It's not saying that regular insulin is only to be given IV. It's saying that regular insulin is the only insulin that you can give IV...which means you don't give other types (like levemir, lantus or 70/30 or aspart insulin) via IV. So you have many different types of insulin that you can give SQ, but regular insulin is the only one if you had to go the IV route.
So when do you give IV insulin ? Pts who have really high blood sugars (hyperglycemia) often need IV insulin to steadily bring it down. You can get a more predictable drop and you can monitor it more closely. So, if a pt has a blood sugar of 900, you would put them on an insulin drip and check their glucose level every hour. The insulin is rapidly absorbed and it is continuous. Then, you adjust the drip based on their blood sugar. If you are to give SQ insulin, there is a period where it gets absorbed...some are within 15-30 minutes while others are longer. If you are trying to rapidly and steadily bring down there blood sugar, SQ insulin isn't going to give you the results quick enough. Plus, with SQ insulin, they get what they get... but with a drip, you can increase it or decrease it every hour, so it's more effective. Once their blood suger is under control, then you can go the SQ route to maintain. IV insulin is also given to post-op cardiac pts, trauma pts, and neurosurgical pt. Well-controlled glucose levels is very important in this pt population for overall management, better healing, decreased mortality, etc.
It can be given IV becasue of it's rapid onset of action and Because it has only recently been approved for this use.......
IV Administration of Insulin Aspart and Human Insulin (NovoLog, Novolin R) for Use in Clinical Settings
On Oct. 21, the FDA approved intravenous administration for insulin aspart [recombinant] and human insulin [recombinant] injections (NovoLog and Novolin R, made by Novo Nordisk, Inc.), allowing intravenous injection of the products under proper medical supervision in a clinical setting for glycemic control.
Because intravenously administered insulin has a rapid onset of action, close monitoring of glucose and potassium levels is recommended to avoid potentially fatal hypoglycemia and hypokalemia.
Recombinant insulin aspart and human insulin were previously indicated for subcutaneous administration to control hyperglycemia in patients with diabetes mellitus.
I have only ever heard of regular insulin being given IV. I had that drilled into my head in nursing school and during my NCLEX review course.
Another reason why you may give regular insulin IV is if a patient presents with hyperkalemia. There is a combination of medications that are given with hyperkalemia. It's usually regular insulin (I always see 10 units) IV along with an amp of D50W (to prevent hypoglycemia) and 10mg of calcium gluconate (to protect the heart). NaHCO3 may be given if acidosis is present as well. Insulin helps shift potassium back into the cells, leading to a temporary fix of hyperkalemia. The potassium will start to leak out of the cells after awhile, though, so this is only a temporary fix. Kayexalate is usually given which will excrete potassium through the GI tract. The patient may receive Lasix which will lower the potassium level. Sometimes albuterol nebs are ordered, too, because they can also lower the potassium level but I usually see this more with peds vs. adults. In extreme situations, the patient may need to go for dialysis.