Room-temperature vs iced saline indicator injection for transpulmonary thermodilution

Purpose: Ice-cold injectate is assumed to provide best accuracy for transpulmonary thermodilution (TPTD)-derived cardiac index (CI), global end-diastolic volume index (GEDVI), and extravascular lung-water index (EVLWI). Room-temperature injectate might facilitate TPTD. Therefore, this study compares TPTD-results derived from iced injectate with room-temperature injectate TPTDs (TPTDRoom).

Materials and methods: Forty-five adult intensive care unit patients with PiCCO monitoring (Pulsion Medical Systems, Munich, Germany) were included in this observational study. Four hundred one sets of TPTDs were recorded. Each set consisted of four 15 mL TPTDs (twice with 21°C and subsequently twice with 4°C saline). Means of 2 TPTDRoom were compared with means of 2 cold TPTDs (primary end point).

Results: Mean CI (4.70±1.60 vs 4.54±1.52 L/min per square meter; P<.001), GEDVI (985±294 vs 954±269 mL/m2; P<.001), and EVLWI (14.4±7.8 vs 13.8±7.3 mL/kg; P<.001) were significantly higher for TPTDRoom compared with TPTD-results derived from iced injectate. Mean bias and percentage error were 0.15±0.52 L/min per square meter and 21.9% for CI, 30±145 mL/m2 and 29.3% for GEDVI, and 0.59±2.1 mL/kg and 29.3% for EVLWI. Percentage error values were higher in case of femoral compared with jugular indicator injection for CI (25% vs 20%), GEDVI (35% vs 25%), and EVLWI (41% vs 23%).

Conclusions: Room-temperature injectate TPTDs results in slight but significant overestimation of CI, GEDVI, and EVLWI. Percentage error values for GEDVIRoom and EVLWIRoom are acceptable only in case of "jugular" indicator injection.