COMPARISON BETWEEN MIXED VENOUS OXYGEN-SATURATION AND THERMODILUTION CARDIAC-OUTPUT IN MONITORING PATIENTS WITH SEVERE HEART-FAILURE TREATED WITH MILRINONE AND DOBUTAMINE

Purpose Although thermodilution cardiac output (COtd) is the accepted method For monitoring patients with heart failure in the intensive car e unit, it is particularly inaccurate in low-flow states and in the pr esence of tricuspid regurgitation; in addition, it does not adequately reflect the interaction between oxygen delivery and tissue oxygen ext raction. We were concerned about the underuse of mixed venous oxygen s aturation (SvO(2)) in this setting and hypothesized that it might be a more useful parameter than COtd for evaluating hemodynamic status and monitoring therapy in patients with severe congestive heart failure. Patients and Methods We determined the correlation coefficients betwee n increasing dose of inotrope and each of the parameters COtd and SvO( 2) in 18 patients with congestive heart failure who received a 3-day t rial of either milrinone or dobutamine during admission to the Veteran s Affairs Medical Center in San Diego. In addition, we analyzed reprod ucibility of repeated COtd and SvO(2) measurements taken at a single d ose of inotrope. Results In patients receiving milrinone the increase in dose correlated much better with SvO(2) (average correlation coeffi cient 0.79) than with COtd; this stronger correlation with SvO(2) was seen in 82% of the trials reviewed (p < 0.05). In addition, we found t hat repeated SvO(2) measurements taken at a single dose of milrinone w ere more reproducible than COtd as indicated by smaller relative 95% c onfidence intervals. In patients receiving dobutamine no significant t rend in correlation coefficients or reproducibility was observed. Conc lusion The knowledge that there is a significant relation between SvO( 2) and increasing dose of milrinone therapy in patients with severe he art failure and tricuspid regurgitation has practical value For physic ians monitoring these patients in the intensive care unit. We believe this study demonstrates the worth of SvO(2) in detecting hemodynamic c hange during trials of milrinone therapy and that this parameter may i n fact be more reproducible than traditional thermodilution methods.