Reader response

Myron Yaster MD

From Debnath Chatterjee, MD, FAAP, Professor of Anesthesiology, Children’s Hospital Colorado/University of Colorado.

Drs. Diane Gordon and Jeffrey Feldman have put together an SPA one-pager on Environmentally Responsible Mask Induction. To summarize:

1. Set the maximum fresh gas flow (FGF) to approximate the patient’s minute ventilation (~150 ml/kg). For small patients, mask ventilation skills are challenging at low flows.

2. Set FGF to use O₂ or O₂/Air only and avoid N₂O.

3. Reduce FGF when the exhaled anesthetic concentration approaches the inspired concentration. Monitor end-tidal anesthetic concentration to ensure adequate depth of anesthesia.

4. Priming the circuit can help speed the induction, but it must be done correctly to minimize pollution. Check out the one-pager for partial vs. complete priming techniques.

SPA one-pagers on a wide range of medical education, faculty development, sustainability, and wellness topics are posted on the SPA website under the education tab.

From Jonathan Blank MD

My personal experience with Sevo is that it’s a miracle drug. Well tolerated and of minimal risk. Its use to aid in rapid inhaled induction is also well documented.
I am older (I grew up with halothane) and still use Nitrous Oxide regularly. Upon induction I start with Nitrous and Oxygen in a 3/3 liter minute or 4-5/2-3 to increase efficiency. I then go straight to 8% sevoflurane. My observation is that sevoflorane smells the same at 2% as it does at 8%. I do this to commander the situation and ensure rapid loss of consciousness. I have seen the slower upward titration rates of sevoflurane on induction rate work successfully with older children but not so much with children under 5 or 6. But there are of course exemptions.

On the other hand, my younger colleagues are more likely to use 100% Oxygen at high flows and slowly raise the Sevoflurane. I switch on some air and sometimes nitrous and lower the flows to decrease drug waste and room pollution. Once induced I lower my flows to under 1 liter to minimize drug waste. And to maintain temperature.
It is interesting that different machines have such a major impact on induction.
I hope to read others thoughts and present experiences

From Gerald A. Bushman MD, Professor of Anesthesiology, Keck School of Medicine at USC, Anesthesia Critical Care Medicine, Children's Hospital Los Angeles

Having chosen the flow uncoupled technology for now two generations of new anesthesia machines across our practice, it is clear that even experienced practitioners fail to understand the technology and the clinical implications of the Drager design on the speed of onloading and offloading of volatile gases, the appearance of the capnograph tracing in small patients, and the accuracy of ET gas monitoring.

In my opinion, the clinical implications of each of these intrusions into the expected behavior of the machine are important to safe and efficient patient care but are even more critical as teaching points to trainees in anesthesia who may have only the most vague understanding of the foundations of anesthesia that are part of the toolkit of more experienced practitioners.

Regarding the dynamics of inhalation induction, overpressurization seems to make the ET gas measurement appear to be accurate but it is likely a vaporizer bias, because during the emergence from anesthesia the inability to accomplish "overpressurization" of offloading results in the Sevo concentration rapidly decreasing to zero while the patient has unmistakable clinical evidence (respiratory mechanics and tidal volume during spontaneous breathing and response to an unpleasant stimulus such as a Larson maneuver (no response versus purposeless response versus purposeful response) that they are still Stage II or a plane of Stage III. A careful model of the gradient between the partial pressure of volatile gas in the uncoupled circuit relative to the respiratory tree during induction and emergence would be a welcome clarification of this reproducibly observable phenomenon. I suspect the machine cannot possibly accomplish the wide gradient seen in the flow coupled machine that is associated with predictably rapid onloading and offloading of gas and apparent coherence of the ET MAC with the clinical appearance of the patient.

The slowness of wakeup can induce throughput pressure in our OR's with the predictable poor choices that may result from that.

It is disappointing that this device issue is not more robustly discussed in the literature and not disclosed or explained by the manufacturer. The only articles that obliquely refer to the different behavior of the machine from a flow coupled device are in the MH literature discussing the prolonged washout required in preparing the machine for use in an MH susceptible patient.

PS from Myron: Over the past 10 years I’ve been concerned by the “arms race” by the anesthesia machine industry to make the anesthesia machine more and more like PICU ventilators (or retrofitting PICU ventilators into anesthesia machines). Do we really need this and its complexity? For those wanting to take a deeper dive (and this would make a great teaching moment) take a look at these articled in OpenAnesthesia

Anesthesia Breathing systems by Connor Malark BS, Henry Tomlinson MD, and Nicole McCoy MD

https://www.openanesthesia.org/keywords/anesthesia-breathing-systems/

Pediatric Ventilation: Anesthesia Ventilators by Drs Anthony Alexander and Jeff Feldman

https://www.openanesthesia.org/keywords/pediatric-ventilation-anesthesia-ventilators/?search_term=anesthesia%20machine

From Tom Mancuso MD Boston Children’s Hospital on Dr. Russ Raphaely and precision of language

My 3 favorite Russ quotes, that I use all the time on PICU rounds:

When the resident says: “The patient is off oxygen”. Invoking Russ, I reply with a smirk “Where is she from? I would die if I were off oxygen!”

“We sent the patient to the floor”…“You sent her to the floor? They don’t have beds?”

And of course “We tubed the patient” “why did you put the patient in a tube?”

From George Gregory MD retired…more on precision of language

“Data in Latin is plural…so it is incorrect to say there is no data…it should be there are no data…”

Resident: : “I’m bagging the patient…” George: “you bag garbage, you ventilate the lungs of the patient”.