Sliding Scale Insulin

A 73-year-old female with a 20-year history of hypertension, type 2 diabetes, dyslipidemia, and stage 3B CKD, typically at treatment goals with oral medications, is being seen. She was discharged yesterday after being hospitalized for three days with community-acquired pneumonia and is here for a follow-up visit.

She states she's feeling much better with less shortness of breath, diminished cough, and sputum production, and is without fever. She mentions that while she was in the hospital that, quote, they changed my diabetes medicine and gave me insulin four times a day to keep my sugar controlled, close quote. A review of her discharge note reveals that rapid acting insulin was given according to blood glucose levels without scheduled basal insulin and this was used from admission to discharge. 

Random glucose today is at 220. The patient asks, should I start back up on those insulin shots? I've never used them before. The NP considers with which of the following.

A. given her random blood glucose is elevated, the use of a sliding scale insulin should be continued for the next week

B. the use of a sliding scale insulin potentially results in wide glucose excursions

C. sliding scale insulin is helpful as it mimics physiologic insulin secretion

D. the sliding scale insulin regimen should now be replaced with a basal insulin

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Transcript

Voiceover: Welcome to NP Certification Q&A presented by Fitzgerald Health Education Associates. This podcast is for NP students studying to pass their NP certification exam. Getting to the correct test answers means breaking down the exam questions themselves. Leading NP expert Dr. Margaret Fitzgerald shares her knowledge and experience to help you dissect the anatomy of a test question so you can better understand how to arrive at the correct test answer. 

So, if you're ready, let's jump right in.

Margaret Fitzgerald: A 73-year-old female with a 20-year history of hypertension, type 2 diabetes, dyslipidemia, and stage 3B CKD, typically at treatment goals with oral medications, is being seen. She was discharged yesterday after being hospitalized for three days with community-acquired pneumonia and is here for a follow-up visit.

She states she's feeling much better with less shortness of breath, diminished cough, and sputum production, and is without fever. She mentions that while she was in the hospital that, quote, "they changed my diabetes medicine and gave me insulin four times a day to keep my sugar controlled," close quote.

A review of her discharge note reveals that rapid acting insulin was given according to blood glucose levels without scheduled basal insulin and this was used from admission to discharge.

Random glucose today is at 220. The patient asks, "Should I start back up on those insulin shots? I've never used them before." The NP considers which of the following:

A. Given her random blood glucose is elevated, the use of a sliding scale insulin should be continued for the next week.
B. The use of a sliding scale insulin potentially results in wide glucose excursions.
C. Sliding scale insulin is helpful as it mimics physiologic insulin secretion.
D. The sliding scale insulin regimen should now be replaced with a basal insulin.
The correct answer is B. The use of sliding scale insulin potentially results in wide glucose excursions.

Where should we start with this question? First, let's determine what kind of a question it is. Given the person has been diagnosed, treated and is being seen in follow-up. This is an evaluation question. In evaluation questions, if you recall, this is looking for response to care. Interestingly, her current pneumonia diagnosis is barely mentioned here and is clearly not the focus of the question. The real focus of the question here is what to do about her blood sugars. Should she be on a sliding scale insulin or not?

There is, I will grant you, a fair amount to unpack in this question. Probably you want more information about what meds she was on for her diabetes prior to developing pneumonia. We're given very little information on that except to say she's usually at treatment goals and all her meds are oral. Well, that covers a multitude of issues, doesn't it? Another point, she mentioned she's never been on insulin in the past. And therefore, what you could say is, all right, she is not somebody whose type 2 diabetes has historically required insulin therapy.

Another key point, she is an older adult with CKD. What we always want to be quite vigilant about in treating anyone with diabetes, but particularly in older adults with CKD, is avoiding hypoglycemia. Aside from the obvious fall risk, hypoglycemia can trigger cerebrovascular or cardiovascular events.

We're given a little bit of information that she's generally feeling better. But again, pneumonia is really just a little part of the story and not the focus of the question. The real point of this question is how do you manage blood glucose in somebody who is recovering from a significant episodic illness like a pneumonia.

But let's get one piece of information clear. Acute illness, particularly infectious disease, creates a situation in a person with diabetes—whether they have type 1 or type 2 diabetes—where blood sugar control is generally a great challenge. Infection yields inflammation. In a nutshell, inflammation worsens insulin resistance and can, in a person with type two diabetes, yield reduced pancreatic insulin production. This is why quite often in a person with type 2 diabetes who's been well-maintained on day to day medication, as mentioned here, is suddenly she has poor glucose control.

Remember this about insulin: it is a bio-identical hormone, and people can receive it even in the presence of acute illness and significant comorbid conditions. Insulin works. If you're in heart failure, liver failure, kidney failure, really doesn't matter what is going on in the body, insulin will work. Now the dose needs to be titrated carefully, but it works regardless of comorbidity.

So let's get back to looking at what she was getting for insulin. You could see she received insulin in response to rising blood sugars and got this four times a day but was not put on a basal insulin. This describes what is often called sliding scale insulin, where a rapid acting insulin is used in response to a rise in blood sugar. The American Diabetes Association has long noted that sliding scale insulin is not an acceptable way to treat hyperglycemia. I'll put in here too, the Beers Criteria also has been loud and clear about avoiding sliding scale insulin in older adults for all the reasons I just rattled off.

Why is sliding scale insulin then not acceptable? Because with this method of glucose control, the blood sugar is allowed to rise and then, if you will, it's chased down with a dose of insulin. This leads to wide excursions in glucose, either hyper or hypoglycemia. I want to make this clear: sliding scale insulin and correction insulin are two entirely different therapeutic modalities. Sliding scale implies just what I said. You're going to let the sugar go up and then you're going to chase it down with insulin. So when you think about it, what sliding scale insulin does is allow for times of hypoglycemia. You're actually anticipating you're going to have times of hypoglycemia in which time the person will be out of range for therapeutic goals. And then you say, okay, the blood sugar is this high. Usually it takes X number of units to bring that down. We'll do that. Whoops. Maybe it was an overcorrection. All right.

And correction insulin is insulin given in response to what's anticipated to be a short-term hyperglycemia. In other words, a person who might present with a pneumonia in the office like this, and let's just pretend this is a person who's well enough to be treated at home, but you detect a temporary hyperglycemia because of the stress of the pneumonia. You give a few units of rapid acting insulin to try to bring the blood sugar more under control. Develop a plan of care of how to use correction insulin. Keep a really close eye on the patient. That's correction insulin. Correction insulin is advised for short-term hyperglycemia, right?

You know, simply put, this is what I often say when I'm teaching pharmacology: Friends don't let friends prescribe sliding scale insulin. Right? You also know since she's older and she has CKD, she's not going to offload insulin as well as a person with a higher GFR. One more time, even more risk for poor glucose control, particularly hypoglycemia.

Do we need more information about her right now to figure out what's the best way of managing her hyperglycemia as she recovers from pneumonia? You bet we do. But we have enough information here to answer the question. And when you're in the midst of the boards, what you can't let yourself do is get frustrated with the "yeah, but"s. Yeah, but I need to know this. Yeah, but I need to know that. You've got enough information here to answer the question.

So with that information in the background, let's take another look at the question.
73-year-old woman with a 20-year history of hypertension, type 2 diabetes, dyslipidemia, and stage 3B CKD, typically at treatment goals with oral medications is seen in primary care. She was discharged yesterday after being hospitalized for three days for community acquired pneumonia and is here for a follow-up visit. She states she's feeling much better with less shortness of breath, diminished cough and sputum production, and is without fever. So, just as an aside, she actually sounds like she's doing really well with her pneumonia. Okay.

She mentions that while in the hospital, "they changed my diabetes med and gave me insulin four times a day to keep my blood sugar controlled." A review of her discharge note reveals rapid acting insulin was given according to blood glucose level without scheduled basal insulin. This was used from admission to discharge. Her random glucose today is 220 without reports of hypoglycemia. The patient asks, "Should I start back up on those insulin shots? I've never been on those before." The NP considers which of the following in the use of sliding scale insulin:
A. Given her random glucose is elevated, the sliding scale insulin should be continued for the next week. This is incorrect. As I've mentioned before, the sliding scale is just not a good idea. In particular, in this scenario, we have literally one elevated blood glucose. We don't have enough information to warrant continuing insulin in any form. And what I also want you to remember is now what this would require would be—she just told you she's never been on insulin before—she would need to be informed on checking her sugar four times a day, injecting herself potentially four times a day, which she's never done before. I mean, it is just not a situation we want to get into.

B. The use of sliding scale insulin potentially results in wide glucose excursions. This is the correct answer. If you're not familiar with the term, glucose excursion simply describes that both hypo and hyperglycemia can be seen with the use of sliding scale insulin. I think I've already made my point, but don't prescribe sliding scale insulin. You will see it done, and particularly you'll notice that the setting of this question was primary care—implied is she's going to go home once she leaves your exam room. And so, just not a good idea.

I'm going to throw in one other thing. I have seen patients come out of the hospital on sliding scale. It's a whole other ball game. We can have another discussion another time about whether they ever should have been on it while hospitalized. But on more than one occasion, I've seen very well-meaning families ask the nurse for a copy of the sliding scale. And then once they get home, they say, "Oh, okay. We're going to make sure Abua—grandmother—gets her insulin after she eats and we'll check her blood sugar like an hour and a half after she eats like they did in the hospital, see how high it is, and then we'll give her her insulin." I've had that happen at least a half a dozen times.

So, one question I always include in a post hospital visit like this, if I'm aware the person received insulin while they were in the hospital, I will always ask did they and then I clarify what the role or not of insulin is now.

Okay. So, option C, sliding scale insulin is helpful as it mimics physiologic insulin secretion. Obviously, that's not correct. Sliding scale absolutely does not mimic physiologic insulin secretion. Physiologic insulin secretion—in other words, the insulin secretion we see in health, in the person without diabetes—consists of roughly 50% of the body's basal insulin, secreted by the pancreas as a background insulin. It's there whether the person is postprandial or fasting. Then once again, the person who does not have diabetes—what happens with physiologic insulin release is the pancreas will release boluses in response to food and snack intake, particularly carbohydrates. Indeed, when prescribing insulin, typically the therapeutic goal is to mimic physiologic insulin secretion. So one more time, chasing down a blood sugar after it went up—this is not mimicking something that's physiologic.

And D, the sliding scale insulin regimen should now be replaced with a basal insulin. Obviously not correct. When considering this answer, think through the pharmacokinetics—what is going to happen with the insulin you're prescribing, with basal insulin in the form of a long acting insulin like glargine, detemir, or the like—this provides that background insulin like physiologic basal insulin. And as I said earlier, we don't have enough information to talk about how to treat her with insulin in any form. In addition, when you think it through, she's been getting four doses of rapid acting insulin a day and now you want to take that away and replace it with a single dose of basal. It doesn't make pharmacokinetic sense. She might benefit from some correction insulin during her recovery, but I wouldn't consider any other insulin.

Key takeaway: insulin is a great drug. It is literally a life-saving drug. Knowing the differences between sliding scale insulin and correction insulin is key to safe prescribing practice.

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