Low-Molecular-Weight Heparins in Renal Impairment and Obesity: Available Evidence and Clinical Practice Recommendations Across Medical and Surgical Settings

OBJECTIVE: To develop practical recommendations for the use of low-molecular-weight heparins (LMWHs) as prophylaxis and treatment of venous thromboembolism and acute coronary syndromes in patients with impaired renal function or obesity. DATA SOURCES: Multiple MEDLINE searches were performed (November 2008) to identify studies for inclusion, using a comprehensive list of search terms including, but not limited to, LMWH, enoxaparin, dalteparin, tinzaparin, obesity, weight, renal, kidney, elderly, monitoring, and anti-Xa. STUDY SELECTION AND DATA EXTRACTION: Only articles published in English that were relevant for this review were included. DATA SYNTHESIS: In the majority of patients, standardized prophylaxis or treatment doses of LMWHs can be used without the need for monitoring and adjusting regimens. For patents with severe renal impairment (estimated creatinine clearance [CrCl] <30 mL/min), doses of some LMWHs should be adjusted or unfractionated heparin should be used instead. CrCl should be estimated using the Cockcroft-Gault method. Differences are noted in the degree of accumulation of various LMWHs in patients with moderate-to-severe renal impairment, and thus, the degree of dose adjustment may differ among the various LMWHs. Increasing the prophylactic doses of LMWH may be appropriate in morbidly obese patients (body mass index >= 40 kg/m(2)). The use of total body weight is appropriate for therapeutic doses of LMWH in obese patients. Laboratory monitoring of the anticoagulation effect of LMWHs is generally not necessary, but should be considered in patients with morbid obesity (weight >190 kg), those with severe renal impairment, and those with moderate renal impairment with prolonged (>10 days) LMWH use. When anti-Xa activity is monitored, it should be determined using a chromogenic method and a calibration curve based on the LMWH used. CONCLUSIONS: Additional data are needed for specific dose guiding in obese and renally impaired patients, who are often excluded from larger clinical trials. Practice recommendations are made based on available evidence and authors' clinical opinions.