A 66-year-old man was diagnosed with stage III colon cancer and underwent laparotomy with resection of the tumor and colostomy placement yesterday. He tolerated general anesthesia without complications and had approximately 100 mL of blood loss during the procedure. He is ambulating, eating, and voiding without problems. He has been wearing intermittent pneumatic compression devices on his legs when in bed since admission. He is also prescribed acetaminophen and oxycodone as needed for postoperative pain.
On physical examination, vital signs are normal. The abdominal incision is intact with no surrounding erythema, induration, tenderness, or exudate. The abdomen is soft and nontender with normal bowel sounds. There is no peripheral edema.
Laboratory studies are significant for a hemoglobin level of 13.8 g/dL (138 g/L) (14.2 g/dL [142 g/L] before surgery), a platelet count of 308,000/µL (308 × 109/L), and a normal serum creatinine level.
Which of the following is the most appropriate management for venous thromboembolism prophylaxis?