**4. Anticoagulant use in renal insufficiency**

Renal clearance is the primary mode of elimination for several anticoagulants, including LMWH, fondaparinux, and the new oral factor Xa and Ha inhibitors. Therefore, with reduced renal function, these drugs may accumulate and may increase the risk of bleeding, particularly in elderly patients and those at high risk for bleeding (53). The relationship between renal impairment and drug accumulation for the various LMWHs appears to be variable and may be related to the chain length distribution of the different LMWH preparations (54). Two recent studies in hospitalized patients, the majority of whom were critically ill and had creatinine clearances less than 30 mL/min, have shown no bioaccumulation of dalteparin 5000 U once daily based on serial anti-factor Xa levels (55,56). Therefore, we do not reduce the prophylaxis dose of dalteparin in patients with renal insufficiency. In patients receiving intermittent hemodialy-sis, we suggest that the LMWH be administered after the dialysis session. With enoxaparin thromboprophylaxis, we suggest that 30 mg once daily be used. We also suggest that fondaparinux, rivaroxaban and dabigatran be avoided unless future evidence demonstrates that these agents can be used safely in patients with severe renal insufficiency.

### **5. Concomitant use of regional anesthesia techniques and anticoagulant prophylaxis**

Neuraxial blockade (spinal or epidural anesthesia and continuous epidural analgesia) results in a significant reduction in cardiopulmonary morbidity compared with general anesthesia and narcotic-based systemic analgesia, as well as better pain control and patient satisfaction (57). However, concerns have been raised about a possible increased risk of epidural or spinal hematoma and spinal cord ischemia or paraplegia with use of concomitant anticoagulant prophylaxis (58,59).We believe that anticoagulant thromboprophylaxis with LMWH or LDH can safely be given along with neuraxial blockade with proper patient selection and timing of doses. Further details can be found in Section 1.5 of the 8th ACCP Prevention of VTE guidelines(3). In summary:

