Effect of Intralipid on measurements of total hemoglobin and oxyhemoglobin in whole blood

A co-oximeter study of whole blood samples containing Intralipid concentrations of 100 to 2000 mg/dl found that the light-scattering effect was greater at lower hematocrits. The methemoglobin reading was affected the most, and led to erroneous displays of total hemoglobin and percent oxyhemoglobin. The O2-content value, however, was accurate over the entire hematocrit and Intralipid concentration range tested. We suggest that an unexplained high methemoglobin value in whole blood samples from patients receiving Intralipid may reflect a light-scattering problem in the instrument.