Chapter 19: Perioperative Assessment of Diabetes

INTRODUCTION

Diabetes is a condition of elevated blood glucose caused by a number of factors and affects approximately 8% of the population.¹ There are 2 types: type 1, which refers to an absolute deficiency, and type 2, which refers to a relative deficiency of insulin. Diabetes is the leading cause of kidney failure and blindness in adults, as well as a major cause of heart disease and stroke. Diabetic patients are challenging to anesthesiologists and often present with comorbidities and complications, including obesity, neurologic disease, kidney disease, cardiovascular disease, and metabolic abnormalities. Perioperative assessment should focus on prevention of complications that occur in higher frequency in diabetic patients. These include postoperative infections and cardiovascular events such as stroke, myocardial ischemia, and heart failure.^{2,3 and 4} The cornerstone of prevention is perioperative glucose control.^{5,6 and 7}

DIAGNOSIS OF DIABETES

In the United States, the Centers for Disease Control and Prevention and the American Diabetes Association estimate that 25% of diabetic patients are unaware that they have the disease. Preoperative glucose testing confirms this finding. Diabetic complications such as retinopathy, nephropathy, neuropathy, or cardiovascular disease may be present before a diagnosis of diabetes is made. A fasting blood glucose obtained in preoperative clinic or on the day of surgery provides an important opportunity to screen patients with suspected or known diabetes.⁸

Perhaps a better measure of glycemic history in diabetic patients is the hemoglobin A1C (presented as the percent of glycosylated hemoglobin). Over the life span of a red blood cell (up to 3 months), glucose will attach to hemoglobin and provide an estimate of average blood glucose levels over several months. In general, ideal hemoglobin A1C levels should be below 8%. More aggressive glucose control to a percentage less than 8% may lead to frequent episodes of hypoglycemia. Criteria used to distinguish normal categories of hyperglycemia are presented in Table 19–1.⁹

Perioperatively, other conditions can increase blood glucose levels including surgical stress, infections, corticosteroid use, total parenteral nutrition, kidney or liver disease, or pregnancy. Perioperative hyperglycemia is associated with increased length of stay, complications, and mortality in surgical and hospitalized patients, even in those without a history of diabetes.^10,11

HEALTH RISKS OF DIABETES

Cardiovascular Problems

Cardiovascular risk is substantial in diabetic patients and is of significant importance to the perioperative physician. ...