Plasma anti-FXa level as a surrogate marker of the adequacy of thromboprophylaxis in critically ill patients: A systematic review.

Critical care patients are prone to venous thromboembolism (VTE) and, thus, pharmacological thromboprophylaxis is generally advised. Low-molecular weight heparins (LMWHs) have become the drug of choice in ICU patients, since their predictable and reproducible dose response. Monitoring their pharmacological effect is not usually necessary except in special occasions (i.e. with obese or renal failure patients), where anti-FXa level measuring is recommended. However, there is neither recommendation of adequate anti-FXa levels in critically ill patients nor is it known whether peak or trough level should be measured. The aim of this systematic review was to evaluate the recommended LMWH doses, and the reasons to monitor anti-FXa levels.