Nine studies (n=627, range 10 to 223) were included in the review: one RCT, seven prospective cohorts and one case-control.
Anti-factor Xa levels (eight studies, n=406):
One nadroparin study found lower mean anti-Xa levels in patients on vasopressors compared to patients without vasopressors (prospective cohort, n=60). One dalteparin study found higher mean levels of anti-Xa levels in patients who received two to three inotropes compared to none or one inotrope (prospective cohort, n=10).
There was no difference in anti-Xa levels in patients with or without edema (one prospective cohort, n=14). There was no difference between patients who received once-daily or twice-daily dosing of certoparin (one prospective cohort, n=62).
Anti-Xa activity clearance was lower in critically ill patients who received enoxaparin compared to medical patients who received enoxaparin (one prospective cohort, n=29). Low molecular weight heparins did not appear to bioaccumulate based on trough anti-Xa levels (two prospective cohorts, n=157). Three studies had no control group (three prospective cohorts, n=246).
Clinical Outcomes:
One study found significantly lower incidence of venous thromboembolism in patients who received nadroparin (15.5%) compared to those who received placebo (28.2%). This study also found no effects of nadroparin on thrombocytopenia (one RCT, n=169). Two studies reported asymptomatic proximal leg deep vein thrombosis in 5.1% to 15.5% of patients who received dalteparin (two prospective cohorts, n=157). Overall bleeding (major and minor events) occurred in 14.6% of patients (one RCT, two prospective cohorts, n=378). No studies found an association between bleeding and the use of Dalteparin or Nadroparin. One study reported that mortality rates were the same in patients who received nadroparin compared to patients who received placebo (RCT, n=169).