Use of the cardiac power index to predict fluid responsiveness in the prone position: a proof-of-concept study

The primary aim of this proof-of-concept study was to investigate whether the Cardiac Power Index (CPI) could be a novel alternative method to assess fluid responsiveness in the prone position. Patients undergoing scheduled elective lumbar spine surgery in the prone position under general anesthesia were enrolled in the criteria of patients aged 19–75 years with American Society of Anesthesiologists (ASA) physical status I–II. The hemodynamic variables were evaluated before and after changes in posture after administering a colloid bolus (5 mL.kg−1) in the prone position. Fluid responsiveness was defined as an increase in the Stroke Volume Index (SVI) ≥ 10%. A total of 28 patients were enrolled. In responders, the CPI (median [1/4Q–3/4Q]) decreased to 0.34 [0.28–0.39] W.m−2 (p = 0.035) after the prone position. After following fluid loading, CPI increased to 0.48 [0.37–0.52] W.m−2 (p < 0.008), and decreased SVI (median [1/4Q–3/4Q]) after prone increased from 26.0 [24.5–28.0] mL.m−2 to 33.0 [31.0–37.5] mL.m−2 (p = 0.014). Among non-responders, CPI decreased to 0.43 [0.28–0.53] W.m−2 (p = 0.011), and SVI decreased to 29.0 [23.5–34.8] mL.m−2 (p < 0.009). CPI exhibited predictive capabilities for fluid responsiveness as a receiver operating characteristic curve of 0.78 [95% Confidence Interval, 0.60–0.95; p = 0.025]. This study suggests the potential of CPI as an alternative method to existing preload indices in assessing fluid responsiveness in clinical scenarios, offering potential benefits for responders and non-responders.