Question about Metabolic Acidosis and Alkalosis

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Specializes in Cardiac Critical Care.

I am reviewing for the NCLEX and really trying to make sure I understand all the basic concepts before I start doing questions... I'm reviewing acid/base balance and am not understanding something 100%. Here's my question: in metabolic acidosis or alkalosis, the lungs always kick in to compensate since the problem is metabolic. The review I'm doing has repeatedly said that since the kidneys are sick, they can't compensate (the lungs have to do it). BUT metabolic acidosis/alkalosis aren't always a result of a kidney problem... starvation is one of the causes (from buildup of ketones as fat & protein are used for energy) so the problem didn't start in the kidneys. Why is it that they don't try to compensate?

Thanks in advance!!

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I believe the compensation comes from breathing off the buildup of ketones, such as in starvation or strict protein diets. The body goes into ketosis and the buildup of ketones can be smelled on the breath. Same as in diabetics going through DB ketoacidosis...they have a fruity, nailpolish like breath. In any state that the body is out of homeostasis it will compensate in some way to achieve balance.

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Specializes in Emergency, Telemetry, Transplant.

The renal compensation takes some time before it takes effect. The respiratory compensation is almost immediate. For example, if a person is suffering from DKA, ketones are building up in the blood, lowering the pH and the person becomes acidotic. The response from the lungs is to "get rid" of acid in the form of CO2. So if a person is becoming acidodic, the person will hyperventilate and "breathe off" the acid (CO2) and this method starts almost immediately. It takes longer for the kidney to begin conserving bicarb to compensate for acidosis.

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Specializes in Cardiac Critical Care.

But eventually they do, correct? That's what I am a little confused on. Thank y'all!!!

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Specializes in Complex pedi to LTC/SA & now a manager.

It depends on the cause of the imbalance, how long before intervention from onset , comirbid conditions, etc. it could reverse but it might not

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I am reviewing for the NCLEX and really trying to make sure I understand all the basic concepts before I start doing questions... I'm reviewing acid/base balance and am not understanding something 100%. Here's my question: in metabolic acidosis or alkalosis, the lungs always kick in to compensate since the problem is metabolic. The review I'm doing has repeatedly said that since the kidneys are sick, they can't compensate (the lungs have to do it). BUT metabolic acidosis/alkalosis aren't always a result of a kidney problem... starvation is one of the causes (from buildup of ketones as fat & protein are used for energy) so the problem didn't start in the kidneys. Why is it that they don't try to compensate?

Thanks in advance!!

They do. Compensation in normal kidneys takes around 24 hours to kick in. In a starvation scenario, though, nobody starves in 24 hours, so the kidneys would very gradually assume compensatory responsibilities by retaining bicarb and keep it up as long as they could.

You are right that metabolic acidoses or alkaloses are not always caused by renal dysfunction; diabetic ketoACIDosis, eating a bottle of acetyl salicylic ACID, or losing a lot of bicarb from the lower GI tract in severe diarrhea are all independent of renal function for causation. The fastest way to compensate for an acid overload is to breathe out CO2; meanwhile, the kidneys (if able) are getting their act together to chip in on the effort.

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Specializes in Hospital Education Coordinator.

The kidneys do attempt to compensate but they are much slower than the lungs. There is a book called "Fluids and Electrolytes Made Incredibly Easy" that might help you understand.

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it has nothing to do with whether the acidosis or alkalosis is metabolic or respiratory or what the cause is. the lungs try to compensate immediately and then the kidneys kick in to try to compensate later if the lungs haven't acquired complete compensation. many times the lungs can compensate completely, or the kidneys can, but also many times these are just partial compensation and medical interventions are necessary for complete compensation - that's ultimately the goal.

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