Continuous cardiac output monitoring after cardiopulmonary bypass: a comparison with bolus thermodilution measurement.
OBJECTIVE
The interchangeability of continuous measurement of cardiac output (CO) with the traditional bolus method in patients after cardiopulmonary bypass (CPB) is uncertain.


METHODS
Prospective observational clinical study.


METHODS
A 20-bed surgical ICU at a university hospital.


METHODS
Fourteen deeply sedated, ventilated, post-cardiac surgery patients, all equipped with a pulmonary artery catheter.


METHODS
Six hours after the end of the CPB, 56 simultaneous bolus and continuous measurements were compared by a linear regression analysis and Bland-Altman analysis. Bolus CO was estimated by averaging triplicate injections of 10 ml room-temperature NaCl 0.9%, delivered randomly during the respiratory cycle. A stringent maximum difference of 0.55 l min(-1) (about 10% of the mean bolus measured) was considered as a clinically acceptable agreement between the two types of measurements. To be interchangeable the limits of agreement (+/-2 SD of the mean difference between the two methods) should not exceed the chosen acceptable difference.


RESULTS
Continuous was correlated with bolus CO, with a correlation coefficient of r(2)=0.68. (p<0.01). The Bland-Altman analysis demonstrated an objective mean bias of 0.33+/-0.6 l min(-1) (confidence interval of -0.87-1.58) with 34% of measured values falling outside of the clinically acceptable limits.


CONCLUSIONS
Our results suggest that, in the first 6 h after CPB, continuous and bolus CO determinations are not interchangeable; one third of the values obtained by continuous CO fell outside the strict limits of clinically useful precision.
Bendjelid
Karim
K
Geneva University Hospitals, Surgical Intensive Care Unit, Department of Anaesthesiology, Pharmacology and Surgical Intensive Care, 1211, Geneva 14, Switzerland. Karim.Bendjelid@hcuge.ch
Schütz
Nicolas
N
Suter
Peter M
PM
Romand
Jacques-Andre
JA
D000368:Aged; D002302:Cardiac Output / Q000502:physiology*; D002315:Cardiopulmonary Bypass; D002407:Catheterization, Swan-Ganz; D005260:Female; D006801:Humans; D007035:Hypothermia; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011446:Prospective Studies; D013815:Thermodilution; D013903:Thoracic Surgery