tokens: Plasma malondialdehyde , which was present in minimal amount at zero time ( 0 . 058 mumol / liter plasma ; SD 0 . 015 ) , increased after 5 min of ischemia , resulting in a fivefold increase after 30 min of carotid occlusion ( 0 . 298 mumol / liter plasma ; SD 0 . 078 ) .