubMed1970

[Development of optical evoked activity in the human].

A comparison with experimental results obtained from animals shows that the development in man of what is called evoked potentials is considerably more complicated. The neonatal type of human response is very similar to the pattern in adult animals. However, for the further development it is not possible to find an analogy in animals. The entire character of the response is changed, the number of waves being increased. Only the changes in latency are comparable with experimental results. The rate of development is different, too. In man, although he belongs to those mammals giving birth to very immature offsprings, the first responses show long before the time of childbirth. For the animals studied to date this is the case postnatally only. The results obtained show that the development of stimulated activity, i. e., of evoked potentials and photic driving, continues through all childhood. The evaluation of the individual parameters, therefore, is a suitable method for evolutionary studies of the human nervous system. It is appropriate to speak of electrophysiological criteria of the state of maturation of the central nervous system. The development of all parameters is most rapid in the first months of life. It certainly is not necessary to stress that this particular fact does not only reflect the conditions in the optical system, but that it is an expression of great and rapid changes in the entire central nervous system.

Adolescent↗