Does Tourniquet Time or Pressure Contribute to Intracranial Pressure Increase following Tourniquet Application?

Objective: The aim of this study was to determine whether an early increase in intracranial pressure (ICP) following the deflation of a tourniquet is related to the tourniquet time (TT) or tourniquet pressure (TP) and to identify a safe cut-off value for TT or TP. Materials and Methods: Patients who underwent elective orthopedic lower-extremity surgery under general anesthesia were randomized into 2 groups: group A (inflation with a pneumatic TP of systolic blood pressure + 100 mm Hg; n = 30) and group B (inflation using the arterial occlusion pressure formula; n = 30). The initial and maximum TPs, TT, and sonographic measurements of optic-nerve sheath diameter (ONSD) and end-tidal CO₂ values were taken at specific time points (15 min before the induction of anesthesia, just before, and 5, 10, and 15 min after the tourniquet was deflated). Results: The initial and maximum TPs were found to be significantly higher in group A than in group B. At 5 min after the tourniquet deflation, there was a significant positive correlation between TT and ONSD ( r = 0.57, p = 0.0001). When ONSD ≥5 mm was taken as a standard criterion, the safe cut-off value for the optimal TT was found to be < 67.5 min (sensitivity 87% and specificity 59.5%). Conclusion: The ICP increase in the early period after tourniquet deflation was well correlated with TT but not with TP. TT of ≥67.5 min was found to be the cut-off value and is considered the starting point of the increase in ICP after tourniquet deflation.