Central venous-arterial carbon dioxide difference as an indicator of cardiac index.
OBJECTIVE
The mixed venous-arterial (v-a) pCO(2) difference has been shown to be inversely correlated with the cardiac index (CI). A central venous pCO(2), which is easier to obtain, may provide similar information. The purpose of this study was to examine the correlation between the central venous-arterial pCO(2) difference and CI.


METHODS
Prospective, cohort study.


METHODS
Intensive care unit of an urban tertiary care hospital.


METHODS
Eighty-three consecutive intensive care unit patients.


METHODS
Simultaneous blood gases from the arterial, pulmonary artery (PA), and central venous (CV) catheters were obtained. At the same time point, cardiac indices were measured by the thermodilution technique (an average of three measurements). The cardiac indices obtained by the venous-arterial differences were compared with those determined by thermodilution.


RESULTS
The correlation (R(2)) between the mixed venous-arterial pCO(2) difference and cardiac index was 0.903 (p <0.0001), and the correlation between the central venous-arterial pCO(2) difference and cardiac index was 0.892 (p <0.0001). The regression equations for these relationships were natural log (CI)=1.837-0.159 (v-a) CO(2) for the PA and natural log (CI)=1.787-0.151 (v-a) CO(2) for the CV (p <0.0001 for both). The root-mean-squared error for the PA and CV regression equations were 0.095 and 0.101, respectively.


CONCLUSIONS
Venous-arterial pCO(2) differences obtained from both the PA and CV circulations inversely correlate with the cardiac index. Substitution of a central for a mixed venous-arterial pCO(2) difference provides an accurate alternative method for calculation of cardiac output.
Cuschieri
Joseph
J
Department of Surgery, Henry Ford Health Systems, Detroit, MI, USA.
Rivers
Emanuel P
EP
Donnino
Michael W
MW
Katilius
Marius
M
Jacobsen
Gordon
G
Nguyen
H Bryant
HB
Pamukov
Nikolai
N
Horst
H Mathilda
HM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001784:Blood Gas Analysis / Q000379:methods*; D002245:Carbon Dioxide / Q000097:blood; D002302:Cardiac Output; D002405:Catheterization, Central Venous; D002407:Catheterization, Swan-Ganz; D005260:Female; D006439:Hemodynamics; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010313:Partial Pressure; D011446:Prospective Studies
D002245:Carbon Dioxide