Can someone please explain how:
head trauma causes respiratory acidosis
anemia causes respiratory alkalosis
fever/sepsis causes metabolic acidosis
The way I memorized ABGs is that CO2 (carbon dioxide) is toxic to the lungs. "Acids are toxic." So, if there's too much CO2, i know that the patient is in an acidotic state.
HC03 (bicarb) is a base or a pH buffer. So, if there's too much HC03, i know that the patient will be in an alkalotic state.
and this: when a patient is hyperventilating (breathing fast), they are blowing out lots of CO2, therefore decreasing PaCO2 levels in the body and increasing the pH of arterial blood thus putting the body in alkalosis
. What do the kidneys do to compensate? Do they release HCO3 or retain HCO3?
and in hypercarbic resp failure, is the patient breathing fast or slow? Wait---if they have too much CO2 in them, that means their hypoventilating. Right? Cuz when you're breathing slow, you're retaining CO2.
I think i'm confusing myself
Hello! This is how I memorized the ABGs...
Think of ROME
= opposite directions
= equal directions
pH 7.35 - 7.45
CO2 35 - 45 mmHg
HCO3 22 - 26 mEq/L
* To determine acidosis or alkalosis, look at the pH value in your problem. Then determine if it's respiratory or metabolic. Is the question talking about a respiratory issue? If not, it's metabolic.
* In order to be respiratory alkalosis
, pH must be greater than 7.45, and CO2 running opposite to below 35 mmHg.
* In order to be respiratory acidosis
, pH must be less than 7.35, and CO2 running opposite to above 45 mmHg.
* In order to be metabolic alkalosis
, pH and HCO3 would both
be greater than their normal value range.
* In order to be metabolic acidosis
, pH and HCO3 would both
be lower than their normal value range.
* Lungs are located higher in the human body than the kidneys, right? So the higher values (35-45 mmHg) pertain to the lungs. The lower values pertain to the kidneys (22-26 mEq/L). (This was the only way I was able to make it stick to my mind, LOL)
** If all three values are out of normal range, look at pH first (for acidosis or alkalosis), then at the CO2 or HCO3 value that is furthest away from its normal range to call it resp/alk, resp/acid, metb/alk, or metb/acid. The closest to the the normal range (CO2 or HCO3) is said to be "compensating" to fix the imbalance.
Disclaimer: This trick only helps you answer some questions. It does not teach you how to think critically. So you must also learn the "why" behind every situation to fully understand what is going on in real life and know what to do about it.
Hope this helps!
Last edit by Devon Rex on Feb 2, '13
: Reason: grammar
Quote from GrnTea
Head trauma causes respiratory acidosis (too much CO2 on board, a respiratory problem) if it results in lousy breathing. Anemia causes respiratory alkalosis because the body being short on oxygen wants to breathe faster, and that blows off the CO2 (too little acid, bicarb hasn't been excreted yet). (Remember, your lungs' first job is NOT bringing O2 in, it's getting CO2 out. If you don't know why, ask me.)Fever/sepsis can cause metabolic acidosis in lots of ways, but the easiest (and most deadly) is if there is so much oxygen being consumed by the tissues working all that fever up that the tissues go into anaerobic metabolism from lack of oxygen. The main byproduct of anaerobic metabolism is...lactic ACID. I LOVE physiology. This is a really short and dirty explanation of these, but I can expand if you like.
I LOVE physiology as well. What a wonderful explanation. Thanks for posting it. Having a GREAT base in A&P led to sooo much less headache in nursing school, because I understood the entire picture. (Double major in Bio)
Last edit by SleeepyRN on Feb 3, '13
: Reason: spelling