Drs Kikura, Takada, and Sato bring to our attention the importance of preexisting factors in overall surgical results. The strength of this study lies in its large database, with 21 903 cases reviewed from January 1, 1991, through December 31, 2002, and the different surgical procedures that were included from general surgery, orthopedic surgery, thoracic surgery, and peripheral vascular surgery.
Certainly this type of study can suggest only associations and not cause-and-effect relationships. For example, the relationship between myocardial infarction and deep vein thrombosis likely relates as much to the nature of the patients being studied as to the biology of the disease processes. This is similar to an association between hypertension and deep vein thrombosis in a study of hospitalized patients.1 Nevertheless, the connection between thrombosis and inflammation may underlie some of the associations documented in this study.2,3 For example, it has been known that when deep vein thrombosis is treated with low-molecular-weight heparin, there is a decrease not only in thromboembolic complications but also in mortality.4 It has been hypothesized that this may be a reflection of the ability of low-molecular-weight heparin to limit inflammation in addition to its anticoagulant effects.5