title: Analysis of Transpulmonary Thermodilution Data Confirms the Influence of Renal Replacement Therapy on Thermodilution Hemodynamic Measurements.
abstract: BACKGROUND
  Transpulmonary thermodilution (TPTD) is used frequently in the intensive care unit to determine cardiac index (CI), intrathoracic blood volume index (ITBVI), and extravascular lung volume index (EVLWI). Renal replacement therapy (RRT) influences TPTD results, but the underlying mechanisms are not completely understood. We hypothesized that RRT blood flow induces errors in TPTD measurements.
  
  
  METHODS
  We analyzed TPTD data available from the PiCCO® plus hemodynamic measurement device on a personal computer using a proprietary Pulsion Medical Systems software. By using the dialysis catheter to inject the thermal indicator, 20 measurement series were performed in 12 intensive care unit patients determining CI, ITBVI, and EVLWI during RRT with the blood pump stopped, and at flows of 100 and 200 mL/min, respectively.
  
  
  RESULTS
  Data export was successful in 17 measurement series and showed a significant decrease in measured CI (6.5 ± 2.5 vs 5.4 ± 1.9 L/min/m, P < 0.001) and ITBVI (1358.8 ± 274.5 vs 1132.8 ± 218.3 mL/m, P < 0.001) with RRT and a significant increase in EVLWI (8.6 ± 4.4, 10.2 ± 4.5 mL/kg, P < 0.001). Blood temperature before and the temperature decrease after injection of the thermal indicator were unchanged by RRT. Mean transit time and downslope time of the thermodilution curve, however, were both increased with the RRT blood pump running (P ≤ 0.001).
  
  
  CONCLUSIONS
  Analysis of TPTD data shows that thermodilution curve forms are modified with RRT, resulting in an erroneous calculation of thermodilution-derived hemodynamic parameters.
authors.affiliation: From the *Department of Nephrology, Charité University Medicine Berlin, Campus Benjamin Franklin, Berlin, Germany; †Department of Medicine I, Universitätsklinikum Marien Hospital Herne, Ruhr-Universität Bochum, Herne, Germany; and ‡Department of Medical Statistics, Informatics and Documentaton, Jena University Hospital, Jena, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Schmidt
authors.forename: Timm
authors.initials: T
authors.lastname: Westhoff
authors.forename: Peter
authors.initials: P
authors.lastname: Schlattmann
authors.forename: Walter
authors.initials: W
authors.lastname: Zidek
authors.forename: Friederike
authors.initials: F
authors.lastname: Compton
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001810:Blood Volume; D001811:Blood Volume Determination; D001831:Body Temperature; D002302:Cardiac Output; D057785:Catheters; D016638:Critical Illness; D015633:Extravascular Lung Water; D005260:Female; D006439:Hemodynamics; D006440:Hemofiltration / Q000009:adverse effects* / Q000295:instrumentation; D006801:Humans; D007362:Intensive Care Units; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D006435:Renal Dialysis / Q000009:adverse effects* / Q000295:instrumentation; D015203:Reproducibility of Results; D013815:Thermodilution / Q000379:methods*