Abstract
BACKGROUND AND AIMS: The performance of non-invasive techniques remains inconsistent in cardiac surgical patients. This study assessed the level of agreement and trending abilities of cardiac index (CI) values obtained using Noninvasive Cardiac System (NICaS™) and FloTrac™ (version 4.0) in adult patients undergoing cardiac surgery. METHODS: This retrospective observational study was conducted over 6 months at a tertiary care centre and included 16 patients undergoing elective cardiac surgery with cardiopulmonary bypass. CI was measured simultaneously using FloTrac™ from the radial (FCIrad) and femoral (FCIfem) arteries and using NICaS™ at corresponding time points (NCIrad and NCIfem). CI measurements were recorded at six time points: baseline (T1), post-induction (T2), post-sternotomy (T3), post-CPB weaning (T4), post-protamine (T5), and post-sternal closure (T6). Agreement between methods was assessed using Bland-Altman analysis, while trending ability was evaluated using four-quadrant and polar plot analyses. A ±30% change in CI relative to FloTrac™ values was considered the acceptable limit of agreement. RESULTS: A total of 90 paired measurements were available for FCIrad-NCIrad and 73 for FCIfem-NCIfem. Bland-Altman analysis showed a bias of 0.33 L/min/m² (limits of agreement: -1.81 to 2.48 L/min/m²) for FCIrad-NCIrad and 0.52 L/min/m² (-2.03 to 3.07 L/min/m²) for FCIfem-NCIfem. Four-quadrant plots demonstrated concordance rates of 69% (radial) and 63.4% (femoral). Polar plot analysis showed angular concordance rates of 46% (radial) and 31% (femoral). CONCLUSION: NICaS™ showed limited agreement and trending ability compared with FloTrac™ at radial and femoral sites, indicating limited interchangeability between the two methods during cardiac surgery.