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Biomedical subjects

P L Hope

Publications and source records attributed to P L Hope.

At least 37 records · Page 2Linked to original sources
PubMed1989

Reproducibility of measurement of pulsatility index by Doppler ultrasound of the anterior cerebral artery of preterm infants.

Ten preterm infants were each studied by three observers using a commercial duplex Doppler ultrasound scanner, in order to determine the intra-observer and inter-observer variability in the measurement of pulsatility index (PI) of the anterior cerebral artery. There was considerable difference in estimates of PI, with a mean range of 0.11 between the three observers for each infant. Intra-observer variability exceeded inter-observer variability and had a coefficient of variation of 8.4%. The five observers involved in this study had less than six months experience of duplex scanning. The results suggest that the PI can be measured with acceptable reproducibility by personnel with limited experience.

Cerebral Arteries↗
PubMed1989

Phosphorus metabolites and intracellular pH in the brains of normal and small for gestational age infants investigated by magnetic resonance spectroscopy.

The brains of 30 normal preterm and term infants whose birth wt were appropriate for gestational age and 13 who were small for gestational age but healthy were studied by phosphorus magnetic resonance spectroscopy to determine values for metabolite concentration ratios and intracellular pH. In the AGA infants, phosphocreatine/inorganic orthophosphate increased between 28 and 42 wk of gestational plus postnatal age, suggesting a rise in the phosphorylation potential of brain tissue. At the same time, the concentration of phosphomonoester (mainly phosphoethanolamine) fell and that of phosphodiester (including phosphatidylethanolamine and phosphatidylcholine) increased. These changes reflected myelination and proliferation of membranes. Intracellular pH was approximately 7.1 and did not change with brain maturation. No differences were detected in these variables between the infants who were small for gestational age and those who were appropriate for gestational age.

Body Fluids↗
PubMed1989

Prognosis of newborn infants with hypoxic-ischemic brain injury assessed by phosphorus magnetic resonance spectroscopy.

To investigate the prognostic significance of abnormalities of oxidative phosphorylation, the brains of 61 newborn infants born at 27-42 wk of gestation and suspected of hypoxic-ischemic brain injury were examined by surface-coil phosphorus magnetic resonance spectroscopy. Of these infants, 23 died, and the neurodevelopmental status of the 38 survivors was assessed at 1 y of age. Of the 28 infants whose phosphocreatine/inorganic orthophosphate (PCr/Pi) ratios fell below 95% confidence limits for normal infants, 19 died, and of the nine survivors, seven had serious multiple impairments (sensitivity 74%, specificity 92%, positive predictive value for unfavorable outcome 93%). Of the 12 infants with ATP/total phosphorus ratios below 95% confidence limits 11 died (sensitivity 47%, specificity 97%, positive predictive value 91%). Among the 46 infants with increased cerebral echodensities, PCr/Pi was more likely to be low, and prognosis poor, in infants whose echodensities were diffuse or indicated intraparenchymal hemorrhage than in infants whose echodensities were consistent with periventricular leukomalacia. We conclude that when reduced values for PCr/Pi indicating severely impaired oxidative phosphorylation are found in the brains of infants suspected of hypoxic-ischemic injury, the prognosis for survival without serious multiple impairments is very poor, and that when ATP/total phosphorus is reduced, death is almost inevitable.

Asphyxia Neonatorum↗
PubMed1988

Prediction in very preterm infants of satisfactory neurodevelopmental progress at 12 months.

This study was performed to find out how well ultrasound brain-scanning and neurological examination of very preterm infants, together and separately, predicted normal neurodevelopmental progress at 12 months corrected age. 111 infants born at less than 33 weeks gestation were scanned at discharge from the neonatal unit, and neurological examinations were performed at a gestation-equivalent age at or near term. During the first year of life repeated neurological and developmental testing was carried out. At 12 months a diagnosis of normal progress or of major or minor neurodevelopmental disorders was made. 56 (50 per cent) infants with both a favourable ultrasound scan and normal neurological findings had a 98 per cent (90 to 99 per cent) probability of normal progress at 12 months, and a 100 per cent (93 to 100 per cent) probability of having no major disorder. Separately, ultrasound scanning and neurological examination were not such good predictors of normal outcome, although they selected larger groups of infants with high probabilities of progressing normally. Ultrasound brain-scanning and neurological examination can be used in combination to identify potentially normal preterm infants when they are discharged to their homes.

Central Nervous System↗
PubMed1988

Precision of ultrasound diagnosis of pathologically verified lesions in the brains of very preterm infants.

Abnormalities detected by a mechanical sector scanner were compared 'blind' with autopsy findings in the brains of 56 infants born at less than 33 weeks gestation. Intraventricular haemorrhage was found in 53 of 112 hemispheres and had been accurately diagnosed by ultrasound (sensitivity 91 per cent; specificity 81 per cent). Isolated germinal layer haemorrhage was less successfully identified (sensitivity 61 per cent; specificity 78 per cent); false-positive diagnoses were partly due to difficulty in distinguishing haemorrhage from the normal choroid plexus in extremely preterm infants. Haemorrhagic parenchymal lesions were correctly identified in nine infants (sensitivity 82 per cent; specificity 97 per cent). Only 11 of 39 hemispheres with histological evidence of hypoxic-ischaemic injury, without marked bleeding, were correctly identified by ultrasound (sensitivity 28 per cent), mainly because of failure to detect small areas of periventricular leucomalacia and diffuse gliosis. 10 hemispheres with periventricular echodensities thought to represent leucomalacia showed no histological evidence of hypoxic-ischaemic injury (specificity 86 per cent). Ventricular dilatation in seven infants was always associated with evidence of hypoxic-ischaemic injury at autopsy.

Brain↗
PubMed1988

Brain metabolism and intracellular pH during ischaemia: effects of systemic glucose and bicarbonate administration studied by 31P and 1H nuclear magnetic resonance spectroscopy in vivo in the lamb.

Brain metabolism and intracellular pH were studied during and after episodes of incomplete cerebral ischaemia in lambs under sodium pentobarbitone anaesthesia. 31P and 1H magnetic resonance spectroscopy was used to monitor brain pHi and brain concentrations of inorganic phosphate (Pi), phosphocreatine (PCr), beta-nucleoside triphosphate (beta NTP), and lactate. Simultaneous measurements were made of arterio-cerebral venous concentration differences (AVDs) for oxygen, glucose, and lactate. Cerebral ischaemia was induced by a combination of bilateral carotid clamping and hypotension, and the acute effects of systemic administration of glucose and sodium bicarbonate were examined. The molar ratio of glucose to oxygen uptake by the brain (6G/O2) increased above unity during cerebral ischaemia. Statistically significant AVDs for lactate were not observed. Cerebral ischaemia was associated with a reduction in brain pHi PCr/Pi ratio, and an increase in brain lactate. No effect of arterial plasma glucose on brain lactate concentration or brain pHi was evident during cerebral ischaemia or in the postischaemic period. Administration of sodium bicarbonate systemically in the postischaemic period was associated with a rise in arterial and brain tissue PCO2. A fall in brain pHi occurred which was attributable in part to coincidental brain lactate accumulation. The increase in brain lactate measured by 1H nuclear magnetic resonance in vivo during ischaemia was insufficient to account for the change in buffer base calculated to have occurred from previous estimates of brain buffering capacity.

Animals↗
PubMed1988

Factors influencing colonisation with gentamicin resistant gram negative organisms in the neonatal unit.

The proportion of babies colonised with gentamicin resistant Gram negative organisms in a nursery over a 30 month period did not correlate with the quantity or duration of aminoglycosides used, but it did correlate with two indicators of workload: the number of baby days and a score based on the level of nursing care required. Spread of resistant organisms may be more likely as workload increases.

Bacterial Infections↗
PubMed1987

Periventricular intraparenchymal cerebral haemorrhage in preterm infants: the role of venous infarction.

Haemorrhage into cerebral parenchymal tissue supero-lateral to the angles of the lateral ventricles is a major cause of death and disability in preterm infants. It is frequently associated with germinal layer and intraventricular haemorrhage but the mechanism by which parenchymal haemorrhage occurs is uncertain. Recent studies have suggested that it is due to bleeding into tissue previously damaged by ischaemia following cerebral hypoperfusion. We have studied 68 preterm infant brains, of which four contained early intraparenchymal haemorrhage supero-lateral to the angles of the lateral ventricles which were associated with large germinal layer and intraventricular haemorrhages. The anatomical distribution and histological features of these haemorrhages suggested that they resulted from venous infarction and that the venous drainage of the periventricular tissues had been obstructed by the germinal layer haemorrhages. In these four infants, bleeding into parenchymal tissues could be regarded as a complication of germinal layer and intraventricular haemorrhage rather than of cerebral hypoperfusion.

Brain Ischemia↗
PubMed1987

Probability of neurodevelopmental disorders estimated from ultrasound appearance of brains of very preterm infants.

The neurodevelopmental status of 342 very preterm infants who had undergone prospective ultrasound brainscans was assessed at a median corrected age of 52 weeks. The probabilities for neurodevelopmental disorders were calculated according to the ultrasound findings. The results showed that the probability of a major or minor disorder was low for infants whose scans did not show periventricular haemorrhage or markedly increased parenchymal echodensities in the first week of life, and for those whose scans at discharge gave no evidence of ventricular dilatation, hydrocephalus or cerebral atrophy. By contrast, the probability of a disorder was very high for infants with markedly increased parenchymal echodensities in the first week, and for infants with evidence of cerebral atrophy at discharge. The majority of the infants could be assigned, on the basis of the ultrasound scan at discharge, either to a large group who were at low risk of neurodevelopmental disorders or to a small group who were at high risk; the remainder were at intermediate risk. These findings may be used as a guide to the prognosis for other infants whose ultrasound scans show similar appearances.

Atrophy↗
PubMed1987

Brain metabolism and intracellular pH during ischaemia and hypoxia: an in vivo 31P and 1H nuclear magnetic resonance study in the lamb.

Brain metabolism and intracellular pH were studied during and after episodes of ischaemia and hypoxia-ischaemia in lambs anaesthetised with sodium pentobarbitone. 31P and 1H magnetic resonance spectroscopy methods were used to monitor brain pHi and brain concentrations of Pi, phosphocreatine (PCr), beta--nucleoside triphosphate (beta NTP), and lactate. Simultaneous measurements were made of cerebral blood flow and cerebral oxygen and glucose consumption. Cerebral ischaemia sufficient to reduce oxygen delivery to 75% of control values was associated with a fall in brain pHi and increase in brain Pi. Progressively severe hypoxia-ischaemia was associated with a progressive fall in brain pHi, PCr, and beta NTP and increase in brain Pi. In two animals the increase in brain lactate during hypoxia-ischaemia measured by 1H nuclear magnetic resonance (NMR) could be quantitatively accounted for by the increased net uptake of glucose by the brain in relation to oxygen, but was insufficient to account for the concomitant acidosis according to previous estimates of brain buffering capacity. In four animals brain pHi, PCr, Pi, and beta NTP had returned to normal 1 h after the hypoxic-ischaemic episode. In one animal brain pHi had reverted to normal at a time when 1H NMR indicated persistent elevation of brain lactate.

Animals↗
PubMed1987

Brain intracellular pH and metabolism during hypercapnia and hypocapnia in the new-born lamb.

1. The effects of hypercapnia and hypocapnia on brain intracellular pH (pHi) and metabolism were investigated in new-born lambs under barbiturate anaesthesia. 2. 31P nuclear magnetic resonance (n.m.r.) spectroscopy was used to determine brain pHi and the relative concentrations of compounds containing mobile phosphorus nuclei including phosphocreatine (PCr), nucleoside triphosphates (NTP) and inorganic phosphate (Pi). Simultaneous measurements were made of the molar ratio of glucose to oxygen uptake by the brain. 3. During normocapnia (arterial partial pressure of CO2 Pa, CO2, 39 +/- 1 mmHg mean +/- S.E. of mean, n = 9) brain pHi was 7.13 +/- 0.02. Hypercapnia (Pa, CO2, 98 +/- 3 mmHg) was associated with a fall in brain pHi to 6.94 +/- 0.03 (n = 19, P less than 0.001), whereas no significant change in brain pHi occurred during hypocapnia (Pa, CO2, 16 +/- 1 mmHg; brain pHi 7.15 +/- 0.01). 4. During hypercapnia there was an increase in the ratio of Pi to NTP from 1.09 +/- 0.08 to 1.47 +/- 0.06 (P less than 0.001) and a decrease in the ratio PCr/Pi from 1.60 +/- 0.08 to 0.93 +/- 0.04 (P less than 0.001). There was a linear correlation between Pi/NTP and brain pHi. 5. Alterations in arterial PCO2 had no significant effect on the molar ratio of glucose to oxygen uptake by the brain, which remained close to unity. 6. The change in brain pHi observed during hypercapnia can be accounted for by the known physico-chemical buffering capacity of brain tissue. Homoeostasis of brain pHi during hypocapnia provides further evidence that additional regulatory mechanisms operate in these circumstances. 7. The observed changes in PCr and Pi can be accounted for in part by the [H+] dependence of the creatine kinase reaction.

Animals↗
PubMed1987

Cerebral monitoring in newborn infants by magnetic resonance and near infrared spectroscopy.

Phosphorus magnetic resonance spectroscopy (MRS) and near infrared spectroscopy (NIRS) have been used to study the brains of normal newborn infants and infants with cerebral disorders admitted to a neonatal intensive care unit. MRS, which involves transporting the infant to the spectrometer, allows measurement of mobile phosphorus compounds such as adenosine triphosphate and phosphocreatine in brain tissue, and has been performed on over 160 babies. NIRS gives cotside information about cerebral oxygenation and haemodynamics and has recently been introduced. These techniques, especially when used together, show promise of providing important information about the mechanisms and prognostic significance of hypoxic-ischaemic damage to the brain--the most important cause of permanent neurodevelopmental disabilities in infants who require intensive care.

Brain↗
PubMed1986

Impaired energy metabolism in brains of newborn infants with increased cerebral echodensities.

Intracellular energy metabolism was studied by phosphorus magnetic resonance spectroscopy in the brains of 27 preterm and term infants with increased echodensities consistent with hypoxic-ischaemic injury and 18 comparable normal infants. In the normal infants the phosphocreatine (PCr)/inorganic orthophosphate (Pi) ratio increased significantly from 0.77 +/- 0.24 (95% confidence limits) at a gestational plus postnatal age of 28 weeks to 1.09 +/- 0.24 at 42 weeks. 9 of the 15 infants with increased echodensities whose PCr/Pi ratios fell below the normal range died; in all 6 survivors cerebral atrophy developed (cysts in brain tissue or microcephaly). In contrast, all 12 infants with increased echodensities whose PCr/Pi ratios remained within the normal range survived, although cerebral atrophy developed in 3 with ratios towards the lower limit of normal.

Age Factors↗
PubMed1985

Investigation of cerebral energy metabolism in newborn infants by phosphorus nuclear magnetic resonance spectroscopy.

31P NMR spectroscopy can be safely and successfully used to study cerebral energy metabolism in sick newborn infants, provided a suitable life support and monitoring system is available. Studies of normal infants have shown characteristic spectral peaks assigned to adenosine triphosphate, phosphocreatine, phosphodiesters plus phospholipids, inorganic orthophosphate, and a large peak at the phosphomonoester resonance frequency that is attributable mainly to phosphoethanolamine, a precursor of membrane phospholipids. Both the PCr/Pi and PCr/ATP ratios were lower in normal newborn infants than reported in studies using invasive techniques in adult animals. Tissue hypoxia-ischemia was associated with a fall in PCr levels and a rise in Pi. The PCr/Pi ratio, which is an index of cerebral energy status, was normal during the first day of life in infants who had suffered severe birth asphyxia, but subsequently fell to levels well below the normal range. The presence of this latent period raises the possibility of effective early treatment following birth asphyxia, before irreversible impairment of cellular energy metabolism occurs. Low PCr/Pi ratios have also been demonstrated in infants with idiopathic cerebral infarction, periventricular leukomalacia and inborn errors of metabolism. Preliminary experience suggests that ratios below 0.8 are associated with irrecoverable failure of energy metabolism and cellular necrosis. 31P NMRS and other spectroscopic NMR techniques utilizing, for instance, 1H and 13C nuclei, have exciting potential for exploring the mechanisms and methods of prevention of various forms of cerebral damage in the newborn period.

Brain↗
PubMed1984

Cerebral energy metabolism studied with phosphorus NMR spectroscopy in normal and birth-asphyxiated infants.

Phosphorus (31P) nuclear magnetic resonance spectroscopy was used to study intracellular metabolism in the brains of 6 normal newborn infants and 10 infants who had been asphyxiated during delivery. In the normal infants spectral peaks mainly attributable to adenosine triphosphate, phosphocreatine (PCr), phosphodiesters plus phospholipids, and inorganic orthophosphate (Pi) were always detected, together with an additional large peak in the phosphomonoester region indicating the presence of a metabolite or metabolites (probably largely phosphoethanolamine) which may be involved in rapid growth of the brain. In the asphyxiated infants, data obtained on the first day of life showed no differences from those in normal infants, but by the second to ninth days inverse changes in the concentrations of PCr and Pi had caused a significant reduction in PCr/Pi. This latency suggest the possibility of effective early treatment before irreversible metabolic damage sets in. Mean intracellular pH when PCr/Pi was minimal was 7.17 +/- 0.10. Values for PCr/Pi below 0.80 were associated with a very bad prognosis for survival and early neuro-developmental outcome.

Adenosine Diphosphate↗