The purpose of the study is to determine whether noninvasive hemoglobin monitoring is sensitive and accurate enough to detect a significant downward trend in hemoglobin in patients at risk for significant bleeding. If this can be shown, it has the potential to spare patients multiple invasive blood draws as well as allow for earlier detection of significant blood loss and therefore positively impact on patient morbidity and mortality. Additionally, it may represent significant financial cost savings in that it may allow for patients to be monitored in a non-intensive care unit setting.