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Biomedical subjects

A G Stuart

Publications and source records attributed to A G Stuart.

16 recordsLinked to original sources
PubMed2005

Understanding cardiac arrhythmias.

This review highlights the applied science intrinsic to the interpretation of the electrocardiogram and cardiac arrhythmias in children.

Arrhythmias, Cardiac↗
PubMed2004

Severe pulmonary hypertension: a frequent complication of stem cell transplantation for malignant infantile osteopetrosis.

This report describes eight infants who developed acute severe pulmonary arterial hypertension (PAH) at days -2 to +89 after allogeneic stem cell transplantation (SCT) for malignant infantile osteopetrosis (MIOP). They were taken from a total of 28 children (frequency 29%) transplanted for this disease at three institutions between 1996 and 2002. Typical presentations were acute dyspnoea, hypoxia and brady/tachycardia usually in the absence of fever, crepitations or other evidence of infection. Six patients (75%) required assisted ventilation and five (62%) died. There was clinical or pathological evidence of veno-occlusive disease (VOD) in three children, but absence of VOD in the remaining five suggests that a separate disease process may be responsible for the PAH. Responses to nitric oxide (NO), defibrotide (DF), nicardipine and steroids in varying combinations were disappointing. Three children showed sustained improvement after administration of epoprostenol (EP, prostacyclin) in conjunction with NO and/or DF and remain well and free of PAH 25, 31 and 32 months post-transplant. PAH must therefore be excluded in any child who becomes acutely breathless after SCT for osteopetrosis.

Antihypertensive Agents↗
PubMed1999

Endothelial function in Marfan syndrome: selective impairment of flow-mediated vasodilation.

BACKGROUND: The cardiovascular complications of Marfan syndrome arise due to alterations in the structural and functional properties of fibrillin, a constituent of vascular connective tissues. Fibrillin-containing microfibrils are closely associated with arterial endothelial cells, indicating a possible functional role for fibrillin in the endothelium. Plasma concentrations of endothelial cell products are elevated in Marfan subjects, which indirectly indicates endothelial dysfunction. This study directly assessed flow- and agonist-mediated endothelium-dependent brachial artery reactivity in Marfan subjects. METHODS AND RESULTS: In 20 Marfan and 20 control subjects, brachial artery diameter, blood flow, and blood pressure were measured by ultrasonic wall tracking, Doppler ultrasound, and photoplethysmography, respectively. Measurements were taken during hand hyperemia (a stimulus for endothelium-derived nitric oxide [NO] release in the upstream brachial artery) and after sublingual administration of the endothelium-independent vasodilator nitroglycerin. In 9 Marfan and 6 control subjects, the above parameters were also assessed during intra-arterial infusions of acetylcholine and bradykinin (agonists that stimulate NO production) and NG-monomethyl-L-arginine (L-NMMA, an inhibitor of NO production). Flow-mediated responses differed markedly between Marfan and control subjects (-1.6+/-3.5% versus 6. 50+/-4.1%, respectively; P<0.0001), whereas nitroglycerin produced similar vasodilation (14.2+/-5.7% versus 15.2+/-7.8%; P=NS). Agonist-induced vasodilation to incremental intra-arterial infusions of acetylcholine and bradykinin were not significantly different between Marfan and control subjects, and intra-arterial L-NMMA produced similar reductions in brachial artery diameter in both groups. CONCLUSIONS: These data demonstrate impaired flow-mediated but preserved agonist-mediated endothelium-dependent vasodilation in Marfan subjects and suggest preservation of basal NO release. Selective loss of flow-mediated dilation suggests a role for fibrillin in endothelial cell mechanotransduction.

Acetylcholine↗
PubMed1998

Medication errors in paediatric practice: insights from a continuous quality improvement approach.

UNLABELLED: The objective was to assess the incidence and consequences of medication errors, highlight sources of recurrent error and institute changes in practice to prevent their recurrence. Utilising a continuous quality improvement approach, a 2-year prospective cohort study was undertaken using an adverse incident reporting scheme. A multidisciplinary committee analysed medication error reports, classifying them according to type (prescription, supply or administration), severity (serious or not serious) and clinical outcome. Changes in policy and practice were implemented to reduce the frequency of errors. There were 441 reported medication errors in the study period, during which 682 patients were admitted for 5315 inpatient days. Errors were more seven times likely to occur in the intensive care setting. Doctors accounted for 72% of errors and prescription errors doubled when new doctors joined the rotation. Most errors (68%) were detected prior to drug administration. Twenty-four serious medication errors were not detected in advance, but only 4 had overt clinical consequences. Excluding prevented errors and appropriate deviations from prescribed therapy, there were 117 actual medication errors (1/5.8 admissions, or 1/45 inpatient days). During the 2nd year of the scheme, the incidence of all reported errors, administration errors and serious errors fell, but the prescription error rate remained constant. CONCLUSIONS: Medication errors occurred commonly in this study, but adverse consequences were rare. The non-punitive, multidisciplinary approach to medication errors utilised in this study increased staff vigilance, highlighted sources of recurrent error, and led to changes in drug policies and staff training, which resulted in improved patient safety and quality of care.

Cohort Studies↗
PubMed1998

Life expectancy in British Marfan syndrome populations.

A total of 206 patients with Marfan syndrome were ascertained throughout genetic clinics in Wales and Scotland during the period 1970-1990. There were 45 deaths representing 22% of the cohort. Mean age at death was 45.3+/-16.5 years. 50% median cumulative survival in the total cohort (n=206) was 53 years for males and 72 years for females. Multivariate analysis confirmed severity as the best independent indicator of survival. These findings and survival curves will assist in the counselling of British families and individuals with Marfan syndrome.

Adolescent↗
PubMed1995

Systemic thromboembolism leading to myocardial infarction and stroke after fenestrated total cavopulmonary connection.

Thromboembolic phenomena involving the caval veins, right atrium, and pulmonary artery are recognised complications after the Fontan operation and other forms of total cavopulmonary connection. A rare case of systemic thromboembolism is reported in a 3 year old girl who had repeated coronary and cerebral thromboembolic events after a fenestrated total cavopulmonary shunt operation. A survey of the 18 paediatric cardiac units in the United Kingdom and Ireland showed a wide discrepancy in anticoagulation policies after Fontan-type operations. Prevention of thrombotic complications by lifelong postoperative anticoagulation may outweigh the risk of haemorrhage.

Aspirin↗
PubMed1995

Cerebral blood flow and metabolism in children with severe head injury. Part 1: Relation to age, Glasgow coma score, outcome, intracranial pressure, and time after injury.

Understanding the pathophysiology of paediatric head trauma is essential for rational acute management. It has been proposed that the response to severe head injury in children differs from that in adults, with increased cerebral blood flow (cerebral hyperaemia) representing the most common cause of raised intracranial pressure, but this has recently been disputed. The relation between the pathophysiological response and time after injury has not been defined in children. This paper describes 151 serial measurements of cerebral blood flow, arteriojugular venous oxygen difference (AJVDO2), and cerebral metabolic rate for oxygen (CMRO2) that were performed in 21 children with severe head injury, mean age 8 (range 2-16) years, Glasgow coma score < or = 8. Absolute cerebral hyperaemia was uncommon, only 10 (7%) of the 151 cerebral blood flow values being at or above the upper limit of the range published in normal children. There was an inverse correlation between cerebral blood flow and intracranial pressure. (r = -0.24, p = 0.009). Contrary to the widespread assumption that cerebral metabolic rate in patients with head injury is always low, CMRO2 was initially within the normal range in 17/21 (81%) children. Both CMRO2 and AJVDO2 fell significantly between the first and third days after injury. There was a non-significant rise in cerebral blood flow over time. These data represent the first evidence that the temporal change in cerebral metabolic rate reported in experimental models of traumatic brain injury also occurs in patients with head injury. The changes in the pathophysiological response over time suggest that the management may need to be modified accordingly. If cerebral metabolic rate and cerebral oxygen extraction are maximal shortly after injury in children with severe head injury then the children are most likely to sustain secondary damage during this period.

Adolescent↗
PubMed1994

Glucose export from the brain in man: evidence for a role for astrocytic glycogen as a reservoir of glucose for neural metabolism.

We report transients of net export of glucose from brain with jugular venous glucose content exceeding arterial by up to 5.3 mmol.l-1 in 19 children undergoing cardiopulmonary bypass surgery. The magnitude of the release implies the presence of a glucose reservoir in brain, the most likely candidate being astrocytic glycogen. These data provide evidence that astrocytic glycogen can be exported as glucose, permitting spatial and temporal modulation of glucose delivery to neurons.

Astrocytes↗
PubMed1993

Cytogenetic abnormalities in a disseminated medulloblastoma.

A 3-year-old girl developed central nervous system, bone and bone marrow metastases, and hypercalcaemia shortly after presentation with medulloblastoma. Cytogenetic studies of the involved bone marrow showed multiple abnormalities including iso(17q). This chromosome rearrangement has been reported in other cases of recurrent or disseminated medulloblastoma. More studies are required relating the karyotypes of medulloblastomas to long-term outcome to determine if the presence of iso(17q) is a prognostic factor in this malignancy.

Bone Neoplasms↗
PubMed1993

Right heart pressure determination by Doppler in infants with tricuspid regurgitation.

Doppler and direct measurements of right ventricle to right atrial pressure drop were made during cardiac catheterisation on 28 occasions in 26 infants with congenital heart disease. Age was 10 days to 12 months (median 4.5 months), and weight was 3.1 to 9.0 kg (median 4.7 kg). We measured peak velocity of tricuspid regurgitation by continuous wave Doppler, and the pressure drop was calculated using the modified Bernoulli equation (delta p = 4v2). There was a high correlation (r = 0.95) between direct and Doppler measurements. Doppler values tended to underestimate the right ventricle to right atrial pressure drop, but this was not of clinical significance (mean 2 mm Hg). The 95% confidence interval for the Doppler velocity was -0.41 to +0.26 m/sec, and was consistent across the range of pressures studied. Variability between observers was tested, by two observers performing sequential paired examinations on 16 newborn babies with tricuspid regurgitation. The coefficient of repeatability was 6.3 mm Hg (95% confidence interval 4.7 to 9.5 mm Hg) or 0.26 m/sec (0.18 to 0.50 m/sec). This method of right ventricular pressure estimation, validated previously only in older children and adults, is a reproducible and accurate technique in infants with tricuspid regurgitation.

Blood Pressure↗
PubMed1991

Hypoplastic left heart syndrome: more potential transplant recipients than suitable donors.

Neonatal cardiac transplantation offers the prospect of survival for babies with hypoplastic left heart syndrome--but only if suitable donors are available. In a retrospective survey in the Northern health region of England and Wales, the likely need for neonatal cardiac transplantation far outweighed the potential availability of donors. Over 8 years (1983-90) hypoplastic left heart syndrome was identified in 38 newborn babies and in 9 fetuses in utero. Of 41 live births (including 3 diagnosed prenatally) 31 would have been candidates for a cardiac transplant, but only 4 suitable donors could be identified (3 with anencephaly born alive during the same period and 1 who died between 1979 and 1986 after a head injury). Analysis of all infant deaths in 1987-89 revealed only 3 potential donors from 426 deaths in the 3 years. Although more widespread antenatal diagnosis may lead to fewer liveborn babies with hypoplastic left heart syndrome, these findings indicate that an alternative source of donors needs to be identified before neonatal cardiac transplantation can be widely used in the treatment of this disorder.

Abortion, Induced↗
PubMed1991

A practical method of serial bedside measurement of cerebral blood flow and metabolism during neurointensive care.

Acute encephalopathy is a major cause of death and neurological handicap in children. The principle aims of treatment are to provide adequate cerebral blood flow for the brain's metabolic needs and to prevent intracranial pressure rising above the level at which brain herniation occurs. Rational management requires an understanding of the pathophysiological changes in cerebral blood flow and metabolism which occur. The paucity of data on this subject reflects the perceived difficulty of measuring cerebral blood flow and cerebral metabolism in children. A modification of the Kety Schmidt technique of measuring cerebral blood flow and cerebral metabolism is described. This modification makes it possible to perform serial bedside measurements in children receiving intensive care. This method was used to perform 348 measurements in 58 children. The method was reproducible and no significant complications were encountered. The results indicated that appreciable changes in cerebral blood flow and metabolism could occur in individual patients over time, emphasising the importance of serial measurements. This technique may provide a practical means of monitoring cerebral blood flow and metabolism in very sick children receiving neurointensive care and evaluating the efficacy of treatment.

Acute Disease↗