#CriticalCare non-COVID teaching case:
An elderly man is admitted to the surgical ICU for monitoring after an uncomplicated kidney transplant. You notice this funny pattern on his arterial line tracing. What’s going on here? #FOAMcc#FOAMed 1/
What’s going on here?
2/
This is pulsus alternans: an alternating strong & weak pulse.
Based on the A-line tracing POCUS was performed that reveled a markedly reduced EF. Coronary angiography showed no obstruction and a diagnosis of stress CM was made. The patient recovered with medical therapies.
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At first glance, differentiating pulsus alternans from exaggerated pulse pressure variation (PPV) can be tricky
*pulsus alternans occurs every other beat
*PPV occurs with the respiratory cycle
Slowing down the display can differentiate: This is what increased PPV looks like 4/
Pulsus alternans was first described by Traube in 1872.
Despite 150 yrs of research, the mechanism is not precisely known.
There are two theories, related to either beat-to-beat variation in pre-load or in contractility.
The *pre-load theory* is that impaired contractility (causing a weak pulse) leads to an increased end diastolic volume at the next systole. With more filling, the next contraction ejects more blood (causing a strong pulse) due to the Frank-Starling principle. 6/
The alternative *contractility theory* is that residual cytoplasmic Ca2+ after a weak systole causes a stronger cardiac contraction on the next beat.
Whatever the mxn, pulsus alternans is associated with poor systolic function.
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🥡Points:
🫀Pulsus alternans on an arterial line tracing can be a useful diagnostic clue for decreased systolic fxn
1⃣📟 See this new ICU OnePager on arterial Lines for more onepagericu.com 8/
📚Historical/literary note:
DH Lawrence beautifully describes Pulsus Alternans in Sons and Lovers:
"…he felt her pulse. There was a strong stroke and a weak one, like a sound and its echo. That was supposed to betoken the end."
9/9
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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/
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/
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.
Damn. Under Trump the White House Medical Unit was a pill-mill. Thousands of ambien & provigil per month.
Worse, for a clinic that doesn’t typically do procedures w/ moderate sedation they sure are they ordering prodigious quantities of morphine, fentanyl, versed, & ketamine…?
Honestly, this reminds me of Norman Ohler’s Blitzed.
The AG report was largely concerned with the enormous cost of prescribing these non-genetic meds.
It’s worth pointing out that dispensing prescription meds without documentation is malpractice. In the case of controlled substances it’s also likely a crime.