Abstract: Objective To investigate the risk factors for blood circulation risk after free flap transplantation and construct 
early warning model to provide reference for the early identification and prevention of high-risk groups in subsequent clinical practice. Methods From January 2011 to January 2024，396 patients underwent free skin flap transplantation in our hospital were included：276 cases underwent predictive model construction （modeling group） and 120 cases underwent internal validation （validation group）. The patients were grouped according to whether vascular crisis occurred within 72 h after surgery， and the independent risk factors of vascular crisis after free skin flap transplantation were evaluated by single factor and multivariate method， and the early warning model was further constructed and the clinical prediction efficiency was analyzed. Results There were 27 cases developed vascular crisis after surgery in all 276 patients （modeling group） with the ncidence of 9.78%. The results of univariate analysis showed that type 2 diabetes， smoking history，24 h postoperative visual  analogue score of pain， immediate postoperative body temperature， postoperative position and postoperative use of  vasodilators may be related to the occurrence of vascular crisis after free flap transplantation （P<0.05）. The results of 
multivariate analysis showed that type 2 diabetes mellitus， smoking history， pain visual analogue score ≥7 in 24 h after surgery，immediate postoperative body temperature <34 ℃， lateral position and vasodilator were independent risk factors for vascular crisis after free flap transplantation （P<0.05）. Based on the results of multi-factor analysis， the regression prediction equation for the risk of vascular crisis after free flap transplantation was established. That is， the risk Logit （Y）=0.72+1.70×combined type 2 diabetes+0.8×smoking history+0.63×pain visual analogue score≥7 points at 24 h after surgery+0.88×immediate postoperative body temperature<34 ℃ +0.52×placement of the affected lateral position+0.46×use of vasodilators after surgery. ROC curve analysis

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