AMPK, Adenosine monophosphate–activated protein kinase; ATP, adenosine triphosphate; CKD, chronic kidney disease; CVD, cardiovascular disease; D2, dopamine-2; DPP, dipeptidyl peptidase; GLP, glucagon-like peptide; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; PPAR, peroxisome proliferator–activated receptor; SB, small bowel.
From Inzucchi SE, Sherwin RS. Type 2 diabetes mellitus. In Goldman L, Schafer AI, et al, eds. Goldman’s Cecil Medicine. 24th ed. Philadelphia: Saunders; 2012:1496.
Insulin preparations
Insulin preparations are generated today by DNA recombinant technology, mimicking the amino acid sequence of human insulin. All insulin formulations in the United States, except for inhaled insulin, are prepared as Unit-100 (100 units/mL).
Insulin preparations differ in onset and duration after subcutaneous administration. In addition to subcutaneous injections, insulin delivery devices (implantable pumps, mechanical syringes) are used to facilitate exogenous administration. The greatest risk with all forms of insulin is hypoglycemia. The major classes of exogenous insulin (regular, rapid acting, inhaled, intermediate acting, and long acting) are listed in the following table.
Pharmacokinetics of Insulin Preparations
IM, Intramuscular; IV, intravenous; NPH, neutral protamine Hagedorn. Subcut, subcutaneous.
It is imperative to know the surgical patient’s normal insulin dosage regimen and treatment compliance. Some patients are on a fixed regimen that consists of a mixture of rapid- and intermediate-acting insulins taken before breakfast and again at the evening meal. Other patients are on multiple injection regimens designed to provide more physiologic glycemic control. To determine the effectiveness and compliance of antidiabetic therapy, hemoglobin A1c (HbA1c glycated hemoglobin) values provide information about the plasma glucose concentration over time. An HbA1c value of 6.5% or greater is indicative of DM.
Intraoperative management
In patients with DM, operations should be scheduled early in the day, if possible, to minimize disruptions in treatment and nutrition regimens. Surgery produces a catabolic stress response and elevates stress-induced counterregulatory hormones. The hyperglycemic, ketogenic, and lipolytic effects of the counterregulatory hormones in patients with DM compound the state of insulin deficiency. For this reason, perioperative hyperglycemia and other metabolic aberrations are common in the surgical patients with DM.
No specific anesthetic technique is superior overall for patients with DM. Both general anesthesia and regional anesthesia have been used safely. General anesthesia, however, has been shown to induce hormonal changes that accentuate glycogenolysis and gluconeogenesis, compounding the patient’s hyperglycemic state. Regional anesthesia may produce less deleterious changes in glucose homeostasis.
The Certified Registered Nurse Anesthetist (CRNA) must be especially careful in positioning and padding patients with DM on the operating table. Decreased tissue perfusion and peripheral sympathetic neuropathy may contribute to the development of skin breakdown and ulceration.
Patients with DM represent a heterogeneous group requiring individualized perioperative care. The specific approach to metabolic management depends on the type of diabetes (type 1 or 2), the history of glycemic control, and the type of surgery being performed. Frequent blood glucose determinations are an integral part of any diabetic management technique. A glucose meter or other accurate and rapid means of monitoring blood glucose levels should be available. At least hourly intraoperative blood glucose measurement is the prudent course for brittle patients with DM, during long surgical procedures, and for major surgery.
Strict control of even short-term elevations in blood glucose improves perioperative morbidity. Persistent hyperglycemia has been shown to impair wound healing and wound strength. In addition, reports suggest that postoperative infection is more prevalent in patients with DM who have uncontrolled blood sugar levels. Studies also provide evidence that hyperglycemia worsens the neurologic outcome after ischemic brain injury. Avoiding perioperative hyperglycemia is advisable, especially in patients at risk for acute neurologic insult (carotid endarterectomy, intracranial surgery, cardiopulmonary bypass).
Various regimens have been tendered on how to best manage the metabolic changes that occur in surgical patients who have DM. Experts differ on optimal protocols for case management and precisely defined target glucose levels. Current debate centers on the risk-to-benefit ratio of intensive or “tight” blood glucose control versus “nontight” control during surgery. The universal goal with all techniques is to avoid hypoglycemia and to minimize metabolic derangements. Patients under anesthesia are generally maintained with a mild transient hyperglycemia to avoid the potentially catastrophic effects of hypoglycemia. Frequent blood glucose determinations during surgery and in the immediate postoperative period are central to safe practice.
Three different approaches to the metabolic management of adult surgical patients with DM are described below; however, readers should note that there are numerous variations.
Intermediate-acting insulin use
This is a traditional method of managing surgical patients with DM and involves less intensive control of plasma glucose but aims to avoid marked hyperglycemia and dangerous hypoglycemia. Variations of this technique are used for stable patients with DM undergoing elective operative procedures. An example of this regimen follows:
