Q: What is the MRD for epinephrine in local anesthesia for patients with hypertension (per appointment)?
(A). 4
(B). 0.4
(C). 0.04
(D). 0.004
MRD stands for maximum recommended dose. In most local anesthetics, a vasoconstrictor is added, which is either epinephrine or levonordefrin. But why adding a vasoconstrictor? It is because the local anesthetic is “vasodilating,” meaning that it “opens up” the blood vessels. The problem with dilated blood vessels is that the local anesthetic “escapes” the area it was injected and get absorbed in the body and circulate to other parts more rapidly. The goal is to keep the local anesthetic “local” diminished. To help counteract the vasodilating effect of an anesthetic, a vasoconstrictor is added.
- The MRD for epinephrine in local anesthesia for medically-compromised patients is 0.04 mg.
- The MRD for epinephrine for healthy patients is 0.2 mg.
Answer: C. 0.04
Learn more for the dental hygiene boards
You may still wonder why the MRD is lower for medically compromised patient. Let’s tackle this as it is crucial for you to UNDERSTAND, not just memorize the information for the WREB or CDCA local anesthesia board exams. If you remember from the explanation above, the vasoconstrictor narrows the blood vessels. If the patient is affected by let’s say hypertension, the vasoconstrictor may significantly increase the blood pressure (which is already high) and cause unwanted consequences.
Maximum Recommended Dose
Now the question is “how many cartridges can I provide?” Well, we did the math for you!
Epinephrine for medically-compromised patients:
- 1.1 cartridges in 1:50,000 concentration
- 2.2 cartridges in 1:100,000 concentration
- 4.4 cartridges in 1:200,000 concentration
Epinephrine for healthy patients:
- 5.5 cartridges in 1:50,000 concentration
- 11.1 cartridges in 1:100,000 concentration
- 22.2 cartridges in 1:200,000 concentration
I know that this was a LOT to remember. To simplify things, remember 2 cartridges and 11 cartridges. Most likely, the dental office or dental hygiene school will use a 1:100,000 epinephrine option.
Dental hygiene boards are waiting and I hope that today’s vitamins gave you some great info! Let’s all get you to the finish line! If you are taking the local anesthesia exam (WREB or CSCE), you do know that StudentRDH has a complete boards review at a low pricing, right? If this is news to you, have a quick look at the topics we cover at StudentRDH for the local anesthesia exam.
Related post in Local Anesthesia: Infraorbital block
(Disclaimer: StudentRDH is NOT affiliated with the NBDHE, NDHCE, CSCE, CDCA, WREB.)
