Why does inadequate oxygenation cause decreased urine output?

[underthecovers]

Sorry if this is posted in the wrong section.

Why does inadequate oxygenation or tissue perfusion from dysrhythmias cause decreased urine output?

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[mvenus929]

Well, decreased tissue perfusion is easy. If you aren't perfusing your kidneys, they can't filter blood to make urine. And if you have low BP, your kidneys are one of the first things that compensate by conserving as much fluid as possible, hence decreased urine output.

Inadequate oxygenation (still pushing blood, but not a high oxygen content) is a bit harder, and one I don't think I can explain without doing some research.

 

[underthecovers]

Thanks. Yeah, I'm getting stuck at the oxygenation part. Tissue perfusion, I understand.

 

[ACSurgeon]

The reason perfusion matters is because of oxygen delivered with perfusion. Poor oxygenation = poor cellular function. This manifests as end organ dysfunction (CNS= confusion, heart= ischemia/MI/etc, kidney=low UOP, etc etc)

 

[underthecovers]

Thanks, that makes sense.

 

[lesterfreamon]

Also, maybe consider methods of autoregulation for other organs? inadequate oxygenation for example would be sensed by the brain as increased CO2, which would then lead to increased perfusion of the brain.

The increased blood that is going to the brain must be coming from somewhere, so maybe renal perfusion decreased to maintain proper oxygenation of other organs?

Just a guess not sure if any of this is true

 

[acapnial]

Maybe this-
Hypoxia -> sympathetic nervous system activation -> afferent arteriole constriction -> less plasma filtered, less urine output. The sympathetic nervous system should also stimulate the renin-angiotensin-aldosterone system, which will also stimulate ADH.

 

[e30ftw]

renal cells, particularly in the medulla, have high oxygen demand. They are metabolically active and to filter blood they use lots of ion pumps.

Renal blood flow is only about 10% of total CO.

Cardiac dysarrhythmias are common sources for tissue ischemia in all organ systems. The most susceptible will be brain/kidney and other tissues with high metabolic demand. This is why we do CPR during cardiac arrest, however even the most effective transthoracic CPR only delivers 20-30% of normal cardiac output.

Hemoglobin carries oxygen to tissues. Cells use oxygen to make energy. If the cells don't have energy they cannot maintain correct intracellular ionic concentrations and will start to die. typically cells in an acute insult try to live so they go down the necrosis pathway and release a lot of damaging interluekins/cytokines/etc. this is like general biology ****.

If you cannot circulate blood because you have a cardiac arrhythmia, your blood will not be effectively oxygenated by the lungs, nor will it flow to purfuse end organ tissue. If highly susceptible tissues such as renal tissue do not get oxygen, they will die and stop working. If the kidneys stop working they will not produce urine.

 

[MerickManual]

Maybe this-
Hypoxia -> sympathetic nervous system activation -> afferent arteriole constriction -> less plasma filtered, less urine output. The sympathetic nervous system should also stimulate the renin-angiotensin-aldosterone system, which will also stimulate ADH.

 

[underthecovers]

Thanks, everybody! Very helpful.

 

[lunalight]

Low O2 is sensed by the peripheral chemoreceptors and causes an increase in ventilation which drops CO2. The drop in CO2 causes alkalosis which is compensated for by kidneys by decreasing urine output to retain H+ to bring the blood pH back to normal.