Pulsed dye densitometry with two different sensor types for cardiac output measurement after cardiac surgery: a comparison with the thermodilution technique

Background: Assessment of cardiac output (CO) by the indocyanine green (ICG) dye dilution technique (IDD) with transcutaneous signal detection may be a less invasive alternative to the pulmonary artery catheter (PAC). The aim of this study was to determine the accuracy and reliability of the DDG2001 analyzer (Nihon Kohden Corp, Tokyo, Japan) using a finger (IDDf) and a nose (IDDn) sensor as compared with the thermodilution technique by PAC. Methods: In 31 consecutive patients after routine cardiac surgery, CO measurements were performed by IDD compared with the thermodilution technique following postoperative haemodynamic stabilization in the intensive care unit. Repeated measurements were made at 30‐min intervals. CO was determined by iced water bolus (IWB: mean of three repeated injections) and IDDf or IDDn, respectively (mean of three repeated ICG injections). Results: Thirty‐three per cent of all measurements for IDDf and 9% for IDDn failed due to a missing signal detection. Mean bias for IDDf to IWB was −0.5 l min−1·m−2 (limits of agreement: −1.8/0.8 l min−1·m−2) and for IDDn to IWB was −0.1 l min−1·m−2 (limits of agreement: −1.6/1.5 l min−1·m−2). Correlation between IDDf and IWB (r = 0.2) was found to be inferior to the correlation between IDDn and IWB (r = 0.5). Conclusion: The IDD showed a systematic bias compared with the IWB and its performance was limited due to signal detection failure. Therefore, the DDG2001 analyzer cannot be recommended as a substitute for the PAC in routine monitoring of cardiac output after cardiac surgery.