Timing of Thromboprophylaxis Withholding Before Surgery
For patients with normal renal function, withhold LMWH 24 hours before surgery (last dose at half the total daily dose), and for patients with impaired renal function requiring therapeutic anticoagulation, extend this to 48-72 hours before high bleeding risk procedures. 1, 2
Standard Preoperative Timing for LMWH
Stop warfarin 5 days before surgery and begin therapeutic LMWH bridging when INR falls below 2.0, typically 3 days preoperatively. 2
Administer the last preoperative LMWH dose 24 hours before surgery at half the total daily dose for patients with normal renal function undergoing standard procedures. 2
For prophylactic-dose LMWH or UFH, the American Society of Hematology defines preoperative dosing as administration 12 hours (or the evening before) prior to the procedure, though they recommend postoperative initiation instead due to bleeding concerns. 3
High Bleeding Risk Procedures
For neuraxial anesthesia, intracranial surgery, or spinal procedures, therapeutic anticoagulation should be withheld for 48-72 hours preoperatively to minimize bleeding complications. 1
The American Society of Regional Anesthesia emphasizes that heparin should be administered 12 hours prior to insertion of epidural catheter to avoid spinal hematoma. 3
Check INR the day before surgery and proceed if INR ≤1.5; if INR is 1.5-1.8, consider low-dose oral vitamin K (1-2.5 mg). 2
Renal Impairment Considerations
Patients with creatinine clearance <30 mL/min should not receive LMWH as first-line therapy due to accumulation risk and should use UFH instead. 3
Renal function must be reassessed postoperatively as it affects LMWH and DOAC dosing, and impaired renal function may require longer withholding periods. 1
Orthopedic Surgery Specific Timing
For major orthopedic surgery (hip/knee arthroplasty), LMWH is preferred with the first dose given at least 12 hours from the time of surgery (either pre- or postoperatively), though postoperative initiation is generally favored. 3
The American College of Chest Physicians recommends at least 10-14 days of thromboprophylaxis, with consideration of up to 35 days for higher-risk patients. 3
Cancer Surgery Protocols
The American Society of Hematology suggests postoperative over preoperative thromboprophylaxis for cancer patients undergoing surgery (conditional recommendation), defining preoperative as 12 hours before the procedure. 3
Despite this recommendation, prophylaxis should be commenced preoperatively according to other guidelines for cancer patients undergoing major surgical intervention, unless contraindicated by active bleeding. 3
Extended prophylaxis with LMWH for up to 4 weeks postoperatively should be considered for patients undergoing major abdominal or pelvic cancer surgery with high-risk features. 3
Liver Surgery Considerations
For liver resection, LMWH or UFH should be initiated 2-12 hours before surgery and continued until patients are fully mobile, with particular attention to epidural catheter timing. 3
A Cochrane meta-analysis supports continued treatment for 4 weeks after hospital discharge particularly in oncologic patients undergoing liver surgery. 3
Common Pitfalls
Never perform spinal/epidural procedures with residual DOAC effect, especially dabigatran in elderly patients or those with renal impairment, as this dramatically increases spinal hematoma risk. 1
Administering therapeutic LMWH too soon after high bleeding risk procedures increases major bleeding to 20%, emphasizing the importance of the 48-72 hour delay. 1
For patients with mechanical heart valves, recent VTE (<3 months), or antiphospholipid syndrome, bridging is essential and the 24-hour preoperative withholding window must be strictly observed. 1, 2
Patients already hospitalized prior to surgery should continue receiving thromboprophylaxis up until the appropriate preoperative withholding period. 3