Discuss thromboembolism prophylaxis and the placement of neuraxial anesthesia.
It is common practice for orthopedists to anticoagulate patients after total joint surgery to prevent thromboembolic events. This is accomplished with a multitude of medications such as unfractionated heparin, low-molecular-weight heparin (LMWH), warfarin, and newer agents such as thrombin inhibitors and fondaparinux. All these medica-tions can place the patient at risk for epidural hematoma if a neuraxial anesthetic is performed.
The American Society of Regional Anesthesia (ASRA) published guidelines in 2002 regarding neuraxial anes-thesia in the anticoagulated patient. Patients who receive subcutaneous heparin can safely receive neuraxial anesthe-sia, although it is probably better to delay heparin adminis-tration until after the block is performed. In addition, if the patient has received subcutaneous heparin for 4 or more days, a platelet count should be done prior to performing a neuraxial anesthetic and before catheter removal.
Patients on LMWH should not have neuraxial anesthe-sia performed until 12 hours after the last dose. For those who receive twice-daily dosing, LMWH should not be administered until 24 hours after surgery.
Epidural catheters should not remain in these patients and LMWH should not be administered until 2 hours after catheter removal. Those who receive single daily dosing can have a catheter safely maintained, and the first dose should begin 6–8 hours postoperatively. Catheters should not be removed until 12 hours after the last LMWH dose and the subsequent dose should not be given until 2 hours after catheter removal.
Those patients who will be initiating warfarin therapy more than 24 hours prior to surgery should have their International Normalized Ratio (INR) assessed. There are no guidelines given by the ASRA for an actual INR ratio below which neuraxial anesthesia can be safely performed, but 1.4 is a commonly agreed upon number. Those patients on chronic warfarin therapy should stop this medication 4–5 days prior to the procedure.
The ASRA guidelines comment that chronic NSAID use is not known to increase the incidence of epidural hematoma after neuraxial anesthesia.
There are no guidelines for the newer anticoagulating agents, such as thrombin inhibitors and fondaparinux, as these have not been time-tested yet. The ASRA recom-mends that the use of neuraxial anesthesia in this setting should be done only in the course of clinical trials.