Nurse Files: Insulin
Or, as I like to call it: unicorn tears
Seriously, insulin has to have mystic properties. One person needs two drops, the next a full syringe. Some people eat a cracker and their glucose skyrockets. Others toss back a soda and nothing happens. Magic, I tell you.
Let’s dive into the types of insulin and why you would administer which one when.
Back to Basics
The human body uses glucose for fuel. Very like gasoline in a combustion engine, it combines with oxygen in the cell to energize particles, which the body then uses to power everything it does.
Insulin is the key that lets glucose into the cells. Only the brain does not need insulin to carry glucose across the cell membrane, which is a safety mechanism to prevent brain death in settings of hypoglycemia.
Insulin is made in the pancreas. Disorders of insulin regulation and production are classified under the diagnosis of Diabetes Mellitus (DM). There are two basic types, Type 1 and Type 2.
Type 1 DM is an inability of the pancreas to make insulin. This is due to auto-immune destruction of the pancreatic beta cells. There is a secondary type 1, which is not auto-immune mediated, but it is quite rare.
Type 2 DM is by far the most common type, like 90% of DM cases. This is a relative insulin deficiency. This is caused by lifestyle and diet, but also carries a strong genetic component. People with DM2 have functional pancreases, but their cells are either resistant to the insulin or their pancreas cannot produce enough insulin to match glucose levels.
This is usually because their baseline blood glucose levels have been high for an extended period. Insulin is produced at a higher rate to match the high blood glucose, but eventually the beta cells wear out. Body cells become saturated and unable to take up more glucose. Blood glucose levels rise and sequela from the hyperglycemia start to stack up.
Not every diabetic will need insulin. For DM2 especially, lifestyle modification and other antihyperglycemic medications can be used to improve pancreatic function and glucose management. However, if not treated many DM2 patients become insulin dependent.
Insulin is a protein. Unfortunately, this means you can’t take it orally. Your digestive enzymes will cheerfully slice it up into amino acids and use it for proteins. If we want to ensure the safe delivery of insulin to our blood stream, we have to inject it and bypass the digestive tract.
Before we could make synthetic insulin, we had to use pig insulin or cadaver insulin. Yes, I said cadaver. It was horribly expensive and a lot of diabetics of both types died prematurely from complications of the disease.
Along came genetically modified organisms, our tiny little buddies. Insulin was the first medication produced by modified bacteria and yeast. Nowadays, lots of medications and substances are produced by GMO micro-organisms, which is why a blanket ban on GMOs is a stupid idea and anyone pushing for that has no idea what they’re talking about (steps off soap box).
After 2006, all insulin in the US is synthetic insulin. Animal insulin is reserved for the rare instance that a person has an allergy to the synthetic form. Extremely rare, as the insulin produced by the GMOs can be identical to human insulin.
But, as with many things, once we got a good idea going, we said, ‘hey, how can we make this better?’ Enter: insulin subtypes. This is where it gets confusing. The premise is simple. Insulin + glucose = happy cells. But we can fine tune when the insulin takes effect and how long it lasts in the body to manage blood glucose better.
Rapid: 5 - 15-minute onset, 3 - 4-hour effect. This is ‘analog’ insulin, acting similar to a normal pancreatic response to eating. This is given to cover carbohydrates eaten with meals.
Short: 30-minute onset, 5 - 8-hour effect. This is ‘regular’ insulin and also used with meals.
Intermediate: 1 - 3-hour onset, 16 - 24-hour effect. This is ‘NPH’ or Neutral Protamine Hagedorn insulin. It has a cloudy appearance which is otherwise a bad sign in insulin. It can also be mixed with other insulins. I give this sometimes, and usually only to people with very well-controlled DM1 with a set insulin regimine.
Long: 1 - 2-hour onset, with a steady effect for about 24-hours. This is usually your ‘basal’ insulin. This mimics the body’s natural continuous low-level insulin secretion to regulate blood glucose between meals.
Ultra-Long: 30 - 90-minute onset, >24-hour effect. I’ve never used this inpatient.
(PS: you will be asked about these sub-types on every nursing test you ever take. Sorry.)
Bedside Considerations
Controlling blood glucose while inpatient can be tricky. Meals can be irregular and missed. Medications can be mixed in dextrose of varying concentrations. Illness messes up glucose levels. Steroids can send it through the roof even in patients with functional endocrine systems.
My take-aways for insulin administration and management:
Insulin is a high-risk medication. If you are ever questioning yourself about administering a dose, stop and run through it with someone else. You can kill with the wrong dose. Label your syringes and double-check yourself. I’ve pulled up insulin with a metric-based syringe instead of a Unit-based syringe because I wasn’t attending. On my double-check, I realized my mistake and corrected it. We will all do something like that in our career. Make it a practice to be extra vigilant with insulin.
Most people who are insulin dependent hate it. You have to stick yourself with needles half a dozen times a day, you have to count your carbs, insulin is expensive, you can’t eat what you want. Good patient education will help, especially since insulin is confusing even for medical professionals. Laymen are at even more of a disadvantage.
Know the effective period or half-life. If you gave rapid-acting insulin for breakfast at 1000 because the patient had a morning procedure, you can’t then give lunch insulin at 1200. They are still inside the window for their first dose. You can compound the insulin effect and send them too low.
I would rather my patients sit a bit too high than too low. Ideally, they will float inside a narrow range just higher than normal. But don’t be surprised if things get wonky. Their pancreas just can’t keep up with the stressors of hospital life.
Give long-acting insulin even if they can’t eat, unless you have a specific order or indication not to, such as acute hypoglycemia. This will prevent swings later on that require larger doses of short-acting insulin.
Know that some people will simply refuse to manage their diabetes, no matter the type. They refuse to check sugars, to take medications, to exercise, to change their habits. You can’t fix that in a 2-day hospital stay. Provide education and move on with your life. They’ll be back with nonhealing wounds, gastroparesis, or keto-acidosis, and maybe will listen to reason at that time. You’re not a super-hero; you’re just a human doing a difficult job.
Oof. This is a hefty topic. I’ve be doing this for 10 years and I still have to relearn the subtypes on a regular basis. Don’t worry about it. Just knowing there are different types means you can go look up current information. We need application of knowledge, not just the acquisition of it. Go forth and control those sugars!
References
Porth’s Pathophysiology: Concepts of Altered Health States (9th Edition). Grossman, S.C., Porth, C.M.
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Enjoy!
Anna, RN, BSN, CCRN
Necessary disclaimer: I am discussing medications and medical conditions in this article based on my personal experiences as a nurse. Your facility may have different requirements and resources. Use your own nursing judgement to assess and treat your patients according to your governing body and facility guidelines. All information within this article is correct to the best of my knowledge, but should be confirmed through verified evidence-based sources. I am not responsible for any clinical decisions made based on this article.