Low tourniquet pressure has less impact on lower extremity nerve innervation: comparison of different tourniquet pressures used with intraoperative neuromonitoring with a randomized controlled study

We aimed to investigate the compression and ischemic effects of two different tourniquet pressures on tissues during surgery show a clinical difference. Patients aged 18–65 years who underwent foot and ankle surgery and applied a tourniquet in a single center between September 2022 and November 2023 were included in this prospective randomized study. Accordingly, tourniquet pressures were applied as limb occlusion pressure (LOP) + 50 mmHg in group 1 (12 patients) and LOP + 100 mmHg in group 2 (12 patients). The time point at which the femoral nerve motor evoked potential (MEP) decreased by 50%, the time point at which the MEP decreased by 100% for all nerves (femoral, tibial, and deep peroneal), and the time point at which all responses returned after the tourniquet was deflated were identified as the time points for analysis. There were no differences in demographic data (age, body mass index, and sex) between the two groups. The mean tourniquet pressure was 191 ± 16 mmHg in Group 1 and 247 ± 21 mmHg in Group 2 (p < 0.001). A 50% decrease in the femoral nerve MEP value was observed at an average of 47 min in Group 1 and 34 min in Group 2 (p < 0.001). A complete loss of MEP responses for all nerves was observed at an average of 69 min in Group 1 and 56 min in Group 2. After the tourniquet was deflated, all MEP responses returned to baseline values at an average of 8.5 min in Group 1 and 12.6 min in Group 2 (p = 0.007). The results showed that lower limb nerve innervation was affected later and returned to normal earlier after deflation of the tourniquet in Group 1 (low tourniquet pressure group). The innervations of the lower extremity nerves were affected later in the group in which low tourniquet pressure was applied (average 191 mmHg). Again, in this group (LOP + 50 mmHg), nerve conduction recovered an average of 10 min after deflation and four minutes earlier than in the high tourniquet pressure group. Level I, diagnostic study. NCT05926154.