Assessing Peripheral Tissue Perfusion and Fluid Responsiveness via PLR and Skin Blood Flow

Overview

This study evaluated the utility of combining passive leg raising (PLR) with skin blood flow (SBF) monitoring to predict microvascular fluid responsiveness in septic patients. The findings suggest that changes in SBF during PLR can serve as a non-invasive predictor of fluid responsiveness, potentially improving personalized fluid resuscitation strategies.

Background

Sepsis is a critical condition characterized by peripheral tissue hypoperfusion, which correlates with organ failure and poor outcomes. Fluid resuscitation aims to restore adequate tissue perfusion but requires careful dosing to avoid under-resuscitation or fluid overload, both linked to increased mortality. Passive leg raising (PLR) is a reversible maneuver that mimics fluid administration and is widely used to assess fluid responsiveness. However, improvements in macrohemodynamics do not always translate to microvascular perfusion, highlighting the need for microcirculatory assessment. Skin blood flow (SBF) monitoring via laser Doppler provides a non-invasive, real-time measure of microcirculatory perfusion and has shown associations with clinical markers of tissue perfusion.

Data Highlights

The study was a 3-month prospective observational trial in an 18-bed ICU involving adult septic patients undergoing fluid expansion. Measurements were taken at four time points: baseline, after 1 minute of PLR, return to baseline, and post volume expansion (500 mL saline over 15 minutes). Macro-hemodynamic parameters (MAP, HR, CO) and microcirculatory markers (capillary refill time, fingertip SBF) were recorded. Fluid responsiveness was defined as a >15% increase in SBF after volume expansion. The target sample size was 40 patients based on power calculations.

Key Findings

• PLR induced a measurable increase in skin blood flow, reflecting a shift of blood volume toward central circulation without fluid administration.
• Changes in SBF during PLR (ΔSBF-PLR) predicted fluid responsiveness defined by a >15% increase in SBF after volume expansion (ΔSBF-VE > 15%).
• Macro-hemodynamic improvements (e.g., cardiac output) did not always correlate with microvascular perfusion changes, indicating loss of hemodynamic coherence in sepsis.
• SBF monitoring using laser Doppler was feasible, non-invasive, and reproducible for assessing microcirculatory changes in critically ill septic patients.
• Combining PLR with SBF measurement may enhance the personalization of fluid therapy by identifying patients likely to benefit from volume expansion.

Clinical Implications

Incorporating SBF monitoring during PLR offers clinicians a practical, non-invasive tool to assess microvascular fluid responsiveness in septic patients. This approach may help tailor fluid resuscitation, avoiding the risks of both under- and over-resuscitation by identifying patients who will truly benefit from fluid administration. Ultimately, this strategy could improve tissue perfusion and patient outcomes in sepsis management.

Conclusion

The combination of passive leg raising and skin blood flow monitoring effectively predicts microvascular fluid responsiveness in septic patients. This method supports more precise and individualized fluid resuscitation strategies, addressing the limitations of relying solely on macro-hemodynamic parameters.

References

1. Surviving Sepsis Campaign/European Society of Intensive Care Medicine 2021 -- Guidelines on fluid therapy in sepsis
2. Jacquet-Lagrèze et al. -- Prior work on SBF and fluid responsiveness
3. Perimed, Jarfalla, Sweden -- Skin laser Doppler technology description