Certified Neuroscience Registered Nurse (CNRN) Practice Exam

For total hip arthroplasty (THA) and total knee arthroplasty (TKA), when should low molecular weight Heparin (LMWH) be withheld?

1. 12 hours before and 6 hours after

2. 24 hours before and 12 hours after

3. 12 hours before and 12 hours after

4. 6 hours before and 24 hours after

The correct answer is: 12 hours before and 12 hours after

Withholding low molecular weight Heparin (LMWH) 12 hours before and 12 hours after total hip arthroplasty (THA) or total knee arthroplasty (TKA) is appropriate because it helps to minimize the risk of bleeding during and after the surgical procedure. These specific time frames are established guidelines based on the pharmacokinetics of LMWH, which has a longer half-life compared to unfractionated heparin. By withholding the medication for 12 hours prior to surgery, practitioners ensure that the anticoagulant effects have diminished enough to reduce bleeding risks during the operation. Likewise, withholding LMWH for 12 hours post-surgery helps to avoid any potential complications associated with bleeding that may arise during the immediate recovery phase, while still allowing for appropriate anticoagulation to be established shortly after. This careful timing is crucial in managing the balance between preventing thromboembolic events and avoiding excessive bleeding, particularly in the context of major orthopedic surgeries such as THA and TKA.