Enoxaparin Before Surgery
Therapeutic vs prophylactic timing with CrCl in mind
Clinicians use enoxaparin for two very different jobs. One is prevention at low dose. The other is treatment at full dose. Those goals have different perioperative timing. Add renal function and neuraxial concerns, and the plan can shift again. This guide gives you a simple way to choose a safe hold and restart for most cases, then shows you when to favor UFH instead.
TL;DR for quick decisions
- Prophylaxis: last dose at least 12 hours before most procedures. Restart about 24 hours after if bleeding risk is low or moderate and hemostasis is secure. Use 48 to 72 hours for higher risk or neuraxial contexts.
- Therapeutic: last dose at least 24 hours before. Restart about 24 hours after if low or moderate risk and hemostasis is secure. Use 48 to 72 hours for higher risk or neuraxial contexts.
- CrCl below 30 mL per min: prefer UFH because enoxaparin accumulates. If LMWH must be used, switch to 1 mg/kg once daily and be extra conservative with timing.
- Neuraxial catheter: never give LMWH while a catheter is in place. Earliest restart is catheter removal plus 4 hours, then take the later of this or the usual post procedure window.
At-a-glance timing
| Scenario | Last pre-op dose | Post-op restart |
|---|---|---|
| Enoxaparin prophylaxis | ≥ 12 h | ~24 h (low/mod); 48–72 h (high/neuro) |
| Enoxaparin therapeutic | ≥ 24 h | ~24 h (low/mod); 48–72 h (high/neuro) |
| CrCl < 30 mL/min | Prefer UFH; if LMWH needed, 1 mg/kg q24h | Be conservative; consider UFH |
| Neuraxial catheter in place | — | Earliest LMWH dose = removal + 4 h; use the later of baseline vs catheter rule |
Why dosing intent matters
Prophylaxis aims to prevent clots in lower risk settings. Typical patterns you see on the floor are 40 mg once daily or 30 mg twice daily.
Therapeutic dosing is full intensity for active VTE, AF with very high risk, or bridging plans. Typical pattern is 1 mg/kg twice daily or 1.5 mg/kg once daily.
Since therapeutic dosing has higher anticoagulant effect, we hold it longer before procedures and we lean conservative on restart.
Pre procedure holds
Prophylactic enoxaparin
- Hold: last dose at least 12 hours before the procedure.
- Use the longer end if your procedure has higher bleeding risk, if neuraxial access is planned, or if there are additional bleeding concerns.
Therapeutic enoxaparin
- Hold: last dose at least 24 hours before the procedure.
- If the operation carries high bleeding risk, consider extending a little further after a risk discussion with the team.
Post procedure restarts
Restart depends on two things. First is the procedure’s bleeding risk and the state of hemostasis. Second is whether the situation is neuraxial.
- Low or moderate bleeding risk: restart about 24 hours after if hemostasis is secure.
- High bleeding risk or neuraxial context: restart 48 to 72 hours after.
- If any bleeding concerns exist, push later. When in doubt, talk to the operator and anesthesia.
Renal function and when to choose UFH
Enoxaparin clears through the kidneys. If CrCl is below 30 mL per min, the drug can accumulate and increase bleeding risk.
- Preferred plan: switch to UFH for the perioperative period. UFH has a short half life, can be checked with aPTT, and can be held on the day of the procedure.
- If LMWH must be used: reduce to 1 mg/kg once daily, monitor closely, and be conservative with holds and restarts.
This is also where the calculator helps, since it uses Cockcroft Gault to classify CrCl and surfaces a reminder to prefer UFH when CrCl is below 30.
Neuraxial anesthesia and catheter rules
- Do not give enoxaparin while an epidural or intrathecal catheter is in place.
- Earliest restart after catheter removal is removal plus 4 hours.
- Always use the later of the baseline post procedure window or the catheter rule.
- Coordinate timing with anesthesia so that removal and first dose are planned together.
For a quick-reference table that includes DOACs and UFH/LMWH catheter rules, see Neuraxial catheter timing.
How this interacts with UFH
- Stop a UFH infusion 4 to 6 hours before the procedure.
- Confirm aPTT is normal if required locally.
- Restart about 24 hours after for low or moderate risk, or 48 to 72 hours for higher risk or neuraxial cases, once hemostasis is secure.
Red flags and when to pause
- A dose was given inside the hold window.
- Traumatic puncture or unexpected bleeding.
- Neuraxial catheter still in place.
- CrCl below 30 mL per min without a shift to UFH.
- Platelets are low or other bleeding risks are present.
- No clear sign of hemostasis or the operator is concerned.
If any of these are true, delay and reassess with the team.
Open the AnticoagPlanner Calculator
Source and conservative alignment
- MD Anderson Peri-Procedure Anticoagulants, V8 (approved 07/15/2025) — LMWH/UFH: Appendix D (pp.13–14) and Appendix H (pp.26–28).
- ASRA/Stanford institutional guidance — neuraxial catheter timing: LMWH restart ≥ removal + 4 h; no dosing with catheter in place.
When sources differ, we favor the longer hold and the later restart, especially for neuraxial access and for renal impairment. Never dose LMWH while a catheter is in place. Earliest restart is removal plus 4 hours, then choose the later of that or the baseline restart window.
This article supports, not replaces, clinical judgment. Confirm local policy and ASRA guidance for neuraxial catheters.
Implements: MD Anderson Peri-Procedure Anticoagulants, V8 (approved 07/15/2025). Last updated: 07 Oct 2025.