Diabetes confers an increased risk of perioperative morbidity and mortality, mostly from infection and cardiovascular events. It is not unusual for surgical patients with diabetes to have a number of comorbidities or underlying chronic vascular complications that put them at risk for cardiovascular events or an infectious complication. Silent ischemia, coronary artery disease, and autonomic neuropathy are common among patients with diabetes, and each can contribute to perioperative morbidity and mortality. These are important considerations since nearly one-fifth of surgical patients have diabetes and since a person with diabetes has a 50% risk of undergoing surgery at some point in his or her lifetime. 1
This article reviews the preoperative evaluation of patients with diabetes, discusses the relation between glycemic control and perioperative outcomes, and examines targets and strategies for glycemic control in patients with type 1 and type 2 diabetes throughout the perioperative period.
The preoperative evaluation must consider first and foremost the status of the patient’s diabetes and his or her surgical risk factors. Also important are the characteristics of the procedure to be performed, the method of anesthesia to be used, and select laboratory values.
The type of diabetes and its treatment must be considered. Type 1 diabetes requires continuous insulin therapy to prevent ketoacidosis; patients with type 2 diabetes are usually treated with oral medications with or without insulin. Baseline control of blood glucose is a predictor of morbidity following surgery. Hypoglycemia is associated with increased morbidity in the inpatient setting, so a history of severe hypoglycemic events or of difficulty recognizing hypoglycemia (hypoglycemia unawareness) should be elicited in the preoperative evaluation. Complications of diabetes and other comorbidities also must be evaluated, along with their treatments.
Surgical risk factors
Patients with diabetes have surgical risk factors specific to their health—namely, cardiovascular risk factors that may or may not have been previously diagnosed. Patients with diabetes may have silent ischemia, atypical manifestations of coronary ischemia, or underlying cardiomyopathy. Many patients with type 2 diabetes have hypertension, which may complicate perioperative management. Other common surgical risk factors in this population include obesity, chronic kidney disease, and undiagnosed autonomic dysfunction, which may compromise hemodynamic stability in the perioperative period. Additionally, patients with long-standing diabetes experience reductions in pulmonary function (eg, forced expiratory volume, peak expiratory flow, and diffusion capacity for carbon monoxide) related to disease duration and vascular injury, 2 which may complicate weaning from ventilatory support.
Characteristics of the procedure and anesthetic
Both surgery and anesthesia may induce an increase in levels of stress hormones (epinephrine, cortisol, growth hormone) and inflammatory cytokines (interleukin-6 and tumor necrosis factor–alpha), resulting in insulin resistance and impaired insulin secretion (even among patients who present with adequate insulin secretion). These in turn contribute to lipolysis and protein catabolism, leading to hyperglycemia and, if a patient is severely insulin deficient, ketoacidosis. Other factors that particularly affect insulin resistance and secretion include cardiovascular bypass surgery, sepsis, the need for total parenteral nutrition, and steroid therapy.
The characteristics of the surgical procedure, including the type of surgery as well as its urgency, duration, and timing (morning vs later in the day), are important in planning for perioperative glycemic management. For example, a short, minor procedure may require only observation, whereas more extensive procedures warrant periodic monitoring and active glycemic management with insulin infusions.