Abstract Body (Do not enter title and authors here): Introduction
Although rare, cardiac arrest during or after total hip arthroplasty (THA) is a life-threatening complication associated with substantial morbidity, ICU admissions, prolonged hospitalization, and increased healthcare costs. This study aimed to identify independent risk factors associated with intraoperative or early postoperative cardiac arrest requiring cardiopulmonary resuscitation (CPR), using a large national surgical database, to inform preoperative risk stratification and guide preventive strategies.

Methods
The American College of Surgeons National Surgical Quality Improvement Program (NSQIP) is a deidentified registry capturing surgical data from over 700 hospitals annually. Patients who underwent primary THA (CPT 27130) from 2017–2021 were identified. Univariate analyses assessed factors associated with intra- or early postoperative cardiac arrest; significant variables were entered into a multivariable logistic regression model. Predictors included demographics, comorbidities (e.g., diabetes, COPD, CHF), functional status, lab values (platelet count, creatinine, INR), ASA classification, and anesthesia type. Significance was set at p < 0.05.

Results
The cohort included 199,960 patients (54.8% male; median age 66). In univariate analysis, significant predictors of cardiac arrest included older age (p<;0.0001), female sex (p=0.0241), higher BMI (p=0.0068), diabetes (p<0.0001), COPD (p<0.0001), CHF (p<0.0001), functional dependence (p<0.0001), elevated ASA class (p<0.0001), and use of general anesthesia (p=0.0020).
Multivariable analysis identified the following independent risk factors:
Advancing age (p < 0.0001)
ASA class 4 vs. 3 (p < 0.0001), 3 vs. 2 (p = 0.0003)
Female sex (p = 0.0013)
Diabetes (p = 0.0015)
COPD (p = 0.0030)
Non-independent functional status (p = 0.0004)
General anesthesia (p = 0.0098)

Non-significant factors included BMI, CHF, creatinine, platelet count, and INR. The strongest predictors in descending order of influence were age, ASA classification, sex, functional status, and COPD history.

Conclusion
This national cohort study found that the risk of intraoperative or early postoperative cardiac arrest following THA was independently associated with older age, higher ASA class, female sex, diabetes, COPD, functional dependence, and the use of general anesthesia. These findings highlight the importance of comprehensive preoperative risk assessment and optimization, particularly in older and comorbid patients undergoing THA.