Aprotinin in Major Orthopedic Surgery: A Systematic Review of Randomized Controlled Trials

Abstract

Cardiac output (CO) determination using transesophageal Doppler is based on the measurement of descending aortic blood flow. Because cerebral blood flow is dependent on Paco2, an increase in Paco2 would result in an increase of CO because of the increase in cerebral blood flow and vice versa. We enrolled 30 patients undergoing off-pump coronary artery graft surgery in the study. The CO was determined by both transesophageal Doppler and thermodilution while Paco2 was maintained at either 30 mm Hg or 40 mm Hg in random order. The CO by thermodilution was significantly higher at Paco2 of 40 mm Hg (4.17 ± 0.94 L/min) than at 30 mm Hg (3.78 ± 0.85 L/min). On the other hand, there were no significant differences in CO by transesophageal Doppler: 3.85 ± 0.76 L/min at Paco2 of 40 mm Hg and 3.77 ± 0.74 at 30 mm Hg. Bland-Altman analysis yielded bias and precision of −0.32 and 0.49 L/min at Paco2 of 40 mm Hg, and −0.01 and 0.34 L/min at 30 mm Hg. These results indicate that both methods of CO measurement are in agreement at 30 mm Hg of Paco2, but the thermodilution method provides higher values at 40 mm Hg of Paco2.