Abstract :
Objectives: older people have an increased risk of Low Molecular weight Heparin accumulation
leading to an increased bleeding risk. The objective of this study was to assess whether reduced glomerular
filtration rate (Gfr), estimated by the cockcroft-Gault or Modification of the Diet in renal Disease (MDrD)
equations, indicates drug accumulation by increased anti-Xa levels in older subjects receiving prophylactic
enoxaparin treatment. Design: cohort study. Setting: acute geriatric units in nancy Hospital. Participants:
ninety-two consenting consecutive patients, 65 and older, confined to bed for an acute medical condition
requiring enoxaparin for prevention of venous thromboembolism, and hospitalized for at least six days were
enrolled. Measurements: serum creatinine and peak plasma anti-Xa levels 3 to 4 hours after the daily injection of
enoxaparin were measured at days 3, 6, 9 and 12 (first dose of enoxaparin at day one). analyses of variance for
repeated measures were used to evaluate significant predictors of peak anti-Xa activity in univariate and
multivariate analyses. Results: a significant correlation was observed between anti-Xa activity and Gfr
estimated with the cockcroft formula r=0.43. following univariate analysis, the three factors associated with
higher anti-Xa levels were a lower cockcroft-Gault Gfr (p=0.0002), female gender (p=0.0003) and a lower
bodyweight (p<.0001). no significant association between anti-Xa levels and MDrD Gfr (p=0.33) was
observed. following multivariate analysis, female gender (p=0.02), bodyweight (p=0.04) and cockcroft Gfr
(p=0.05) remained independent determinants of anti-Xa levels. Conclusion: in hospitalized patients older than 65
years old, the cockcroft-Gault equation, in contrast to the MDrD equation, is able to predict the risk of higher
anti-Xa levels.
