The effectiveness of two different methods for calculating the arterial occlusion pressure (AOP) to set tourniquet inflation pressures were assessed in patients underwent knee arthroscopy. Eighty patients were included in this study. Tourniquet inflation pressure was set by adding 20 mmHg of safety margin above the AOP value which was calculated by either the Tuncali et al. formula or Hong-yun Liu et al. formula. Primary outcome measures were the initial and maximum SBP, initial and maximum tourniquet inflation pressure, the secondary outcomes were the surgeon rating of the bloodlessness of the surgical field and tourniquet associated complications. There was significant difference in the initial tourniquet pressure (mmHg); it was 208 ± 12 and 262 ± 18 for group (A) and (B) respectively; also there was significant difference in the maximum tourniquet pressure (mmHg), it was 229 ± 14 and 283 ± 19 for group (A) and (B) respectively. There was no significant difference in the initial SBP-to- tourniquet inflation time, the initial SBP or the maximum SBP between the groups. Also, there was no significant difference in surgeon rating of the bloodlessness of the surgical field, at the start, middle and end of surgery. Hong-yun Liu et al. mathematical formula was found to be less effective than Tuncali et al. formula to estimate the least effective tourniquet pressure in lower limb surgery and we might consider it invalid to be used in the lower limb.Clinical trials registration number: NCT03706859 (Clinicaltrials.gov) and registration date: January, 2019. https://clinicaltrials.gov/ct2/show/NCT03706859.
Keywords: Arterial occlusion pressure; Estimation method; Mathematical method; Tourniquet inflation pressure.