Variation of hemodynamic parameters after fluid challenge
© BioMed Central Ltd 2008
Published: 13 March 2008
We compared thoracic electrical bioimpedance (TEB) with transpulmonary thermodilution (TT) to evaluate the accuracy of cardiac index with the ICG (CI-I) and cardiac index with the PiCCO (CI-P) before and after fluid challenge (FC), to determine the correlation between intrathoracic blood volume (ITBV) and corrected flow time (FTc) before and after FC, to verify the parameters' response after FC, and to establish the credibility of total fluid content (TFC) as a pulmonary fluid index in comparison with extravascular lung water (EVLW).
We recruited 33 patients from May 2006 to July 2007. Inclusion criteria: instable hemodynamic conditions, mechanic ventilation. Exclusion criteria: intraaortic balloon pump, aortic failure. We used 7 ml/kg hydroxyethyl starch 6% in 30 minutes for the FC. We used the PiCCO (Pulsion Medical Systems AG) and the ICG (Solar ICG module; GE Medical Systems Technology, Milwaukee, USA) to monitor hemodynamic parameters. We studied the strength of the association between all of the hemodynamic parameters of the ICG and the PiCCO with the correlation coefficient (P < 0.005).
The correlation coefficient between the differences of CI-I and CI-P before and after FC is 0.6090 (P = 0.0002). The correlation coefficient between the differences of EVLW and TFC before and after FC is 0.1192 (P = 0.51). The correlation coefficient between the differences of FTc and ITBV before and after FC is 0.3443 (P = 0.04).
The study demonstrates that the ICG can individuate an increase of cardiac output after FC, but less than the PiCCO. The correlation coefficient between CI-P and CI-I results is inferior after FC, so CI-I seems less accurate in identifying the filling response. There is an agreement between TFC and EVLW before the FC. The ITBV from the PiCCO demonstrates more clinical utility in identifying a response to FC. Even if TEB is clinically useful, it does not represent an available option instead of the TT. The parameters we studied have less clinical efficacy than the classic methods of TT, as recent studies of the literature demonstrate. TEB should be used when catheterization of a central artery is contraindicated, when there is no other method to monitor and especially when there is a need for rapid monitoring.