Diary of a Lost Student: From Theory to Practice -Foundational Anesthesia Concepts for All Providers

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The Shunt Equation: Why More Oxygen Won't Fix True Shunt

Every arterial blood gas is a mixture of two streams — blood that saw ventilated alveoli and picked up oxygen, and blood that skipped them entirely. The shunt equation solves for what fraction came from the second stream.

This episode covers: the mass-balance algebra of Qs/Qt = (CcO₂ − CaO₂) / (CcO₂ − CvO₂); PAO₂ versus PaO₂; why normal shunt sits near 5% and anything above 10% is pathologic; true shunt versus V̇/Q̇ mismatch; the FiO₂ test; mixed venous sampling and why cardiac output changes the answer; the Riley–Cournand history; the perioperative causes — atelectasis, pneumonia, hemothorax, ARDS — and the anatomic ones: PFO, ASD, VSD, pulmonary AVM; and why PEEP — not more oxygen — is the response to true shunt.

Against true shunt, extra FiO₂ is shouting at a room no one is in.

Key Takeaways

• Qs/Qt = (CcO₂ − CaO₂) / (CcO₂ − CvO₂) — the shunt fraction.

• PAO₂ is calculated. PaO₂ is measured.

• Normal shunt ≈ 5% — thebesian and bronchial veins. Above 10% is pathologic.

• True shunt ignores FiO₂. V̇/Q̇ mismatch doesn't.

• FiO₂ test: PaO₂ above 200 on 100% oxygen suggests mismatch; below 200 suggests true shunt.

• Anatomic shunts — PFO, ASD, VSD, pulmonary AVM — ignore FiO₂ too.

• A falling cardiac output deepens hypoxemia from an unchanged shunt.

• PEEP reopens the lung. More oxygen doesn't.

Timestamps

00:00 — Two pipes, one mixing chamber

01:53 — The equation, term by term

03:14 — PAO₂ versus PaO₂

04:06 — Normal shunt and the 10% line

04:19 — True shunt versus V̇/Q̇ mismatch

05:08 — The FiO₂ test

05:24 — Why cardiac output changes the answer

05:56 — Riley, Cournand, and Swan-Ganz

06:48— From Theory to Practice

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0.9% Sodium Chloride: The Drug We Give Without Thinking (Free Preview) | Anesthesia Drug Compendium Series

Normal" saline is not normal. Plasma runs Na⁺ ≈ 140 and Cl⁻ ≈ 100; the bag holds 154 of each at 308 mOsm/L. The supraphysiological chloride — half again above normal — defines everything modern medicine worries about in the bag.

This episode covers: the 1832 cholera outbreak that invented IV fluid resuscitation, Hamburger's 1896 red-cell experiments that gave us the "0.9%" (and overshot the true isotonic value), hyperchloremic metabolic acidosis via the Stewart strong-ion-difference mechanism, the 2018 SMART and SALT-ED trials, and the three jobs no balanced crystalloid does better than normal saline.

The full episode, available on Supercast >>> https://diaryofaloststudent.supercast.com/

Timestamps

00:42 — "Normal" is not normal

01:16 — The modern formulation

01:40 — The full episode continues on Supercast...

Full Episode

The complete saline episode — is on Supercast https://diaryofaloststudent.supercast.com/

If this made something click, leave a 5-star rating and follow the show. That's how other anesthesia providers — residents, SRNAs, SAAs, CRNAs, and anesthesiologists — find it. New episodes every week.

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Massive Transfusion Protocol: The 1:1:1 Ratio, and the Diamond of Death | Anesthesia Clinical Concepts

Ten units of red cells in 24 hours. That was the old definition — arbitrary, borrowed because ten units approximates one adult blood volume. It never accounted for rate. A patient can lose half their volume in an hour and never reach ten units before they arrest. Massive transfusion is not a number. It is a physiology problem with a clock attached.

This episode covers the protocol from activation to deactivation — the ABC score, the 1:1:1 ratio, and what the PROPPR trial actually showed. Then the mechanism underneath: the lethal triad of hypothermia, acidosis, and coagulopathy, plus the fourth variable that turns a triad into a death spiral — ionized hypocalcemia from citrate. Viscoelastic testing, tranexamic acid, calcium, warming, and the team roles that decide outcomes.

Key Takeaways

• Massive transfusion is traditionally defined as 10 or more units of red cells in 24 hours. Modern practice favors dynamic criteria

• The ABC score uses four bedside variables — penetrating mechanism, positive FAST, systolic BP ≤90, heart rate ≥120. Two or more activates the protocol.

• Balanced resuscitation with a 1:1:1 ratio of plasma to platelets to red cells improves early hemorrhage control. The PROPPR trial showed no significant 24-hour mortality difference versus 1:1:2, but more patients in the 1:1:1 group achieved hemostasis and fewer died of exsanguination.

• The lethal triad — hypothermia, acidosis, and coagulopathy. Citrate is the fourth variable that creates the diamond. Every unit of blood carries citrate that binds ionized calcium. Hypothermia and hypoperfusion slow citrate metabolism, prolonging hypocalcemia and worsening coagulopathy.

• Transexamic acid works by blocking plasmin activation, preventing clot degradation rather than promoting clot formation.

• Rapid infusers warm and deliver 200–1,200 mL/min. Warming is not comfort — it is coagulation management.

Timestamps

00:00 — The falling wall

02:00 — 1:1:1 ratio

02:36 — The lethal triad and the diamond of death

03:33 — Calcium, Transexamic Acid, Cryoprecipitate

04:10 — The rediscovery of balance

05:05 — PROPPR Trial

05:31 — From Theory to Practice

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Phase 2 Conjugation: Glucuronidation and Why Some Drugs Last Longer | Anesthesia Foundational Concepts

Imagine trying to catch a very slippery fish with your bare hands. It keeps slithering away. Now imagine someone glues a heavy, easy-to-grip handle onto the fish. Suddenly you can catch it.

That is conjugation. Fat-soluble drug molecules are the slippery fish — they slip through the kidneys, get reabsorbed, and stick around in the body. Phase II enzymes glue a polar handle onto each drug molecule, usually glucuronic acid, and the resulting compound is water-loving enough for the kidneys to grab and flush out.

This episode covers how that works, why almost every drug needs chemical alteration before it can leave the body, the difference between Phase I and Phase II and the role of glucuronidation. Then it follows conjugation to the bedside, where two stories anchor almost everything anesthesiology needs to know.

Key Takeaways

• Phase II conjugation attaches a large polar group to a lipid-soluble drug so the kidneys can excrete it.

• Glucuronidation is the busiest pathway.

• Morphine is the famous exception.

• Morphine-6-glucuronide (M6G) is roughly twice as potent as morphine at the μ-opioid receptor and accounts for about 10 percent of metabolites.

• Acetaminophen overdose works through the same machinery. Glucuronidation and sulfation saturate, more drug shunts through CYP2E1 to NAPQI, glutathione depletes, and NAPQI binds hepatocyte proteins. N-acetylcysteine replenishes glutathione so conjugation of NAPQI can resume.

• Phase II is relatively preserved in liver disease.

• Newborns have immature UGT capacity. That shortfall is behind neonatal jaundice.

Timestamps

00:00 — The slippery fish

01:17 — Two fates, two phases

02:00 — Phase I versus Phase II

02:30 — Glucuronidation and the other tags

03:17 — Immature at birth: jaundice and gray baby

03:46 — The exception: morphine-6-glucuronide

04:55 — From Theory to Practice

05:06 — Morphine and renal failure

06:09 — Acetaminophen and NAPQI

07:19 — One habit of mind

If this made something click, leave a 5-star rating and follow the show. That's how other anesthesia providers — residents, SRNAs, SAAs, CRNAs, and anesthesiologists — find it. New episodes Tuesday and Friday.

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INTRALIPID 20%: The Lipid Emulsion That Reverses LAST (Free Preview) | Anesthesia Drug Compendium Series

The same bag of fat that feeds the sickest patients is the antidote that restarts a poisoned heart. It was built to feed people — the world's first safe intravenous fat, a soybean-oil emulsion held in water by egg-yolk phospholipid, developed by the Swedish biochemist Arvid Wretlind at the Karolinska Institute and approved in 1962 after a decade spent taming the toxicity of the fat solutions that came before it.

Intralipid 20% is a milky white emulsion of 20% soybean oil, 1.2% egg yolk phospholipids, and 2.25% glycerin.

The full episode, available on Supercast, goes underneath: How it was discovered, the mechanism and dosing and exactly how a bag of nutrition restart and feeds a poisoned heart and Key Takeaways.

Timestamps

00:00 — The miracle of a bag of fat

01:35 — The full episode continues in Supercast....

FULL EPISODE

The complete Intralipid 20% episode — is on Supercast:

https://diaryofaloststudent.supercast.com/

If this made something click, leave a 5-star rating and follow the show. That's how other anesthesia providers — residents, SRNAs, SAAs, CRNAs, and anesthesiologists — find it. New episodes Tuesday and Friday.

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Local Anesthetic Systemic Toxicity: The Signal Jammer You Have to Recognize Early | Anesthesia Clinical Concepts

LAST is rare — roughly 0.27 episodes per 1,000 peripheral nerve blocks — but when it happens, it is one of the few true emergencies in anesthesia where the clock, not the diagnosis, decides who lives.

The reason it kills is not that it is hard to treat. It is that it is hard to see. AUnder sedation or general anesthesia, the classic neurologic prodrome — circumoral numbness, metallic taste, tinnitus, agitation — is gone. All you have is a patient who suddenly does not look right.

This episode covers the mechanism, the history, and the response. It talks about the ASRA response and the ASRA-modified resuscitation protocal.

One last point that saves lives: up to a quarter of patients can relapse. Highly lipophilic agents redistribute and produce delayed recurrence. Observe long enough after apparent recovery to catch it.

Key Takeaways

• Under sedation or general anesthesia, the neurologic prodrome may be absent. Isolated cardiovascular collapse can be the first sign.

• Intravascular injection produces symptoms in one to three minutes. Overdose may peak at twenty to thirty minutes.

• Mechanism: sodium channel blockade. At toxic concentrations, that block reaches the myocardium — reduced action potential duration, bradycardia, hypotension, collapse.

• Treatment order: stop injecting, call for help, 100% oxygen, benzodiazepines for seizures, 20% lipid emulsion early for serious LAST.

• Lipid emulsion dosing: 1.5 mL/kg bolus over one minute, then 0.25 mL/kg/min. Double to 0.5 mL/kg/min if blood pressure remains low. Cumulative ceiling roughly 12 mL/kg.

• ASRA-modified resuscitation: avoid large epinephrine doses, vasopressin, calcium channel blockers, and beta-blockers — they may worsen toxicity.

• Relapse is real. Up to 25% of patients develop recurrent toxicity. Observe long enough after apparent recovery to catch it.

Timestamps

00:00 — The signal Jammer

01:52 — One trick pony

02:35 — First, the brain, then the heart

03:26 — Bupivicaine: the one to fear

04:22 — The safer cousins

04:36 — Antidote is not a channel drug but fat

05:01 — History: a single alarmed editorial

06:58 — From Theory to Practice

08:46 — The ASRA Sequence

09:26 — The price tag on every local anesthetic

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Tochen's Formula: Neonatal Endotracheal Tube Depth, Explained | Pediatric Anesthesia Concepts

A term newborn's entire trachea is about four centimeters long — shorter than your thumb — and the tube tip has to stop in the middle of it, below the vocal cords and above the point where the airway splits to the two lungs. That leaves a safe window measured in millimeters: an error of a single centimeter drives the tip down a mainstem bronchus, ventilating one lung, or back up through the cords and out. Tochen's formula is the elegant answer to that narrow target: the depth to insert an oral tube, measured at the lip, is simply the infant's weight in kilograms plus six.

This episode covers — the single 1979 study, how to use Tochen's formula to get it right on the first attempt, required confirmations and primary checks, updates to the Neonatal Resuscitation Program guidelines, and how it relates to everyday practice.

Key Takeaways:

• Tochen's formula is the elegant answer to that narrow target: the depth to insert an oral tube, measured at the lip, is simply the infant's weight in kilograms plus six.
• It pairs naturally with the vocal-cord depth marker many neonatal tubes carry
• Goal: you want it mid-trachea, around the first or second thoracic vertebra on an X-ray, halfway between the cords and the carina.
• Confirm with symmetric chest rise, listen for equal breath sounds in both axillae, look for a sustained capnography trace, and get an X-ray.
• Neonatal Resuscitation Program's 7th edition in 2016 stepped back from weight-plus-six as its primary method, adopting instead a gestational-age insertion-depth table and the nasal-tragus length.

Timestamps

00:00 — The narrow landing strip

02:12 — The 7-8-9 rule

03:04 — Trachea length to body weight

03:34 — Primary tube confirmation

03:52 — Head-dependance link

04:33 — A single 1979 study

06:06 — From Theory to Practice

07:35 — Know where the rule frays

08:46 — An emblem of good Pediatric practice

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Dantrolene: The Only Drug That Stops Malignant Hyperthermia at Its Source

You shut off the volatile, pour on the cooling, chase the acidosis and the soaring potassium — and a jammed calcium channel deep in the muscle keeps emptying its stores into the cell anyway. In malignant hyperthermia, everything you do buys time. One drug reaches the leak itself.

Dantrolene binds the ryanodine receptor and shuts it — the only intervention that ends the crisis rather than managing it, and the reason a supply sits in every place on earth that delivers anesthesia.

The full episode, available on Supercast, goes underneath: why the gate fails to reseal in the first place, why no amount of cooling from outside can close it, how the dosing matches the danger, and why a molecule that does exactly one thing can reverse a catastrophe the whole body is feeding.

Key Takeaways

• In malignant hyperthermia, every intervention except one buys time rather than ending the crisis.
• Dantrolene binds the ryanodine receptor and stabilizes its closed state — the only drug that reaches the cause.
• The defect lives in the muscle's own calcium store. External cooling and buffering cannot reach it.
• No other drug in the crisis touches the cause. That's why a supply sits in every place that delivers anesthesia.
• Malignant Hyperthermia Hotline
  • North America: 1-800-644-9737 (1-800-MH-HYPER)
  • Outside of North America: 001-209-417-3722

  Provides 24/7 by the Malignant Hyperthermia Association of the United States (MHAUS).

Timestamps

00:00 — The fire you can't put out from outside

00:45 — The one drug that reaches the leak

01:35 — What the full episode answers

FULL EPISODE

The complete Dantrolene episode — the failed gate, the mechanism, dosing, and selectivity — is on Supercast:

https://diaryofaloststudent.supercast.com/

If this made something click, leave a 5-star rating and follow the show. That's how other anesthesia providers — residents, SRNAs, SAAs, CRNAs, and anesthesiologists — find it. New episodes twice a week.

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

Malignant Hyperthermia: Why ETCO₂ Rises Before Temperature

A single anesthetic trigger jams the muscle's calcium gate open, and metabolism runs away faster than the body can shed the heat — a rare inherited crisis, loud on the monitor before the skin ever warms, where minutes and Dantrolene decide the outcome.

This episode covers the mechanism — RYR1, CACNA1S, and the runaway calcium release that drives the storm — then follows it to the bedside. Also, why the anesthesia machine itself must be made safe, the trigger-free anesthetic, and why up to a quarter of patients relapse within a day.

Key Takeaways

• MH is a mutation in the skeletal-muscle calcium machinery
• The earliest sign is a rising end-tidal CO₂ that outruns any minute ventilation. Hyperthermia is a late byproduct of the heat, not the first sign.
• Dantrolene binds RYR1 and shuts the runaway calcium release at its source
• The anesthesia machine must be made safe.
• The trait is inherited. Definitive testing is the caffeine-halothane contracture test on fresh muscle biopsy, still the gold standard, alongside RYR1 genetic screening.
• Malignant Hyperthermia Hotline
  • North America: 1-800-644-9737 (1-800-MH-HYPER)
  • Outside of North America: 001-209-417-3722

  Provides 24/7 by the Malignant Hyperthermia Association of the United States (MHAUS).

  https://www.mhaus.org/healthcare-professionals/

Timestamps

00:00 — The jammed accelerator

01:36 — One gene, two triggers

02:26 — Why ETCO₂ rises before temperature

03:05 — Dantrolene releases the pedal

04:53 — Denborough, the pigs, and 1975

06:09 — From Theory to Practice

07:50 — Relapse, testing, and the family

If this made something click, leave a 5-star rating and follow the show. That's how other anesthesia providers — residents, SRNAs, SAAs, CRNAs, and anesthesiologists — find it. New episodes twice a week/

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Fick's Law of Diffusion: The Equation Behind Every Inhaled Anesthetic

Stuff spreads from where it is crowded to where it is not. Fick's law is that intuition written as arithmetic — and it governs every membrane in the body, from the alveolar wall between air and blood to the cell membrane between an anesthetic in your bloodstream and the neuron it needs to reach.

This episode unpacks each lever, then follows them to the bedside. Preoxygenation and apneic oxygenation. Why a volatile agent crosses more slowly in both directions when the membrane is compromised, so induction and emergence both drag. Why a recruitment maneuver or a little PEEP speeds a sluggish case back up. And why a widening alveolar-to-arterial oxygen gradient is the fingerprint of a membrane that has lost area or gained thickness.

Key Takeaways

• Diffusion runs down a gradient and spends no energy. The working anesthesia form: rate ∝ (A × ΔP × solubility) / (T × √MW).
• Five levers — surface area, gradient, thickness, solubility, molecular weight. Area, gradient, and thickness move the rate one-for-one; molecular weight moves it only by its square root.
• "Crosses faster" is not "faster onset."
• Preoxygenation is Fick's law in action
• In a healthy lung, oxygen transfer is perfusion-limited, not diffusion-limited. Disease flips it

Timestamps

00:00 — The pool and the fence

02:57 — Five levers, one equation

04:07 — Why CO₂ crosses faster than O₂

05:05 — The word that trips everyone: solubility

06:00 — Fick, Fourier, and a borrowed equation

07:07 — From Theory to Practice

07:20 — Apneic oxygenation and THRIVE

08:30 — When disease flips the levers

09:12 — Atelectasis, PEEP, and the sigh

If this made something click, leave a 5-star rating and follow the show. That's how other anesthesia providers — residents, SRNAs, SAAs, CRNAs, and anesthesiologists — find it. New episodes twice a week.