Performing surgery on diabetic patients is common, and the precautions we need to take in order to see them through the perioperative process aren't usually complex. But ambulatory surgery patients leave our hands fairly quickly, and the care that we provide patients diagnosed as diabetic can set them on the path to continued health or open the door to potential complications. Here's a summary of the current thinking on the management of diabetes in the surgical arena.

Too high? Too low?
In general, optimal glucose control (roughly defined as a blood glucose level of 60mg/dL to 160mg/dL) is important for reducing morbidity and mortality events with regard to a patient's health. Diabetic patients are at increased risk of perioperative cardiovascular complications, and studies have shown better outcomes after cardiac events if glucose is well-controlled. Glucose control also fosters better wound healing and reduces the risk of surgical site infections.

However, some recent studies from intensive care units have shown that an overemphasis on glucose control might cause more harm than good. Hypoglycemia, a common result of intensive glucose control, can cause somnolence, coma and even death. As a result, overzealous attempts to keep glucose levels low may be counterproductive, and a trend has emerged to let perioperative glucose levels run a little higher than was previously allowed.

Ideally, the surgeon, the anesthesia provider or a member of the perioperative staff will meet with patients a few days before surgery, discuss their glucose control regimen, ensure that their monitoring and medication are appropriate and instruct them on how to adjust the medication as they approach the day of surgery. Some patients are very knowledgeable about managing their disease, so don't ignore their input.

Since anesthesia's effects mask the usual symptoms of hyper- and hypoglycemia, and since surgery itself causes the release of stress hormones that naturally increase the amount of glucose produced by the body, it's important to start the case with optimal control of the patient's glucose level. When the patient presents for surgery, take a blood sample from a fingerstick or from the IV for glucose testing.

If the level is too low, administer glucose intravenously. If it's too high, administer insulin. The aim is not to micromanage the level, but to improve it, remembering that the surgical process tends to increase glucose levels. Blood should be tested intraoperatively as well, and before diabetic patients are discharged, at which point they should be reminded to resume a normal caloric intake, monitoring and medication regimen.

Fasting and fluids
Pre-operative fasting (and unexpected pre-operative delays) can upset glucose control even among stable diabetic patients who assiduously manage their levels. Since diabetic patients sometimes experience reduced gastric emptying due to gastroparesis (a dysfunction of the stomach muscles) and are thus at increased risk of aspiration pneumonitis, solid food must certainly be limited pre-operatively. But it's likely that some aspiration occurs in most patients, and the evidence that restricting clear fluids reduces the risk of pneumonitis from this aspiration is very limited.

Drinking clear fluids may actually decrease the consequences of aspiration. The gastric contents of a nearly empty stomach are very acidic. Aspirated into the lungs, that acid will cause damage. But clear fluids will dilute the acidity, and with a very short half-life, they are absorbed quickly. You might consider letting your patients, especially diabetic ones, take clear fluids closer to surgery.

The American Society of Anesthesiologists' guidelines on the issue allow clear fluid up to 2 hours before surgery. But you should monitor the developing research in this area, as evidence is building that a more liberal pre-operative oral fluid policy offers advantages in glucose control, prevention of dehydration, recovery of gastric peristalsis and patient comfort. Pre-operative fasting rules that were initiated about 70 years ago in response to a few cases of aspiration pneumonitis in pregnant patients may not be the best practice for most patients, let alone diabetics.

Insulin issues
Patients with Type 1 diabetes are insulin-dependent due to a complete, or nearly complete, inability of the pancreas to produce insulin. They must continue to receive some insulin throughout the perioperative process, even if they're not consuming calories.

On the other hand, you must constantly monitor for hypoglycemia. In the past, perioperative glucose events were sometimes brought under control by means of a sliding scale of insulin: The higher a patient's glucose level, the more insulin they were administered. This can be a harmful approach, however, since by the time glucose is high, the damage has been done and it is difficult to re-establish control. Most hospitals now have more comprehensive protocols for adjusting insulin proactively with smoother control.

A basal-bolus insulin regimen has become a popular way for patients to control their glucose. Don't alter the basal insulin (which supplies the patient's continuing need irrespective of food intake) during the perioperative fast. Because it's long-acting, with a half-life of 24 to 48 hours, decreasing it won't affect the patient during the perioperative period, but will increase the likelihood that he'll suffer hyperglycemia a day later, after he's left your care. When the perioperative fast begins, instruct patients to stop the bolus of short-acting insulin that they administer immediately before meals. They can resume the bolus when they resume eating after surgery.

Patients with Type 2 diabetes suffer not from a lack of insulin but from a resistance to it. While their bodies often produce some insulin, it's not enough to handle their glucose levels and they may need exogenous insulin as part of a glycemic control regimen. During a pre-operative period of fasting, adjust insulin administration as described previously for Type 1 diabetics. Instruct patients to take oral medications for either type of diabetes as usual up to the night before surgery, but to skip them on the day of the procedure.

Guide or manage?
Some diabetic patients have poorly managed and chronically inadequate glucose control. Postponing surgery to let them gain control of their glucose levels might seem like a sound strategy, but it may be a vain attempt, especially if the condition for which they require surgery gets worse during that delay. What's more, it's possible to safely control glucose levels during the perioperative process. In the end, we must decide between taking advantage of the pre-op consults to guide patients down a road of better health by outlining the ways they can improve their glucose control, or moving forward with needed surgery in the face of increased, but manageable, risks.