Oxyhemoglobin saturation of mixed venous blood (SV̄(O2)) reflects a balance between oxygen supply and demand. Many physicians have used this parameter to evaluate the adequacy of oxygen transport in the critically ill and in patients undergoing major surgery. The saturation measured by catheter oximetry correlates well with values obtained from a laboratory co-oximeter, particularly when a three wavelength catheter is used. Previous reports have drawn attention to the association between artifactual decreases in oxyhemoglobin saturation as measured by pulse oximetry (Sp(O2)) and intravenously administered dyes. The effects of intravenously administered methylene blue on continuous mixed venous oximetry have not yet been described. We report two cases in which the iv administration of methylene blue caused a significant decrease in the oxyhemoglobin saturation measured by the Opticath® pulmonary artery catheter (Sx(O2)). (Abbott Critical Care Systems, Mountain View, California).
ASJC Scopus subject areas
- Anesthesiology and Pain Medicine