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My Latest For MashUpMD –

For the last half year or so, I have been writing a newsletter for MashUpMD. I grab some interesting lingos from around the web, string them together with some of my thoughts and they send it out packaged with a handful of ads. And I get paid.

All and all it feels like blogging. Having someone give me a deadline and a small check apparently is what it took to bring me back to blogging.

I am going to try to bring these posts to PBFluids, but what you should really do is subscribe to me through MashUpMD.

Here is the most recent newsletter…

Hello and welcome to the NKF Spring Clinical Meetings. Follow @Neph_Times on X for updates. I will be live-tweeting the meeting on that account. Also, come to the Westin hotel bar tonight (Wednesday) to say “hi” and clink glasses with the “NephJC” posse.

Today’s email does a deep dive into an unfortunate case of osmotic demyelinating syndrome. We should try to learn all we can from these bad outcomes to protect future patients. 

The next group of links concerns a new study in JAMA that aims to improve our basic cardiovascular (CV) risk models by adding contemporary CV blood tests. It does not go well and is a cautionary tale for all of those business plans built around high-margin executive physicals.

I close out with the latest results of the USMLE part 1. This is the second set of scores since the test went pass-fail in 2022, and the pass rate is down… again. But don’t jump to any conclusions before reading the thread in the link.

Thanks, and see you at the NKF Spring Clinical Meetings.

Joel Topf, MD

Reading List

Expert Witness Newsletter: Central Pontine Myelinolysis

Terrible case of a patient who was admitted with hyponatremia, sodium 118 mmol/L. Using 3% saline, the team brought the sodium up to 125 but it then drifted back down to 121. This prompted a nephrology consult who recommended salt tablets, fluid restriction and tolvaptan 15mg. The next day the sodium was up to 125 and the then nephrologist bumped the tolvaptan to 30 mg. The next day the sodium riose 133 and the patient was discharged on 30 mg of tolvaptan daily. The following day the patient was confused and had sodium is 152! The patient presented to the ER the next day with a sodium of 170! I don’t use tolvaptan often, but when I do, I don’t pair it with another therapy for hyponatremia (no fluid restriction, no salt tablets, no urea).

Equivalent Efficacy and Decreased Rate of Overcorrection in Patients With Syndrome of Inappropriate Secretion of Antidiuretic Hormone Given Very Low-Dose Tolvaptan

This article by Rastogi and Velez looked at both tolvaptan’s efficacy and the risk of sodium over correction at two different doses. They found that the standard 15 mg dose regularly over corrects the sodium, using 8 mEq/L per day as their target, in SIADH. This is important. This study was practice changing for me. When the patient has SIADH, and I want to use tolvaptan, I use 7.5 mg. If there was a lower dose I would use that, but since tolvaptan is a triangular, crumbly pill, it is had to get a reliable dose less than 7.5 mg.

Rapidity of Correction of Hyponatremia Due to Syndrome of Inappropriate Secretion of Antidiuretic Hormone Following Tolvaptan

Tolvaptan’s effectiveness is highly dependent on the diagnosis. The risk of rapid correction with 15 mg was 84% less likely with heart failure as compared to SIADH. The authors found a low BUN (consistent with SIADH) and a low sodium to be the best predictors of rapid correction. The low sodium is consistently a risk factor for rapid correction. As sodium’s fall below 120 be more and more careful about overcorrection. I don’t use tolvaptan in those patients, and prefer 3% saline because I can turn it off if things go sideways.

Prognostic Value of Cardiovascular Biomarkers in the Population

These investigators looked at over 160,000 people from 28 cohorts in 12 countries to try to improve the traditional CV risk assessment. Surely adding high sensitivity troponin-I, nt-ProBNP, and hsCRP to the traditional risk factors (age, gender, race, systolic blood pressure, HDL and total cholesterol, smoking, and diabetes status) would provide greater accuracy, and they do! But the headline is how little they move the needle. The area under the curve (or C-statistic) moved from 0.812 with traditional risk factors to 0.8194 with the addition of all 4 blood tests!

ROC Curves and the C statistic

If you are a little soft on receiver operator characteristics and the C statistic, Medical College of Wisconsin has you covered.

Why Cardiac Biomarkers Don’t Help Predict Heart Disease

Perry Wilson breaks down why these’d tests yield so little information.

The USMLE Step 1 pass rate for first-time test-takers dropped again, now down to 92%.

Bryan Carmody does his usual amazing job at dissecting this data without the typical sky-is-falling mentality found on X. Do not miss the expanded Y graph and the reminder of what the test scores means for individual test takers and their reproducibility.

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