Abstract: ObjectiveTo evaluate the effects of different doses of ketamine and lidocaine on free radical production
after tournique-induced ischemia-reperfusion injury in patients undergoing knee arthroplasty. Methods A total of 120
patients who planned to undergo knee arthroplasty were included in this study. Patients were randomly divided into the
lidocaine group, the ketamine group and the saline group, with 40 patients in each group. The lidocaine group was given
lidocaine intravenously with 1 mg/kg 10 min before anesthesia induction. In the ketamine group, 0.5 mg/kg ketamine was
slowly injected intravenously 10 min before anesthesia induction. The saline group was intravenously injected with 0.9%
sodium chloride 10 mL. Data of systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) of three
groups were recorded before anesthesia (T0), 5 min after infusion of intervention drugs (T1), 30 min after applying tourniquet
(T2), and 15 min after removing tourniquet (T3). Peripheral venous blood samples were collected at T0, T2 and T3 to detect
lactic acid level and ischemia modifier albumin (IMA) level in the three groups. The time of extubation, incidence of
intraoperative hypotension, intraoperative hypertension, postoperative nausea and vomiting, agitation during recovery,
delayed awakening and other adverse reactions were recorded. ResultsA total of 113 patients were enrolled, including 38
in the lidocaine group, 38 in the ketamine group, and 37 in the saline group, respectively. At T1, SBP, DBP and HR were
higher in the ketamine group than those in the lidocaine group and saline group (P＜0.05). There were no significant
differences in SBP, DBP and HR between the lidocaine group and the saline group (P＞0.05). At T2, SBP and DBP were
significantly higher in the ketamine group than those in the lidocaine group and the saline group (P＜0.05), but there was no
significant difference in HR between the two groups (P＞0.05). At T3, there were no significant differences in SBP, DBP and
HR between the 3 groups. At T2 and T3, the serum levels of lactic acid and IMA were significantly lower in the lidocaine
group than those of the ketamine group and the saline group, while the level was significantly lower in the ketamine group
than that of the saline group (P＜0.05). There were no significant differences in the time of extubation, intraoperative
hypertension, incidence of intraoperative hypotension, postoperative nausea and vomiting, agitation in recovery period and
delay in recovery between the three groups (P＞0.05). Conclusion Both lidocaine and ketamine can protect against
tourniquet-induced ischemia-reperfusion injury in patients undergoing knee arthroplasty, but lidocaine is more effective.

Key words: lidocaine, ketamine, reperfusion injury, lactic acid, arthroplasty, replacement, knee, ischemia modifier albumin