A nurse is caring for a client 24 hours after total knee replacement surgery. Which assessment finding requires the most immediate nursing intervention?

Sudden severe calf pain with positive Homan's sign suggests deep vein thrombosis, a life-threatening complication post-knee replacement requiring immediate intervention to prevent pulmonary embolism. Other findings like pain or drainage are less urgent.

Understanding the Priority
The sudden onset of severe calf pain accompanied by a positive Homan's sign is the most critical finding because it strongly suggests the development of a deep vein thrombosis (DVT). In the context of a total knee replacement, this is a potentially life-threatening emergency requiring immediate intervention to prevent a pulmonary embolism (PE).

Why DVT is the Immediate Priority
Major orthopedic surgery, particularly total knee arthroplasty (TKA), carries a significant risk for postoperative venous thromboembolism (VTE), which includes both DVT and PE ^[4]. The clinical burden of VTE is substantial, and the risk is elevated in this postoperative period ^[4]. A new, acute onset of symptoms like severe unilateral calf pain and a positive Homan's sign is a classic clinical red flag for a DVT. The immediate danger is that a fragment of the clot can dislodge, travel through the venous system to the lungs, and cause a PE, a rapidly fatal complication. While prophylactic anticoagulation is a cornerstone of care to mitigate this risk , a breakthrough thrombotic event demands urgent diagnostic testing and therapeutic intervention, not just continued prophylaxis.

Analysis of Other Options
- Option 1: Postoperative pain rated 7/10 despite analgesia is a common and important comfort issue after TKA, but it does not signal an immediately life-threatening complication. It requires reassessment of the pain management plan but can be addressed after ruling out the emergent vascular issue.
- Option 2: 50 mL of serosanguineous drainage from a surgical drain over 8 hours is an expected finding 24 hours post-TKA. It reflects normal postoperative oozing and does not indicate active hemorrhage or a complication requiring immediate intervention.
- Option 3: Inability to perform a straight leg raise due to quadriceps weakness is a common finding related to postoperative pain, swelling, and muscle inhibition. It is an expected functional deficit at this early stage that will be addressed through physical therapy and is not an emergency.

Pathophysiology and Clinical Reasoning
The pathophysiology of DVT in this setting is explained by Virchow's triad: venous stasis from immobility, endothelial injury from the surgery itself, and a hypercoagulable state induced by the surgical stress response. The prophylactic strategies evaluated in the provided evidence, such as comparing aspirin to direct oral anticoagulants (DOACs) or enoxaparin, are designed to counteract this hypercoagulability [1, 3]. The fact that a patient can develop a DVT despite these prophylactic measures highlights the critical importance of the nurse's clinical assessment. A systematic review comparing aspirin and enoxaparin for thromboprophylaxis underscores the ongoing effort to optimize prevention, but the nurse's role in early detection of a breakthrough event remains paramount . A positive Homan's sign, while not highly specific on its own, becomes a powerful indicator when combined with the acute, severe pain presentation in a high-risk postoperative patient, necessitating immediate notification of the rapid response team or primary provider to arrange for a stat venous duplex ultrasound and initiation of therapeutic anticoagulation.