Pannucci CJ, et al. - Via a nonrandomized clinical trial that recruited 116 patients who underwent colorectal surgery who received enoxaparin, 40 mg per day, for venous thromboembolism prophylaxis at a single institution, researchers ascertained the proportion of patients who were undergoing colorectal surgery who received adequate anticoagulation on the basis of the peak anti-factor Xa (aFXa) levels while receiving enoxaparin at 40 mg per day. Seventy-two of 106 patients whose peak aFXa level was nearly drawn, received inadequate anticoagulation (aFXa < 0.3 IU/mL) with enoxaparin, 40 mg per day. Weight and peak aFXa levels were inversely associated with one another. A trough aFXa level that was not discoverable was noted in 47 patients (ie, most patients had no detectable level of anticoagulation for at least 12 hours per day). Real-time enoxaparin dose adjustment was efficient. Patients were significantly more inclined to accomplish an in-range peak aFXa with real-time dose adjustment as opposed to fixed dosing alone. Thus, most patients undergoing colorectal surgery get insufficient prophylaxis from enoxaparin, 40 mg once daily. Also, these findings may define the high rate of “breakthrough” venous thromboembolism noted in many clinical trials.