In this episode I’ll:
1. Discuss an article comparing two insulin doses for the treatment of hyperkalemia in patients with renal insufficiency.
2. Answer the drug information question “How long can you use high dose insulin for a calcium channel blocker overdose?”
3. Share a resource for learning about pharmacologic issues in anesthesia.
The article for this episode recently appeared in a weekly literature digest for members of my Critical Care Pharmacy Academy. Every week I send Academy members a summary of the most important critical care pharmacy articles, including my analysis of where the article fits in practice. You can find out more at pharmacyjoe.com/academy.
Article
A comparison of insulin doses for the treatment of hyperkalemia in patients with renal insufficiency
Lead author: Heather LaRue
Published in Pharmacotherapy October 2017
Background
Hyperkalemia is a frequently encountered medical emergency in hospital patients and those presenting to an emergency room. The typical dose of 10 units IV insulin and 25 grams IV dextrose for hyperkalemia treatment is arbitrary. There has never been a dose-finding study to determine the optimal dose of insulin to treat hyperkalemia.
An internal study at Rush University Medical Center revealed that the majority of hyperkalemia patients that experience hypoglycemia were non-diabetics with renal insufficiency. This internal study prompted many clinicians to reduce the dose of insulin used for hyperkalemia treatment to 5 units instead of the usual 10 units.
Methods
The authors of this study conducted a retrospective review of the safety and efficacy of 5 units versus 10 units of insulin for the treatment of hyperkalemia in patients with renal insufficiency.
675 patients met the inclusion criteria of age 18 years and older, serum potassium greater than 5 mEq/L, renal insufficiency, 5 units or 10 units of intravenous regular insulin administered in the emergency department, and blood glucose documented within five hours after insulin administration. Of these patients, about 20% received 5 units of insulin and 80% received 10 units of insulin.
Results
The primary outcome was the incidence of blood glucose less than 70 mg/dL. Secondary outcomes were the incidence of blood glucose less than 40 mg/dL, and change in serum potassium after insulin therapy. Hypoglycemia occurred in 19.5% of patients who received 5 units of insulin and 28.6% of patients who received 10 units. This difference was statistically significant. Severe hypoglycemia, with blood glucose less than 40 mg/dL occurred less frequently in patients who received 5 units of insulin, however, the confidence interval included 0.
Unexpectedly, the change in serum potassium was similar between groups with a decrease of 0.8 mEq/L in the 5 unit group and a decrease of 0.7 mEq/L in the 10 unit group.
Conclusion
The authors concluded:
In patients with renal insufficiency and hyperkalemia, 5 units of insulin reduced serum potassium to the same extent as 10 units of insulin, but with a lower rate of hypoglycemia. Further controlled studies are needed to confirm these findings.
Discussion
I need to see controlled data before abandoning the standard 10 units of insulin for hyperkalemia. However, I have heard other clinicians advocate for giving 50 grams of dextrose as opposed to just 25 grams after giving insulin for hyperkalemia. Until the 5 unit insulin dose performs well in a randomized trial I would rather give more dextrose than less insulin to combat hypoglycemia during hyperkalemia treatment.
Drug information question
Q: How long can you use high dose insulin for a calcium channel blocker overdose?
A: The optimal duration of high dose insulin therapy is unknown. Case reports describe the use of high dose insulin therapy for up to 49 hours.
Non-insulin treatments often fail when treating calcium channel blocker overdose, and some calcium channel blockers such as amlodipine have half-lives exceeding 30 hours. For this reason, I would continue high dose insulin therapy for as long as a patient with calcium channel blocker overdose requires inotropic support to maintain adequate hemodynamics.
Resource
The resource for this episode is the free, online encyclopedia provided by openanesthesia.org. OpenAnesthesia is sponsored by the International Anesthesia Research Society. Their online encyclopedia contains hundreds of entries, many of which provide pharmacologic explanations for various areas of anesthesiology. For example, the encyclopedia contains a useful entry on the pharmacology of inhaled anesthetics.
If you like this post, check out my book – A Pharmacist’s Guide to Inpatient Medical Emergencies: How to respond to code blue, rapid response calls, and other medical emergencies.
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