There have been surprisingly few studies on postoperative mortality and morbidity comparing diabetic with non-diabetic subjects. Diabetes was certainly considered to be a major risk factor for surgery in past decades. An American study in 1963 reported a 5% mortality postoperatively in a large (487) group of surgical diabetic patients, the major causes of death being ketoacidosis, infection and myocardial infarction (Galloway and Shuman 1963). It is likely, however, that methods of management were highly sub-optimal compared with modern management principles. A more recent study (Hjortrup et al 1985), using modern treatment methods, has shown no difference in mortality between diabetic and non-diabetic subjects (2.2% versus 2.7% respectively). Some specific surgical procedures may have increased risk in diabetic patients, however, notably vascular procedures. Thus, aortic and lower limbs revascularization procedures carry increased mortality in diabetic compared with non-diabetic patients (Melliere et al 1999). However, this is obviously a selected diabetic group with established advanced large vessel disease, and such an outcome difference may not be surprising. Nevertheless, such results are of relevance to surgery in the elderly, as in this study the mean age of the diabetic group was 68 years.
Turning to morbidity, there is little conclusive evidence that diabetes per se causes increased risk. Diabetic patients with pre-existing cardiac or renal problems may have increased morbidity, but not if surgery is relatively uncomplicated and properly managed (MacKenzie and Charlson 1988; Sandler, Maule and Baltus 1986). Risk of postoperative infection also does not appear definitely increased, contrary to normally accepted clinical dogma (Hjortrup et al 1985; Sandler et al 1986). In the Danish study of Hjortrup et al (1985), for example, the wound infection rate was identical amongst diabetic (13/224 or 5.8%) and non-diabetic (12/224 or 5.4%) patients. A recent study of diabetic patients undergoing coronary artery surgery showed an increased risk of post-surgical infections, but this was accounted for by excessive postoperative hyperglycaemia (Golden et al 1999). Overall, critical assessment of the available literature does not support a generally increased risk for diabetic patients undergoing surgery, in terms of both mortality and postoperative complications.
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