To the Editor.
—Dr Boyd and colleagues1 conclude from their study that "[p]erioperative increase of oxygen delivery with dopexamine hydrochloride significantly reduces mortality and morbidity in high-risk surgical patients." I do not understand why they elect to report their results in terms of an increase in oxygen delivery (Do2I), and I do not believe that their results support this interpretaton.They set out to control the arterial oxygen saturation and hemoglobin in the two groups of patients, and the results indicate that they accomplished this goal; there were no statistically significant differences between the groups in these measured variables. Cardiac index was significantly different between the two groups, as a direct effect of the intervention. Since the formula for calculating Do2I uses arterial oxygen saturation, hemoglobin, and cardiac index, the difference in Do2I between the two groups depends only on the difference in
Dale V. Increasing Oxygen Delivery in Surgical Patients. JAMA. 1994;271(17):1321. doi:10.1001/jama.1994.03510410033026