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Blood pressure, heart rate, plasma epinephrine, norepinephrine and vasopressin concentrations increased slightly in response to laryngoscopy and intubation, all returning to or below baseline 5 min later with no change in angiotensin converting enzyme activity in normotensive patients.

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ObjectiveThe aim of this study was to compare the limb occlusion pressure (LOP) determination and arterial occlusion pressure (AOP) estimation methods for tourniquet pressure setting in adult patients undergoing knee arthroplasty under combined spinal-epidural anesthesia.MethodsNinety-three patients were randomized into two groups. Pneumatic tourniquet inflation pressures were adjusted based either on LOP determination or AOP estimation in Group 1 (46 patients, 38 female and 8 male; mean age: 67.71 ± 9.17) and Group 2 (47 patients, 40 female and 7 male; mean age: 70.31 ± 8.27), respectively. Initial and maximal systolic blood pressures, LOP/AOP levels, required time to estimate AOP/determinate LOP and set the cuff pressure, initial and maximal tourniquet pressures and tourniquet time were recorded. The effectiveness of the tourniquet was assessed by the orthopedic surgeons using a Likert scale.ResultsInitial and maximal systolic blood pressures, determined LOP, estimated AOP, duration of tourniquet and the performance of the tourniquet were not different between groups. However, the initial (182.44 ± 14.59 mm Hg vs. 200.69 ± 15.55 mm Hg) and maximal tourniquet pressures (186.91 ± 12.91 mm Hg vs. 200.69 ± 15.55 mm Hg) were significantly lower, the time required to estimate AOP and set the tourniquet cuff pressure was significantly less (23.91 ± 4.77 s vs. 178.81 ± 25.46 s) in Group II (p = 0.000). No complications that could be related to the tourniquet were observed during or after surgery.ConclusionTourniquet inflation pressure setting based on AOP estimation method provides a bloodless surgical field that is comparable to that of LOP determination method with lower pneumatic inflation pressure and less required time for cuff pressure adjustment in adult patients undergoing total knee arthroplasty under combined spinal epidural anesthesia.

Clinical utilization of the AOP estimation formula is a practical and effective way of setting tourniquet pressures for lower limb surgery. Its usage allows achievement of a bloodless field with inflation pressures lower than those previously recommended in the literature for lower limb tourniquets.

Our results showed that activation of occlusion alarms on both pumps takes a considerable time, and that the mean time to alarm activation was longer with low infusion rates and larger syringes. To reduce occlusion alarm delays smaller sized syringes with low compliance should be used and staff be alerted when using low flow rates with highly concentrated potent drugs.

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