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Macro drip set

Discussion in 'ALS Discussion' started by cointosser13, Jun 8, 2018.

  1. cointosser13

    cointosser13 Forum Crew Member

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    When uing a macro drip set (10 gtts/ml), is there really any difference between using a 18 G vs a 16 G? A 16 G has a max flow rate of 220 ml/min. But what about the macro drip set, doesn’t that have a certain flow rate (due to size of tube and resistance)? I didn’t see a “max flow rate” on the macro drip set package.
     
  2. Remi

    Remi Forum Deputy Chief Premium Member

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    I can't say that I've ever looked closely, and it probably varies by manufacturer, but the lumen in the top of the drip chamber is probably significantly larger in diameter than a 16g or even a 14g IV catheter. And remember you only need a small increase in diameter to get a big increase in flow. Have you ever seen IV fluid run wide open through large-bore access (or into a trash can) such that there were no drips, just constant flow through the drip chamber? That tells you that the chamber is capable of pretty high flow rates.

    That said, just keep in mind that there are a lot of variables that determine flow rate. The length of the IV tubing has an impact, as does the length of the IV catheter and the length and diameter of any saline lock or extension tubing being used. Among other things.
     
    DesertMedic66 likes this.
  3. climberslacker

    climberslacker Forum Crew Member

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    The macro set will not reduce flow-rates significantly. However with the majority of locks, they will reduce it to roughly the flow rate of an 18g. I work for a service without locks but in your suspected massive hemorrhage patients, you should skip the lock and go straight to the catheter with the macro set.
     
  4. cointosser13

    cointosser13 Forum Crew Member

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    My bad, I meant the IV lock not the macro set. Don’t most IV locks have a set flow rate? If you guys can give me numbers or studies, I would love it. Just trying to prove to a friend of mine that it really doesn’t matter if you use a 18G vs 16G - the IV lock can only have so much fluid run through it at one given moment.
     
  5. Akulahawk

    Akulahawk EMT-P/ED RN Community Leader

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    Where I work, I currently use one of two types of lock sets. One is a two-lumen set that allows me to connect two primary lines to a single catheter and the other is a "standard" single-lumen set that basically is an 8" extension set that only allows me to connect a primary line to the catheter. What I have seen is the two-lumen extension set does have a slightly smaller bore than the primary line or the single lumen extension set and as such it does slow flow rates just a little bit. Using a 20g catheter and the two-lumen set, I have noted it takes about 43 minutes to completely empty a 1 liter bag of saline whereas using the slightly larger bore single-lumen set (or direct connect a primary line to the catheter) it only takes 38 minutes. With an 18g catheter, I have noticed the times are about 36 minutes and 28 minutes respectively. So, there is a difference in flow rates depending upon which extension set used. I very rarely will place a catheter bigger than an 18 so I do not have much experience with flow rates using those catheters with either extension set, not enough to make a reasonable generalization about how long it takes to drop 1 liter.
     
  6. VFlutter

    VFlutter Flight Nurse

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    The limiting factor is almost always the "J Loop" or extension. IV tubing should flow as fast as you will ever need for a PIV, especially with a pressure bag. If you truely need high flow then hook the IV tubing directly to the hub of a large bore IV. Or use a stop cock, preferably one with a yellow top, if you need to push meds or disconnect quickly.

    Remember that very few patients truely need rapid infusion but for those that do, do it right.

    I think Bioconnector refers to a standard anti-reflux valve. I would assume extension sets would be even slower.
    [​IMG]
     
  7. Peak

    Peak ED/Prehospital Registered Nurse

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    Like others have said much of this depends on what equipment you use, but yes a 16 gauge angio can flow much quicker than a 18. Our buff caps are high flow, we typically directly connect them to the angio and then connect our administration sets, we don't usually use extension sets on large bore IV access; using a high flow stopcock or directly connecting the administration set would decrease resistance.

    I have seen various buff cap designs that do very significantly slow down flow rates, including those used by some of the other local EMS and hospital systems. If these were all that we had supplied I would opt to directly connect the drip set every time.
     
  8. NPO

    NPO Forum Deputy Chief

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    A 3-way stopcock is a nice alternative. It's far less restrictive than a traditional saline lock, but still affords you some convince.
     
  9. NomadicMedic

    NomadicMedic EMS Edumacator

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    While this is a good discussion, isn’t it really just academic? We’re not pounding fluid to patients like we used to and if you really need to rapid bolus fluid, you should be using a larger bore (18g or bigger) cath and a pressure infuser.
     
    hometownmedic5 likes this.
  10. hometownmedic5

    hometownmedic5 Forum Asst. Chief

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    About the only time I think you’d see a return on the investment of committing this to memory is if you have the opportunity to debate some meat whistle still stuck in to 80’s EMS mentality with twin 14’s running like a Kenyan on marathon day.

    We know we shouldn’t be hammering 99.9% of patients with crystalloids(and the remainder is high surface area burn patients that aren’t likely to be in our care long enough to get too deep into parkland anyway, and even with extreme examples aren’t going to need buckets of fluid in the first hour anyway), so the flow rates between our stocked angios, locks, and admins sets becomes little more than the EMS version of arguing engine displacement at the bar.
     
  11. NPO

    NPO Forum Deputy Chief

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    Parkland?! Who is still using parkland?!
     
  12. hometownmedic5

    hometownmedic5 Forum Asst. Chief

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    It’s still being taught, so it must still be in use somewhere, along with backboards, lasix, and so on...
     
    NPO likes this.
  13. Remi

    Remi Forum Deputy Chief Premium Member

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    Or we could start to catch up with the rest of medicine and realize that having a solid understand of how your equipment works is a good thing.

    No one said anything about memorizing anything or slamming large volumes of fluid or arguing over any of it.
     

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