Measurement of oxygenation, perfusion and tissue hemoglobin in the tourniquet and operative clamping model with a hyperspectral camera system.

(A) Using the TIVITA Tissue system, acquisition of the tissue Oxygenation (StO2) showed a significant reduction of oxygenation in the low-pressure tourniquet group at a force of 0.4 N with no further reduction of oxygenation by rising pressure. The low-pressure tourniquet group showed a higher reduction of oxygenation than the operative clamping method. (B) Live images of the oxygenation visualization exemplary at a force of 0 N, 2 N, after reperfusion and with the open clamping technique. The yellow arrow marks the compromised hind limb. (C) Measurement of the near-infrared (NIR) perfusion index showed a significant steady reduction of the hind limb perfusion starting with a force of 0.4 N. In the tourniquet group this force showed a significantly higher reduction of perfusion than the operative clamping technique. (D) Live images of the NIR exemplary at a force of 0 N, 2 N, after reperfusion and with the open clamping technique. The yellow arrow marks the compromised hind limb. (E) Measurement of Tissue-Hemoglobin-Index showed no significant change either in the tourniquet group or in the operative clamping group compared to control (0 N). (F) Live images of the Tissue-Hemoglobin-Index exemplary at a force of 0 N, 2 N, after reperfusion and with the open clamping technique. The yellow arrow marks the compromised hind limb. Results are shown as means ± SEM. P-value: # < 0.05; § < 0.001 (two sample t-test), n = 4.