ICM TEACHES – Changing the way we think!

🧵Why does low protein intake cause hyponatraemia?

Most people find this confusing.

But the underlying physiology is beautifully simple.

Let’s walk through it 👇#Hyponatraemia #FluidBalance #MedTwitter #FOAMed pic.twitter.com/MvLZIwYfs9

— Turning the Tide (@Turningthe_Tide) July 7, 2025

🧵 Albumin in Critical Care: 70 Years, 700 Papers… Zero Benefit

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Albumin is the most studied fluid in critical care.
Decades of trials. Endless meta-analyses.
And yet – not a single clinically meaningful benefit.

Here’s why the entire theory collapses once you understand… pic.twitter.com/z1qes97PPG

— Ashley Miller (@icmteaching) November 24, 2025

🧵 "What really determines tissue perfusion?"

– and why most explanations get it wrong.

Let’s sort out MAP, CVP, CCP, autoregulation, vasopressors, and the flow that actually reaches your organs.
👇 pic.twitter.com/b7faVYLXsV

— Ashley Miller (@icmteaching) July 27, 2025

🧵 Thread: Why cardiovascular physiology feels confusing (even to experts)

Part 1 of my 'The physics of circulation' series

Cardiovascular physiology isn’t confusing because it’s complex.
It’s confusing because we routinely mix up description with causation. And our language… pic.twitter.com/PgrJv1tSjR

— Ashley Miller (@icmteaching) January 27, 2026

Pressure 🧵

The physics of circulation part 2

We use the word pressure constantly in medicine (blood pressure, filling pressure, perfusion pressure).
And we usually treat pressure as an agent.
It isn’t.👇 pic.twitter.com/rdOvuUxtOH

— Ashley Miller (@icmteaching) January 29, 2026

Flow 🧵

The physics of circulation part 3

We talk a lot about flow in cardiovascular physiology.
But our understanding is often weaker.

Flow isn’t a substance.
It doesn’t get pushed. pic.twitter.com/r6lRY9pbPU

— Ashley Miller (@icmteaching) January 31, 2026

Resistance vs Impedance 🧵

The physics of circulation part 4

We’re taught that resistance controls flow.

Sometimes that intuition works.
Often, in the circulation, it fails.

Here’s why. 👇 pic.twitter.com/1moFADJMWz

— Ashley Miller (@icmteaching) February 5, 2026

Afterload 🧵

The physics of circulation part 5

Afterload is tricky to understand.

It is not blood pressure.
It is not SVR.
It is not “how tight the arteries are.”

To understand it, we need to separate three things that are routinely blurred. pic.twitter.com/pKa9wnuSLj

— Ashley Miller (@icmteaching) February 16, 2026

Coupling 🧵

The physics of circulation part 6

In the last thread we described afterload as “how hard it is for the ventricle to eject”

Let’s sharpen that.

Mechanically:

Afterload = wall stress during ejection.

But whether the ventricle is appropriately matched to the… pic.twitter.com/LBWDfEBuLL

— Ashley Miller (@icmteaching) February 21, 2026

🧵 What drives blood flow – the heart or the vessels?

Eminent physiologists have argued this for decades.

The disagreement survives because of imprecise causality.

Here’s the resolution 👇 pic.twitter.com/7Xkq5ByDgC

— Ashley Miller (@icmteaching) December 21, 2025

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Most people think the heart drives circulation.
But what if that’s backwards?
Anderson’s model flips the whole idea of cardiac output on its head — and it changes how you think about fluid, flow, and failure.
🧵👇#physiology #FOAMed #MedTwitter #criticalCare #cardiacOutput pic.twitter.com/aRd20xVqyE

— Ashley Miller (@icmteaching) June 27, 2025

🧵 Preload is one of the most misleading terms in clinical physiology.
It shapes how we think, prescribe, and teach – but it’s wrong in all the ways that matter.
This builds on Saturday’s Starling’s Law thread ↓
🔗 https://t.co/dYJMFYH2nk

Let’s fix it 👇 pic.twitter.com/YX6d7PNMyj

— Ashley Miller (@icmteaching) July 10, 2025

🧵 Afterload, resistance, and why the heart isn’t “pushing against” pressure 👇 pic.twitter.com/FEwAb3gPfs

— Ashley Miller (@icmteaching) January 7, 2026

🧵What makes the blood go round?

And why does such a simple sounding question cause such heated arguments between physiologists?

Everyone agrees on the observations.
The disagreement is about causality. 👇#FOAMed #Physiology #MedX pic.twitter.com/CFUz5BFC6Z

— Ashley Miller (@icmteaching) December 17, 2025

🧵 Inlet impedance: the missing determinant of cardiac output
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What really limits cardiac output: the heart or the circulation delivering blood to it?
This question has sparked heated arguments between physiologists for decades.
To answer it, you first need to understand inlet… pic.twitter.com/ADO4D6ewpr

— Ashley Miller (@icmteaching) December 14, 2025

Left atrial “reservoir strain” (LARS) is usually taught as an atrial property.
That framing fails physiologically.
LARS is best understood as a signal of ventriculo–atrial coupling. pic.twitter.com/nYGE54yiKH

— Ashley Miller (@icmteaching) December 13, 2025

🧵 What is Critical Closing Pressure — and why does it matter for perfusion?

A thread to clear up one of the most misused and misunderstood ideas in circulatory physiology.
👇 pic.twitter.com/DtE1gK8VDt

— Ashley Miller (@icmteaching) July 29, 2025

Why I’m rethinking extubation timing in fluid-overloaded ICU patients (a physiology thought experiment 🧵👇 pic.twitter.com/vdHMEAgxb7

— Ashley Miller (@icmteaching) January 5, 2026

🧵 Why you cannot be oedematous and hypovolaemic at steady state

“Puffy but intravascularly dry”?

⚠️The most persistent myth in IV fluid therapy#FOAMed #physiology #MedX pic.twitter.com/OJFjOb11hW

— Ashley Miller (@icmteaching) November 14, 2025

1️⃣We talk endlessly about “capillary leak” – but most of what we say about it is wrong.

Here’s what actually drives fluid movement across the microcirculation – and why Starling’s model needed an upgrade. A 🧵👇 pic.twitter.com/r3V0ciCPyW

— Ashley Miller (@icmteaching) November 6, 2025

1️⃣
We can remove fluid at rates up to 12 mL/kg/h and blood pressure often holds.
That limit isn’t arbitrary – it comes from dialysis data showing steep rises in hypotension and mortality above it.
It marks the upper boundary of how fast plasma can be refilled from the… pic.twitter.com/aJb9yK3Uqm

— Ashley Miller (@icmteaching) November 9, 2025

🧵 Why it’s so hard for the body to get rid of IV fluid

1️⃣ Hook:
We talk endlessly about “fluid resuscitation” – but far less about how the body gets rid of excess fluid once we’ve given too much.
Here’s the physiological problem 👇#MedX #Physiology #Fluids pic.twitter.com/lrKHyf2rHW

— Turning the Tide (@Turningthe_Tide) October 25, 2025

https://t.co/yhFDiKmDlj

— Ashley Miller (@icmteaching) January 6, 2026

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Not all heart failure is low-output.
Sometimes the heart pumps harder than ever — and still fails.
High-output failure explained 🧵#FOAMed #MedX pic.twitter.com/ioJzEScz29

— Ashley Miller (@icmteaching) August 29, 2025

🧵 The Cardiac Function Curve — why it misleads (Part 1)
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The cardiac function curve is one of the most recognisable images in physiology.
Unfortunately, it’s also one of the most misdrawn, mislabelled, and misunderstood.
Let’s redraw it — and see what it really tells us about… pic.twitter.com/cDRMT5jO4z

— Ashley Miller (@icmteaching) October 10, 2025

🧵 Part 2 — The Venous Return Curve

1️⃣
Last time, we fixed the cardiac function curve.
Now let’s look at the other half of the story — venous return — and how the circulation really feeds the heart.#FOAMed #MedX #physiology pic.twitter.com/0wh0dEy8JS

— Ashley Miller (@icmteaching) October 13, 2025

🧩 Part 3 – Why you usually can’t move one curve without the other
1️⃣
So far, we’ve treated the cardiac and venous return curves as two lines that meet.
In theory, you can move one without the other – and sometimes that’s true.
But in physiology, they almost always move together… pic.twitter.com/3aV20c61iF

— Ashley Miller (@icmteaching) October 16, 2025

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SVR looks precise: (MAP – RAP)/CO.

But this neat number hides traps. It’s not “afterload,” it’s not pure “tone,” and sometimes it’s not even valid.

A thread on why systemic vascular resistance misleads — and when it still helps. 🧵 #MedX pic.twitter.com/WBNumH8m3G

— Ashley Miller (@icmteaching) September 16, 2025

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You might think:
"Why give NaCl to someone overloaded with salt and water? Shouldn’t we be pulling sodium out, not putting it in?"
🧂💧
It feels wrong — but correcting chloride can unlock natriuresis.
Let’s break the paradox. 🧵 pic.twitter.com/OpjS8MMu1l

— Turning the Tide (@Turningthe_Tide) June 8, 2025

🧵1/
Hypovolaemia is the most overdiagnosed concept in medicine.
We say it reflexively — especially in sepsis.
But here’s the uncomfortable truth:
We can’t measure blood volume.
We infer it.
Often wrongly.
Let’s unpack why that matters. 👇#MedTwitter #FOAMed pic.twitter.com/x2l76OvbMw

— Turning the Tide (@Turningthe_Tide) June 21, 2025

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IV fluids have two main purposes:
💧 To maintain daily needs
🔄 To replace losses

(We’ll come back to whether we should even use the term 'resuscitation' fluid in a future thread).

Let’s talk about maintenance fluids – when they’re needed, and when they’re not.

🧵 #MedX… pic.twitter.com/NXHUAdKExo

— Turning the Tide (@Turningthe_Tide) July 24, 2025

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Last time we tackled maintenance fluids – what the body needs day to day. https://t.co/l8xX11eiHs
Now let’s talk about replacement fluids – what to give when something’s been lost.
Same volume. Same composition. That’s the key.
Let’s keep it physiological. 💧

— Turning the Tide (@Turningthe_Tide) July 31, 2025

1/ 💉 Resuscitation fluids – life-saving in true hypovolaemia.

Give them for the wrong reason and you harm patients.

We’ve covered maintenance & replacement fluids — now the trilogy ends with resuscitation. Here’s how to get it right. #MedX pic.twitter.com/EirSmA1N52

— Turning the Tide (@Turningthe_Tide) August 15, 2025

1️⃣
Some patients with severe venous congestion have almost no oedema — and that’s confusing at first.
It only starts to make sense once you unpack the physiology. 👇 https://t.co/iOrlhwTXYg

— Ashley Miller (@icmteaching) October 6, 2025

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Why do we keep reaching for IV fluids, even when we have evidence they can cause harm?
It's not based on physiology — it’s cognitive bias.
🧵 pic.twitter.com/VKCI7X3S5p

— Turning the Tide (@Turningthe_Tide) September 12, 2025

We give fluids for problems they can’t fix — driven more by cognitive biases than physiology. Important thread from @Turningthe_Tide 👇https://t.co/Nhy5a9IL9Q

— Ashley Miller (@icmteaching) August 23, 2025

🧵 Hypertonic hyponatraemia: when low sodium isn’t a sodium problem

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Not all hyponatraemia is created equal.
Most cases are hypotonic – from too much ADH or too little solute (e.g. low protein states).

But high glucose causes hypertonic hyponatraemia – a water shift, not… pic.twitter.com/9Ro2WFP60E

— Turning the Tide (@Turningthe_Tide) July 19, 2025

💧Fluid creep accounts for more fluid than resuscitation in ICU.
But nobody prescribes it — and most don’t even notice it.
The truth?
🧨 Most ICU patients don’t need routine maintenance fluids.

Here’s what’s really going on 👇🧵 pic.twitter.com/VmDCVaX39a

— Turning the Tide (@Turningthe_Tide) July 13, 2025

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Shock isn’t “give fluids, then pressors, then inotropes.”
That recipe misses the physiology.
Here’s how to manage shock properly: 🧵#MedX #haemodynamics pic.twitter.com/T4AWzqgHVK

— Ashley Miller (@icmteaching) August 16, 2025

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Shock is complex. But our tools are often simplistic.
This paper proposes a new model:
🩸 Four circulatory interfaces that must stay coupled to maintain perfusion.
Uncouple any one — and shock worsens.#Shock #MedX #FOAMcc
Here’s the framework.
🔗 https://t.co/8xxEcdzYUw pic.twitter.com/YQhvW62MJZ

— Ashley Miller (@icmteaching) July 13, 2025

💉 “Give a fluid challenge — see if we can get the norad down.”

We’ve all heard it. Boluses are often given just to reduce vasopressor doses.
Why?
• Fear that pressors are harmful
• Pressure to keep patients off ICU
But topping up to drop the norad might not be the best move… pic.twitter.com/DjShOi9XUJ

— Turning the Tide (@Turningthe_Tide) July 9, 2025

🧵“Thresholds, consensus & physiology”

Decades of critical care research have produced few reproducible breakthroughs.
Maybe the problem isn’t our interventions — it’s that we reduce patients to syndromes, instead of treating them as individuals with distinct physiology.

— Ashley Miller (@icmteaching) September 4, 2025

🧵 Part 2. Heterogeneity vs Colliders in Critical Care RCTs

1. The puzzle

Critical care RCTs keep failing.
The usual explanation?
“Patients are too heterogeneous.”
That’s partly true — but there’s a deeper problem.

Part 2 of a 3-thread series on why ICU trials fail and why…

— Ashley Miller (@icmteaching) September 6, 2025

🧵 Part 3 — Why ICU RCTs fail (beyond colliders)

1. The puzzle

Decades of critical care RCTs.
Huge effort. Tens of thousands of patients.
Very few reproducible breakthroughs.
This is Part 3 of my series on why ICU trials fail — and why physiology must guide us. pic.twitter.com/IdQFJWWAwl

— Ashley Miller (@icmteaching) September 12, 2025

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Fluids can harm.
But fluids also save lives.
Let’s talk about the life-saving side of fluid therapy — from IV resuscitation in cholera to global oral rehydration campaigns. 💧🧵#MedTwitter #FOAMed #CriticalCare pic.twitter.com/urewwzQeRf

— Turning the Tide (@Turningthe_Tide) June 28, 2025

🧵 Starling’s Law: Misunderstood, Misapplied, and Still Misleading
1
🚨 “Starling’s Law explains how the heart increases cardiac output.”

You’ve probably heard this a thousand times.
But it’s wrong.
Or at least – very incomplete.
Let’s fix it.
Because this matters – for heart…

— Ashley Miller (@icmteaching) July 5, 2025

🫁 What happened to ARDS?

20 years ago ARDS was everywhere.

Now we rarely see it.

We didn't cure it.
We just stopped causing it.
Here’s how IV fluids quietly created (and solved) an epidemic of iatrogenic lung injury 🧵 pic.twitter.com/1On4NlBEkJ

— Turning the Tide (@Turningthe_Tide) June 14, 2025