what would you say is the max dose

[urge]

of a phenylephrine infusion?

For a drug that we use every day, nobody seems to know.

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[floridaboy18]

I would say probably 200 mcg/minute. By that, I mean that when I get to the point that I am on that much phenylephrine, I am likely considering an additional drip (vasopressin, nor-epi, whatever).

 

[Noyac]

I didn't know there was one.

 

[Planktonmd]

of a phenylephrine infusion?

For a drug that we use every day, nobody seems to know.

There is no max dose

 

[sevoflurane]

If it's not working switch or add something else.

 

[urge]

Ok, no concrete answer as expected.

What is your personal max dose at which you say it is no longer working?

 

[pjl]

Mini dripper wide open.
I start a drip if I go through a syringe. When I cant turn the minidripper up without it being a steady stream, I start a different drug. Obviously my actual choices are more based on overall clinical picture, and causes of hypotension, but probably those are as close as I can get to a concrete set of rules I have for myself.
200 is pretty high if I am actually using it on a pump though...that is what like 300 drips a minute?

 

[codeb1ue]

What are your thoughts of continuing that dose after starting Levo? My thought is that once I get Levo going at a decent enough dose (> 8-10 mcg/min) the Neo becomes pointless since levo is a much stronger alpha agonist.

 

[deleted171991]

It doesn't really make sense using both at the same time.

 

[Triple AAA]

Max dose = dose at which tachyphylaxis sets in and the drug pretty much becomes useless. I have no idea what number that is, and I imagine it varies from patient to patient.

 

[pgg]

When you're not getting the effect you desire, it's time to consider other drugs ... or the possibility that the hypotension isn't really an alpha agonist deficiency. For me, that might be somewhere around 200 mcg pushed with minimal observed effect, or a need for another 200 mcg a minute later.

I can't say I've ever really encountered what I'd call tachyphylaxis with phenylephrine, in the context of a surgical case. Yes with other indirect-acting drugs (eg ephedrine with NE depletion), or those with side effects (eg SNP with CN- and met acidosis and ? disulfide IIRC) but not so much the drugs that have direct receptor effects. With prolonged infusions there can be some receptor downregulation, as you might see with a patient getting days and days of a phenylephrine or NE infusion in the ICU. But I'm not sure I'd ever blame tachyphylaxis if phenylephrine wasn't getting it done in the OR.


Edit - You've also got to be cautious with vasoconstrictors so that you're not propping up measured BP for the sake of a number, while there's so much peripheral vasoconstriction that tissues aren't actually getting perfused. So even if I was getting a nice BP out of >200 mcg/min or thereabouts I wouldn't necessarily believe I was perfusing things well.

 

[btbam]

I'd think you would switch to something more powerful e.g. Norepi or Vasopressin long before you reach the "max" dose of Neo...

 

[BuzzPhreed]

We've adopted weight-based dosing at our institution. The range is 0.2-5.0 mcg/kg/min. Once you get past 5 mcg/kg/min, you're probably getting maximum bang for your buck and it's time to add something else. (Feel free to argue with me.)

I've been to places that run it "wide open" on a micro drip without a pump. I have no clue how you can defend that in court, in this day and age, if someone strokes out during a case.

 

[BuzzPhreed]

Edit - You've also got to be cautious with vasoconstrictors so that you're not propping up measured BP for the sake of a number, while there's so much peripheral vasoconstriction that tissues aren't actually getting perfused. So even if I was getting a nice BP out of >200 mcg/min or thereabouts I wouldn't necessarily believe I was perfusing things well.

^^^^^ This.

It makes me recollect a case I took over from a locum tenens who was covering us several years back. It was a urologic case. This practitioner started a phenylephrine infusion when the patient clearly needed fluid. I kid you not, it wasn't 15-20 minutes after I took over that the patient coded on me. I was ****ing pissed. And that particular person never worked with our group again needless to say.

 

[Planktonmd]

We've adopted weight-based dosing at our institution. The range is 0.2-5.0 mcg/kg/min. Once you get past 5 mcg/kg/min, you're probably getting maximum bang for your buck and it's time to add something else. (Feel free to argue with me.)

I've been to places that run it "wide open" on a micro drip without a pump. I have no clue how you can defend that in court, in this day and age, if someone strokes out during a case.

The amount of vasoconstriction obtained from a certain dose of phenylephrin is not constant and it is influenced by patient specific factors like the existence of vasodilation caused by anesthetics or sepsis, the antihypertensive medications the patient is on, electrolyte imbalances, acid base balance...
So it is really impossible to predict a max dose that works for all.

 

[BuzzPhreed]

The amount of vasoconstriction obtained from a certain dose of phenylephrin is not constant and it is influenced by patient specific factors like the existence of vasodilation caused by anesthetics or sepsis, the antihypertensive medications the patient is on, electrolyte imbalances, acid base balance...
So it is really impossible to predict a max dose that works for all.

Oh, I agree. But you gotta stop somewhere. And you know how people (ahem... nurses and pharmacists) like to have "hard stops".

 

[BuzzPhreed]

A true "placeholder".

Dude it was a total "WTF!!" moment when I went in to take over the case. I immediately told the surgeon that this patient was in deep ****, I apologized for the bad care up to that point, and I opened the stopcocks on the fluids. It was about a 4 hour case at the point I took over and the patient had only gotten about one liter of fluid! I immediately put in an a-line and got an iStat. The base deficit was like -11. The pressure sucked on about 300mcg/minute of Neo. Then the **** hit the fan. I was so friggin' pissed. I was a junior consultant at that point, and I made sure everyone knew that I wasn't the one who'd f*cked up that case.

 

[BLADEMDA]

Usual Adult Dose for Hypotension
IM or subcutaneous: 2 to 5 mg every 1 to 2 hours as needed.

IV bolus: 0.2 mg/dose (range: 0.1 to 0.5 mg/dose) every 10 to 15 minutes as needed (initial dose should not exceed 0.5 mg)

IV infusion: 100 to 180 mcg/min initially. The usual maintenance dose is 40 to 60 mcg/min.
Alternatively, 0.5 mcg/kg/minute; titrate to desired response. Dosing ranges between 0.4 to 9.1 mcg/kg/minute have been reported.

Usual Adult Dose for Shock
IM or subcutaneous: 2 to 5 mg every 1 to 2 hours as needed.

IV bolus: 0.2 mg/dose (range: 0.1 to 0.5 mg/dose) every 10 to 15 minutes as needed (initial dose should not exceed 0.5 mg)

IV infusion: 100 to 180 mcg/min initially. The usual maintenance dose is 40 to 60 mcg/min.
Alternatively, 0.5 mcg/kg/minute; titrate to desired response. Dosing ranges between 0.4 to 9.1 mcg/kg/minute have been reported.

 

[BuzzPhreed]

Oh, I agree. But you gotta stop somewhere. And you know how people (ahem... nurses and pharmacists) like to have "hard stops".

Another story.

I recently had a patient that I was helping with in our ICU (as I said recently on another thread I'm not gonna out myself but I spend a lot of time in our ICU and cath lab as part of our agreement at my current gig) and the cardiologist came in and took the dopamine off the pump and opened it wide-open. The ICU nurse practically **** her pants and started moaning and complaining saying "you can't do that" and whatnot. The cardiologist, more cool than the Fonz, says, "Oh yeah? Watch me."

The guy still died.

 

[Planktonmd]

Another story.

I recently had a patient that I was helping with in our ICU (as I said recently on another thread I'm not gonna out myself but I spend a lot of time in our ICU and cath lab as part of our agreement at my current gig) and the cardiologist came in and took the dopamine off the pump and opened it wide-open. The ICU nurse practically **** her pants and started moaning and complaining saying "you can't do that" and whatnot. The cardiologist, more cool than the Fonz, says, "Oh yeah? Watch me."

The guy still died.

And the cardiologist probably got written up by the nurse

 

[urge]

Max dose = dose at which tachyphylaxis sets in and the drug pretty much becomes useless. I have no idea what number that is, and I imagine it varies from patient to patient.

The amount of vasoconstriction obtained from a certain dose of phenylephrin is not constant and it is influenced by patient specific factors like the existence of vasodilation caused by anesthetics or sepsis, the antihypertensive medications the patient is on, electrolyte imbalances, acid base balance...
So it is really impossible to predict a max dose that works for all.

That's not how people practice in real life. Your answers imply that you are perfectly content at running the drip at 1 mcg/kg/min, 10mcg/kg/min, or even 1000 mcg/kg/min. I bet that neither of you have ever run it higher than 2 mcg/kg/min in your life. Granted, we all know that on the internet you can claim that you run it routinely at 1,000,000 mcg/kg/min for your ear tubes.

We've adopted weight-based dosing at our institution. The range is 0.2-5.0 mcg/kg/min. Once you get past 5 mcg/kg/min, you're probably getting maximum bang for your buck and it's time to add something else. (Feel free to argue with me.)

Now, that is a good honest answer.

 

[pgg]

The ICU nurse practically **** her pants and started moaning and complaining saying "you can't do that" and whatnot. The cardiologist, more cool than the Fonz, says, "Oh yeah? Watch me."

So call me crazy, but that's wrong for a reason totally unrelated to whether or not dopamine can be given off a pump ...

The RN sure should've been calmer about it and voiced her concern in a less strident and declaratory fashion ... but being cool like the Fonz and ignoring her isn't the right answer either. A simple "in this case it's appropriate to give off pump, we can talk about why later" would've been better. He could've asserted his authority and continued doing what he was doing without either escalating the word fight, validating her crankiness ... or teaching the junior RNs who were watching that doctors don't care what nurses think.

Maybe next time, that cardiologist will be making an actual error and another nurse who witnessed that exchange won't say anything. Medical errors kill and hurt a lot of people. We want people (nurses, techs, whoever) to speak up when they see something they think isn't right. Sarcastic dismissal isn't the right answer.

 

[deleted171991]

I find that it's inappropriate for a nurse to say "you can't do that" to a doctor. What they can and should say is: "Are you 100% sure (it won't harm the patient)?"

And that's why I always tell them: Just trust me on this. I'll explain when we have some time.

 

[deleted171991]

I know that the word "doctor" comes from (among others) "teacher", but I personally am getting tired of explaining myself to nurses. Somebody stupid teaches almost all of them that they are there to defend patients from their doctors.