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Introduction: Clinicians treat hypotension to maintain organ perfusion in sick preterm infants including that to the brain. However, the critical level of mean blood pressure (BP) below which cerebral perfusion [...]

Cardiac output is a determinant of systemic blood flow and its measurement may therefore be a useful indicator of abnormal hemodynamics and tissue oxygen delivery. The purpose of this study was to investigate in very premature newborn infants the relationships between cardiac output (left and right ventricular outputs), systemic blood pressure, peripheral blood flow (PBF) and two indicators of cerebral oxygen delivery (cerebral electrical activity and cerebral fractional oxygen extraction (CFOE)). This was a prospective observational study performed on 40 infants of less than 30 wk gestation. Digital electroencephalograms (EEGs) were recorded for one hour every day during the first four days after birth and subjected to qualitative and quantitative analysis. Left and right ventricular outputs, mean blood pressure (MBP), CFOE, PBF and arterial blood gases were measured at the same time. Within the ranges studied, there was no apparent relationship between left or right ventricular output (RVO), PBF and indicators of cerebral perfusion (cerebral electrical activity and CFOE). The EEG was normal in infants with low left and right ventricular outputs (<150 mL/kg/min) and MBP > 30 mm Hg. Infants with low cardiac output and normal MBP seem able to maintain cerebral perfusion, possibly through vasodilatation of the cerebral microvasculature.

There is uncertainty about the level of systemic blood pressure required to maintain adequate cerebral oxygen delivery and organ integrity. This prospective, observational study on 35 very low birth weight infants aimed to determine the mean blood pressure (MBP) below which cerebral electrical activity, peripheral blood flow (PBF), and cerebral fractional oxygen extraction (CFOE) are abnormal. Digital EEG, recorded every day on the first 4 d after birth, were analyzed a) by automatic spectral analysis, b) by manual measurement of interburst interval, and c) qualitatively. CFOE and PBF measurements were performed using near-infrared spectroscopy and venous occlusion. MBP was measured using arterial catheters. The median (range) of MBP recorded was 32 mm Hg (16-46). The EEG became abnormal at MBP levels below 23 mm Hg: a) the relative power of the delta (0.5-3.5 Hz) frequency band was decreased, b) interburst intervals were prolonged, and c) all four qualitatively abnormal EEG (low amplitude and prolonged interburst intervals) from four different patients were recorded below this MBP level. The only abnormally high CFOE was measured at MBP of 20 mm Hg. PBF decreased at MBP levels between 23 and 33 mm Hg. None of the infants in this study developed cystic periventricular leukomalacia. One infant (MBP, 22 mm Hg) developed ventricular dilatation after intraventricular hemorrhage. The EEG and CFOE remained normal at MBP levels above 23 mm Hg. It would appear that cerebral perfusion is probably maintained at MBP levels above 23 mm Hg.

Decreased arterial carbon dioxide tension (PaCO2) results in decreased cerebral blood flow, which is associated with diminished cerebral electrical activity. In such a situation, cerebral fractional oxygen extraction (CFOE) would be expected to increase to preserve cerebral oxygen delivery. This study aimed to determine whether changes in blood gases in infants less than 30 wk' gestation were associated with changes in background electroencephalograms (EEG) and CFOE. Thirty-two very low birth weight infants were studied daily for the first three days after birth. Digital EEG recordings were performed for 75 min each day. CFOE, mean blood pressure and arterial blood gases were measured midway through each recording. EEG was analysed by (a) spectral analysis and (b) manual calculation of interburst interval. Blood pressure, pH and PaCO2 did not have any effect on the EEG. On day one, only PaCO2 showed a relationship with the relative power of the delta frequency band (0.5-3.5 Hz) and the interburst interval. The relative power of the delta band remained within normal limits when PaCO2 was between 24 and 55 mmHg on day one. There was a negative association between PaCO2 and CFOE. The associations between PaCO2 and EEG measurements were strongest on day one, weaker on day two, and absent on day three. The slowing of EEG and increased CFOE at lower levels of PaCO2 are likely to be due to decreased cerebral oxygen delivery induced by hypocarbia. When PaCO2 was higher, there was suppression of the EEG.

Continuous EEG monitoring has not been used widely in neonatal intensive care, especially in the care of extremely premature infants, probably in part because of a lack of a reliable quantitative method. The purpose of this study was to quantify the EEG of the very premature infants just after birth by using spectral analysis and to describe the characteristics of the spectral signal when infants were clinically stable. Digital EEG recordings were performed on 53 infants who were < or =30 wk gestation for 75 min each day during the first 4 d after birth. Artefact was rejected manually after visual inspection of trace. The EEG was analyzed by manual measurement of interburst interval and automatically by spectral analysis using Fast Fourier Transformation. Spectral analysis generated the normal ranges of the relative power of the delta (0.5-3.5 Hz), theta (4-7.5 Hz), alpha (8-12.5 Hz), and beta (13-30 Hz) frequency bands, spectral edge frequency, and symmetry. The median (range) relative power of the delta band increased significantly from 68% (62-76%) on day 1 to 81% (72-89%) on day 4 (p=0.001). The interburst intervals became progressively shorter between days 1 [14s (10-25)] and 3 [8s (6-12)]; there were no significant differences between days 3 and 4. The relative power of the delta band seemed to be the most useful and repeatable spectral measurement for continuous long-term monitoring. However, automatic artefact rejection software needs to be developed before continuous quantitative EEG monitoring can be used in the neonatal intensive care environment.

This audit evaluated the role and usefulness of ambulatory cassette EEG recordings without simultaneous video monitoring in children with paroxysmal episodes including epilepsy. Fifty-four children underwent ambulatory EEG recordings for 48 hours over a 12 month period. Only 31 of the 54 children experienced one of their typical clinical episodes during their recordings. Fifteen of these 31 patients were considered to have epilepsy, only three of whom had a clinical episode at the time of their recording and in all three the EEG demonstrated abnormal (generalized spike and slow wave or focal, rhythmic slow wave) activity. All 10 patients who were considered to have non-epileptic episodes showed no electrical change during their EEG recordings. The results of the ambulatory cassette EEG recordings were considered to have been helpful and to have contributed to the management of only 17 (31%) of the 54 patients in this audit. Stricter clinical criteria for undertaking ambulatory recordings and improved technology are likely to increase the role and usefulness of this procedure., (Copyright 2001 BEA Trading Ltd.)

Background: Björk-Shiley 60 degrees convexo-concave prosthetic heart valves (Shiley, Inc, Irvine, Calif, a subsidiary of Pfizer, Inc) continue to be a concern for approximately 35,000 nonexplanted patients worldwide, with approximately 600 events reported to the manufacturer to date. Fractures of the outlet struts of the valves began to appear in the early 1980s and have continued to the present, but their causes are only partially understood., Methods: A matched case-control study was conducted evaluating manufacturing records for 52 valves with outlet strut fractures and 248 control subjects matched for age at implantation, valve size, and valve position., Results: In addition to the risk factors recognized as determinants of outlet strut fracture, the United Kingdom case-control study has observed 7- to 9-fold increased risk with performance of multiple hook deflection tests. This test was performed more than once, usually after rework on the valve. Six valves in this study underwent multiple hook deflection tests, of which 4 experienced an outlet strut fracture. Cracks and further rework were noted for these valves. Significant associations were also observed between outlet strut fracture and disc-to-strut gap measurements taken before the attachment of the sewing ring., Conclusions: It is our view that a combination of factors related to valve design, manufacturing process, and patient characteristics are responsible for outlet strut fractures of Björk-Shiley convexo-concave valves. Multiple hook deflection tests have emerged as a potential new risk factor for outlet strut fracture in both The Netherlands and the United Kingdom. This factor appears to be correlated with the presence of other abnormalities. A further study is needed to investigate the factors correlated with multiple hook deflection tests. On confirmation of risk, the presence of multiple hook deflection tests may be added to equations, quantifying the risk of outlet strut fracture for comparison against risk of mortality and serious morbidity from explant operations.

Photosensitivity is reported to occur in approximately 40% of patients with juvenile myoclonic epilepsy. Our experience suggests that the prevalence is higher and may be related to both the duration of intermittent photic stimulation and also the age at which the procedure is undertaken. A two-year retrospective review of all EEGs was undertaken on all children attending a paediatric EEG department to identify those with juvenile myoclonic epilepsy. Photosensitivity was defined as a generalized spike or spike-wave paroxysm occurring at least twice during intermittent photic stimulation. Sixty-one children with a diagnosis of juvenile myoclonic epilepsy with a median age of 13 (range 7-16) years were identified, 55 (90%) of whom were photosensitive. Eighteen of these 55 patients showed photosensitivity only after four minutes of continuous photic stimulation. The prevalence of photosensitivity in juvenile myoclonic epilepsy is likely to be higher than previously reported. When a diagnosis of juvenile myoclonic epilepsy is being considered, the initial diagnostic EEG should include intermittent photic stimulation for up to five minutes, or less if the patient shows evidence of photosensitivity. The identification of photosensitivity may have important management implications.

The practical value or usefulness of any investigation is dependent upon the clinical information provided and subsequent interpretation; this is particularly important in the investigation and classification of the epilepsies. For two months the histories from clinicians and EEG technicians were prospectively evaluated from 255 consecutive patients. The histories were interpreted by a single paediatric neurologist who was blinded to their origin. The histories were reported as "adequate' or "inadequate', and "diagnostic' or "non-diagnostic' (of epilepsy). Overall 92% and 40% of technicians' and 41% and 13% of clinicians' histories were considered to have been "adequate' and "diagnostic', respectively. These results have implications for the electro-clinical interpretation of the EEG.

The Oily Bird Syndrome (OBS) was successfully reproduced in broilers under laboratory conditions which included elevated temperatures simulating summer conditions and feeding high energy diets with a relatively wide calorie to protein ratio. No significant difference in incidence of the syndrome was detected in broilers fed a corn-soy diet, or one with 13% animal protein concentrates and 7.5% bakery product, or with a diet containing 10% distillers dried gains with solubles. Substituting animal tallow for poultry oil significantly (P less than .05) increased the incidence of the syndrome. Feeding diets with a more narrow calorie to protein ratio significantly reduced incidence in one experiment, and feeding an unpelleted diet from 3 to 7 weeks of age also significantly reduced the incidence below that of birds fed the same diet in pelleted form. Incidence of OBS was significantly less for birds housed in a separate building with lower temperature conditions than those maintained in a house with a higher environmental temperature. The OBS could best be observed under commercial processing conditions. Results of these experiments show that growing broilers at a high environmental temperature and feeding diets with wide calorie to protein ratios provide conditions conducive to the development of OBS. Further studies will be necessary to determine the specific etiology of the syndrome.

Three experiments were conducted using commercially available broiler chicks to study the influence of high levels of pyridoxine on incidence of twisted legs. Chicks were grown in wire floored battery brooders to two weeks of age when they were weighed and visually scored for twisted legs. Supplementation of a diet containing 2.2 mg synthetic vitamin B6/kg with 10 and 20 mg/kg pyridoxine resulted in a significant decrease (P less than or equal to .05) in incidence of twisted legs in Experiment 1. In Experiment 2, supplementation with 30, 60, or 100 mg/kg numerically reduced incidence, but the differences were not statistically significant. Incidence of twisted legs was significantly increased by injecting chicks with .5 ml physiological saline at 1 and 7 days of age in comparison to noninjected controls. Including 10 mg pyridoxine HCl in the saline reduced the incidence but it was still numerically higher than the noninjected controls. Factors other than vitamin B6 nutrition appear to play a more important role in the etiology of twisted legs in broiler chicks.