HOW DO pH INDICATORS WORK? pH indicators detect the presence of H+ and OH-. They do this by reacting with H+ and OH-: they are themselves. weak acids and bases. If an indicator is a weak acid and is coloured and its conjugate base has a different. colour, deprotonation causes a colour change.
Have varicose veins, which are a common cause of superficial thrombophlebitis. Have a pacemaker or have a thin, flexible tube (catheter) in a central vein, for treatment of a medical condition, which may irritate the blood vessel wall and decrease blood flow. Are pregnant or have just given birth.
Causes of venous thromboembolism. As Virchow postulated in 1884, it is now known that venous thromboembolism occurs as a result of at least one of the following: Endothelial damage, blood stasis and blood hypercoagulability. The more risk factors a person has, the greater the chance for occurrence of a venous thromboembolic event.