title: Continuous cardiac output measurements do not agree with conventional bolus thermodilution cardiac output determination.
abstract: OBJECTIVE
  To evaluate the performance of two different continuous cardiac output monitoring systems based on the thermodilution principle in critically ill patients.
  
  
  METHODS
  Nineteen cardiac surgical patients were randomly assigned to continuous cardiac output monitoring using one of the two systems under study (group I, IntelliCath(TM) catheter, n=9; group II, Opti-Q(TM) catheter, n=10). Each patient was studied over a period of three hours. Conventional bolus thermodilution cardiac output measurements were carried out every 15 min leading to 13 measurements in each patient. The continuous cardiac output values were compared with the bolus thermodilution measurements. Bias (mean difference between continuous and bolus thermodilution) and precision (SD of differences) were calculated as a measure of agreement between the respective continuous method and conventional bolus thermodilution.
  
  
  RESULTS
  The range of measured cardiac outputs was 3.8-15.4 L*min(-1) (IntelliCath(TM)) and 3.5-8.3 L*min(-1) (OptiQ(TM)). Bias and precision was 0.06 +/- 0.76 L*min(-1) (IntelliCath(TM)) and -0.04 +/- 0.74 L*min(-1) (OptiQ(TM)), respectively. There was no difference in bias between the two systems (P=0.38). +/- 2 SD of the differences (i.e., 95% of the differences) did not fall within the predetermined limits of agreement of +/- 0.5 L*min(-1).
  
  
  CONCLUSIONS
  There was no difference between the two systems regarding the agreement with conventional bolus thermodilution as the standard. A discrepancy between bolus and continuous thermodilution cardiac output measurement techniques above the clinically acceptable limits suggest that they are not interchangeable.
authors.affiliation: Departments of Anesthesiology, and Cardiac Surgery, Ludwig-Maximilians University of Munich, Munich, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Zöllner
authors.forename: A E
authors.initials: AE
authors.lastname: Goetz
authors.forename: M
authors.initials: M
authors.lastname: Weis
authors.forename: K
authors.initials: K
authors.lastname: Mörstedt
authors.forename: B
authors.initials: B
authors.lastname: Pichler
authors.forename: P
authors.initials: P
authors.lastname: Lamm
authors.forename: E
authors.initials: E
authors.lastname: Kilger
authors.forename: M
authors.initials: M
authors.lastname: Haller
mesh_terms: D000328:Adult; D000368:Aged; D002302:Cardiac Output / Q000502:physiology*; D006348:Cardiac Surgical Procedures; D002404:Catheterization; D003422:Critical Care; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D011446:Prospective Studies; D011651:Pulmonary Artery / Q000502:physiology; D013815:Thermodilution