Assessment of stroke volume index with three different bioimpedance algorithms: lack of agreement compared to thermodilution.
OBJECTIVE
The accuracy of bioimpedance stroke volume index (SVI) is questionable as studies report inconsistent results. It remains unclear whether the algorithms alone are responsible for these findings. We analyzed the raw impedance data with three algorithms and compared bioimpedance SVI to transpulmonary thermodilution (SVI(TD)).


METHODS
Prospective observational clinical study in a university hospital.


METHODS
Twenty adult patients scheduled for coronary artery bypass grafting (CABG).


METHODS
SVI(TD) and bioimpedance parameters were simultaneously obtained before surgery (t1), after bypass (t2), after sternal closure (t3), at the intensive care unit (t4), at normothermia (t5), after extubation (t6) and before discharge (t7). Bioimpedance data were analyzed off-line using cylinder (Kubicek: SVI(K); Wang: SVI(W)) and truncated cone based algorithms (Sramek-Bernstein: SVI(SB)).


RESULTS
Bias and precision between the SVI(TD) and SVI(K), SVI(SB), and SVI(W) was 1.0+/-10.8, 9.8+/-11.4, and -15.7+/-8.2 ml/m2 respectively, while the mean error was abundantly above 30%. Analysis of data per time moment resulted in a mean error above 30%, except for SVI(W) at t2 (28%).


CONCLUSIONS
Estimation of SVI by cylinder or truncated cone based algorithms is not reliable for clinical decision making in patients undergoing CABG surgery. A more robust approach for estimating bioimpedance based SVI may exclude inconsistencies in the underlying algorithms in existing thoracic bioimpedance cardiography devices.
de Waal
Eric E C
EE
Division of Perioperative and Emergency Care, University Medical Center, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands. e.e.c.dewaal@azu.nl
Konings
Maurits K
MK
Kalkman
Cor J
CJ
Buhre
Wolfgang F
WF
D000465:Algorithms; D002307:Cardiography, Impedance / Q000379:methods*; D001026:Coronary Artery Bypass; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care; D011446:Prospective Studies; D015203:Reproducibility of Results; D013318:Stroke Volume; D013815:Thermodilution