Acidosis causes decreased contractility?

[MudPhud20XX]

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FA lists acidosis being one of the causes for decreased contractility, can anyone think of the mech?

 

[dfib slim]

When the pH is <7.1 myocardial responsiveness to catecholamines decreases.

 

[Jabbed]

H/K exchange → hyperkalemia → flaccidity

 

[Brorthopedic]

H/K exchange → hyperkalemia → flaccidity

^I would learn it this way instead. Remember that K+ is a vasodilator.

To answer your question, acidosis is caused by the hyperkalemia. Hyperkalemia causes partial depolarization of the cell membrane which decreases the amount of Ca2+ available for cardiac contractility. If you lower the calcium, you decrease the strength of contractility.

 

[Tajima]

Acidosis can also contribute to reduced contractility by denaturing proteins required for contraction or the reactions involved.

 

[worldbeater]

H/K exchange → hyperkalemia → flaccidity

Basic question, but why would it be hyperkalemia instead of hypokalemia?

I thought it would be hypokalemia: increased acidosis would "kick out" potassium -> causing hypokalemia -> potassium efflux causing weakness/flaccidity

 

[worldbeater]

FA lists acidosis being one of the causes for decreased contractility, can anyone think of the mech?

Above poster is correct..denaturing of protein

In addition to decreased contractility, acidosis causes:
hyperkalemia (which was correct by the other poster, still not sure why, maybe because the H/K exchange pump stops, and potassium gets trapped?)
GABA
kussmaul breathing

 

[acceptmeplease]

Hyperkalemia due to H/K pump and the intrinsic nature of acids being proton donors. Sustained acidosis drives the H/K pump in a manner that favors H in, K out.

 

[worldbeater]

Nice point, yeah I made a basic mistake of thinking hyperkalemia referred to the cell, it's the blood that has high potassium.