Biomedical subjects

Andre Chow

Publications and source records attributed to Andre Chow.

4 recordsLinked to original sources

PubMed2006

Multi-slice computed tomography in coronary artery disease.

Multi-slice computed tomography technology is emerging as a realistic investigation in patients with suspected disease in native, stented or grafted coronary arteries. A non-invasive diagnostic tool is desirable as these patients are at high risk for complications of invasive angiography. A 64-slice CT may achieve the desired diagnostic accuracy, and overcome the limitations of spatial resolution, respiratory motion, artifacts from calcification and stents, and radiation dose considerations to produce reliable image quality. These advances, as well as the capacity for integrated functional cardiac assessment, may change the referral patterns in patients who have had previous bypass surgery or percutaneous intervention. This review outlines the debated issues about 64-slice cardiac CT in patients before and after coronary artery bypass surgery, as well as coronary stenting and functional assessment. A review of the recent literature on native coronary artery and bypass graft assessment by multi-slice CT is also performed.

Calcinosis↗

PubMed2006

Does serum procalcitonin have a role in evaluating the severity of acute pancreatitis? A question revisited.

PURPOSE: This study was designed to evaluate the diagnostic accuracy of serum procalcitonin (PCT) for the diagnosis of severity in acute pancreatitis (AP), compared with routine clinical, biochemical, radiological, and combination severity scoring systems. METHODS: Quantitative meta-analysis was performed on prospective studies, comparing serum PCT, against validated scoring systems for diagnosing severe AP. The sensitivity, specificity, and diagnostic odds ratio were calculated for each study. Summary receiver operating characteristic (SROC) curves and subgroup analysis were undertaken. Study quality and heterogeneity were evaluated. Meta-regression meta-analysis was used to evaluate the effect of using serum PCT in the diagnostic accuracy severity scoring in AP. RESULTS: Summary receiver operating characteristic analysis of nine studies showed an overall sensitivity and specificity of 74% (range: 66%-81%) and 83% (range: 79%-87%), respectively. Overall unweighted area under the curve (AUC) was 0.91 (DOR = 16.26 95% CI: 5.68-46.60), demonstrating significant heterogeneity (Q-value = 25.32; P = 0.001). When high-quality studies alone were evaluated, there was an increase in the overall sensitivity (89%); however, specificity was similar (82%), with an overall unweighted AUC of 0.94 (DOR 41.46, 95% CI: 17.95-95.80), with no significant heterogeneity. Meta-regression analysis confirmed the significant effect of study quality on the diagnostic accuracy of severity scoring using serum PCT (P = 0.025). CONCLUSIONS: The use of PCT for severity scoring in AP has a moderate sensitivity but higher specificity. However, the overall accuracy for predicting severity in AP is high. The prognosis of severity, especially early on (<48 hours from onset of symptoms), and the evaluation of potential infectious complications of AP may be the most useful factors to assess in subsequent clinical trials to identify its exact application in clinical practice in the management of AP.

Acute Disease↗

PubMed2005

Xenon and hypothermia combine to provide neuroprotection from neonatal asphyxia.

Perinatal asphyxia can result in neuronal injury with long-term neurological and behavioral consequences. Although hypothermia may provide some modest benefit, the intervention itself can produce adverse consequences. We have investigated whether xenon, an antagonist of the N-methyl-D-aspartate subtype of the glutamate receptor, can enhance the neuroprotection provided by mild hypothermia. Cultured neurons injured by oxygen-glucose deprivation were protected by combinations of interventions of xenon and hypothermia that, when administered alone, were not efficacious. A combination of xenon and hypothermia administered 4 hours after hypoxic-ischemic injury in neonatal rats provided synergistic neuroprotection assessed by morphological criteria, by hemispheric weight, and by functional neurological studies up to 30 days after the injury. The protective mechanism of the combination, in both in vitro and in vivo models, involved an antiapoptotic action. If applied to humans, these data suggest that low (subanesthetic) concentrations of xenon in combination with mild hypothermia may provide a safe and effective therapy for perinatal asphyxia.

Analysis of Variance↗

PubMed2004

Dexmedetomidine enhances analgesic action of nitrous oxide: mechanisms of action.

BACKGROUND: Nitrous oxide and dexmedetomidine are thought to mediate analgesia (antinociception in a noncommunicative organism) via alpha 2B- and alpha 2A-adrenergic receptor subtypes within the spinal cord, respectively. Nitrous oxide and dexmedetomidine exert diametrically opposite effects on neuronal activity within the locus ceruleus, a pivotal site for modulation of analgesia. Because of these differences, the authors explored whether the two analgesics in combination would provide satisfactory analgesia. METHODS: The analgesic effects of nitrous oxide and dexmedetomidine given both intraperitoneally and intrathecally were evaluated using the tail-flick latency test in rats. For investigation of the interaction, rats were pretreated with dexmedetomidine, either intraperitoneally or intrathecally, immediately before nitrous oxide exposure such that peak antinociceptive effects of each drug coincided. For assessment of the effect on tolerance, dexmedetomidine was administered as tolerance to nitrous oxide developed. Expression of c-Fos was used to assess neuronal activity in the locus ceruleus. RESULTS: Nitrous oxide and dexmedetomidine increased tail-flick latency with an ED50 (mean +/- SEM) of 55.0 +/- 2.2% atm for nitrous oxide, 27.6 +/- 5.1 for microg/kg intraperitoneal dexmedetomidine, and 2.9 +/- 0.1 microg for intrathecal dexmedetomidine. Combinations of systemically administered dexmedetomidine and nitrous oxide produced an additive analgesic interaction; however, neuraxially administered dexmedetomidine interacted synergistically with nitrous oxide. Tolerance to nitrous oxide was reversed by coadministration of dexmedetomidine. Prazosin, the alpha 1-/alpha 2B-adrenoceptor antagonist, attenuated the analgesic effect of nitrous oxide and prevented dexmedetomidine-induced reversal of tolerance to nitrous oxide. Nitrous oxide-induced increase of neuronal activity in the locus ceruleus was reversed by dexmedetomidine. CONCLUSION: The synergistic analgesic interaction between nitrous oxide and dexmedetomidine within the spinal cord is obscured by a supraspinal antagonism when dexmedetomidine is administered systemically in the pretolerant state. After tolerance to nitrous oxide develops, supraspinal functional antagonism no longer obtains exposing the synergistic action at the level of the spinal cord, which expresses itself as a reversal of the tolerant state. The authors speculate that the addition of dexmedetomidine to nitrous oxide is likely to provide enhanced and more durable analgesia in settings in which nitrous oxide is currently used alone (e.g., labor and dental surgery).

Analgesics↗