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Perioperative management of diabetes: Translating evidence into practice

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ABSTRACT

Glycemic control before, during, and after surgery reduces the risk of infectious complications; in critically ill surgical patients, intensive glycemic control may reduce mortality as well. The preoperative assessment is important in determining risk status and determining optimal management to avoid clinically significant hyper- or hypoglycemia. While patients with type 1 diabetes should receive insulin replacement at all times, regardless of nutritional status, those with type 2 diabetes may need to stop oral medi­cations prior to surgery and might require insulin therapy to maintain blood glucose control. The glycemic target in the perioperative period needs to be clearly communicated so that proper insulin replacement, consisting of basal (long-acting), prandial (rapid-acting), and supplemental (rapid-acting) insulin can be implemented for optimal glycemic control. The postoperative transition to subcutaneous insulin, if needed, can begin 12 to 24 hours before discontinuing intravenous insulin, by reinitiation of basal insulin replacement. Basal/bolus insulin regimens are safer and more effective in hospitalized patients than supplemental-scale regular insulin.

KEY POINTS

  • Surgery and anesthesia can induce hormonal and inflammatory stressors that increase the risk of complications in patients with diabetes.
  • Elevated blood glucose levels are associated with worse outcomes in surgical patients, even among those not diagnosed with diabetes.
  • The perioperative glycemic target in critically ill patients is 140 to 180 mg/dL. Evidence for a target in patients who are not critically ill is less robust, though fasting levels less than 140 mg/dL and random levels less than 180 mg/dL are appropriate.
  • Postoperative nutrition-related insulin needs vary by nutrition type (parenteral or enteral), but ideally all regimens should incorporate a basal/bolus approach to insulin replacement.


 

References

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.

PREOPERATIVE EVALUATION

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.

Diabetes status

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.

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