Please see Bibliography of References for a list of abstracts, manuscripts and posters.

StO₂ Proof of Concept

Simultaneous multi-depth assessment of tissue oxygen saturation in thenar and forearm using near-infrared spectroscopy during a simple cardiovascular challenge

Bezemer R, Klijn E, Karemaker J, Ince C. Int Care Med. 2009;35(Suppl 1):S27.

Background: Hypovolemia and hypovolemic shock are life-threatening conditions that occur in numerous clinical scenarios. Near-infrared spectroscopy (NIRS) has been widely explored, successfully and unsuccessfully, in attempt to function as an early detector of hypovolemia by measuring tissue oxygen saturation (StO₂). In order to investigate the measurement site- and probe-dependence of NIRS in response to hemodynamic changes, such as hypovolemia, we applied a simple cardiovascular challenge; a posture change from supine to upright, causing a decrease in stroke volume (as in hypovolemia) and a heart rate increase in combination with peripheral vasoconstriction to maintain adequate blood pressure.

Methods: Multi-depth NIRS was used in nine healthy volunteers to assess changes in peripheral vascular tone in the thenar and forearm in response to the hemodynamic changes associated with a posture change from supine to upright.

Results: A posture change from supine to upright resulted in a significant increase (***) in heart rate. Thenar StO₂ did not respond to the hemodynamic changes following the posture change, whereas forearm StO₂ did. In the forearm, StO₂ was significantly lower (***) in the upright position with respect to the supine position.

Conclusion: The primary findings in this study were that (1) forearm StO₂ is a more sensitive parameter to hemodynamic changes than thenar StO₂ and (2) the depth at which StO₂ is measured is of minor influence. Our data support the use of forearm StO₂ as a sensitive parameter for the detection of central hypovolemia and hypovolemic shock in (trauma) patients.