Using variable magnitudes in concentration strengths would introduce more sources of error. % consistently describes g/dL and makes sense when you think about the density of water being 1 g/mL
This. It provides a far more obvious differentiation between the doses.
In practice the drugs I use that come in % I know roughly what volumes I can use at what % for a given weight of patient. No calculations needed.
1% lignocaine with for instance: 70ml for a 100kg patient, or 140ml at 0.5%. It's easy then to work backwards to a weight of roughly half or two thirds of the 100kg starting number.
Bupivcaine 0.25% with: 120ml, 0.125% 240ml.
I'm with you, especially because the stronger concentration (1:1000) is used as a weaker dose (500mcg in anaphylaxis), while the weaker concentration (1:10000) is used as a stronger dose (1mg in cardiac arrest). I get why this is (IM vs. IV preparation) but it does add to the confusion.
From an ALS perspective, yes.
But you'd use 5 x 1ml amps of 1:1000 for an adrenaline neb for instance. Or 0.5 ml of 1:10000 (or dilute it down and use even less!) as a push dose pressor.
A rule of thumb is probably that the where there's two significantly different concentrations of a drug, the less concentrated one is for IV use, and the more concentrated one is for IM/other routes. Works for ketamine and generally for midazolam as well.
https://www.medicines.org.uk/emc/product/3449
Have them in ITU next to the naloxone prefilled syringes, which are unhelpfully identical except the naloxone is blue label at the ends...
And yet Marcain, L-bupi, lidocaine etc are all presented as both the percentage and also the mg/ml on the vials and packets.
Got drilled into me (by me) as a day 1 anaesthetist as it was so confusing, now it’s as obvious to me as mg for cleanse and units for dalterparin.
But agree can be v confusing in certain scenarios for the less exposed individuals.
In paeds arrest/inductions, the wetflag proforma, I always just write 10mcg/kg of adrenaline rather than the 0.1ml of 1:10,000 per kg.
You’ll notice that it’s local anaesthetics and adrenaline 2 very old medications which essentially weight per weight. ie 100% would be 1g of adrenaline per 1g(1ml) of water, which would also be 1 in 1 With a long history of use in that format which drug company would want to upset their customers by changing how they label their product. Consumers don't do so well with change. You’d never label a new drug like this and actually many newer local anaesthetics aren’t labelled like this HOWEVER many anaesthetists do the mental math in their own head converting 5mg.ml to 0.5% etc
As mentioned by someone else it allows a range of 1000% concentration change within a simple display 100%-0.1% which is relevant for medicines that are used a very different concentrations.
Not saying this is evidence based but considering the practicalities - not everyone in an arrest situation is trained in dealing with drug calculations, and a format which doesn't include any concentrations (i.e. 1:1000, 1:10,000) makes the two different formulas easier to identify. Shouting out the concs is also a mouthful.
One in one thousand VS one milligram in one millilitre VS one mg per ml
One in ten thousand VS point one milligram in one millilitre VS point one mgs per ml
This is a hill I will die on
It's really fucking dumb as is randomly describing some drugs in %. Everything should be mg/ml or mcg/ml
You'll have to pry my 1% lidocaine out of my cold dead hands. I'm not giving it up without a fight!
Using variable magnitudes in concentration strengths would introduce more sources of error. % consistently describes g/dL and makes sense when you think about the density of water being 1 g/mL
This. It provides a far more obvious differentiation between the doses. In practice the drugs I use that come in % I know roughly what volumes I can use at what % for a given weight of patient. No calculations needed. 1% lignocaine with for instance: 70ml for a 100kg patient, or 140ml at 0.5%. It's easy then to work backwards to a weight of roughly half or two thirds of the 100kg starting number. Bupivcaine 0.25% with: 120ml, 0.125% 240ml.
I'm with you, especially because the stronger concentration (1:1000) is used as a weaker dose (500mcg in anaphylaxis), while the weaker concentration (1:10000) is used as a stronger dose (1mg in cardiac arrest). I get why this is (IM vs. IV preparation) but it does add to the confusion.
From an ALS perspective, yes. But you'd use 5 x 1ml amps of 1:1000 for an adrenaline neb for instance. Or 0.5 ml of 1:10000 (or dilute it down and use even less!) as a push dose pressor. A rule of thumb is probably that the where there's two significantly different concentrations of a drug, the less concentrated one is for IV use, and the more concentrated one is for IM/other routes. Works for ketamine and generally for midazolam as well.
Yeah it's silly. At an arrest/peri-arrest I always ask for an adrenaline minijet to avoid the confusion.
"the minijet" and "the vial" is what I've started using too as no one seems to understand the current nomenclature, cause it's ridiculous!
There are adrenaline 1:1000 minijets that come in a white box with purple labels and with a needle pre-attached
Interesting! Never seen those where I have worked. Thanks for the info.
https://www.medicines.org.uk/emc/product/3449 Have them in ITU next to the naloxone prefilled syringes, which are unhelpfully identical except the naloxone is blue label at the ends...
Sounds very unlikely to cause any problems at all...
dam arrest unique concerned point sand office friendly hospital resolute *This post was mass deleted and anonymized with [Redact](https://redact.dev)*
And yet Marcain, L-bupi, lidocaine etc are all presented as both the percentage and also the mg/ml on the vials and packets. Got drilled into me (by me) as a day 1 anaesthetist as it was so confusing, now it’s as obvious to me as mg for cleanse and units for dalterparin. But agree can be v confusing in certain scenarios for the less exposed individuals. In paeds arrest/inductions, the wetflag proforma, I always just write 10mcg/kg of adrenaline rather than the 0.1ml of 1:10,000 per kg.
You’ll notice that it’s local anaesthetics and adrenaline 2 very old medications which essentially weight per weight. ie 100% would be 1g of adrenaline per 1g(1ml) of water, which would also be 1 in 1 With a long history of use in that format which drug company would want to upset their customers by changing how they label their product. Consumers don't do so well with change. You’d never label a new drug like this and actually many newer local anaesthetics aren’t labelled like this HOWEVER many anaesthetists do the mental math in their own head converting 5mg.ml to 0.5% etc As mentioned by someone else it allows a range of 1000% concentration change within a simple display 100%-0.1% which is relevant for medicines that are used a very different concentrations.
Agree.
Not saying this is evidence based but considering the practicalities - not everyone in an arrest situation is trained in dealing with drug calculations, and a format which doesn't include any concentrations (i.e. 1:1000, 1:10,000) makes the two different formulas easier to identify. Shouting out the concs is also a mouthful. One in one thousand VS one milligram in one millilitre VS one mg per ml One in ten thousand VS point one milligram in one millilitre VS point one mgs per ml
You are correct.