Low flow is better at decreasing waste since you're not pushing out agent molecules as quickly to the scavenger.
Climate Alarmists: Volatile Anesthetics Must Be Abandoned
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deleted875186
Yes, plus they have done studies of peds inductions with high versus low flow and it’s not that much different. Yoj go to low flows, and just crank the dial up.
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Because minute ventilation is low: there's no point dialing 8L/min when the kid has a minute volume of 4.
Minute ventilation is a product of tidal volume and respiratory rate, not anesthesia machine fresh gas flow.
You don't need to have fresh gas flow any higher than replacement of consumed oxygen and losses from leaks (cuff, circuit, metabolism of vapor), regardless of pediatric/adult minute ventilation requirements.
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Power statement!
Can you provide references pls. What did the studies consider high vs low flows?
This might be true for maintenance but not for induction. You need higher flows to prevent rebreathing and dilution of inhaled vapour.
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deleted126335
Actually, on the older machines Fresh gas flow rates did affect minute ventilation. In our practice, the last of these machines was phased out about a dozen years ago. I saw one of these in a veterinary office just a few years ago.
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deleted162650
We've still got a couple of those old narcomeds at one of our hospitals where the tidal volumes change when you change the FGF. Drives me nuts.
They even still have the Halothane vaporizers attached (dry obviously).
It's always amusing to see our fresh grad new hires walk into one of those rooms for the first time and no have idea WFT they're looking at.
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In mechanical ventilation not SV
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deleted875186
Error - Cookies Turned Off
There was another paper I remember but I will have to see if I can find it.
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deleted875186
Comparison of low‐fresh gas flow technique to standard technique of sevoflurane induction in children—A randomized controlled trial
Summary
Background
Although sevoflurane is preferred for inhalational induction in children, financial and environmental costs remain major limitations. The aim of this study was to determine if the use of low‐fresh gas flow during inhalational induction with sevoflurane could significantly reduce agent consumption, without adversely affecting induction conditions.
Methods
After institutional ethical committee approval, 50 children, aged 1‐5 years, undergoing ophthalmic procedures under general anesthesia, were randomized into two groups—standard induction (Group S) and low‐flow induction (Group L). A pediatric circle system with 1 L reservoir bag was primed with 8% sevoflurane in oxygen at 6 L min−1for 30 seconds before beginning induction. In Group S, fresh gas flow was maintained at 6 L min−1until the end of induction. In Group L, fresh gas flow was reduced to 1 L min−1 after applying facemask (time = T0). In both groups, sevoflurane was reduced to 5% after loss of eyelash reflex (T1). Once adequate depth of anesthesia was achieved (regular respiration, loss of muscle tone, and absence of movement to trapezius squeeze), intravenous access was secured (T2), followed by insertion of an appropriately sized LMA‐Classic™ (T3). Heart rate and endtidal sevoflurane concentration were measured at each of the above time points, and at 15 seconds following laryngeal mask airway insertion (T4). The total amount of sevoflurane consumed during induction was recorded.
Results
Sevoflurane consumption was significantly lower in Group L (4.17 ± 0.70 mL) compared to Group S (8.96 ± 1.11 mL) (mean difference 4.79 [95% CI = 4.25‐5.33] mL; P < 0.001). Time to successful laryngeal mask airway insertion was similar in both groups. There were no significant differences in heart rate, incidence of reflex tachycardia, or need for rescue propofol.
Conclusion
Induction of anesthesia with sevoflurane using low‐fresh gas flow is effective in reducing sevoflurane consumption, without compromising induction time and conditions.
Summary
Background
Although sevoflurane is preferred for inhalational induction in children, financial and environmental costs remain major limitations. The aim of this study was to determine if the use of low‐fresh gas flow during inhalational induction with sevoflurane could significantly reduce agent consumption, without adversely affecting induction conditions.
Methods
After institutional ethical committee approval, 50 children, aged 1‐5 years, undergoing ophthalmic procedures under general anesthesia, were randomized into two groups—standard induction (Group S) and low‐flow induction (Group L). A pediatric circle system with 1 L reservoir bag was primed with 8% sevoflurane in oxygen at 6 L min−1for 30 seconds before beginning induction. In Group S, fresh gas flow was maintained at 6 L min−1until the end of induction. In Group L, fresh gas flow was reduced to 1 L min−1 after applying facemask (time = T0). In both groups, sevoflurane was reduced to 5% after loss of eyelash reflex (T1). Once adequate depth of anesthesia was achieved (regular respiration, loss of muscle tone, and absence of movement to trapezius squeeze), intravenous access was secured (T2), followed by insertion of an appropriately sized LMA‐Classic™ (T3). Heart rate and endtidal sevoflurane concentration were measured at each of the above time points, and at 15 seconds following laryngeal mask airway insertion (T4). The total amount of sevoflurane consumed during induction was recorded.
Results
Sevoflurane consumption was significantly lower in Group L (4.17 ± 0.70 mL) compared to Group S (8.96 ± 1.11 mL) (mean difference 4.79 [95% CI = 4.25‐5.33] mL; P < 0.001). Time to successful laryngeal mask airway insertion was similar in both groups. There were no significant differences in heart rate, incidence of reflex tachycardia, or need for rescue propofol.
Conclusion
Induction of anesthesia with sevoflurane using low‐fresh gas flow is effective in reducing sevoflurane consumption, without compromising induction time and conditions.
Thx. The circuit was primed for 30s. I see what they did there...Error - Cookies Turned Off
onlinelibrary.wiley.com
There was another paper I remember but I will have to see if I can find it.
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I'm imaginging one of my bosses straight-up thinking I plan to gas induce someone with my maintinence flows of ~0.3. Like I'm the special education trainee the college forced upon him.
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Doesn't matter - when alfaxalone gets approved for human use, we are all out of job anyway.
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deleted171991
This is for the nitrous haters: Penguin poop creates a buttload of laughing gas, researchers find
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It looks like they tried to market this before. Why did it failure the first time? (Over 30years ago)
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A brief Wikipedia lit review makes it look like it was originally dissolved in Cremophor, a surfactant that had high rates of anaphylaxis. So it wasn't an issue with the active ingredient. Always funny how things like that can totally taint a drug's future.
Alfaxalone - Wikipedia Under history section.
