An optical blood monitoring system includes a sensor clip assembly and a blood chamber. The blood chamber has an internal flow cavity for extracorporeal blood flow and viewing lenses to enable the sensor clip assembly to monitor the blood when it is mounted on the blood chamber. The sensor clip assembly includes an annular shroud surrounding the LED emitters and another annular shroud surrounding the photodetectors, both for the purpose of blocking ambient light and limiting light piping. The blood chamber includes separate, distinct shroud mating surfaces to engage the shrouds on the sensor clip assembly.
