How To Achieve Optimal Perioperative Glycemic Control In Patients With Diabetes
Emphasizing The Importance Of Tighter Glycemic Control
Even though glycemic control seems to be of obvious importance in the perioperative period, the saying “better sweet than sour” is still a frequent consensus. The reasons to maintain an inpatient’s blood glucose levels somewhat higher than normal in preparation for surgery are often multifactorial. However, recent literature has been rife with data regarding tighter control of glucose in the perioperative setting. Although the exact mechanism is not fully understood, researchers have shown in multiple publications that hyperglycemia, especially blood glucose levels greater than 200 mg/dL, increases the risk of developing postoperative infections.7,8 A recent article by Hruska, et. al., clearly showed that instituting a strict blood glucose level between 120 and 160 mg/dL immediately following open heart surgery resulted in a statistically significant decrease in postoperative infection rates in their diabetic patients. After patients maintained well controlled blood glucose levels through an insulin infusion, researchers found that the infection rate diminished from 73 percent to 25 percent in their diabetic population.9 Various researchers have also demonstrated that good glucose control minimizes perioperative morbidity and mortality. The classic prospective randomized study Diabetes Mellitus Glucose Infusion in Acute Myocardial Infarction (DIGAMI) showed the long-term benefit and reduction in mortality from myocardial infarction due to tight glucose control with the use of initial intravenous insulin infusion.10 There have been several subsequent studies that have looked at the positive impact that insulin may have on improving operative outcomes, particularly with cardiothoracic surgery.11 The reason for improved survival was probably multifactorial and included improved glucose homeostasis and possible improved oxygenation of the tissues through insulin’s vasodilatory effects to skeletal muscle via increased production of nitric oxide in vascular endothelium.12,13 Hyperglycemia may also accentuate the risk of thrombotic complications.14 Finally, studies have shown that hyperglycemia has deleterious effects on essential wound healing events such as decreased chemotaxis, polymorphonuclear leukocyte mobilization and phagocytosis. When it comes to patients with diabetes, skin fibroblasts reportedly do not proliferate as well in a hyperglycemic milieu and this may impair wound closure.15,16,17 Indeed, there are a multitude of reasons to avoid hyperglycemia, even for short-term intervals. Therefore, it is probably not ideal to aim for higher glucose levels than outpatient goals due to the fear of perioperative hypoglycemia. However, future prospective, controlled, randomized studies are necessary for further evaluation of safe modalities to improve glycemic control in the perioperative period. At Beth Israel Deaconess Medical Center (BIDMC), our relationship with the Joslin Diabetes Center allows for frequent collaboration and many of our glycemic control practices are a result of those interactions. As we noted previously, while clinicians utilize many approaches, this following protocol is the one we employ most frequently.