Thread by @jeffrey_vinocur

#EPeeps Brief 🧵 on beta blocker hyperkalemia which is unfamiliar to many

The mechanism is the opposite of why we use albuterol to treat hyperkalemia - beta receptor modulation of Na K ATPase, the sodium potassium exchange channel [1/]

See great diagram from @paulpengmdphd

Beta blockers rarely cause hyperkalemia in isolation, but can contribute in at-risk patients.

The patient who prompted this discussion (see link) had complex multi-system illness. Ectopy was exacerbated by diuretic-induced hypoK so had MRA + scheduled enteral KCl [2/]

https://twitter.com/jeffrey_vinocur/status/1579316779301580800

One day, because of hypoK on labs, he received IV KCl replacement almost concurrent with scheduled enteral KCl… probably would not have been a big deal, except for propranolol impairing ability to transport extracellular K intracellular [3/]

By coincidence, fluctuation in ventilatory status led to respiratory acidosis at the same time, impairing the ability of the hydrogen/potassium exchange channel to buffer [4/]

So the original ECG? Sinus rhythm with horrendous QRS changes from flecainide+potassium. Ugly, but not VT. Do not shock it.

Calcium appropriate but actually we had premixed Na bicarb handy and one quick dose fixed the ECG - can you think of reasons why? [5/]

Sodium bicarbonate is good for excessive sodium channel blockade. It also stabilized the acidosis which was contributing via H+/K+ exchange to hyperkalemia, and was probably not helping the myocardium any either.

Repeat ABG showed potassium < 5 after the bicarb [6/6]

P. S. Shout out to the multiple people who thought of TCA toxicity, and to @pcg69572504 who proposed propofol infusion syndrome - although I think the appearance was not quite classic for that, it is very important to keep high index of suspicion for such a rare but severe issue

@pcg69572504 P. P. S. The ICU team was skeptical of the idea of hyperkalemia, because the blood gas slip from only an hour earlier showed hypokalemia

I didn’t realize until later that it was the beta blocker effect that set the whole thing up