Bedside diagnosis of stenosis of middle cerebral artery.
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Cerebrovascular Circulation↗
Biomedical subjects
F J Kirkham
Publications and source records attributed to F J Kirkham.
Transcranial measurement of blood velocities in the basal cerebral arteries using pulsed Doppler ultrasound: a method of assessing the Circle of Willis.
Transcranial pulsed Doppler ultrasound and spectral analysis were used for detection of blood velocities in the basal cerebral arteries. The Doppler transducer was placed superior to the zygomatic arch and during insonation of the middle cerebral artery care was taken to obtain maximum Doppler-shift frequency signals since this allowed a small angle between the ultrasound beam and this artery. Doppler signals were obtained from the middle, anterior, and posterior cerebral arteries in 20 volunteers with the average depth of the Doppler gate at 4.9 (4.6-5.2 cm), 5.2 (4.9-5.4 cm), and 6.3 cm (6.0-6.9 cm), respectively. These measurements were in agreement with those obtained for 15 cadaver studies, in whom the distance from the proposed site of the Doppler transducer to each basal cerebral artery was measured as 4.7 +/- 0.6, 5.3 +/- 0.5, and 5.9 +/- 0.9 cm, respectively. The reproducibility of middle cerebral artery blood velocity values was tested in seven subjects and showed a variation of not more than 8% in any individual. The method was used in combination with common carotid compression to assess four patients who had occlusive extracranial carotid disease; in three the disease was more severe on one side and reversal of blood flow in the proximal ipsilateral anterior cerebral artery was demonstrated, consistent with cross flow from the contralateral side via the anterior communicating artery of the Circle of Willis. In the fourth patient augmentation of posterior cerebral artery blood velocities during common carotid compression indicated the major collateral source was from the vertebrobasilar system.
Adult↗
Transcranial measurement of blood velocities in the basal cerebral arteries using pulsed Doppler ultrasound: velocity as an index of flow.
Blood velocities have been measured transcranially, at small Doppler angles, in the middle cerebral artery of normal volunteers. Cerebral blood flow was changed by varying carbon dioxide tension. In four volunteers, the relationships between arterial pCO2 and percentage change in intensity weighted mean, median, and maximum Doppler-shifted frequencies in the internal carotid and middle cerebral arteries were linear with slopes of 2.5 and 2.8% per mm Hg change in pCO2. In 38 volunteers, the relationship between end-expiratory pCO2 and time-averaged maximum Doppler frequency was linear over the range of pCO2 20-60 mm Hg with slopes of 2.5 and 2.9 percentage change per mm Hg, for internal carotid and middle cerebral, respectively. These results are very similar to those reported using direct methods of measuring cerebral blood flow. As the transcranial Doppler method is reproducible, this indicates that changes in middle cerebral blood velocity may be used to monitor changes in flow.
Adult↗
Successful management of severe intracranial hypertension by surgical decompression.
Because of the rather disappointing results in the treatment of acute head-injury in adults, surgical decompression has been little used in the management of severe intracranial hypertension. The authors report the successful use of the technique for a child with encephalitis in whom cerebral perfusion was compromised.
Child↗
Anatomical validation of middle cerebral artery position as identified by transcranial pulsed Doppler ultrasound.
The basal cerebral arteries were insonated using transcranial pulsed Doppler ultrasound (TPDU) at 2 MHz. The Doppler sample volume (SV) depths at which signals were obtained which could be attributed to the middle, anterior and posterior cerebral arteries (MCA, ACA and PCA) were compared with measurements in adult cadavers and with B-scan ultrasound studies in infants. The depth of the internal carotid artery (ICA) terminal division into ACA and MCA was closely correlated for both groups. In adults, it was found at 5.6 +/- 1.0 cm using TPDU while in cadavers it was found at 5.3 +/- 0.5 cm from the temporal bone. In infants, it was found at 3.2 +/- 0.3 cm for the right side, and 3.2 +/- 0.2 cm for the left side using TPDU, and at 3.4 +/- 0.4 cm and 3.4 +/- 0.5 cm for right and left sides respectively using B-scan ultrasound. The mean depth of the MCA mid-point in infants as defined by TPDU and B-scan was also closely correlated, with values of 2.8 +/- 0.3 cm and 2.7 +/- 0.3 cm for right and left sides respectively using TPDU and of 2.8 +/- 0.4 cm and 2.7 +/- 0.4 cm for right and left sides respectively using B-scan ultrasound. Values for the most lateral part of the MCA did not correlate. In adults, signals from the ACA and PCA were obtained at greater SV depth than the MCA, thus preventing confusion.
Adult↗
Ontogeny and neonatology of circulating endogenous inhibitor(s) of prostaglandin synthase in the human.
To further understand the mechanism by which in vivo prostaglandin synthesis may be orchestrated, plasma levels of endogenous inhibitor(s) of prostaglandin synthase (EIPS) in the human fetus, neonate and adult have been measured. In general, a reciprocal relationship was found between plasma EIPS levels and previously reported plasma prostaglandin concentrations. This result supports a role for EIPS in the control of prostaglandin biosynthesis in the human.
Adult↗
Recognition and prevention of neurological complications in pediatric cardiac surgery.
Because of advances in surgical and cardiopulmonary bypass techniques it is now possible to definitively repair the vast majority of congenital heart disease in infancy or childhood. Although the majority of survivors do not have obvious cerebral sequelae, there is increasing disquiet about the high incidence of acute neurological events in the immediated postoperative period as well as evidence that at long-term follow-up there are subtle cognitive and motor deficits in many. Some children are more at risk of neurodevelopmental problems, either because of their cardiac (e.g. , extensive aortopulmonary collaterals) or cerebrovascular (e.g., the propensity to large vessel dissection) anatomy or because of genetic predisposition (e.g., to prothrombotic disorders). The incidence may vary with the surgery (e.g., the Fontan operation) and the cardiopulmonary bypass technique necessary to achieve an adequate technical repair (e.g., low or no flow at deep hypothermia). Recognition of the population at risk will lead to prevention of serious sequelae. Data collected in adults may be misleading, and many pediatric units have developed their own practice, but recent studies in animal models of child surgery and in children have produced some evidence to guide management to ensure the optimal cerebral as well as cardiac outcome. Pump flow should be maintained at least 30 ml/kg/min where possible, with inotropic support to maintain blood pressure if necessary. If pump flow must be lowered or circulatory arrest is essential, thorough cerebral cooling to deep hypothermic temperatures is mandatory; a pH-stat strategy may make this easier, but an alpha-stat strategy may be better in those operations that can be performed at moderate hypothermia. There is no evidence that the available pulsatile pumps offer an advantage. Tissue oxygenation may reach critical levels and a high hematocrit and oxygen tension may reduce the risk of significant hypoxia. There is a risk of embolization in children, which can be reduced with membrane oxygenators and careful monitoring; the role of arterial filtration remains controversial. The only protective agent that can currently be recommended is methylprednisolone to protect the spinal cord (e.g., in operations on the aortic arch). Further studies are needed in this important area.
Adolescent↗
Coma scales for children with severe falciparum malaria.
The Blantyre coma scale (BCS) is used to assess children with severe falciparum malaria, particularly as a criterion for cerebral malaria, but it has not been formally validated. We compared the BCS to the Adelaide coma scale (ACS), for Kenyan children with severe malaria. We examined the inter-observer agreement between 3 observers in the assessment of coma scales on 17 children by measuring the proportion of agreement (PA), disagreement rate (DR) and fixed sample size kappa (kappa n). We assessed the sensitivity and specificity of the scales in detecting events (seizures and hypoglycaemia) in 240 children during admission and the usefulness of the scales in predicting outcome. There was considerable disagreement between observers in the assessment of both scales (BCS: PA = 0.55, DR = 0.09 and kappa n = 0.27; ACS: PA = 0.36, DR = 0.31, and kappa n = 0.31), particularly with the verbal component of the BCS (kappa n = 0.02). Compared to the ACS, the BCS was more specific (0.85 for BCS and 0.80 for ACS), but less sensitive (0.25-0.69 vs. 0.38-0.88 respectively) in detecting events and was a worse predictor of neurological sequelae. The BCS provided a better overall assessment of a child's incapacity from falciparum malaria, but the ACS was more useful in assessing neurological disturbances.
Age Factors↗