Diabetes Mellitus

GENERAL PRINCIPLES

• Medical and surgical patients with hyperglycemia are at increased risk for poor outcomes.¹⁰²

• The fact that hyperglycemia is a marker for poor outcomes appears to be relatively clear.

TREATMENT

• Elective surgery in patients with uncontrolled diabetes mellitus should preferably be scheduled after acceptable glycemic control has been achieved. If possible, the operation should be scheduled for early morning to minimize prolonged fasting. Frequent monitoring of blood glucose levels is required in all situations.

• Type 1 diabetes

î Some form of basal insulin is required to prevent ketosis.

î On the evening prior to surgery, the regularly scheduled basal insulin should be continued. If taken in the morning, it is still recommended to give the regularly scheduled basal insulin without dose adjustment.¹⁰³ However, patients who are tightly controlled may be at increased risk for hypoglycemia and will need to be monitored closely. A decrease in the last preoperative basal insulin dose may be considered in this circumstance.

î Glucose infusions (e.g., D5-containing fluids) can be administered to avoid hypoglycemia while the patient is NPO and until tolerance of oral intake postoperatively is established.

î For complex procedures and procedures requiring a prolonged NPO status, a continuous insulin infusion will likely be necessary.

î Caution should be exercised with the use of subcutaneous insulin in the intraoperative and critical care settings, as alterations in tissue perfusion may result in variable absorption.

• Type 2 diabetes

° Treatment of type 2 diabetics varies according to their preoperative requirements and the complexity of the planned procedure.¹⁰⁴

° Diet-controlled type 2 diabetes can generally be managed without insulin therapy.

î Type 2 diabetes managed with oral therapy

■ Short-acting sulfonylureas and other oral agents should be withheld on the operative day.

■ Metformin should be withheld 1 day before planned surgical procedures. Metformin is generally held for 48 hours postoperatively provided there is no acute renal injury. Other oral agents can be resumed when patients are tolerating their preprocedure diet.

■ Glucose values should be checked regularly and elevated levels (>180 mg/dL) can be treated with intermittent doses of short-acting insulin.

î Type 2 diabetes managed with insulin

■ Long-acting insulin (e.g., glargine insulin) can be given at 50% of the usual dose the day of surgery.

■ Intermediate-acting insulin (e.g., Neutral Protamine Hagedorn) can be given at one-half to two- thirds of the usual morning dose.

■ Dextrose-containing IV fluids may be required to avoid hypoglycemia.

■ The usual insulin treatment can be reintroduced once oral intake is established postoperatively.

• Target glucose levels

° There are no generally agreed-upon target glucose levels applicable to the entire postsurgical population. Pending further research, a goal of maintaining glucose levels 3 weeks and patients who are clinically “cushingoid” in appearance can be expected to have significant suppression of adrenal responsiveness.

î The function of the hypothalamic-pituitary axis cannot be readily predicted in patients receiving doses of prednisone 5-20 mg for >3 weeks.

DIAGNOSIS

Cosyntropin stimulation test may also be performed to determine adrenal responsiveness, measuring a single cortisol level at 60 minutes after 250 μg of cosyntropin. This can be done any time of day and baseline cortisol is not needed. Levels >18 μg∕dL at 60 minutes generally suggest an intact hypothalamic- pituitary axis.

TREATMENT

• If there is concern for secondary adrenal insufficiency, it is reasonable to simply continue prior steroid dosing perioperatively.¹⁰⁶ It may be prudent to switch to an IV formulation to ensure it is not withheld while the patient is NPO.

• For patients with primary adrenal insufficiency, a stress stratification scheme has been developed, based on expert opinion.