A Question For Sdn 1977

[jetproppilot]

Heres a scenerio that we are commonly confronted with, Sir.

I have my own (i think its correct) way of doing this, but I wanna run it by a drug-czar like yourself.

You wanna initiate a dopamine infusion of 5ug/kg/min.

Your patient is a five-foot-four, 110 kg person.

And no, she is not in contention for Ms Olympia with 4% bodyfat.

She is morbidly obese, suffering from W.T. (whopper toxicity).

So alotta her bodyweight is fat.

What do you use for the kilogram part of the equation when figuring a drug dose for a drug that is a per-kilo drug?

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[militarymd]

Heres a scenerio that we are commonly confronted with, Sir.

I have my own (i think its correct) way of doing this, but I wanna run it by a drug-czar like yourself.

You wanna initiate a dopamine infusion of 5ug/kg/min.

Your patient is a five-foot-four, 110 kg person.

And no, she is not in contention for Ms Olympia with 4% bodyfat.

She is morbidly obese, suffering from W.T. (whopper toxicity).

So alotta her bodyweight is fat.

What do you use for the kilogram part of the equation when figuring a drug dose for a drug that is a per-kilo drug?

From a non-pharmacy guy...I use IBW + 30% of the difference from actual weight....

Although with dopamine it's been demonstrated that weight based doses essentially gives you a scatter gram of serum concentrations in different patients of the same weight.

 

[Noyac]

I do IBW and titrate up from there.

And another thing you GUYS may want to know:










SDN is a chick!!!!!!

 

[jetproppilot]

I do IBW and titrate up from there.

And another thing you GUYS may want to know:

SDN is a chick!!!!!!

Uhhhhhhhhh.....geez......sorry I can't reply since I've got my size 13 Nike between my incisors.

Sorry, Ms SDN 1977, M'aam, Sirrette, Dudette, uhhhhh,

thanks. Sorry. Hows the weather in CO, Noy? Anybody awaiting football season?

i'm just gonna leave now.....................i'll be back later.....................

 

[sdn1977]

Hmmm....if you stopped by the OR pharmacy & asked me off the top of my head (like that would ever happen ) I'd say....dose on IBW + 10-20% depending on what you want to accomplish with the infusion. If you just wanted to bump the renal beds, I'd start low & watch for effect. If you need a rescusitating response now - go high now.

A drug you titrate is not so much an issue with weight based dosing since you've got good dose/effect control. It is more of an issue of wanting to get a dose-response with an initial dose (like sevo's diltiazem). Its also an issue with drugs who have very low lipophilicity (vecuronium) or very narrow therapeutic ranges (digoxin, phenytoin). - dose on IBW. After the initial dose distributes, then elimination rate kinetics take over.

I could go on and on with what affects the volume of distribution (which is what we're talking about). It also changes if you're talking about starting the dopamine in the OR or having to maintain the dose after in the ICU because the steady state Vd & apparent terminal elimination half life changes with the dose. Same principle applies...each hour, day, whatever, you evaluate & adjust the dose.

But....my final answer....start w/ IBW + 10-20% (hmmm.....I'm guessing mil got the $$$$ on this one - huh?)

Yeah - I admit it - I'm a girl - what can I say But...I look great in a dress - does that count for anything????

And....yes - I am waiting for football season & the return (will they ever return) of the 49'ers - remember the 80's???

Take your Nike out of your mouth jet - basketball is a foul enough sport as it is! (IMO )

 

[jetproppilot]

Yeah - I admit it - I'm a girl - what can I say But...I look great in a dress - does that count for anything????

Uhhhhhhh.......

What were we talking about?

What was the question/subject?

I'm a little disoriented........


All kidding aside,

thanks SDN.

 

[sdn1977]

Uhhhhhhh.......

What were we talking about?

What was the question/subject?

I'm a little disoriented........


All kidding aside,

thanks SDN.

No problem!

& in all good fun.....you've got my number.....1977

 

[cloud9]

basketball is a foul enough sport as it is!

Basketball...foul.... Nice one. Intended, I trust.

 

[sdn1977]

Basketball...foul.... Nice one. Intended, I trust.

yep - you got it I apologize to basketball fans!

Mil - I should have responded to what you observe with regard to dose & drug levels of dopamine.

Actually - few studies have been done on the kinetics of dopamine distribution. One was done & reported in Anesthesiology in 2000. It was an observational study only on 9 health pts. The attempt was to try to predict dopamine concentration from the infusion dose based on known pharmacokinetic models. They used a program developed at UCSF to try to determine optimal compartmental pharmacokinetic models. Pharmacists like to know where the drug is at any given time & why .

Well...what they found was despite a homogeneous (albeit small) population & using weight based dosing...there was huge intersubject variability (10-75 fold variance) in plasma levels. It suggests there is marked variability - both intraindividual & interindividual involving either/or distribution or metabolism. The closest they came was to describe the kinetics as a 2 compartment model - a rapid 2 min distribution & a later distribution phase. This doesn't fully explain the kinetics, however, because we know dosing changes as the infusion continues (ie - ICU pt requiring long term dopamine), but this is suggested to be due to saturable elimination phase changes.

As to why you choose IBW - dopamine is only moderately lipid soluble so start here then add a % (whatever % you feel comfortable with based on your experience & pts clinical condition) to compensate for whatever amount will distribute to the adipose tissues after the initial 2 min phase.

I wish I could tell you more about dopamine kinetics, but I don't know anymore - sorry.

 

[dogbone65]

AAAAHHHHH...............good stuff..................good stuff

 

[militarymd]

SDN is a chick!!!!!!

SDN ....great posts!!! I've always advocated having pharmacists on ICU rounds....

However.....

 

[rn29306]

SDN ....great posts!!! I've always advocated having pharmacists on ICU rounds....

However.....

Looks great in a skirt huh? Prove it.

 

[sdn1977]

SDN ....great posts!!! I've always advocated having pharmacists on ICU rounds....

However.....

heres one:

http://www.accelrys.com/reference/gallery/life/dopamine.gif

ooops - not what you're talking about - my bad !

 

[Dr. J?]

heres one:

http://www.accelrys.com/reference/gallery/life/dopamine.gif

ooops - not what you're talking about - my bad !

Nice atoms!!!

 

[Idiopathic]

If you just wanted to bump the renal beds, I'd start low & watch for effect.

So weve had several conversations on the efficaciousness of 'renal dosing' dopamine. Obviously it would work theoretically, but I dont believe any studies show better outcomes (doesnt the big one even show increased M+M with renal dose dopamine?...Ill have to look it up).

How do you feel about this.

 

[Mapleson D]

The big trial was the ANZICS one:

Australian and New Zealand Intensive Care Society (ANZICS) Clinical Trials Group. "Low-dose dopamine in patients with early renal dysfunction: a placebo-controlled randomised trial." Lancet 2000;356:2139–43.

It didn't specifically show increased morbidity with renal dose dopamine, just no difference between dopamine and placebo in death rate, max. creatinine, ICU & hospital stay length, time to return of renal function, etc. There have been a number of other studies suggesting various morbidities from renal dose dopamine, though.

I'll let SDN1977 give her take on the matter . . .

 

[sdn1977]

So weve had several conversations on the efficaciousness of 'renal dosing' dopamine. Obviously it would work theoretically, but I dont believe any studies show better outcomes (doesnt the big one even show increased M+M with renal dose dopamine?...Ill have to look it up).

How do you feel about this.

I'm really not qualified to give you an opinion, which is why I didn't enter into that conversation. From a pharmacologic standpoint, it should increase perfusion...which is does when tested in both healthy & sick individuals. But...I'm fully aware that data does not always translate to positive patient outcome.

Honestly, I have not kept up on this area of applied dopamine pharmacology, only dosing with regard to volume of distribution & metabolism. I gave an opinion only on the dose of the drug jet asked about & interpreted it to be a question on when to dose on IBW or ABW, not on whether to use it or not. Perhaps I misinterpreted.

In my area of practice....I am not asked if dopamine should or should not be used to maintain renal perfusion (thus....my comment...."as if that would ever happen..."). Some of the physicians I work with use it, some don't.....I have no basis on which to discuss the issue since it doesn't come up in P&T discussions, in our morbidity & mortality review nor is it an economic issue.

I don't mean to be side-stepping your question. I just have no valid basis on which to state an opinion.

 

[militarymd]

I'm really not qualified to give you an opinion, which is why I didn't enter into that conversation. From a pharmacologic standpoint, it should increase perfusion...which is does when tested in both healthy & sick individuals. But...I'm fully aware that data does not always translate to positive patient outcome.

Honestly, I have not kept up on this area of applied dopamine pharmacology, only dosing with regard to volume of distribution & metabolism. I gave an opinion only on the dose of the drug jet asked about & interpreted it to be a question on when to dose on IBW or ABW, not on whether to use it or not. Perhaps I misinterpreted.

In my area of practice....I am not asked if dopamine should or should not be used to maintain renal perfusion (thus....my comment...."as if that would ever happen..."). Some of the physicians I work with use it, some don't.....I have no basis on which to discuss the issue since it doesn't come up in P&T discussions, in our morbidity & mortality review nor is it an economic issue.

I don't mean to be side-stepping your question. I just have no valid basis on which to state an opinion.

Read up folks....this is a very insightful and wise post.

Although pharmacology and physiology are important aspects of anesthesia (and just about everyone who wants to do anesthesia say they really enjoy P & P, blah, blah, blah...)

The things that is discussed in P&P are surrogate endpoints that do not necessarily translate into desirable clinical outcomes.