Objective:To investigate the risk factors and treatment outcome of persistent inflammation-immunosuppression-catabolism syndrome (PICS) in patients with extensive burns.Methods:A retrospective case series study was conducted. From January 2017 to December 2021, 220 patients with extensive burns who were admitted to Guangzhou Red Cross Hospital of Jinan University met the inclusion criteria, including 168 males and 52 females, aged 18-84 (43±14) years. According to the occurrence of PICS, the patients were divided into PICS group (84 patients) and non-PICS group (136 patients). The general data such as sex, age, complication of underlying diseases and acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) score on admission, sepsis-related organ failure evaluation (SOFA) scores on admission and 14 days post admission, and proportion of patients with mechanical ventilation over 48 h during treatment, special conditions such as total burn area, full-thickness burn area, proportion of patients admitted within 48 h post injury, and exposed deep wound area at the 30 th day post injury, outcome indicators such as hospitalization day, total cost of hospital stay, number of surgeries, and death of patients in the 2 groups were collected and analyzed. Data were statistically analyzed with independent sample t test, Mann-Whitney U test, and chi-square test. The multivariate logistic regression analysis was performed on the indicators with statistically significant differences between the two groups except for outcome indicators, and the independent risk factors influencing secondary PICS in patients with extensive burns were screened. Results:The APACHE Ⅱ and SOFA scores on admission, and proportion of patients with mechanical ventilation over 48 h during treatment of patients in PICS group were significantly higher than those in non-PICS group ( t=6.78, Z=-4.75, χ2=4.74, respectively, P<0.05). There were no statistically significant differences in the rest of general data of patients between the two groups ( P>0.05). The total burn area, full-thickness burn area, and exposed deep wound area at the 30 th day post injury in PICS group were significantly greater than those in non-PICS group ( t=6.29, Z=-7.25, Z=-8.73, P<0.05), the exposed deep wound areas at the 30 th day post injury in PICS group and non-PICS group were respectively 25% (15%, 35%) total body surface area (TBSA) and 8% (0, 13%) TBSA, while the proportion of patients admitted within 48 h post injury was significantly lower than that in non-PICS group ( χ2=6.13, P<0.05). The hospitalization day, total cost of hospital stay, and number of surgeries of patients in PICS group were significantly higher than those in non-PICS group (with Z values of -7.12, -8.48, and -6.87, respectively, P<0.05), while the deaths of patients in the 2 groups were similar ( P>0.05). The APACHE Ⅱ score on admission and exposed deep wound area at the 30 th day post injury both were the independent risk factors for PICS in patients with extensive burns (with odds ratios of 1.15 and 1.07, 95% confidence intervals of 1.06-1.25 and 1.05-1.10, respectively, P<0.05). Conclusions:The APACHE Ⅱ score on admission and exposed deep wound area at the 30 th day post injury are the independent risk factors for PICS in patients with extensive burns. The patients with secondary PICS had good prognosis with more surgical intervention and hospitalization day, and higher total cost of hospital stay.