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

Background: 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.

Methods: 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%.

Results: 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].

Conclusion: 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.