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Erschienen in:
01.12.2007 | Brief Report
Lack of agreement between thermodilution and electrical velocimetry cardiac output measurements
Erschienen in: Intensive Care Medicine | Ausgabe 12/2007
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Objective
The modified algorithm for the non-invasive determination of cardiac output (CO) by electrical bioimpedance—electrical velocimetry (EV®)—has been reported to give reliable results in comparison with echocardiography and pulmonary arterial thermodilution (PA-TD) in patients either before or after cardiac surgery. The present study was designed to determine whether EV®-CO measurements reflect intraindividual changes in CO during cardiac surgery.
Design
Prospective, observational study.
Setting
Operating room (OR) and intensive care unit (ICU) of a university hospital.
Patients
Twenty-nine patients undergoing elective cardiac surgery.
Interventions
None.
Measurements
CO was determined simultaneously by PA-TD and EV® after induction of anesthesia (t1) and 4.9 ± 3.5 h after ICU admission (t2).
Results
TD-CO was 3.9 ± 1.4 and 5.4 ± 1.1 l/min at t1 and t2 ( p < 0.0001). EV®-CO was 4.3 ± 1.1 and 4.9 ± 1.5 l/min at t1 and t2 ( p = 0.013). Bland–Altman analysis showed a bias of −0.4 l/min and 0.4 l/min and a precision of 3.2 and 3.6 l/min (34.3% and 67.4%) at t1 and t2, respectively. Analysis of the individual pre- to postoperative changes in CO with both methods revealed bidirectional changes in n = 12 patients and unidirectional changes with a difference greater than 50% and less than 50% in n = 9 and n = 8 patients, respectively.
Conclusions
The disagreement between PA-TD and EV®-CO measurements after anesthesia induction and after ICU admission, as well as the fact that thoracic bioimpedance did not adequately reflect pre- to postoperative changes in CO, questions the reliability of EV®-CO measurements in cardiac surgery patients and contrasts sharply with previous studies.