The type of anesthesia should also be considered. Compared with epidural anesthesia, general anesthesia is associated with greater stimulation of the sympathetic nervous system and increased catecholamine levels, resulting in more pronounced hyperglycemia. 3
Preoperative testing and laboratory evaluation should include, at minimum, an electrocardiogram, a basic metabolic panel to assess renal function, electrolyte levels, and hemoglobin A 1c measurement. For low-risk procedures in patients with adequate exercise tolerance, no diagnostic tests might be needed. In any case, knowledge of the hemoglobin A 1c level may help not only to classify perioperative risk but also to determine postoperative care, including the choice of antiglycemic medications at discharge.
IMPORTANCE OF GLYCEMIC CONTROL
Preoperative glycemic control has a significant impact on the risk of infectious complications—including pneumonia, wound infection, urinary tract infection, and sepsis—in patients with diabetes across a variety of surgical procedures. 4 Similarly, postoperative glycemic control—to a mean blood glucose level less than 200 mg/dL in the immediate postoperative period—significantly reduces the incidence of deep sternal wound infection after open heart surgery. 5
Among patients undergoing cardiothoracic surgery, both cardiac-related and overall mortality are greater with increasing postoperative blood glucose levels, although a cause-and-effect relationship has not been established. 6
Glycemic control matters regardless of diabetes status
Hyperglycemia affects mortality regardless of diabetes status. In a study of 779 consecutive patients admitted for acute myocardial infarction, mortality at 180 days was highly associated with hyperglycemia on admission independent of a history of diabetes; the highest mortality was among hyperglycemic patients without previously known diabetes. 7 Similarly, a large study of glycemic control in intensive care unit (ICU) patients receiving insulin found that mortality in nondiabetic patients increased with median glucose level and was higher than mortality in diabetic patients. 8 These findings suggest a need for vigilance in the perioperative and critical care management of all patients with hyperglycemia, regardless of preadmission diabetes diagnosis, as they carry significant morbidity and mortality risk.
GLYCEMIC CONTROL IN THE CRITICALLY ILL: SOME SUPPORT FOR A MODIFIED TARGET, BUT VIGILANCE FOR HYPOGLYCEMIA NEEDED
The landmark study by Van den Berghe et al of intensive insulin therapy in surgical ICU patients demonstrated significant reductions in morbidity and mortality when glucose levels were controlled aggressively (80 to 110 mg/dL; average, 103 mg/dL) compared with conventional control (180 to 200 mg/dL). 9 The benefit of intensive glycemic control was evident on outcomes such as the occurrence of sepsis, need for dialysis, need for blood transfusion, and development of acute polyneuropathy. Intensive insulin therapy was also associated with cost savings compared with conventional insulin therapy in mechanically ventilated patients. 10
However, a number of subsequent studies have clearly shown that as blood glucose levels approach normoglycemia, the risks of hypoglycemia, especially severe hypoglycemia, can offset the benefits of tight blood glucose control.
A follow-up study by Ven den Berghe et al in a medical ICU failed to show a mortality benefit from tight glycemic control, though patients in the intensive control arm experienced less renal injury, faster weaning from ventilation, and earlier discharge from the ICU and hospital. 11