Targeting Extended Thromboprophylaxis after Surgery Through Multidimensional Dynamic Pulmonary Embolism Risk Assessment: Development and Temporal Validation in 4.8 Million Operations.

BACKGROUND

Extended thromboprophylaxis reduces postoperative venous thromboembolism but is inconsistently used because pulmonary embolism (PE) risk varies across operations and may change after discharge. We developed and temporally validated a two-stage calculator to estimate PE risk at discharge and update risk after unplanned readmission or reoperation.

STUDY

DESIGN

ACS-NSQIP adult operations from 2020-2023 were used for development (n=3,864,605), with 2024 operations reserved for temporal validation (n=956,434). The primary outcome was 30-day postoperative PE. Penalized logistic regression modeled discharge risk using patient, surgical, and early postoperative variables; dynamic reassessment added timing of first unplanned readmission and reoperation. A prespecified 0.5% predicted-risk threshold was evaluated.

RESULTS

Among 4,856,597 operations, 17,045 patients developed PE (0.35%). In temporal validation, the discharge model demonstrated AUC 0.811 (95% CI, 0.801-0.818), calibration slope 1.024, and intercept 0.036. Dynamic reassessment improved discrimination to AUC 0.892 (95% CI, 0.887-0.897), with calibration slope 0.991 and intercept 0.030. Among 57,840 patients with an unplanned-return event, reassessment moved 24,320 patients above the 0.5% treatment-consideration threshold despite being below threshold at discharge. This newly flagged group had 711 observed PEs, a 2.92% PE rate, and 1 PE within 30 days for every 34.2 newly flagged patients under usual care. Sensitivity analyses indicated that unplanned-return occurrence, rather than exact postoperative day, was the durable risk signal.

CONCLUSIONS

Across adult surgery, dynamic PE reassessment after unplanned readmission or reoperation identifies an actionable high-risk postoperative state not captured at discharge. This surgeon-facing calculator can make extended-prophylaxis reconsideration reproducible when prevention remains possible.