UBC Theses and Dissertations
Development, validation and application of analytical methods to measure prognostic biomarkers in patients receiving on-pump coronary artery bypass grafting surgery Hui, Yu
Temporary interception and then re-infusion of oxygenated blood into heart during on-pump Coronary Artery Bypass Grafting (CABG) surgery causes ischemia-reperfusion injury (IRI). Propofol is an intravenous anesthetic agent that maybe potentially cardioprotective against IRI. This thesis presents the development, validation and application of analytical methods for monitoring propofol and a series of prognostic biomarkers in hope of identifying contributory factors to IRI and propofol cardioprotection. I developed a Capillary Electrophoresis (CE) method to quantify propofol concentrations in blood. Propofol concentrations in the μg/mL range were measured from 400 μL samples. A dosefinding study using this method determined a practical infusion rate of 120 μg•kg•min⁻¹ to achieve the target blood concentration of 5 μg•mL⁻¹. To measure the oxidative stress biomarker, 15-F₂t₋isoprostane, the nitrosative stress biomarker, 3-nitrotyrosine, the myocardial protective factor, adenosine, and the cardiovascular risk factor, asymmetric dimethylarginine (ADMA), I developed simple, sensitive and robust Liquid Chromatography-Mass Spectrometry (LC-MS) or Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) methods. Briefly, a basic mobile phase and base-resistant column were used for the LC-MS analysis of 15-F₂t-isoprostane. A one-step solid phase extraction and pentafluorophenyl (PFP) core-shell column were employed for the LC-MS/MS analysis of 3- nitrotyrosine. A Strong Cation Exchange (SCX) solid phase extraction and modifier-free mobile phase were implemented for the LC-MS/MS analysis of adenosine. A new derivatization method to enable baseline separation of ADMA and its regio-isomer symmetric dimethylarginine (SDMA) was developed for the ADMA LC-MS/MS quantitation. Performance parameters for these methods, including linearity, precision, accuracy, Limit of Detection (LOD), Limit of Quantitation (LOQ), Lower Limit of Quantitation (LLOQ) and stability were found satisfactory. Concentrations of 15-F₂t₋isoprostane, 3-nitrotyrosine and adenosine were found to rise after on-pump CABG surgery. However, these changes were not able to explain the cardioprotective effect of propofol. Nonetheless, the correlations of 15-F₂t₋isoprostane with diabetes, glucose concentration and PTEN level were significant. Patients with low cardiac output syndrome experienced more 3-nitrotyrosine increase than patients without this syndrome. The basal adenosine level was found to increase more in patients with low left ventricular ejection fraction. These findings and the underlying methodologies are important for identifying new prognostic biomarkers.
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