TILIF #16: From behind the ether screen

A surgeon observing a case today asked if it would be okay if he peered over the blood brain barrier. This was a tongue in cheek reference to the cloth drape that separates the sterile surgical field ("blood") from the head ("brain") of the patient, behind which the anesthesiology provider monitors the airway. The double meaning, is that the surgeons our glorified mechanics that deal with blood and the anesthesiologists are "the brains," doing a lot of physics, physiology and pharmacology, to keep the patient alive despite the surgeons best efforts to the contrary.

TILIF that the original name for this dividing drape was the "ether screen." The first widely used anesthetic was ether, a clear volatile liquid that quickly turns to a gas when not in an enclosed bottle. This is also the substance that you see depicted on TV and film by splashing a bottle onto a rag before holding the rag to a unsuspecting victim's face before they promptly fall asleep*.

So, back before we had well-controlled anesthesia techniques and form-fitting plastic facial masks, the ABSOLUTELY BONKERS standard of care was called "open drop" ether anesthesia. The anesthesiologist would simple drip ether slowly from a bottle onto a rag that was placed on the patient's face. As the liquid evaporated, the patient would breath it in and lose feeling/consciousness. You titrated the dose by... dripping it from the bottle faster or slower. But recall that there aren't any masks or tubes involved, which means that this gas is free to spread anywhere, including to the surgeons who may be quite close to the patient's face. To limit the intoxicating effects on the people with the knives, anesthesiologists started putting up a barrier to keep this heavier than air gas from wafting down the body. Interestingly, the anesthesiologists did not have any such protections,

*This would actually be pretty dangerous, as an overdose would cause the patient not just to pass out, but to stop breathing, likely for long enough to cause serious hypoxic injury.

TILIF #15: Testing 1... 2... 3...

Test #1: I'm (hopefully) done with my pediatric boards! As mentioned in my previous post, I took this 9-hour exam in mid-October and will hear back about if I passed at some point in the next several weeks. It was grueling but so was every other major exam I've taken up to this point, so here's hoping I survived. Next up, Pediatric Critical Care Medicine boards in 2024!

Apologies for the absence of blog posts in the past two months. I had planned to take some dedicated time off to study but then some serious family health issues came up that stopped me earlier than expected. I hope all three of my dedicated readers can forgive me.

Test #2: TILIF, towards the end of the major work of a spinal fusion surgery, the patient is briefly allowed to wake up to make sure they can still move all their limbs. This is crazy.

A spinal fusion is typically the last resort for kids with terrible scoliosis, where the spine weaves side to side like a big 'S'. The procedure it truly the goriest surgery I've ever seen.

{WARNING: Gross details ahead}

from Spinal News International at https://spinalnewsinternational.com
/depuy-synthes-receives-us-fda-clearance-for-cement-
augmented-pedicle-screw-systems/

The surgeons place the patient face down and then splay open the back, spreading apart the muscles to expose the spine. They then clip away the ligaments and extra pieces of bone to make space for their hardware. Next, bolts with slots in the heads are drilled into each side of the affected vertebrae. Then comes the hard part; you have to you have to weave the misaligned vertebrae onto the straight steel bar. This take A LOT of force - specifically the amount of force of two grown men putting all their weight onto some wrenches attached to a child's spine.

Right as they are starting on placing the second bar, the anesthesiologist turns off all sedation, with the hope of timing it such that when all the hardware (and bones) are in their final place, that the patient will briefly wake up just long enough to wiggle their finger/toes before being quickly re-sedated and then sewn back up. It is wild that we woke up a child with her spine fully exposed, just to ask her to wiggle her toes.

{End of gross details}

Test #3: The other test to monitor for nerve damage during spinal surgery is the aptly named intraoperative neurophysiological monitoring system whereby you place dozens of electrodes all over the body and monitor for electrical signals being transmitted by both sensory and motor neurons. It's finicky and prone to equipment problems, which is why the crude-but-effective method described above is also performed. The sensory nerves can be monitored continuously but the motor ones can only be tested by making the patient move. So once every 10 minutes or so, the technician asks the surgeons to hold off on cutting/hammering/cranking/etc for a few seconds to send a twitch pulse to all the electrodes and see the response as the patient briefly convulses.

Whenever a patient is brought to the PICU post-operatively, there is a verbal hand-off from the surgery and anesthesia teams to the PICU team. More than once I had received hand-off after one of these big spinal cases and been told what seemed like gibberish about them having "lost SEPs on part of the left leg, but had good movement during the wake-up test." Thanks to sitting in on this case today, I not only got another intubation attempt (which was successful, BTW) but also learned how orthopaedic and neurosurgery folks monitor for nerve damage in surgeries that often land patients in the ICU for a few days.

TILIF #14: Boardom

One of the many strange things about medical education is the seemingly random interval between the various standardized competency exams that you take along the way to becoming a fully licensed, board-certified physician. For example, your medical licensing exams happen in four parts: the first after two years of medical school, the next two after the third year of medical school, and the final test is taken up to a year after you've completed medical school. From there, the next big hurdle is becoming board certified by whichever medical board oversees your residency. Completing this signifies being able to practice independently in your chosen field. But some specialties have a multi-step board exam just like for medical licensing while others just require that you take your boards at some point following completion of your residency training.

The American Board of Pediatrics, for which I have recently become board eligible, gives us seven years post-graduation to take our board exam which is held on every year in mid-October. Generally, everyone aims to take the exam as soon as possible (so three months after graduating from residency), to allow the least time for forgetting the sorts of minute details that are ingrained into you during residency for this exam but that will rarely if ever come up during your day-to-day practicing of either general or specialty pediatrics. For most people, this means dedicating as much as possible of the three months after graduation to studying. If you're going into private practice, you might ask for a delayed start time or a extended vacation to properly prepare. If you're going into fellowship, most programs will allow for a lighter schedule during this time so that you can get this test out of the way and concentrate the remainder of your fellowship time on mastering the more specialized knowledge of that field.

Unfortunately, I have picked one of the very few fields where the luxury of taking it easy for a few months is not entertained. Pediatric critical care programs are easily some of the most clinically heavy fellowships out there. Most other fellowships expect you to spend approximately two of your three years on research projects to better establish yourself in the field and add to the collective knowledge of the discipline. In the pediatric ICU, we spend roughly 18 of our 36 months on service in the ICU, pulling 12-13 hour shifts with the occasional 25-hour in-house call.

In regards to this, I've been given some rather frustrating advice. Somehow I'm supposed to focus as much of my energy as possible on passing boards during these first three months. But I'm also trying to navigate that steep learning curve that comes with being immersed so fully in this completely new level of care. Thankfully there are pretty low expectations for a new fellow in regards to both knowledge and skill, so, if I don't mind playing the fool, I can coast on my current ineptitude until November. The real problem though is that the work that we're trying to do is to take care of very sick children, so giving it any less than your all really doesn't feel great, even if there are many other people to pick up the slack.

Rant over. I know it's not all that bad. I'm pretty sure there's a way to strike a reasonable balance; I just don't like to multitask in that way at work. Hopefully I figure it out soon!

TILIF: Thrombopoietin mimetics, are drugs that mimic the hormones that stimulate the production of platelets.

A "walking taco" is apparently a midwestern state fair and tailgating staple that involves taking a bag of nacho cheese Doritos or Fritos and pouring into it your favorite taco toppings. This makes it easy to carry one-handed, leaving the other hand available for an alcoholic beverage.

Elastance is a totally made-up-sounding word that means the opposite of (or, mathematically, the inverse of) compliance.

Neurally Adjusted Ventilatory Assist (NAVA) is a cool way of signalling a ventilator to give a breath in sync with a patient's natural breathing pattern. It involves placing a sensor down the patient's esophagus and detecting the nervous signals to the diaphragm that would normally trigger a breath. That way you know when an attempted breath is happening sooner than the traditional way of watching for pressure/flow changes through the vent tubing.

TILIF #13: ♬ ♫ ♪ I've got you under my skin ♪ ♫ ♬

Last Monday, I had my first successful solo arterial line placement! Woot!

One of the defining parts of the job description of an intensivist is being comfortable doing minor sterile procedures at the bedside. So, while we are not surgeons, we need to be able to place arterial and central venous lines and do the associated cutting and sewing. Just like with normal surgeries, our patients are usually asleep and family is usually not around, which means, just like with normal surgeries, there is often music playing!

I know this is not what is portrayed on most medical dramas, but most ORs are playing the spotify playlist of the most senior surgeon in the room. I've listened to classic rock, rap, pop, folk, classical, country. And you never know what the whims of any particular surgeon will be on any particular day.

It's a strange sort of status symbol to be the one in the room with a half-dozen people to get  to pick the music. You'll notice if an attending scrubs out of a case and lets the resident finish closing the wound (a tedious and not particularly technically difficult task), that the resident may get to pick the music for the remainder of the time.

Well, our procedures may not be as big of a deal, but we still can play music and this was the first time I had (a) put in a line by myself, and, more importantly, (b) been the one to pick the music. Once all of our sterile gear was opened and the patient was comfortably sedated, the nurse for the room pulled up YouTube on the patient's entertainment screen and asked, "What'll it be, doc?"

I was a bit nervous about the procedure and initially tried to defer to whatever anyone else wanted, but she ignored call-outs from the resident and the other supervising fellow in the room and made clear eye-contact with me indicating that this was as necessary as the safety "time-out" we had just completed. Well, I had been on a big band kick recently and decided that I might as well dive on in. "Frank Sinatra, please!" 

She was initially taken aback but then I got an approving nod. "Haven't heard that one before. I like it!" And just like that we had a Sinatra playlist setting the mood for my (very slow and very cautious) placing of this kid's arterial line. It was actually really nice. I know Frank like the back of my hand, so it was like having a familiar beat to perform to. My favorite part though, was when, after I had already successfully placed the line, and was suturing in place, the song I've Got You Under My Skin came on. "A little on the nose," I said to groans.

TILIF: Pulmonary vascular resistance (PVR) has really weird units. PVR is the resistance that blood must overcome to pass through the pulmonary vasculature. It is defined analogously to Ohm's law for electrical resistance (resistance = voltage/current), except voltage is the pressure gradient through the lungs and the current is the cardiac output. Pressure can be measured in mmHg and the cardiac output is L/min. So, while you could keep the units as a simple mmHg⋅min/L, by swapping things out for slightly dated units of force, you get units of dynes⋅sec/cm⁵, which is, for some reason, the continued standard. At some point people were annoyed with this convoluted and completely unintuitive mess and named an entirely new unit after one of the pioneers in PVR research, Paul Woods. So you will sometimes see PVR listed in WUs, or Wood's Units.

Apparently John Deere is a big deal in Iowa. John Deere, the person, founded his company in the appropriately named middle-of-nowhere town of Grand Detour, IL before moving operations to the Mississippi River in the IL/IA state-line-spanning Quad Cities area. Also, apparently there are several very regionally dominant farming companies that have prominent color associations reminiscent of college sports with the Americana brand-loyalty of mid-century car companies.

To give a patient a granulocyte (a type of white blood cell) transfusion, you need 24-48 hours of lead time. This is because these cells don't keep and have to be very closely matched to the recipient. So you need to find the appropriate donor, give them a medication that causes granulocyte cell overproduction, wait at least a day for it to work, then transport them to your patient.

TILIF #12: Yeah-huh tagbacks!

"Tag-g-g! You're it!" This was not what I was expecting when beckoned into my patient's room. He had been coloring with crayons and waved me into the room as I walked past.

There's an adage in pediatrics that, compared to adults, kids get sick faster. They have a lot of physiologic reserve, so they are fine... they are fine... they are fine... until they are not. Accordingly, if a patient suddenly looks worse on the general pediatric floors, don't ignore it - they may need the ICU and soon. But the corollary is that children often quickly turn the corner toward recovery too.

As kids get sicker and get better they are moved in and out of the intensive care unit. The move to "the unit" is usually pretty quick. We always have a bed or two ready to emergently accept patients and can speedily adapt our nursing distribution to cover the other patients while we stabilize the new kid. Moving to the general floors, however, can be a bit of a waiting game. The stars need to align to have an appropriate room, bed/crib, nurse, and doctor ready at the same time to safely transfer care. And there's less urgency because the child's clinical condition is necessarily stable or improving for them to be leaving the ICU. Worst-case scenario, the child is getting a higher level of care than they need while they wait to transfer.

As I reach to tag my patient back, he squirms away in his hospital bed and stutters, "No tag-g-backs!" I'm a little shocked that he had thought this through so well.

While we grumble about how long it takes to transfer kids out of the unit, sometimes it's nice to have a relatively healthy kid around for a while. After all, everyone in the PICU has trained in general pediatrics first, so we've played games to get our physical exam more painlessly, chatted about Paw Patrol and Frozen ad nauseum, gotten countless high-fives, and waved "bye-bye" leaving each room^*. When most of your patients are either heavily sedated or just too sick to have normal kid interactions, you have to take every opportunity to remind yourself what you're working so hard to restore to your patients: the simple joys of being a kid. 

I snap my fingers and facetiously say, "Drat!" I scan the otherwise empty room for someone else to tag.

"G-go g-get the n-nurse!" he says excitedly.

That morning, the unit had an honor walk. This is the solemn event when all the available staff in the unit line the hallways to bear witness to an organ donor being escorted by their family to the operating room. It is such a hard decision that no parent expects to have to make. To be an eligible donor, the organs must be in pretty good condition, so these are usually children that were healthy and vibrant a few days ago until some tragic circumstance changed everything.

In this horrible moment, we - and by "we" I mean very experienced social workers - ask these parents to consent to sending the body of their recently deceased child, still in the hospital bed on "life-support," to undergo one last surgery to scavenge the usable tissues and ship them out to other nameless patients in desperate need. We try to remain as neutral as possible while presenting the choice, so as not to bias them towards doing something they don't believe in or will regret. But everyone involved is hoping beyond hope that they will say yes. It is so tempting to walk these parents to the opposite hallway in the unit were a patient and their family has been waiting for months for a new organ - their only chance for continued survival.

As I run out of the room and towards the nurses' station, the patient's nurse looks up with mild concern. "What's going on? Do you need something?" she asks.

"I just needed to tell you that..." [I poke her shoulder] "you're it! No tag-backs!"

An honor walk is an emotionally taxing event to participate in. The ICU can usually pause for a moment, but it doesn't stop. Other patients need our help and they can't wait for us to collect ourselves before returning to the job at hand. The ICU is always in motion. There are always new kids coming in and improved ones going out. There are always unstable patients that you need to pass-off to the night team, who will pass them right back to you in the morning, having taken the next steps toward whichever outcome.

But even knowing the emotional toll that participating will take, when you have taken care of a patient that eventually has an honor walk, you kind of want to be there when it happens. You may have been with that family as they arrived, as they were told that their baby wasn't coming back from this, and sometimes (as was the case for me today) you may have been part of the team that did the brain death exam. When those patients head to the OR for the final time, you kinda hope to be stuck holding the hot-potato; you gladly allow yourself to be "it" in the game of Tag.

"What?!" the nurse yells, so that our patient can hear, giggling in his bed. She storms towards the room on faux-outrage, "You got the doctor to tag me?! Well, you're it again! No tag-backs!"

TILIF: The pores of Khon are connections between alveoli (tiny air sacs) in the lungs and appear around the second year of life. A similar structure called the canals of Lambert connect bronchioles (the smallest air tubes of the respiratory tree) to adjacent alveoli. The canals develop around age 6. These two structures allow for the passage of fluid and bacteria, possibly contributing to increased risk of pneumonia, but they also allow for connections between adjacent parts of lungs, which decreases the risk of lung collapse or atelectasis, which is seen more commonly in children than adults.

*Teenagers particularly enjoy when you wave bye-bye

TILIF #11: Class is in session... again!

Tuesday is lecture day for the PICU fellows. As we continue along the protracted, gradual transition from students to student doctors to doctors, dedicated didactic time decreases but never truly stops. In undergrad or early med school lectures were all day everyday. Then you start clinical rotations, and it becomes more sporadic, with lectures at the beginning of a rotation and a half day or two each week. In residency you have some sort of educational conference on most days, like morning report, noon case conference, grand rounds, morbidity and mortality (M&M) conferences in addition to a half day of protected didactic time per week.

The protected aspect is important, because it is easy to make excuses to take care of sick kids, or for other members of the care team to guilt you into putting lectures on the back-burner. But you still have a lot to learn and you will take care of your patients better if you dedicate some time to studying with your full attention*. As I move on to PICU fellowship, there are still hour-long lectures scattered throughout the week, but they are not protected - it's generally thought to be more educational to be at the bedside for a procedure or acute management of a critically ill child.

A fun thing about lectures this week is that they are PICU lectures! Each step from undergrad to now, it is really exciting to have the first few months of lectures. At the end of each the previous stage, you get quite comfortable with most of the content. Rarely do you get exposed to something you've never seen before; you either know it, or know you should know it.

Tuesday's lecture was considered quite basic and yet half of it might as well been a different language. And that's exciting! This is the time of my training that I am expected to know nothing, so I'm not going to disappoint anyone by honestly saying "I don't know" or asking "what does that term mean?" I have everything to learn and this stuff is really interesting to me, which is why I went into this field.

Original content by Christopher Monson - ok for non-commercial reuse

TILIF: The waveform of the arterial line can be super informative. Up until this point, I've really only cared about the accurate blood pressures and easily accessible arterial blood that you can get from having an arterial line in the patient. But if you graph the blood pressures over time, you get a wave that has even more information packed into, if you know how to interpret it.

I made a diagram (seen on the right)! In the red area, the blood pressure goes up as the heart squeezes blood out. In the blue area, the heart isn't able to push any harder, but the wave of blood needs time to spread out to the distant tissues. What about the squiggle in the green area? That's the "dicrotic notch" which is a little pulse of pressure radiating out through the arterial blood vessels caused by the aortic valve slapping closed, closing off the heart so that it can fill back up with more blood for the next beat. 

One cool thing about this notch is that it can tell you how far away your sensor is from the heart. The vessels by the head are relatively close to the heart, so the wave comes earlier - closer to the peak. Similarly, your arms see that pressure wave before the legs. By the time you reach the feet, the notch is all the was at the bottom of the downslope.

*Of course this is a "do as I say not as I do" moment, since I am usually falling asleep in my chair  during even the most riveting lecture

TILIF#10: Jury-rigger extraordinaire!

I love problem solving; more specifically, I love finding a way to use a limited set of tools or resources to find creative solutions to problems. I've always been drawn to this sort of activity: assembling custom Lego creations using the pieces from random old sets, building imaginary spaceship instrument panels out of the doodads from my dad's workbench, or playing Minecraft in survival mode where you need to harvest limited resources before you can construct anything.

That limitation fosters creativity and forces you to think outside the box. My favorite real-world example of this is depicted in the famous scene from Apollo 13, where the flight director gathers the smartest engineers at his disposal into a small room and dumps a box of parts on the desk, explaining that they need to find a way to fit a square tube into a round hole with only these supplies and then come up with a procedure so the astronauts can follow those instructions to fix the crippled spacecraft.

The ICU is always pushing the boundaries in medicine, so we often don't have the technology mass-produced to fix the problems we see. Often these kids have very unique problems. One of my favorite examples is chronically trach dependant kids who have a hole in their neck with a tube that goes in and takes a 90° turn into the trachea. As you might expect, such an unnatural connection between a foreign device and the body leads to funky changes to the tissues in the area (think earring hole mixed with a callus). Every tracheostomy tract is a little different and most kids need a custom tube that's a certain width, depth, length, flexibility, etc.

If that tube gets plugged up, suddenly the kid can't breath. Usually you can just replace the tube, but sometimes tissue damage can make that very difficult, so you may have to find creative ways to ventilate the patient. You can try passing a long flexible oral tube through the hole in the throat. You can essentially plug up the hole with your finger and use a bag-mask over their mouth (assuming their upper airway connects, which is not always the case!). You could even put a mask over their neck if you can get a good seal and plug up the mouth and nose. Whatever works!

One of the goals of fellowship is to accumulate a magic show's worth of tricks that you can adapt to any audience. It's amazing to see some of my attendings' ability to pull a rabbit out of a hat, even if they've only managed that trick once or twice... often in their fellowships.

TILIF: "Post-pump slump" is a phenomenon seen after children come off of cardiopulmonary bypass. When you are doing open heart surgery, you need to divert blood to a mechanical pump that keeps the blood oxygenated and flowing until you can put back together and restart the patient's heart. After these kids return to the PICU, you need to watch them closely - for lots of reasons, one of which is a period of low cardiac output that is not entirely understood but seen fairly frequently.