PubMed Health⌕ Search

Biomedical subjects

Martyn G Boutelle

Publications and source records attributed to Martyn G Boutelle.

8 recordsLinked to original sources
PubMed2006

Evaluation of laser speckle flowmetry for imaging cortical perfusion in experimental stroke studies: quantitation of perfusion and detection of peri-infarct depolarisations.

Laser speckle imaging of the exposed cerebral cortex allows detailed examination of the time course and topography of perfusion under different experimental conditions. Here we examine the quantitative capacity of the method and its sensitivity for the detection of peri-infarct depolarisations (PIDs). In four cats anaesthetised with chloralose, the right hemisphere was exposed and the right middle cerebral artery was occluded. The brain was illuminated with a laser diode, the speckle pattern was imaged, and images of inverse speckle correlation time (ICT) were derived from the calculated speckle contrast images. We examined the relationship of ICT with perfusion, as imaged quantitatively using umbelliferone clearance (CBF(umb)). Values of ICT and CBF(umb) were compared and regression parameters were calculated for each experiment. In eight cats, cortical surface direct current (DC) potential was monitored at two locations and detection of PIDs by DC potential and ICT change was compared. ICT- and CBF(umb)-derived values of perfusion were closely correlated, with a high degree of significance (P<0.0001). Overall, monitoring of DC potential detected 90% of PIDs, whereas ICT detected 56%. We conclude that (1) laser speckle imaging provides an index of perfusion that has a linear relationship with the clearance rate of umbelliferone within the range of levels of perfusion examined; (2) this relationship is relatively stable between experiments; and (3) the method's ability to detect blood flow changes associated with PIDs likely depends on the noise level of the speckle measurements.

Animals↗
PubMed2006

Application of rapid-sampling, online microdialysis to the monitoring of brain metabolism during aneurysm surgery.

OBJECTIVE: To introduce rapid-sampling microdialysis for the early detection of adverse metabolic changes in tissue at risk during aneurysm surgery. METHODS: A microdialysis catheter was inserted under direct vision into at-risk cortex at the start of surgery. This monitoring was sustained throughout the course of the operation, during which intraoperative events, for example, temporary arterial occlusion or lobe retraction, were precisely documented. A continuous online flow of dialysate was fed into a mobile bedside glucose and lactate analyser. This comprises flow-injection dual-assay enzyme-based biosensors capable of determining values of metabolites every 30 seconds. RESULTS: Eight patients underwent clipping or wrapping of intracranial aneurysms and were monitored. Time between events and detection: 9 minutes. Mean change in metabolite value +/- standard deviation: temporal lobe retraction lactate, +656 +/- 562 micromol/L (n = 7, P < 0.05); glucose, -123 +/- 138 micromol/L (n = 6, P = 0.08). Glucose intravenous bolus infusion glucose, +512 +/- 244 micromol/L (n = 5, P < 0.01); peak at mean time after bolus, 16 minutes. Temporary proximal clip lactate, +731 +/- 346 micromol/L (n = 6, P < 0.01); glucose, -139 +/- 96 micromol/L (n = 5, P < 0.05); mean clip time, 8.6 minutes. CONCLUSION: The technique detects changes 9 minutes after intraoperative events occur (limited only by probe-to-sensor tubing length and dialysate flow rate). This provides reliable information to the surgeon and anesthetist promptly. It is a useful method for monitoring glucose and lactate in dialysate, particularly when rapid, transient changes in brain analyte levels need to be determined and the alternative offline methodology would be inadequate.

Adult↗
PubMed2005

Transient changes in cortical glucose and lactate levels associated with peri-infarct depolarisations, studied with rapid-sampling microdialysis.

Peri-infarct depolarisations (PIDs) contribute to infarct expansion in experimental focal ischaemia; furthermore, depolarisations propagate in the injured human brain. Glucose utilisation is increased under both conditions, and depletion of brain glucose carries a poor prognosis. We studied dynamics of cerebral glucose and lactate in relation to PID patterns in experimental stroke. The middle cerebral artery was occluded for 3 h in 23 cats under terminal chloralose anaesthesia. We used fluorescence imaging to detect occurrence of PIDs, and rapid-sampling online microdialysis (rsMD), coupled to a flow-injection assay, to examine changes in cerebral cortical extracellular glucose and lactate at intervals of 30 sec each. After 30 min' ischaemia, lactate had increased by 43.6+/-s.d. 45.9 micromol/L, and stabilised in that range for 3 h. In contrast, glucose fell only slightly initially (11.9+/-9.7 micromol/L), but progressively decreased to a reduction of 56.7+/-47.2 micromol/L at 3 h, with no evidence of stabilisation. There was a highly significant inverse relationship of frequency of PIDs with plasma glucose (P<0.001). The results also characterise a metabolic signature for PIDs for possible application in clinical work, and emphasise potential risks in the use of insulin to control plasma glucose in patients with brain injury.

Animals↗
PubMed2005

Dynamic changes in brain glucose and lactate in pericontusional areas of the human cerebral cortex, monitored with rapid sampling on-line microdialysis: relationship with depolarisation-like events.

The pathophysiology of peri-lesion boundary zones in acute brain injury is highly dynamic, and it is now clear that spreading-depression-like events occur frequently in areas of cerebral cortex adjacent to contusions in the injured human brain. An automated method to assay microdialysate from peri-lesion cerebral cortex in 11 patients with intracranial haematomas requiring surgery was used. Perfusate (2 microL/min) flowed directly into a flow-injection system for assay of glucose and lactate at intervals typically of 30 secs each. Four channels of electrocorticogram (ECoG) were recorded from a subdural strip adjacent to the catheter. Several patterns of change in metabolites were identified in different time domains. Overall, the number of transient lactate events was significantly correlated with the number of glucose events (r2=0.48, P=0.027, n=10). Progressive reduction in dialysate glucose was very closely correlated with the aggregate number of ECoG events (r2=0.76, P=0.0004, n=11). It is proposed that the recently documented adverse impact of low dialysate glucose on clinical outcome may be because of recurrent, spontaneous spreading-depression-like events in the perilesion cortex.

Adult↗
PubMed2002

Cooperative anion binding and electrochemical sensing by modular podands.

A series of podands based on two or three hydrogen bonding "arms" situated in mutually ortho, meta, or para relationships about an aryl core have been prepared, and their affinities for simple inorganic anions were measured. Of the two-arm hosts the meta compound and to a lesser extent the ortho host exhibit a cooperative anion binding effect. The two arms function essentially independently in the para derivative. The mutually meta three-arm host shows dramatically enhanced cooperative binding. Conformational changes within the meta two-arm host result in significantly enhanced electrochemical anion sensing compared with the more conformationally rigid three-arm host.

Anions↗
PubMed2002

Spreading and synchronous depressions of cortical activity in acutely injured human brain.

BACKGROUND AND PURPOSE: Cortical spreading depression (CSD) has been much studied experimentally but never demonstrated unequivocally in human neocortex by direct electrophysiological recording. A similar phenomenon, peri-infarct depolarization, occurs in experimental models of stroke and causes the infarct to enlarge. Our current understanding of the mechanisms of deterioration in the days after major traumatic or ischemic brain injury in humans has not yielded any effective, novel drug treatment. This study sought clear evidence for the occurrence and propagation of CSD in the injured human brain. METHODS: In 14 patients undergoing neurosurgery after head injury or intracranial hemorrhage, we placed electrocorticographic (ECoG) electrodes near foci of damaged cortical tissue. RESULTS: Transient episodes of depressed ECoG activity that propagated across the cortex at rates in the range of 0.6 to 5.0 mm/min were observed in 5 patients; this rate of propagation is characteristic of CSD. We also observed, in 8 of the 14 patients, transient depressions of ECoG amplitude that appeared essentially simultaneous in all recording channels, without clear evidence of spread. CONCLUSIONS: These results indicate that CSD or similar events occur in the injured human brain and are more frequent than previously suggested. On the basis of these observations, we suggest that the related phenomenon, peri-infarct depolarization, is indeed likely to occur in boundary zones in the ischemic human cerebral cortex.

Blood Flow Velocity↗