Letters To The Editor

In reply: Insulin before surgery

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In Reply: We appreciate the kind words of Drs. Ditch and Moore , as well as their opinion.

Our article was intentionally brief—a 1-Minute Consult—and so could not cover all specific situations we encounter in clinical practice. We meant only to provide a general approach in this matter.

Quite often before surgery, patients receive less basal insulin than needed, or none at all, rather than too much. It has to be borne in mind that perioperative hyperglycemia—not just hypoglycemia—is linked with poor outcomes in cardiac 1 and noncardiac surgery. 2,3

Through our scenarios and suggestions, we have taken steps to err on the side of preventing hypoglycemia while averting hyperglycemia, at the same time making it easy to calculate the dose. In a scenario in which the basal insulin dose is about the same as the total of the prandial boluses, we have not yet seen evidence that raises concern for hypoglycemia, maybe because many of the patients with type 2 diabetes seen in our institution for surgery take, in addition to insulin, oral agents or noninsulin injections (which are appropriately withheld before surgery), and have suboptimal glycemic control on their home regimen. But if a physician has concerns for hypoglycemia, a dose reduction should be made.

There were some differences between the RABBIT 2 trial in medical patients 4 and the RABBIT 2 Surgery trial 5 that would make the results not completely comparable. In RABBIT 2, the medical patients included were on diet alone or any combination of oral antidiabetic agents (not on insulin), and they were started on a total daily dose of insulin of either 0.4 or 0.5 U/kg/day, depending on the glucose level. In RABBIT 2 Surgery, patients who were on insulin at home with a total daily dose of 0.4 U/kg or less were also included, and the starting daily dose of insulin was 0.5 U/kg (unless they were older or had a high serum creatinine).

In view of all the above, we agree with Drs. Ditch and Moore that if there is concern for hypoglycemia, the clinician should reduce the insulin dose in the manner that evidence from the local practice suggests, without causing undue hyperglycemia and postsurgical complications.

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Is hemoglobin A1c an accurate measure of glycemic control in all diabetic patients?

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