title: Simultaneous multi-depth assessment of tissue oxygen saturation in thenar and forearm using near-infrared spectroscopy during a simple cardiovascular challenge.
abstract: 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 an attempt to use it as an early detector of hypovolemia by measuring tissue oxygen saturation (StO2). In order to investigate the measurement site dependence 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 StO2 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 (P < 0.001) in heart rate. Thenar StO2 did not respond to the hemodynamic changes following the posture change, whereas forearm StO2 did. Forearm StO2 was significantly lower (P < 0.001) in the upright position compared to supine for all probing depths.
  
  
  CONCLUSIONS
  The primary findings in this study were that forearm StO2 is a more sensitive parameter to hemodynamic changes than thenar StO2 and that 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.
authors: Department of Translational Physiology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands. r.bezemer@amc.uva.nl
authors: Rick
authors: R
authors: Bezemer
authors: John M
authors: JM
authors: Karemaker
authors: Eva
authors: E
authors: Klijn
authors: Daniel
authors: D
authors: Martin
authors: Kay
authors: K
authors: Mitchell
authors: Mike
authors: M
authors: Grocott
authors: Michal
authors: M
authors: Heger
authors: Can
authors: C
authors: Ince
mesh_terms: D000328:Adult; D003935:Diagnostic Techniques, Cardiovascular / Q000592:standards; D005260:Female; D005542:Forearm / Q000098:blood supply / Q000502:physiology*; D006225:Hand / Q000098:blood supply / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology*; D011187:Posture / Q000502:physiology; D019265:Spectroscopy, Near-Infrared / Q000379:methods* / Q000592:standards