Home Feature How to match insulin regimens to different nutritional needs

How to match insulin regimens to different nutritional needs

NPO, TPN and grazing patients? Tips for tailoring basal-bolus regimens

April 2008

Published in the April 2008 issue of Today’s Hospitalist

Hospitalized diabetic patients who can’t eat regular meals can be among the trickiest patients to manage. Give conventional sliding-scale insulin, and those patients are likely to experience a roller-coaster of hyper- and hypoglycemia.

Related article: Tips for calculating a daily dose of insulin.

While basal-bolus regimens, also known as physiologic insulin, are the preferred way to give insulin to patients in the hospital, these regimens bring their own set of challenges. Inpatients may be eating one minute, then being told to stop for a procedure, throwing up or being switched to an entirely different type of feeding.

“For any IV contrast studies, our radiology department now is asking patients to be NPO.” 

cherylomalley~ Cheryl O’Malley, MD
Banner Good Samaritan Medical Center

Here’s a look at several strategies to help you tailor insulin dosing to different feeding regimens.

If a patient is not eating at all “either for only a short time because of a procedure or surgery, or for a prolonged period “giving basal insulin (usually glargine) in a dose based on a patient’s body weight is generally OK.

(The rule of thumb is to calculate a patient’s insulin needs based on body weight. Give half as basal insulin and half as nutritional bolus insulin, as long as patients are getting some form of nutrition.)

That approach works physiologically, but only if you can convince nurses to go along with the plan. Kevin Larsen, MD, a hospitalist at Hennepin County Medical Center in Minneapolis and a member of the Society of Hospital Medicine (SHM) glycemic control task force, says that changing nurses’ minds can be difficult.

“It’s so ingrained in nursing education that you hold insulin when someone is going to be NPO,” Dr. Larsen explains. “We’ve done extensive training, but we still run into that knee-jerk reaction.”

But attitudes aren’t the only issue hospitalists face with NPO patients. A major problem is that patients switch in and out of NPO status almost constantly.

“It’s not just for abdominal CTs or other situations where you would expect patients to become NPO,” says Cheryl O’Malley, MD, a member of the SHM glycemic control task force who championed a sub-Q insulin protocol at Banner Good Samaritan Medical Center in Phoenix. “The nurses just told me that for any IV contrast studies, our radiology department now is asking patients to be NPO.”

To work around that growing variability, Dr. O’Malley says that her hospital’s standing order set instructs nurses to continue basal and correction insulin doses, but to hold scheduled nutritional insulin when patients are NPO. “That way, the nurses don’t have to call the physician or guess what the doctor wants them to do,” she points out.

Handling the insulin requirements of patients getting total parenteral nutrition can be fairly simple, say diabetes experts, as long as hospitalists follow some basic principles of physiologic insulin.

“Recommendations are to run a separate IV insulin infusion and then figure out from that how much insulin patients need on average for the next 24 hours,” Dr. O’Malley says. “You then add 80% of that to the TPN bag the next day. If the TPN stops, so does the insulin.” She adds that patients may need some sub-Q insulin as a correction factor.

At Hennepin Medical Center, Dr. Larsen says physicians have that insulin IV drip information if patients are coming out of the ICU. One big advantage that physicians at Hennepin have, Dr. Larsen points out, is clinical pharmacists on all the wards.

“Our clinical pharmacists discourage putting insulin into the TPN,” he says. Instead, the pharmacists help devise an individualized insulin management plan. While that plan typically involves insulin infusion in the ICU, “on the wards it entails our standard sub-Q strategy.”

Continuous tube feeds
Because no regimen is clearly superior for patients on continuous tube feeds, hospitalists have to do the best they can based on their understanding of physiologic insulin. This is one area, Dr. O’Malley adds, “where we see a lot of trouble with hypoglycemia if tube feeds are stopped or if patients pull out the tube, which happens frequently.”

At Banner Good Samaritan, a separate order set for patients on tube feeds instructs nurses to “substitute D10 at the same rate that the tube feed was running as a safety measure.” Patient monitoring increases during that time, she explains, and the rate of D10 is reduced if a patient develops hyperglycemia.

“This automatic action provides a measure of safety for patients during this high-risk transition,” says Dr. O’Malley. “Patients on continuous tube feeds may be cognitively impaired and therefore unable to reliably report symptoms associated with hypoglycemia.” Another problem, she adds: Providers are busy and may forget that they need to do something to prevent hypoglycemia in these cases.

At Loyola University Medical Center in Chicago, on the other hand, the protocol for patients with continuous tube feeds calls for one shot of slow-release glargine, plus a blood sugar check every six hours “and using correction factor dosing to lower an elevated glucose,” says Mary Ann Emanuele, MD, a professor of endocrinology and medicine.

When tube feeds are interrupted, “patients must be started on IV fluids,” Dr. Emanuele adds. The protocol calls for physicians to match “cc for cc with D5 solution until the tube feeding is restarted.”

Night-time tube feeds
Another tricky situation occurs when patients try to eat during the day but get most of their nutrition overnight enterally.

Dr. Emanuele says that while it’s OK to give the patient some basal insulin during the day, most of the insulin should be given at night. In this type of situation, she prefers NPH given right before the tube feed is turned on.

Because her group has not been able to find a good formula to determine the quantity of NPH to use based on a patient’s body weight, Dr. Emanuele uses the following rule of thumb: Give 10 units of NPH and take a fasting blood sugar the next day. Based on that result, she may increase the next night’s NPH to 15 and then to 20 units.

At Banner Good Samaritan, Dr. O’Malley points out, night-time tube feeds are relatively uncommon. When they take place, physicians use a correction scale with rapid-acting insulin every four hours for the first night of feeds. Once their insulin requirements are known, patients are converted to a dose of NPH, which is given when the tube feed is started.

Grazing patients
For grazing patients who are well-versed in adjusting their own insulin based on what they eat, “we have an option for them to count carbohydrates, using patients as an important team member if they can do that effectively,” says Dr. O’Malley.

At Hennepin Medical Center, Dr. Larsen says the nurses are able to give nutritional insulin after the patient’s meal, not before. That way, nurses can judge whether grazing patients really need the insulin. But as far as writing orders is concerned, he says, “We have a moratorium on carb counting.”

The problem crops up when endocrinology fellows want to write carb counting orders, he explains. While Dr. Larsen adds that he thinks carbohydrate counting is a terrific idea that is definitely part of hospitalists’ future, there’s an immediate barrier: “We don’t have the resources in place to do all that teaching.”

Deborah Gesensway is a freelance writer reporting on U.S. health care from Toronto, Canada.

Check out the Today’s Hospitalist Clinical Protocol Web page for the tube feed sub-Q insulin order set used at Banner Good Samaritan Medical Center in Phoenix. Go to Clinical Protocols.

Insulin-dosing pearls

      1. Don’t use sliding scale. Replace it with the more rational “physiologic insulin” dosing system, generally giving half as basal insulin and half as nutritional, as long as patients are getting some nutrition.

2. Ask whether patients with diabetes are on the simplest feeding regimen possible. That way, patients get what they need but are easier to manage from a diabetes standpoint.

3. Measure blood sugar often (with meals or at least every six hours) so that insulin can be modified at least daily to meet patients’ needs.

4. Try to move to a system where nurses are giving insulin after meals, not before, based on what a patient actually ate. This usually requires education and systems changes.