Brief communication: Preoperative anticoagulant activity after bridging low-molecular-weight heparin for temporary interruption of warfarin.
BACKGROUND
Preoperative low-molecular-weight heparin (LMWH) is often used when warfarin therapy is interrupted for surgery.


OBJECTIVE
To determine the preoperative anticoagulant activity of LMWH following a standardized "bridging" regimen.


METHODS
Prospective cohort study.


METHODS
Single university hospital.


METHODS
Consecutive patients who had warfarin therapy interrupted before an invasive procedure.


METHODS
Enoxaparin, 1 mg/kg of body weight, twice daily. The last dose was administered the evening before surgery.


METHODS
Blood anti-factor Xa heparin levels measured shortly before surgery.


RESULTS
Preoperative anti-Xa heparin levels were obtained in 80 patients at an average of 14 hours after the last dose of enoxaparin was administered. The average anti-Xa heparin level was 0.6 U/mL. The anti-Xa heparin level, measured shortly before surgery, was 0.5 U/mL or greater in 54 (68%) patients and 1.0 U/mL or greater in 13 (16%) patients. A shorter interval since the last dose (P < 0.001) and a higher body mass index (P = 0.001) were associated with higher preoperative anti-Xa heparin levels.


CONCLUSIONS
The small sample size limits accurate estimates of the frequency of the clinical outcomes. A single regimen of LMWH was evaluated.


CONCLUSIONS
Anti-Xa heparin levels often remain high at the time of surgery if a last dose of a twice-daily regimen of LMWH is given the evening before surgery.
O'Donnell
Martin J
MJ
McMaster University and Hamilton Health Sciences Foundation, Hamilton, Ontario, Canada. odonnm@mcmaster.ca
Kearon
Clive
C
Johnson
Judy
J
Robinson
Marlene
M
Zondag
Michelle
M
Turpie
Irene
I
Turpie
Alexander G
AG
D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects / Q000493:pharmacokinetics*; D004334:Drug Administration Schedule; D017984:Enoxaparin / Q000008:administration & dosage* / Q000009:adverse effects / Q000493:pharmacokinetics*; D015951:Factor Xa / Q000378:metabolism; D005260:Female; D006470:Hemorrhage / Q000139:chemically induced; D006801:Humans; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care / Q000379:methods*; D012307:Risk Factors; D018401:Sample Size; D013923:Thromboembolism / Q000139:chemically induced; D014859:Warfarin / Q000627:therapeutic use; D028761:Withholding Treatment
D000925:Anticoagulants; D017984:Enoxaparin; D014859:Warfarin; D015951:Factor Xa