Benzocaine-induced methemoglobinemia

[Guest27531]

In our unit we use cytocaine spray to block a patient's gag reflex during transesophageal echo. Rarely, the medication can cause methemoglobinemia. We had this happen on our unit yesterday and the problem was properly diagnosed but there was quite a bit of discussion about the dose of methylene blue to give and the preferred IV administration technique. The patient recovered but we are considering what standards we should institute so the dosing does not cause treatment delays if this should ever happen again.

Does your place of practice have a standard of care for this rare occurence?

[core0]

In our unit we use cytocaine spray to block a patient's gag reflex during transesophageal echo. Rarely, the medication can cause methemoglobinemia. We had this happen on our unit yesterday and the problem was properly diagnosed but there was quite a bit of discussion about the dose of methylene blue to give and the preferred IV administration technique. The patient recovered but we are considering what standards we should institute so the dosing does not cause treatment delays if this should ever happen again.

Does your place of practice have a standard of care for this rare occurence?

The PI says .1-.2 mg/kg which is the pretty standard dose. We use doses up to 2 mg per Kg in refractory hypotension so anything in that range should be OK.

[GreyGull]

we do continuous monitoring during procedures to prevent [color=#231f20][color=#231f20][color=#231f20]methb levels from reaching a point of requiring treatment since methylene blue is controversial in itself for dosing and rebound.

[Guest27531]

we do continuous monitoring during procedures to prevent [color=#231f20][color=#231f20][color=#231f20]methb levels from reaching a point of requiring treatment since methylene blue is controversial in itself for dosing and rebound.

could you please tell me more about what you mean regarding the controversy surrounding treatment? our research indicates this is standard treatment for confirmed methemoglobinemia and i haven't seen anything to contradict this or even to suggest this isn't exactly the right treatment medication. in our situation, the methylene blue wasn't in question, only the dosing and method of iv administration. do you mean your physicians question the correctness of the treatment drug, itself?

regarding continuous monitoring - of course we monitor o2sat continuously during the procedure, however, the cause of the adverse effect is the cytocaine which is administered before the procedure is started. so, i'm unclear what you mean by "we do continuous monitoring during procedures to prevent methb levels from reaching a point of requiring treatment". could you explain.

thank you.

[Guest27531]

The PI says .1-.2 mg/kg which is the pretty standard dose. We use doses up to 2 mg per Kg in refractory hypotension so anything in that range should be OK.

That is what the physicians decided to use (.1mg/kg) but both pharmacy and physicians were puzzled by the situation and reluctant to treat. My research indicated that for our situation 1-2mg/kg was indicated and widely used (which is really why I'm asking to see if I can find centers that actually use this as a standard). Our patient did improve rapidly but not as quickly as the case studies have indicated with 1-2mg/kg, which is why I'm hoping we resolve the dosing issue. She did need to spend the night in the CCU, while case studies indicated that with 1-2mg/kg dosing she might have been fully recovered in 20 minutes.

Thank you.

[blondy2061h, MSN, RN]

We occasionally use benzocaine for sore throats. Many of the nurses think it's okay for the patient to keep at bedside, however, my facility's policy prevents this due to this. They had to start sending the bottles up with labels saying they're not to be kept at bedside. I've seen methemoglobinemia once, but it was from an anesthesia agent (not sure what) not benzocaine. She was treated successfully with methylene blue. I'm sorry, I don't have much to contribute.

[GreyGull]

Could you please tell me more about what you mean regarding the controversy surrounding treatment?

As I stated earlier, it is the rebound that some don't consider. Also, in adults (and kids who may need certain procedures), there are many meds and associated organ problems like with the kidneys which can complicate any administration just like any other medication consideration.

Regarding continuous monitoring - Of course we monitor O2Sat continuously during the procedure, however, the cause of the adverse effect is the Cytocaine which is administered before the procedure is started. So, I'm unclear what you mean by "we do continuous monitoring during procedures to prevent MetHb levels from reaching a point of requiring treatment". Could you explain.

Thank you.

SpO2 is not accurate in the face of MetHb just like COHb. We use Masimo pulse oximetry which can do MetHb and is also used when Nitric Oxide is running in the ICUs. We just use this pulse ox with MetHb and CO to monitor during procedures so we know the SpO2 is accurate and there is not an effect from any of the -caines we administered or may need to repeat.

[Guest27531]

Thank you all!