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@DrPhilipVerhoef

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Nick Mark MD

@nickmmark

Oct 1

New favorite physiology paper: Central Venous Pressure in Space.

So much space & cardio physiology to unpack here including:
- effects of posture, 3g shuttle launch, & microgravity on CVP
- change in the relationship between filling pressure (CVP) & LV size
- Guyton curves!
1/

To measure CVP in space they needed two things:
📼 an instrument/recorder that could accurately measure pressure despite g-force, vibration, & changes in pressure. They built & tested one!
🧑‍🚀👩‍🚀👨‍🚀 an astronaut willing to fly into space with a central line! 3 volunteered!
2/

The night before launch they placed a 4Fr central line in the median cubital vein & advanced under fluoro.

🚀The astronauts wore the data recorder under their flight suit during launch.

🌍The collected data from launch up to 48 hrs in orbit.
3/

Read 16 tweets

Nick Mark MD

@nickmmark

Jul 16

https://twitter.com/matt4va/status/1813202802337779731

The media silence on this is deafening.

Did he have a head CT? What did it show?
Did he have stitches? Tetanus shot?

The NYT ran nonstop stories about Biden’s health after the debate but can’t be bothered to report on the health of someone who was literally shot in the head?

https://twitter.com/matt4va/status/1813202802337779731

To the people in the replies who say it’s impossible because of “HIPPA”
1. I assume you mean HIPAA
2. A normal presidential candidate would allow his doctors to release the info. This is exactly what happened when Reagan survived an assassination attempt.
washingtonpost.com/obituaries/202…

My advice to journalists is to lookup tangential gunshot wounds (TGSW).

Ask questions like:
- what imaging has he had?
- what cognitive assessments?
- has he seen a neurosurgeon or neurologist?
- he’s previously had symptoms like slurred speech, abnormal gait - are these worse?

Read 4 tweets

Nick Mark MD

@nickmmark

Jun 30

You've probably heard "don't give lactated ringers because it raises lactate"

This statement is ~98% false, but there's one crucial practice-changing fact that you need to know.

A 🧵 all about lactic acid and lactated ringers!
1/

First off, we should ackowledge the obvious: Lactated ringers does in fact contain lactate... 28 mEq/L in fact

BUT there's one little detail to remember:
Lactate ≠ Lactic acid

When we measure "lactate" we care about the ACID (H+) which lowers pH & causes organ dysfunction
2/

But the correlation between pH & lactate is really bad!

Look at this analysis of lactate vs pH in 171 ICU patients.

There is a *weak* correlation in people with arterial lactate > 5, but even w/ lactate =10, pH ranged from 7.5 to 7.05. Quite a spread!

3/ ncbi.nlm.nih.gov/pmc/articles/P…

Read 10 tweets

Nick Mark MD

@nickmmark

Jun 13

If you intubate you need to read the #PREOXI trial!
-n=1301 people requiring intubation in ED/ ICU were randomized to preoxygenation with oxygen mask vs non-invasive ventilation (NIV)
-NIV HALVED the risk of hypoxemia: 9 vs 18%
-NIV reduced mortality: 0.2% vs 1.1%

#CCR24
🧵
1/

Hypoxemia (SpO2 <85%) occurs in 10-20% of ED & ICU intubations.

1-2% of intubations performed in ED/ICU result in cardiac arrest!

This is an exceptionally dangerous procedure and preoxygenation is essential to keep patients safe.

But what’s the *BEST* way to preoxygenate?
2/

Most people use a non-rebreather oxygen mask, but because of its loose fit it often delivers much less than 100% FiO2.

NIV (“BiPAP”) delivers a higher FiO2 because of its tight fit. It also delivers PEEP & achieves a higher mean airway pressure which is theoretically helpful!
3/

Read 15 tweets

Nick Mark MD

@nickmmark

Jun 12

Results from #PROTECTION presented #CCR24 & published @NEJM.
- DB RCT of amino acid infusion vs placebo in n=3511 people undergoing cardiac surgery w/ bypass.
- Reduced incidence of AKI (26.9% vs 31.7% NNT=20) & need for RRT (1.4% vs 1.9% NNT=200)

Potential game changer!

🧵
1/

I work in a busy CVICU & I often see AKI following cardiac surgery.

Despite risk stratification & hemodynamic optimization, AKI remains one of the most common complications after cardiac surgery with bypass.

Even a modest reduction in AKI/CRRT would be great for my patients.
2/

During cardiac surgery w/ bypass, renal blood flow (RBF) is reduced dramatically. This causes injury, especially in susceptible individuals.

But what if we could use physiology to protect the kidneys?

Renal blood vessels dilate after a high protein meal increasing RBF & GFR!
3/

Read 11 tweets

Nick Mark MD

@nickmmark

May 3

A slightly tricky blood gas case:

77 yo with respiratory distress, RR 30, SpO2 80% on non-rebreather at 15 lpm

CXR & TTE are unrevealing

pH 7.58 / PaCO2 24 / PaO2 >500 / HCO3 22

MetHb 0% CarboxyHb 0%

The ABG looks like this:

The answer is sulfhemoglobinemia.

Sulfhemoglobinemia is a *permanently* modified hemoglobin associated with exposure to TMP/SMX, dapsone, phenazopyridine, & other amino & nitro compounds.

It has an altered oxy-hemoglobin dissociation curve.

2/

Sulfhemoglobinemia is easily confused with methemoglobinemia. Both have very dark colored blood & present with cyanosis. Diagnosis typically requires a specialized lab.

Spoiler: you may have heard that SulfHb is green. It isn’t really. You’re thinking of Vulcans’ blood.

3/

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