# A 70-year-old client with mechanical mitral valve has been on chronic warfarin and is scheduled for an elective hip replacement on Tuesday at 7 AM. The provider has stopped warfarin five days before surgery and is bridging with therapeutic enoxaparin 1 mg/kg subcutaneous every 12 hours. Which instruction by the nurse about the last bridging dose is correct?

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> url: https://mymerci.kr/pages/nclex_q.php?qn_id=374969&lang=en  
> language: en  
> subject: Medical Emergencies  
> category: PA

## Question

A 70-year-old client with mechanical mitral valve has been on chronic warfarin and is scheduled for an elective hip replacement on Tuesday at 7 AM. The provider has stopped warfarin five days before surgery and is bridging with therapeutic enoxaparin 1 mg/kg subcutaneous every 12 hours. Which instruction by the nurse about the last bridging dose is correct?

## Option

1. Discontinue enoxaparin one week before surgery to eliminate any residual anticoagulant effect, as is done with warfarin, and do not restart until post-operative hemostasis is confirmed.
2. Administer the final enoxaparin dose at 6 AM on the day of surgery, approximately one hour before the procedure, to maintain therapeutic anticoagulation until the very last moment and minimize stroke risk.
3. Take the last enoxaparin dose approximately 24 hours before the scheduled surgery (e.g., on Monday morning), then hold all further doses until the surgeon clears restart of anticoagulation post-operatively. **✔ Correct answer**
4. Maintain the enoxaparin regimen of every 12 hours, including a dose on the morning of surgery, to ensure the INR remains within the therapeutic range throughout the perioperative period.

**Correct answer: 3**

## Explanation

Bridging anticoagulation around elective surgery
Patients with high thromboembolic risk (mechanical mitral valve, recent VTE within 3 months, severe thrombophilia) are bridged when warfarin is held for elective surgery. The standard plan:
• Stop warfarin 5 days before surgery (longer half-life: ~36–42 h; this lets INR drift below 1.5).
• Begin therapeutic-dose LMWH (e.g., enoxaparin 1 mg/kg q12h) when INR drops below the therapeutic range, typically Day -3.
• Last enoxaparin dose: 24 hours before the scheduled procedure. For neuraxial anesthesia (spinal or epidural) the recommended interval is at least 24 hours after a treatment dose and at least 12 hours after a prophylactic dose to avoid spinal hematoma.
• Resume LMWH 24–48–72 h post-op depending on bleeding risk; reintroduce warfarin same day or next day with overlap until INR therapeutic, then stop LMWH.
• Clear written plan: dates, doses, who to call, signs of bleeding/clotting; verify on day of surgery.

Options 1, 3 give too close to surgery → bleeding risk. Option 1 stops too early → thrombosis risk during the gap.

## In-depth explanation

Clinical reasoning summary
Bridging anticoagulation around elective surgery
Patients with high thromboembolic risk (mechanical mitral valve, recent VTE within 3 months, severe thrombophilia) are bridged when warfarin is held for elective surgery. The standard plan:
• Stop warfarin 5 days before surgery (longer half-life: ~36–42 h; this lets INR drift below 1.5).
• Begin therapeutic-dose LMWH (e.g., enoxaparin 1 mg/kg q12h) when INR drops below the therapeutic range, typically Day -3.
• Last enoxaparin dose: 24 hours before the scheduled procedure. For neuraxial anesthesia (spinal or epidural) the recommended interval is at least 24 hours after a treatment dose and at least 12 hours after a prophylactic dose to avoid spinal hematoma.
• Resume LMWH 24–48–72 h post-op depending on bleeding risk; reintroduce warfarin same day or next day with overlap until INR therapeutic, then stop LMWH.
• Clear written plan: dates, doses, who to call, signs of bleeding/clotting; verify on day of surgery.

Options 1, 3 give too close to surgery → bleeding risk. Option 4 stops too early → thrombosis risk during the gap.

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