Neuraxial blockade should be avoided in the presence of prophylactic or therapeutic anticoagulation because of the increased risk of epidural hematoma formation. Massachusetts General Hospital guidelines regarding neuraxial anesthesia in anticoagulated patients are listed in Table 20.3.

1. Oral anticoagulants. In patients receiving low-dose oral anticoagulants (warfarin), regional techniques may be performed if the thromboprophylaxis was initiated less than 24 hours previously. If epidural or spinal anesthesia is planned, hold warfarin 3 to 5 days before the operation, and the patient’s international normalized ratio (INR) should be checked before the operation. An INR less than or equal to 1.5 is generally acceptable for many anesthesiologists, but there is no definite cutoff value above which epidural or spinal anesthesia is specifically discouraged.
2. Unfractionatedheparin. Twice-daily subcutaneous heparin prophylaxis is not a contraindication for the use of neuraxial techniques. There is an unknown risk with prophylactic subcutaneous heparin dosed three times per day. In these cases, a coagulation profile should be obtained. Caution should be used in debilitated patients, in whom the action of the drug may be prolonged and in whom neurologic monitoring may be difficult. IV heparin should be stopped 2 to 4 hours before the initiation of neuraxial blockade, and a repeat coagulation profile should be obtained if there is any question about the state of anticoagulation. Administration of heparin should be delayed for at least 2 hours after placement. Removal of a catheter should be treated with the same anticoagulation guidelines as the placement of a catheter.
3. Low-molecular-weight heparin. Patients receiving low-molecular-weight heparin (LMWH) for thromboembolism prophylaxis have altered coagulation parameters. Spinal or epidural needle placement should not be done for at least 12 hours after the last dose. Patients receiving higher doses of LMWH (enoxaparin 1 mg/kg twice daily) will require longer delays (24 hours). In patients requiring continuing LMWH administration, spinal or epidural catheters should be removed before administration of LMWH. The subsequent administration of LMWH should be delayed for 4 hours after catheter removal.
4. Antiplatelet drugs. Patients receiving aspirin or nonsteroidal anti-inflammatory drugs do not appear to be at higher risk for epidural hematoma formation. These drugs could contribute to an increased bleeding risk, however, if they are used concurrently with other anticoagulants. With regard to thienopyridine derivatives (ticlopidine and clopidogrel), the suggested time interval between discontinuation of medication and initiation of neuraxial block is 14 days for ticlopidine and 5 to 7 days for clopidogrel. Following platelet GPIIb/IIIa inhibitors, normal platelet function returns in 24 to 48 hours with abciximab and in 4 to 8 hours with eptifibatide and tirofiban.
5. Fibrinolytic and thrombolytic agents. Although the plasma half-life of thrombolytic drugs is only for hours, it takes several days before thrombolytic effects disappear. Surgery or puncture of noncompressible vessels within 10 days of thrombolytic therapy is contraindicated. There is no definitive guideline regarding the neuraxial anesthesia and thrombolytic therapy. Measurement of the fibrinogen level may be helpful in guiding the decision.
6. Herbal medication (see Chapters 1 and 38). Herbal medications including garlic, ginkgo, and ginseng are all known to affect coagulation. Currently, there are no specific guidelines for timing the neuraxial block in relation to herbal medication use. Because it is not known at which doses potential coagulopathies occur, management decisions are often based more on a clinical history of abnormal bleeding. Herbal medications are thought to be more problematic when taken concurrently with other conventional anticoagulant medications.