Closed-loop fluid resuscitation: robustness against weight and cardiac contractility variations

Area of Science:

• Anesthesiology
• Critical Care Medicine
• Biomedical Engineering

Background:

• Surgical patients exhibit significant variability in body size, baseline volume status, and cardiac function.
• Automated fluid administration systems must be robust to these physiological differences.
• Control engineering principles were applied to assess system stability and robustness.

Purpose of the Study:

• To evaluate the stability and robustness of a closed-loop fluid administration system.
• To test the system's performance against variations in patient body size, initial volume status, and cardiac contractility.
• To assess the system's ability to maintain optimal blood volume targets.

Main Methods:

• A validated hemodynamic simulation model incorporating blood volume and cardiac contractility was utilized.
• Monte Carlo simulations were performed across two phases, varying body weight and initial blood volume (Phase 1), and cardiac contractility and initial blood volume (Phase 2).
• Controller performance was measured by blood volume error from the optimal set point, with <250 mL defined as successful resuscitation.

Main Results:

• Across 1000 simulations per phase, mean blood volume errors were 25 ± 59 mL (Phase 1) and -60 ± 89 mL (Phase 2).
• The lower 95% confidence interval for successful resuscitation (within 250 mL of optimal) was 99.6% for Phase 1 and 97.1% for Phase 2.
• The system demonstrated high accuracy in achieving target blood volumes.

Conclusions:

• The closed-loop fluid administration controller is highly effective in targeting optimal blood and stroke volumes.
• System performance remains robust irrespective of patient weight, cardiac contractility, or initial blood volume.
• This technology shows promise for automated fluid management in diverse surgical populations.