Lack or withdrawal of informed consent INTERVENTION AND COMPARATOR: • LMWH group: patients in this group will be administered enoxaparin at standard prophylactic dosage. • LMWH + steroid group: patients in this group will receive enoxaparin at standard prophylactic dosage and methylprednisolone. • UFH + steroid group: patients in this group will receive UFH at therapeutic dosages and methylprednisolone.