Levels of the Alkoxy Radical in Patients with Brain Death

Lipid peroxidation is induced by reactive oxygen species and is involved in acute neuronal damage. Thus, controlling this process may be a realistic therapeutic strategy for treating or preventing neuronal damage. However, the study of free radicals in body fluids is currently severely hampered by technical difficulties in their detection. We have developed an ex vivo electron spin resonance (ESR) method, that employs 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap, to measure the alkoxyl radical (OR) in human blood. We found that this method can detect OR produced by treating human blood ex vivo. Analysis of jugular venous and radial arterial blood from patients with acute neuronal damage revealed higher OR levels in the venous blood compared to arterial samples. In brain death patients, however, the jugular vein OR spectrum was similar to the radial artery OR level. The ratio between radial artery and jugular vein levels, expressed as the RI (radical intensity) ratio = aORI/jORI, was calculated. A rterial-jugular bulb RI ratio below 1, together with accepted clinical criteria (unresponsive coma with brainstem areflexia), may provide a non-invasive assessment of cerebral circulatory arrest that can help to predict brain death. This novel ex vivo ESR method may be very useful for measuring oxidative stress in patients with acute neuronal damage.