A comparative evaluation of thermodilution and partial CO2 rebreathing techniques for cardiac output assessment in critically ill patients during assisted ventilation.
OBJECTIVE
To evaluate the reliability and clinical value of partial noninvasive CO2 (NICO2) rebreathing technique for measuring cardiac output compared with standard thermodilution in a group of intensive care nonpostoperative patients.


METHODS
Clinical investigation in a university hospital ICU.


METHODS
Twelve mechanically ventilated patients with high (n=6) and low (n=6) pulmonary shunt fractions.


RESULTS
Thirty-six paired measurements of cardiac output were carried out with NICO2 and thermodilution in patients ventilated in pressure-support mode and sedated with a sufentanil continuous infusion to obtain a Ramsay score value of 2. The mean cardiac output was: thermodilution 7.27+/-2.42 l/min; NICO2 6.10+/-1.66 l/min; r2 was 0.62 and bias -1.2 l/min+/-1.5. Mean values of cardiac output were similar in the low shunt group (Qs/Qt < 20), with r2=0.90 and a bias of 0.01 l/min+/-0.4; conversely, in the high pulmonary shunt group (Qs/Q > 35%) the mean was 9.32+/-1.23 l/min with thermodilution and a mean NICO2CO value was 6.97+/-1.53 l/min, with r2 of 0.38 and a bias of -2.3 l+/-1.2 min.


CONCLUSIONS
The partial CO2 rebreathing technique is reliable in measuring cardiac output in nonpostoperative critically ill patients affected by diseases causing low levels of pulmonary shunt, but underestimates it in patients with shunt higher than 35%.
Rocco
Monica
M
Department of Anesthesiology and Intensive Care, University of Rome La Sapienza, Viale del Policlinico 155, 00161 Rome, Italy. monica.rocco@uniroma1.it
Spadetta
Gustavo
G
Morelli
Andrea
A
Dell'Utri
Donatella
D
Porzi
Patrizia
P
Conti
Giorgio
G
Pietropaoli
Paolo
P
D018686:Anesthetics, Intravenous / Q000627:therapeutic use; D015982:Bias; D001944:Breath Tests / Q000379:methods*; D002245:Carbon Dioxide; D002302:Cardiac Output; D016292:Procedural Sedation / Q000379:methods; D003422:Critical Care / Q000379:methods / Q000592:standards; D016638:Critical Illness / Q000628:therapy; D006785:Hospitals, University; D006801:Humans; D016014:Linear Models; D008991:Monitoring, Physiologic / Q000379:methods / Q000592:standards; D010092:Oximetry / Q000379:methods* / Q000592:standards; D018579:Patient Selection; D011175:Positive-Pressure Respiration / Q000379:methods; D011652:Pulmonary Circulation; D011659:Pulmonary Gas Exchange; D017409:Sufentanil / Q000627:therapeutic use; D013815:Thermodilution / Q000379:methods* / Q000592:standards; D013990:Tidal Volume
D018686:Anesthetics, Intravenous; D002245:Carbon Dioxide; D017409:Sufentanil