How do you make a spinal medication hypo/iso/ or hyperbaric?

[jd1572]

How do you make a spinal medication hypo/hyper/or isobaric? Specifically, how many milliliters of sterile water or dextrose would you add? I've been trying to find a good reference on how much dextrose or sterile water to add.

For example, my spinal kit comes with bupivicaine, so how much dextrose or sterile water could/should you add to that to make the medication hypo- or hyperbaric?

If I remember correctly, tetracaine comes in powder form, so how much dextrose or sterile water would you add to that for a hyper, hypo, or isobaric solution?

Also, does anyone do a spinal, get CSF return, and then mix the patient's CSF with the spinal local anesthetic before injecting it? Does this do anything to the baricity?

Thanks!

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[Bertelman]

The spinal bupiv in our kits is hyper. It comes in .75% dextrose.

I usually aspirate ~ .5cc CSF before injecting, so I guess you could say I am mixing, but really I just want to make sure I am in the space. Not really sure what you mean by "mixing" beyond the mixing inherent with confirming adequate CSF aspiration.

 

[pgg]

If I remember correctly, tetracaine comes in powder form, so how much dextrose or sterile water would you add to that for a hyper, hypo, or isobaric solution?

We have ampules of 2 mL of 10% dextrose. When I want a hyperbaric tetracaine spinal I use that so it works out to 20 mg of tetracaine in 2 mL D10, or a 1% hyperbaric solution..

Also, does anyone do a spinal, get CSF return, and then mix the patient's CSF with the spinal local anesthetic before injecting it? Does this do anything to the baricity?

A small aspiration to see the swirl and confirm the needle is intrathecal probably doesn't change baricity much. Pulling out CSF to mix with your solution will of course both dilute your drug and push its baricity toward isobaric.

 

[2ndyear]

Our spinal kits have 1% tetracaine, not in powder form, as well as D10. Equal volumes will get you 0.5% tetracaine and D5, with a specific gravity of 1.01 to 1.02, so reliably hyperbaric. Equal volumes with water gets 0.5% tetracaine with SG of less than 1, so hypobaric.

The kit we use also has hyperbaric lidocaine and bupivacaine. I can't think of any time I've made my own hyperbaric solution outside of tetracaine. If I want a relatively isobaric longer acting drug, then I will use 0.5% bupivacaine (SG 1.000-1.005) and adjust the dose to anticipated length with or without epi. Chloroprocaine 2% is a great short acting drug regardless of baricity (relatively iso).

Spinal baricity is one of those things that can be quite complicated to read about, but in practice is fairly easy. You just need to know what level you need and go from there. If you are below L1 you can do pretty much whatever you want. I keep it simple. 0.5% bupiv will do most total hips, knees, old fragile hip fractures, etc. I don't mess around with affected side down and what not. Above L1 (belly stuff or c sections) hyperbaric will move to the dependent area, T4-T8. You need some level above L1 for sections.

Mixing with equal volumes of CSF will get closer to isobaric, but don't get hung up on this point too much in practice. Pick a drug that is close to isobaric if that is what you want. Trying to dilute heavy bupivacaine with CSF would probably be an exercise in futility.

 

[Planktonmd]

Our spinal kits have 1% tetracaine, not in powder form, as well as D10. Equal volumes will get you 0.5% tetracaine and D5, with a specific gravity of 1.01 to 1.02, so reliably hyperbaric. Equal volumes with water gets 0.5% tetracaine with SG of less than 1, so hypobaric.

The kit we use also has hyperbaric lidocaine and bupivacaine. I can't think of any time I've made my own hyperbaric solution outside of tetracaine. If I want a relatively isobaric longer acting drug, then I will use 0.5% bupivacaine (SG 1.000-1.005) and adjust the dose to anticipated length with or without epi. Chloroprocaine 2% is a great short acting drug regardless of baricity (relatively iso).

Spinal baricity is one of those things that can be quite complicated to read about, but in practice is fairly easy. You just need to know what level you need and go from there. If you are below L1 you can do pretty much whatever you want. I keep it simple. 0.5% bupiv will do most total hips, knees, old fragile hip fractures, etc. I don't mess around with affected side down and what not. Above L1 (belly stuff or c sections) hyperbaric will move to the dependent area, T4-T8. You need some level above L1 for sections.

Mixing with equal volumes of CSF will get closer to isobaric, but don't get hung up on this point too much in practice. Pick a drug that is close to isobaric if that is what you want. Trying to dilute heavy bupivacaine with CSF would probably be an exercise in futility.

Wow, a spinal kit that has Tetracaine, hyperbaric Lido and Bupivacaine!
I don't think I've ever seen that.

 

[dfk]

How do you make a spinal medication hypo/hyper/or isobaric? Specifically, how many milliliters of sterile water or dextrose would you add? I've been trying to find a good reference on how much dextrose or sterile water to add.

For example, my spinal kit comes with bupivicaine, so how much dextrose or sterile water could/should you add to that to make the medication hypo- or hyperbaric?

If I remember correctly, tetracaine comes in powder form, so how much dextrose or sterile water would you add to that for a hyper, hypo, or isobaric solution?

Also, does anyone do a spinal, get CSF return, and then mix the patient's CSF with the spinal local anesthetic before injecting it? Does this do anything to the baricity?

Thanks!

i personally have only had liquid 0.75% marcaine with epidural/SAB kits. FWIW: dextrose = hyperbaric; NS0.9% = isobaric; sterile water = hypobaric.
as for your last part, i am interpreting that you are wondering if people use the 'swirl' as an indicator. i do it always, however have heard that this is, and is not good practice (diluting the SAB dose/volume/effect)...

 

[urge]

I have never used tetracaine. In fact, I have never even seen it. 🙁

All I know about that drug is that it sucks. I would rather rely on an epidural.

 

[lobelsteve]

I used Articaine last week for the first time. Patient documented allergy to lido and bupi, was unsure of others but her dentist had been using Articaine without issue. I had to order some and it came in dental cartridges. It took an 18G in the bottom and a 22G 3.5" to push down on the plunger just to load it up in my syringes.

I used it for local and medial branch blocks.

 

[2ndyear]

Wow, maybe we have weird spinal kits or something! Our kits in residency had the tetracaine as well. They did not have the hyperbaric lidocaine. I can't say I use tetracaine often. I tried it in residency just to try it, but now the only time I may think about it is in long vascular cases. The sensory block can be less predictable with tetracaine and I can get a lot of mileage out of isobaric bupivacaine with epi 0.2 mg.

 

[Planktonmd]

I used Articaine last week for the first time. Patient documented allergy to lido and bupi, was unsure of others but her dentist had been using Articaine without issue. I had to order some and it came in dental cartridges. It took an 18G in the bottom and a 22G 3.5" to push down on the plunger just to load it up in my syringes.

I used it for local and medial branch blocks.

Your patient had a reaction to 2 Amide local anesthetics.
This drug (Articaine) is an amide that also contains an ester group, which means that it is metabolized by both the liver and the plasma cholinesterase.
It seems to me that a drug that has both an ester and an amide group might cause an allergy in people who have allergies to either one, and the fact that this patient did not react to it makes you think that she might not be allergic to either one, and that she might actually be allergic to the Paraben preservative.
It might have been enough to use any preservative free local anesthetic after a negative skin test.