Near-infrared spectroscopy of the thenar eminence: comparison of dynamic testing protocols.
BACKGROUND
Near-infrared spectroscopy of the thenar eminence (NIRSth) is a non-invasive bedside method for assessing tissue oxygenation. The vascular occlusion test (VOT) with a pressure cuff can be used to provide a dynamic assessment of the tissue oxygenation response to ischaemia. VOT has been applied to assess the microcirculation by NIRSth in critically ill patients. The optimal mode of performing such VOT, however, remains controversial.


METHODS
Prospective observational study among a cohort of 11 healthy volunteers in a tertiary intensive care department.


METHODS
Measurement of NIRS-derived parameters using 1-, 2- and 3-minute VOTs or VOT to 40% tissue oxygen saturation (StO(2)).


METHODS
Changes in StO(2) and tissue haemoglobin index (THI) over time, and relative change from baseline for StO(2) and THI.


RESULTS
Mean baseline StO(2) was 80% (SD, 5%) and mean THI was 13.7 (SD, 1.9). The lowest StO(2) at the end of the VOT was 39% (SD, 13%) and 39% (SD, 2%) in the 3- minute and the 40% StO(2) VOTs, respectively. The duration of the 40% StO(2) VOT ranged from 1:35 to 8:21 minutes (median, 3:29 min). There was a difference between the StO(2) curves for the 3-minute and 40% StO(2) VOT (P = 0.005) but not the THI curves. Reported pain score was a median of 3.5 (IQR, 2.5-5.5) and 4 (IQR 2-4) for the 3-minute and 40% StO(2) VOTs, respectively.


CONCLUSIONS
The 3-minute VOT and the 40% StO(2) appear equivalent. However, the 3-minute VOT carries a degree of decreased patient discomfort and shorter overall duration of execution.
Department of Surgery, Section of Anaesthesiology and Intensive Care, Uppsala University, Uppsala, Sweden.
Miklós
M
Lipcsey
Glenn M
GM
Eastwood
Nicholas C Z
NC
Woinarski
Rinaldo
R
Bellomo
D000328:Adult; D015331:Cohort Studies; D005260:Female; D006225:Hand / Q000098:blood supply*; D006801:Humans; D007511:Ischemia / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D008833:Microcirculation / Q000502:physiology; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D019095:Point-of-Care Systems; D015203:Reproducibility of Results; D019265:Spectroscopy, Near-Infrared / Q000379:methods*