Reliability of a new 4th generation FloTrac algorithm to track cardiac output changes in patients receiving phenylephrine

Fuhai Ji, Jian Li, Neal Fleming, David Rose, Hong Liu

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Phenylephrine is often used to treat intra-operative hypotension. Previous studies have shown that the FloTrac cardiac monitor may overestimate cardiac output (CO) changes following phenylephrine administration. A new algorithm (4th generation) has been developed to improve performance in this setting. We performed a prospective observational study to assess the effects of phenylephrine administration on CO values measured by the 3rd and 4th generation FloTrac algorithms. 54 patients were enrolled in this study. We used the Nexfin, a pulse contour method shown to be insensitive to vasopressor administration, as the reference method. Radial arterial pressures were recorded continuously in patients undergoing surgery. Phenylephrine administration times were documented. Arterial pressure recordings were subsequently analyzed offline using three different pulse contour analysis algorithms: FloTrac 3rd generation (G3), FloTrac 4th generation (G4), and Nexfin (nf). One minute of hemodynamic measurements was analyzed immediately before phenylephrine administration and then repeated when the mean arterial pressure peaked. A total of 157 (4.6 ± 3.2 per patient, range 1–15) paired sets of hemodynamic recordings were analyzed. Phenylephrine induced a significant increase in stroke volume (SV) and CO with the FloTrac G3, but not with FloTrac G4 or Nexfin algorithms. Agreement between FloTrac G3 and Nexfin was: 0.23 ± 1.19 l/min and concordance was 51.1 %. In contrast, agreement between FloTrac G4 and Nexfin was: 0.19 ± 0.86 l/min and concordance was 87.2 %. In conclusion, the pulse contour method of measuring CO, as implemented in FloTrac 4th generation algorithm, has significantly improved its ability to track the changes in CO induced by phenylephrine.

Original languageEnglish (US)
Pages (from-to)467-473
Number of pages7
JournalJournal of Clinical Monitoring and Computing
Issue number4
StatePublished - Sep 30 2014


  • Arterial pressure
  • Phenylephrine
  • Pulse contour analysis
  • Stroke volume

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine
  • Critical Care and Intensive Care Medicine
  • Health Informatics


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