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Novel Doppler technique to assess systemic vascular resistance: the snuffbox technique
Koji Ban1, Kazuhiro Kochi, Katsuhiko Imai
1Department of Surgery, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan. ban@hiroshima-u.ac.jp
Summary
The anatomical snuffbox (SB) resistive index (RI) effectively monitors peripheral circulation in ICU patients. This ultrasound method offers a reliable alternative to systemic vascular resistance index (SVRI) for assessing peripheral vascular resistance.
Area of Science:
- Medical Ultrasound
- Cardiovascular Physiology
- Intensive Care Medicine
Background:
- Systemic vascular resistance index (SVRI) is a key metric for peripheral circulation monitoring in intensive care units (ICUs).
- Limitations exist in current methods for peripheral circulation assessment in critically ill patients.
- Exploring alternative, reliable monitoring tools is crucial for effective patient management.
Purpose of the Study:
- To evaluate the resistive index (RI) measured via Doppler ultrasound in upper extremity arteries as an alternative to SVRI.
- To determine the correlation between RI and vascular resistance in both in vitro and in vivo settings.
- To assess the feasibility of using RI at specific anatomical locations for peripheral circulation monitoring.
Main Methods:
- In vitro assessment using a mock circulation system to correlate RI with known vascular resistance.
- In vivo study of 15 post-open-heart surgery ICU patients.
- Simultaneous measurement of hemodynamic parameters (MAP, CVP, CO) for SVRI calculation and Doppler ultrasound of brachial artery (BA), radial artery (RA), and radial artery at the anatomical snuffbox (SB) for RI calculation.
Main Results:
- In vitro, RI showed a strong positive correlation with vascular resistance (r = 0.982, p < 0.0001).
- In vivo, significant correlation between SVRI and RI was found only for the anatomical snuffbox (SB) (p < 0.0001), not for BA or RA.
- Doppler analysis at the SB revealed diastolic flow reversal with increased SVRI, and consistent correlation across all patients.
Conclusions:
- The anatomical snuffbox (SB) provides an optimal ultrasound incidence angle for accurate blood flow velocity measurement.
- Resistive index (RI) measured at the SB serves as a reliable indicator of peripheral vascular resistance.
- This ultrasound-based RI measurement is effective for evaluating peripheral circulatory disturbances in ICU patients.