Quantification of metabolism and oxidative and nitrosative stress

Supervisor: P. Radermacher

Circulatory shock lead to metabloc stress, the biological hallmarks being hyperglycemia and hyperlactatemia. Differentiation of the contribution of endogenous glucose formation, glucose oxidation, and/or peripheral glucose disposal requires assessment of whole-body energy expenditure using indirect calorimetry (i.e. O2-uptake (VO2) and CO2-production (VCO2) from the respiratory gases) together with the quantification of glucose turnover rates derived from blood glucose isotope and 13CO2/12CO2-isotope enrichment during „steady state“-infusion of 1,2,3,4,5,6-13C6-glucose. The standard technique for the measurement of the 13CO2/12CO2-isotope-enrichment, „non-dispersive infrared spectrometry“ (NDIRS) cannot be used during administration of increased inspiratory O2-concentrations due to moelcular collisions.

Numerous chronic and acute diseases lead to excess formation of O- and N-radicals (reactive oxygen species, ROS; reactive nitrogen species, RNS). Due to their short half life and their reactivity, ROS and RNS formation is currently evaluated using surrogate parameters. The “gold standard” for the direct measurement of ROS/RNS release, electron spin resonance (ESR) is technically complex and unavailable for serial, bedside measurements due cumbersome equipment.

The current project ist to test i) miniaturised IR-sensors for the online measurement of the 13CO2/12CO2-isotope enrichment during mechanical ventilation with increased inspiratory O2-concentrations, and ii) a miniaturized ESR-sensor for the measurement of ROS- and RNS-release in the blood under well-defined conditions of increased oxidative and nitrosative stress.