Summary Response:
Edema has a minimal effect on thenar eminence StO2.1
Background:
Edema can affect StO2 measurements by acting as a “spacer” between the skin surface where the probe is located and the underlying muscle layer where the measurement should occur. Edema primarily accumulates in tissues with high adipose contentand thus has greater effect on StO2 measurements in tissues with more adipose content.2 The degree of edema and adipose thickness in patients with septic shock were confounding factors during the measurement of muscle StO2 using NIRS at a variety of different monitoring sites on the body. This created more variability in StO2 values, particularly at non-thenar monitoring sites. The thenar muscle showed the lowest variance.2
Evidence:
1Myers D. Unpublished Hutchinson Technology data, 2007.
2Poeze M. Tissue-oxygenation assessment using near-infrared spectroscopy during severe sepsis: confounding effects of tissue edema on StO2 values. Int Care Med. 2005,32:788-789.