[Risk factors associated with interleukin 6 level in serum after total knee arthroplasty]

To explore the risk factors associated with interleukin 6 (IL-6) level in serum after total knee arthroplasty (TKA).

A retrospective study was made on the clinical data of 273 patients underwent primary unilateral TKA between July 2015 and April 2017. There were 50 males and 223 females with an average age of 66.3 years (range, 36-89 years), and the body mass index (BMI) was (25.5±3.7) kg/m ². Of them, 256 patients suffered with osteoarthritis, and the other 17 patients with rheumatoid arthritis. Univariate analysis was made to find the related factors between IL-6 level in serum at 1 day after operation and preoperative data including gender, age, BMI, diagnosis, comorbidities, preoperative American Society of Anesthesiologists (ASA) grade, preoperative varus or valgus deformity, range of motion of the knee, preoperative level of C-reactive protein (CRP) and IL-6 in serum, operation time, intraoperative blood loss, usage of drainage tube and catheter, and dosage of tranexamic acid and dexamethasone used on day of operation. Furthermore, the multiple linear regression analysis was performed to identify the risk factors.

The operation time was (79.7±15.6) minutes, and the intraoperative blood loss was (107.8±25.3) mL. Drainage tubes were used in 111 patients and catheters were used in 41 patients after operation. The dosage of tranexamic acid and dexamethasone used on day of operation were (3.2±0.8) g and (15.1±6.6) mg, respectively. The levels of IL-6 in serum were (4.48±3.05), (42.65±37.09), and (28.21±26.44) pg/mL before operation and at 1 and 3 days after operation, respectively. Univariate analysis showed that the level of IL-6 in serum at 1 day after operation was significantly higher in variables as follows: age, diagnosis, history of lung infection, range of motion, preoperative levels of CRP and IL-6 in serum, intravenous dosage of tranexamic acid and dexamethasone on day of operation ( P<0.05). Multiple linear regression analysis showed that range of motion less than 90°, intravenous dosage of tranexamic acid on day of operation less than 3 g, and dosage of dexamethasone on day of operation less than 10 mg were significant risk factors ( P<0.05).

Range of motion less than 90°, intravenous dosage of tranexamic acid on day of operation less than 3 g, and dosage of dexamethasone on day of operation less than 10 mg were independent risk factors that resulted in increased level of IL-6 in serum at 1 day after TKA.