No abstract

The study prospectively compared the kinetics of post-deflation tissue oxygen recovery between tourniquets with distinct inflation pressures. Forty knee arthroscopy patients were randomized into standard (350 mmHg) or reduced inflation pressure groups. In the latter group, arterial occlusion pressure was calculated according to a formula [(SBP+10)/K TP ], where SBP is the systolic blood pressure and K TP is the tissue padding coefficient based on limb circumference; a safety margin of 40-80 mmHg was added based on occlusion pressure. Pulse oximeter probes were applied to operative and nonoperative second toes and connected to a vital signs monitor. After tourniquet inflation, arthroscopy, and cuff deflation, arterial oxygen saturation was measured and recorded by the monitor every minute for 15 minutes. Standard inflation pressure group tourniquet time averaged 50 minutes at 350 mmHg; the respective values in the reduced pressure group were 51 minutes and 256 mmHg. Oxygen saturation recovery in the studied extremity was immediate after cuff deflation, with a transient drop at 5 minutes and recovery at 13 minutes. The drop was later and lesser in the reduced pressure group. In the control extremity, a transient decrease occurred at 3 minutes, with recovery at 12 minutes. The dip was again less pronounced in the reduced pressure group. In the reduced pressure group bleeding into the arthroscopic field was noted in multiple procedures. Enrollment was stopped early, as the impaired visualization was a safety concern. Unlike in the standard inflation pressure group, a bloodless arthroscopy field was not maintained in the reduced pressure group. The kinetics of post-deflation oxygen saturation recovery was not significantly different between the two groups; however, a transient decrease occurred in post-deflation oxygen saturation in both the operative and nonoperative limbs. This suggests that elective tourniquet use can have systemic effects post-cuff deflation, which warrants further investigation.