BALANCING ACT Using insulin to lower glucose levels can decrease some risks while simultaneously increasing others.

We know surgical site infections are common in diabetic patients, and even more common in patients (known diabetics and others) with higher pre-operative glucose and hemoglobin A1C levels. Insulin normalizes glucose and also has anti-inflammatory benefits that are known to reduce SSIs in diabetics and non-diabetics. So you'd probably assume that using pre-operative insulin infusions to reduce glucose levels would reduce the risk of SSIs and overall morbidity.

Not necessarily.

While it's true that high glucose produces an environment that interferes with healing and predisposes patients to infections, it's likely that many of the SSIs suffered by diabetics come from secondary conditions, such as neuropathy and microcirculatory deficits. And those are conditions that can't be changed quickly. In addition, stress increases glucose levels, so high glucose may be as much a marker of increased perioperative risk as a cause of it. Complicating matters further is the fact that while high glucose is bad, so is low glucose. You may reduce some risks by lowering glucose levels, but you also might increase others.

It's easy to say that patients with poor glucose control simply shouldn't have elective surgery, but unfortunately, some patients are unlikely to ever achieve great control. In some cases, the reason for surgery — for example, infection or inflammation — is contributing to the poor glucose control. So postponing surgery probably won't provide a significant short-term net benefit. All of which begs the question: What's the best way to deal with the propensity of diabetic patients to develop surgical site infections?

Control glucose with caution
Use the pre-operative assessment as an opportunity to optimize glucose control. Tight glucose control is a noble goal — but only if you're also adequately monitoring to detect and treat hypoglycemia. Ultimately, you need to balance how much control you can safely achieve. It may be safer and more practical to accept "loose" control of hyperglycemia, as the benefits of tighter control may not warrant what it takes to avoid the dangers of hypoglycemia.

Set realistic goals
A pre-operative hemoglobin A1C of less than 7.5 and a glucose level less than 120 mg/dl are practical goals for most facilities. How far can you stray from those goals? It depends. The textbook answer is that no surgery should be performed if hemoglobin A1C is greater than 10 or blood glucose is greater than 250. But we all know patients who live quite asymptomatically at much higher levels, and postponing surgery is not without risk, let alone inconvenience. It comes down to a case-by-case determination. A skin graft warrants more rigid standards for postponement than laparoscopy.

Look at the bigger picture
Diabetics are at high risk for several perioperative events, and glucose control is only part of the management they need. Routine pre-op optimization measures are even more important for diabetics. All surgery results in some contamination of wounds, but as long as the amount of organisms is minimized and host defenses are adequate, no clinically significant infection occurs. So there are 2 overriding goals:

• Minimize contamination. Timely administration of pre-op antibiotics, which is a foundation of current perioperative culture, is important, but it's a double-edged sword. Yes, it does generally reduce risk of infections, but it also contributes to resistance, so when infections do occur, they're harder to treat. Hair clipping, as opposed to shaving, and pre-op showers reduce skin contaminants, although probably not as much as we'd like.

• Maintain tissue oxygenation. Host defenses are largely dependent on tissue oxygenation. Anesthesia and the paralysis needed for surgery slow the metabolism, so limiting the length of surgery as much as possible is important. There's also some evidence that the vasodilation that accompanies neuraxial anesthesia may reduce SSIs. So here's something that warrants at least as much attention as glucose control: If you can get diabetic patients to stop smoking, even a few days before surgery, that will reverse the vasoconstriction caused by nicotine, and will probably reduce risks as much as any other single measure.

Leverage the opportunity
There's never an excuse to ignore short-term glucose control, but the best approach is to leverage the opportunity to improve long-term therapy. In our sometimes-fragmented healthcare system, it's critical to use the perioperative contact to improve overall health. This requires some creative and progressive resource allocation among the surgical, anesthesia, endocrine and primary care clinicians.

Sometimes the only practical option for urgent management of a pre-op patient with high glucose is a referral to the emergency department or pre-admission. Similarly, insulin pumps may trigger an endocrine consult. This is an inefficient use of resources. The medical management isn't usually complex, but it does require someone with the confidence, time and authority to institute protocols and adjust insulin doses. A clinician with diabetes management experience "on loan" to the pre-op clinic may be a more efficient and patient-centered model of care. As payments for perioperative care become more global in nature, this cooperation will become more critical for financial viability, as well as for good patient care.