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Biomedical subjects

F J Kirkham

Publications and source records attributed to F J Kirkham.

At least 19 recordsLinked to original sources
PubMed1998

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↗
PubMed1997

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↗
PubMed1997

Noonan syndrome and moyamoya.

We report a patient with Noonan syndrome and asymptomatic cardiac disease (supravalvular aortic stenosis and pulmonary valvular stenosis) who had frequent transient ischemic attacks. Bilateral moyamoya was evident; in addition, he manifested activated protein C resistance and was heterozygous for the factor V Leiden mutation. Anticoagulation abolished his episodes and, despite extensive cerebrovascular disease, he has no permanent neurologic deficits. The association between Noonan syndrome and moyamoya has not previously been described. Disruption of vascular development in prenatal life may have resulted in both cardiac and cerebrovascular disease in this child.

Anticoagulants↗
PubMed1997

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↗
PubMed1997

Variable presentation of cerebrovascular disease in monovular twins.

We describe twin girls with bilateral cerebrovascular disease. In one child, a diagnosis of moyamoya disease was made after presentation in infancy with an acute hemiparesis; her asymptomatic sibling was found to have significant bilateral cerebrovascular disease after neuropsychological evaluation and assessment with transcranial Doppler ultrasound. Both subjects showed a discrepancy between verbal and performance IQ and deficits on a test of frontal-lobe function suggesting that these domains should be targeted in cognitive assessment. Family members of subjects with moyamoya are at risk of cerebrovascular disease. Clinical symptoms do not reliably predict disease and those at risk should be offered screening with non-invasive vascular imaging.

Cerebral Angiography↗
PubMed1997

Intracranial hypertension in Africans with cerebral malaria.

The causes of death and neurological sequelae in African children with cerebral malaria are obscure. Intracranial pressure (ICP) was monitored and cerebral perfusion pressure (CPP) calculated in 23 Kenyan children with cerebral malaria. Four children had severe intracranial hypertension (ICP > 40 mm Hg, CPP < 40 mm Hg): two died, one with an ICP of 158 mm Hg and signs of transtentorial herniation, the other one with an ICP of 42 mm Hg and cardiorespiratory arrest. The other two survived with severe neurological sequelae. Nine had intermediate intracranial hypertension (ICP > 20 mm Hg, CPP < 50 mm Hg) and 10 had mild intracranial hypertension (maximum ICP 10-20 mm Hg); all survived without severe sequelae. Mannitol controlled the ICP in children with intermediate intracranial hypertension, but it did not prevent the development of intractable intracranial hypertension in children with severe intracranial hypertension. Intracranial hypertension is a feature of Kenyan children with cerebral malaria and severe intracranial hypertension is associated with a poor outcome.

Child↗
PubMed1997

Mechanisms of ischaemic stroke after chickenpox.

Ischaemic stroke is a recognized complication of chickenpox. Seven cases of ischaemic stroke in children after recent varicella infection are discussed in detail to emphasise that there are several mechanisms by which this may arise.

Cerebral Infarction↗
PubMed1997

Diffusion weighted magnetic resonance imaging of compromised tissue in stroke.

Diffusion weighted imaging (DWI) and T2 weighted magnetic resonance imaging were performed on at least two occasions in 28 children presenting with stroke. In previous reports of DWI in human stroke, eventual infarction was observed (with only one exception) in all regions in which early DWI hyperintensity occurred. In the present report, two children had regions of DWI hyperintensity which did not progress to infarction. One patient who presented with right hemiplegia showed extensive high signal on DWI, with T2 evidence of tissue swelling but without hyperintensity. DWI changes persisted over weeks, with no imaging indication of infarction. This child recovered completely. A second child who had a major vessel infarct with concomitant regions of hyperintensity on T2 weighted imaging and DWI, also had DWI hyperintensity in an adjacent territory which did not develop any subsequent evidence of infarction. Thus in clinical practice DWI can demonstrate tissue which is compromised but not irreversibly so.

Brain↗
PubMed1997

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↗
PubMed1996

Perturbations of cerebral hemodynamics in Kenyans with cerebral malaria.

The mechanisms of death and neurologic sequelae in African children with cerebral malaria are undetermined. Because pathologic features are confined to the cerebral vasculature, perturbations in cerebral hemodynamics may be responsible. We compared the transcranial Doppler findings in 50 children with cerebral malaria with those of 115 conscious Kenyan children. In addition, 10 children with cerebral malaria were studied during intracranial pressure monitoring and nine children were studied during the agonal stages. In the children with cerebral malaria, cerebral blood flow velocity was increased in 30%, usually associated with seizures. Of the 11 children who developed neurologic sequelae, six had sonographic abnormalities associated with lateralizing deficits, including four children with hemiparesis (in two children the contralateral middle cerebral artery could not be insonated and two had transient increases in blood flow velocity associated with seizures). In the children with severe intracranial hypertension, there was a significant linear relationship between the cerebral perfusion pressure and blood flow velocity, suggesting that autoregulation was impaired. Sonographic features of progressive intracranial hypertension, were observed in three children with cerebral malaria who died. Perturbations of cerebral hemodynamics are associated with a poor outcome in Kenyan children with cerebral malaria.

Blood Flow Velocity↗
PubMed1996

Painful and painless ophthalmoplegia with cavernous sinus pseudotumour.

Acquired isolated ophthalmoplegia in childhood has many potential causes. Although other ophthalmological or clinical features may aid lesion localisation, the absence of these does not preclude structural pathology. Two cases of cavernous sinus pseudotumour presented as ophthalmoplegia with and without pain. Magnetic resonance imaging of the cavernous sinus revealed the presence of enhancing tissue consistent in appearance with pseudotumour in both cases, and they responded well to steroid treatment. These cases emphasise the importance of detailed imaging of the cavernous sinus in the investigation of these symptoms in order to exclude this treatable condition.

Adolescent↗
PubMed1995

Inter-observer agreement of the assessment of coma scales and brainstem signs in non-traumatic coma.

The authors evaluated the inter-observer agreement between two experienced clinicians examining 19 unconscious children who were not paralysed or ventilated. Inter-observer reliability was assessed by proportion of agreement, disagreement rate and kappa statistics. Corneal reflexes, pupillary responses to light and motor responses were the most reliably elicited. Reduction of the number of categories improved inter-observer agreement. Some of the disagreement may be attributed to changes in the child's condition during the period of assessment. There was more agreement about the five-category 0-IV scale than the summated Adelaide (10-category) and Jacobi (13-category) scales. The ability of these scales to follow changes in the patient's condition and to predict outcome needs to be evaluated in a prospective trial.

Brain Stem↗
PubMed1995

Incidence of neurological complications of surgery for congenital heart disease.

A total of 523 cardiac surgical discharge summaries were searched for recorded evidence of adverse neurological events occurring between operation and time of discharge. Neurological events were recorded in 31 and included one or more of seizure disorder (n = 16), pyramidal signs (n = 11), extrapyramidal signs (n = 8), coma (n = 6), and neuro-ophthalmic deficits (n = 6). There were significantly more adverse neurological events after repairs for arch anomalies (16.6% of cases). There was also an association with the length of cardiopulmonary bypass and a period of low perfusion pressure either intraoperatively or postoperatively. Of the 19 out of 23 survivors in whom long term outcome data were available, four were normal and six had persisting neurological problems directly related to the perioperative period. In a further nine of the 19 survivors, established preoperative neurodevelopmental abnormality probably contributed to their present neurological status, in addition to perioperative events. In view of the way these data were collected, this study must represent the minimum incidence of neurological events in children undergoing cardiac surgery.

Blood Pressure↗