Propaganda or science? Biological warfare and the people of Iraq.
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Biological Warfare↗
Biomedical subjects
I G Roberts
Publications and source records attributed to I G Roberts.
Measurement of cerebral blood flow during cardiopulmonary bypass with near-infrared spectroscopy.
OBJECTIVE: A novel noninvasive method for repeatedly measuring cerebral blood flow during cardiopulmonary bypass by near-infrared spectroscopy is described. The reproducibility of the method is investigated and a comparison is made with an established technique. METHODS AND RESULTS: The method is derived from the Fick principle and uses indocyanine green dye, injected into the bypass circuit, as an intravascular tracer. Cerebral blood flow was measured in nine children undergoing cardiopulmonary bypass on a total of 49 occasions. Results from this study suggest that an integrating period of 4 seconds provided a consistent measurement of global cerebral blood flow. The values obtained ranged from 3.2 to 32.4 (median 15.9) ml.100 gm-1.min-1. In an additional 10 children in whom repeated measurements were made, the coefficient of variation was 11% +/- 7% (mean +/- standard deviation). In a further study, the method was compared with microsphere injection in five piglets undergoing cardiopulmonary bypass. The comparison within each animal with the linear least squares method gave values for R2 in the range 0.91 to 0.99. The gradients of the fits ranged from 0.5 to 1.8 (median 1.0). The mean difference between the two techniques was 5.7 ml.100 gm-1.min-1 or 7%. The coefficient of variation for the piglets was 14% +/- 9% (mean +/- standard deviation). CONCLUSIONS: Indocyanine green and near-infrared spectroscopy allow frequent and repeated measurements of cerebral blood flow during cardiopulmonary bypass. The measurements are reproducible and accurately reflect changes in cerebral blood flow. It may be widely applicable both in research and clinical practice.
Animals↗
The relation between pump flow rate and pulsatility on cerebral hemodynamics during pediatric cardiopulmonary bypass.
OBJECTIVES: Neurologic impairment, at least partly ischemic in origin, has been reported in up to 25% of infants undergoing cardiopulmonary bypass, with or without circulatory arrest. Controversy continues about the effect of pump flow, pulsatile or nonpulsatile, on the brain and in particular on cerebral blood flow. This study examines the relationship between pump flow rate and cerebral hemodynamics during pulsatile and nonpulsatile cardiopulmonary bypass. METHOD: Near-infrared spectroscopy was used to determine cerebral blood flow and cerebral blood volume (measured as concentration change) in a randomized crossover study. Pulsatile and nonpulsatile flow were used for six 5-minute intervals at each of three different pump flow rates (0.6, 1.2, and 2.4 L x m2 x min(-1)) in 40 patients, median age 2 months (range 2 weeks to 20 years 5 months). The relations between pulsatile flow, pump flow rate, cerebral blood flow, hemoglobin concentration change (cerebral blood volume), mean arterial pressure, arterial carbon dioxide tension, and hematocrit value were prospectively examined by means of multivariate analysis. RESULTS: Cerebral blood flow decreased 36% per L x m(-2) x min(-1) decrease in pump flow rate and was associated with changes in mean arterial pressure but did not differ according to pulsatility. Change in hemoglobin concentration was unrelated to changes in pulsatility of pump flow. CONCLUSION: Cerebral blood flow is related to pump flow rate. Pulsatile flow delivered with a Stöckert pump does not increase cerebral blood flow or alter hemoglobin concentration during cardiopulmonary bypass in children.
Blood Volume↗
The relation between arterial oxygen tension and cerebral blood flow during cardiopulmonary bypass.
OBJECTIVES: Neurological impairment occurs in up to 25% of infants undergoing cardiopulmonary bypass with or without circulatory arrest. Potential causes include alterations in cerebral blood flow, hypoxia and embolisation. During cardiopulmonary bypass, arterial oxygen tension is maintained at levels which under normal conditions cause cerebral vasoconstriction; this is a potential mechanism for ischaemia. The aim of this study was to explore the relation between arterial oxygen tension and cerebral blood flow during cardiopulmonary bypass. METHODS: Near infrared spectroscopy was used to explore the relation between arterial oxygen tension and cerebral blood flow in 14 patients (median age 8 months; range 1 month to 10 years 11 months). The relations between arterial oxygen tension, arterial carbon dioxide tension, temperature, haematocrit, pump flow rate, mean arterial pressure and cerebral blood flow, were examined using multivariate analysis. RESULTS: There was no relation between cerebral blood flow and arterial oxygen tension, but a highly significant relation was observed between cerebral blood flow and pump flow rate, with cerebral blood flow decreasing 4.2-fold per L.m-2.min-1 decrease of pump flow rate. CONCLUSION: There was no relation between arterial oxygen tension and cerebral blood flow during cardiopulmonary bypass, but low pump flow rate may lead to reduced cerebral blood flow.
Blood Flow Velocity↗
Stöckert roller pump generated pulsatile flow: cerebral metabolic changes in adult cardiopulmonary bypass.
There is evidence that during cardiopulmonary bypass (CPB), pulsatile pump flow improves cerebral metabolism. This was a study to explore the effect of pulsatile versus nonpulsatile perfusion on cerebral lactate, pyruvate, glucose and beta-hydroxybutyrate using a Stöckert roller pump. We found no significant differences between the arterial-venous (A-V) differences of lactate, glucose and beta-hydroxybutyrate (p > 0.05). When the upward trend of A-V pyruvate was accounted for, there was again no difference (p = 0.2). Arterial lactate:pyruvate ratios were not significantly different between pulsatile and nonpulsatile pump flow (p > 0.05). Venous lactate:pyruvate ratios were significantly higher during pulsatile bypass, but when the downward trend was accounted for, the differences between pulsatile and nonpulsatile values were no longer significant (p = 0.4). Therefore, the metabolic changes were not significant. There was no significant difference in systemic vascular resistance (SVR) during pulsatile and nonpulsatile flow (p = 0.4). Pulsatile flow delivered by the Stöckert roller pump appears to have no metabolic or SVR advantages in adults undergoing CPB.
3-Hydroxybutyric Acid↗
An evaluation of the effects of susceptibility changes on the water chemical shift method of temperature measurement in human peripheral muscle.
Divergencies between chemical shift measurements of temperature and directly measured values using optical sensors have been studied in vivo in human peripheral muscle with the assistance of a variety of experimental and theoretical techniques. These include the modelling of both thermal and susceptibility changes using two- and three-dimensional finite element methods, as well as the use of multi-wavelength near-infrared observations. The conclusion of these studies is that a simple temperature calibration is not accessible, with results affected by the complex response of the tissue itself.
Humans↗
Cerebral blood volume response to changes in carbon dioxide tension before and during cardiopulmonary bypass in children, investigated by near infrared spectroscopy.
Neurological impairment may occur following cardiopulmonary bypass (CPB) and the effect of CPB on cerebrovascular control may be important in the mechanism of cerebral injury. We have used near infrared spectroscopy (NIRS) to observe cerebral haemodynamics non-invasively before and during CPB. We measured the change in cerebral blood volume (CBV) associated with changing PaCO2 (CBVR). Patients (n = 19) were aged from 1 to 135 (median 14) months. The cerebral blood volume response was determined pre-operatively at normothermia under the influence of standardised anaesthesia employing isoflurane (up to ET conc 0.5%) and during steady-state hypothermic bypass (22-32 degrees C) at an arterial pump flow rate of 1.9-2.4 lm-2.min-1. Complete data was available for 10 patients. The relation between CBV, arterial carbon dioxide tension (PaCO2), mean arterial pressure (MAP) and central venous pressure (CVP) was examined using analysis of covariance (P < or = 0.05) was accepted as significant). The change in CBV associated with changing PaCO2 was corrected for the effects of MAP and CVP. Preoperatively the median CBVR was 0.130 (25th-75th percentile 0.079-0.243) ml.100 g-1.kPa-1 and during hypothermic bypass the median CBVR was 0.093 (25th-75th percentile 0.026-0.255) ml.100 g-1.kPa-1. These values were compared with our reference range derived for normal conscious children using the Kruskal-Wallis test. There was not statistically significant difference between the three groups (P = 0.35). These results, indicating preservation of CBVR during the conditions of anaesthesia and bypass used, are consistent with the observations of previous authors who measured cerebral blood flow response to carbon dioxide by a variety of other methods. Near infrared spectroscopy is proving to be a reliable, non-invasive technique for the investigation of cerebral haemodynamics during CPB.
Adolescent↗
Pedestrian exposure and the risk of child pedestrian injury.
The authors used data from the New Zealand Household Travel Survey to examine the extent to which children's pedestrian exposure varies with age, sex and household income. Pedestrian injury morbidity data were combined with pedestrian exposure data to examine age-specific pedestrian injury risk. The annual number of road crossings for girls was greater than that for boys. Pedestrian exposure increased with increasing age. Children aged 5-9 years in the lowest household income bracket crossed approximately 50% more roads than those in the middle and upper income brackets. However, for children aged 10-14 years there was little variation with household income. Sex differences in pedestrian injury rates cannot be explained by differences in exposure although increased exposure may partly explain the increased injury rates for children in lower socio-economic groups. Prevention strategies might aim to reduce pedestrian exposure for alternatively to reduce pedestrian injury risk per unit of exposure by making safer urban living environments.
Accidents, Traffic↗
The time course and location of cerebral evoked activity associated with the processing of colour stimuli in man.
Area V4 has been located in man in the region of the fusiform gyrus on the inferior surface of the occipital lobe. Using multiple dipole source analysis on multichannel EEG recordings of visual evoked potentials to coloured 'Mondrian' stimuli in man, we have confirmed that activity is consistently seen in this area regardless of the retinal area stimulated and have obtained new information concerning its time course. Three different localized centres of activity follow the visual stimulus, with peak latencies of 90, 110 and 160 ms, and arising respectively in the region of visual areas V1, V2/V3 and V4. The time course and character of the V4 dipole activity to a colourless black-and-white Mondrian is indistinguishable from that to the coloured Mondrian, supporting the evidence that the cells of V4 are not exclusively concerned with colour processing.
Brain Mapping↗
International trends in pedestrian injury mortality.
Trends in pedestrian injury mortality for children aged 0-4 and 5-14 for England and Wales, Denmark, Sweden, the USA, and New Zealand were examined from 1968 onwards. While there has been a reduction in the pedestrian mortality in all these countries, there are striking international differences in the extent of these reductions. Denmark has achieved the greatest fall in mortality with the smallest decrease seen in New Zealand. Countries which have experienced major decreases in pedestrian mortality are distinguished by having placed greater emphasis on environmentally based prevention strategies rather than pedestrian skills education.
Accidents, Traffic↗
Health problems associated with nuclear war.
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Burns↗
Individual-level injury prevention strategies in the clinical setting.
Health care providers have numerous opportunities to intervene with parents and children to promote child safety practices that reduce rates of unintentional injuries. These individual-level interventions may be delivered in a variety of settings such as physician offices, clinics, emergency departments, or hospitals. This article systematically reviews 22 randomized controlled trials (RCTs) that examined the impact of interventions delivered in the clinical setting on child safety practices and unintentional injuries. The results indicate that counseling and other interventions in the clinical setting are effective at increasing the adoption of some safety practices, but not others. Specifically, motor vehicle restraint use, smoke alarm ownership, and maintenance of a safe hot tap water temperature were more likely to be adopted following interventions in the clinical setting. Clinical interventions were not proven effective at increasing a variety of safety practices designed to protect young children from injuries in the home, increasing bicycle helmet use, or reducing the occurrence of childhood injuries, though few studies examined the latter two outcomes. Clinical interventions were most effective when they combined an array of health education and behavior change strategies such as counseling, demonstrations, the provision of subsidized safety devices, and reinforcement. The article concludes with implications for research and practice.
Child↗