alkalosis and acidosis--is there and easy way to see how they work?
I need to have a grasp of the normal values of metabolic/respiratory acidosis and alkalosis and how they all work. How do you discern is someone has alk/acidosis metabolically or via respiration and how do you tell if it is compensated?
Can anyone tell me what patients with any of these problems would look like when you see them?
Thanks VERY much in advance!
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Hope you're sitting down. This is going to take a while.
Carbon Dioxide and Bicarbonate form the basis of the PH in the blood. When co2 is released by the cells as waste it combines with h2o to form carbonic acid, H2CO3. This is a weak acid. To buffer this there is bicarbonate, HCO3. The H2CO3 loses a hydrogen ion in the lungs becoming H2O and CO2. The CO2 is released into the alveoli and exhaled. That hydrogen ion that was lost is picked up by the bicarbonate to form H2CO3 which again goes to the lungs etc. If there are too many hydrogen ions around the blood becomes acidotic and the body tries to compensate for this by making more bicarbonate to combine with the hydrogen ion.
I assume you are a student in a Respiratory Therapy program is you're asking this question.
The PH, PCO2 and HCO3 in the blood gases are your guide to compensation.
Respiratory acidosis results from hypoventilation and not enough Co2 being blown off. The Ph goes down. There is a direct relationship between Ph and Pco2. For every milimeter increase in Co2 the Ph will drop 0.01. example: Pco2 goes up to 50 mmhg the ph would become 7.30. The opposite is also true. Compensation occurs when the ph increases (alkalosis) or decreases (acidosis). If a patient is in respiratory failure his co2 will go up making the ph go down.If this is an acute thing there is very little if any compensation. That takes time. If the pco2 is chronically elevated than the hco3 increases to compensate so both numbers will be elevated. As in COPD pts. The ph in this circumstance wil be just slightly acidotic as the compensation stops when the ph approches normal. The patient is said to be in a compensated respiratory acidosis.Get it?
Ok let's move on. If a patient presents with diabetic ketoacidosis his HCO3 will be low because it's root cause is a metabolic problem. They will be breathing to beat the band to blow off enough Co2 to bring his PH back to normal levels. It's called Kussmal breathing after the doctor who described it. The doctors in the Er wil give the pt. HCO3 to bring his ph back up to normal. That is an example of a metabolic acidosis.The doctors are trying to compensate for the increased hydrogen ion levels.
Respiratory alkalosis results from hyperventilation. It could be from anxiety, fear or whatever. Sometimes we do this when we have the pt on mechanical ventilation and are overdoing it a bit. That's why we monitor blood gases to make sure we are not over or under ventilating a pt. In the ER with an anxiety pt they usually make the pt breth into a paper sack so they can rebreath their own co2.
Metabolic alkalosis results from a chemical imbalance in the blood usually the electrolytes. This has to treated by a doctor
The best transfer of oxygen to the cells takes place at a PH of 7.40
Deviation from that will effect how well the hemoglobin can take up or release the O2. But that is a topic for another timw.
God bless and keep you healthy.. (
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How would you expect this to affect blood ph and respiratory rate and is this a state of acidosis or alkalosis?
Patient ingested E Coli and was diagnosed with food poisoning and has had chronic diarrhea for the past 24 hours. The patient has a medical history of Chron's Disease. The diarrhea has been going on nonstop for 24 hours. How would you expect this to affect the blood ph and respiratory rate? Is the patient suffering from a state of acidosis or alkalosis and would you expect this to be related to metabolic or respiratory disorder and why?
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To answer this, you need more information. Renal function and pulmonary function will influence the end result. Also the activity of the Crohn's needs to be established, and whether an enteroenteric fistula is present.
However: Assuming he has non-secretory diarrhea (ie not bicarbonate wasting as in a villous adenoma of the colon), then the primary event will be a metabolic alkalosis due to volume contraction. If his kidney function is normal, he will attempt to retain sodium (along with bicarbonate) and lose potassium in the urine. Due to some fairly complex actions in the proximal and distal tubule, he will effectively retain bicarbonate, leading to the alkalosis.
If he has normal pulmonary function, he will probably not have a respiratory compensation (it would have to be hypoventilation, which is hard to do unless other things are going on (such as sedatives, altered level of conciousness etc).
As time goes by, and if the diarrhea persists, in the absence of volume replacement, he will ultimately develop pre-renal azotemia, which will affect the metabolic component (he will develop a metabolic acidosis that is distinct from the metabolic alkalosis he already has).
If he goes on to develop hypeovolemic shock, other things come into play - etc etc etc.
Its not always straighforward. I hope this helps. (
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How does CNS depression cause respiratory alkalosis?
Now as far as I knew, CNS depression caused a decreased respiratory rate and would therefore cause hypoventilation and would therefore cause respiratory acidosis, however my sources say that CNS depression causes hyperventilation and therefore is a cause of respiratory alkalosis. Can anyone explain the pathophysiology of this to me so I can understand it?
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Yes, quite simply. Your sources are wrong. (
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How does excessive vomitting cause metabolic alkalosis and why normal saline can be used to correct it?
Your body has a finite amount of hydrogen ions. If you were to lose those ions through vomiting gastric acid you might for a short while have an excess of bicarbonate and the hyperventilation associated with that much vomiting would further increase the pH. But this condition is self limiting.
As to n/s to correct it I'm not sure how that would help unless it was to increase the chloride content and cause a metabolic acidosis to compensate. (
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How does the renal system compensate for respiratory alkalosis?
Respiratory Alkalosis is caused by hyperventilation. You are breathing so fast you are losing too much of your body's acid-CO2 and the HCO3 levels (the body's base) build up. The respiratory system governs the CO2 by either speeding up or slowing down your rate of breathing to raise or lower CO2 levels. The renal system governs the bodys base-HCO3 by excretion through the kidneys. They excrete more or less HCO3 when needed. In Respiratory Alkalosis, the renal system increases excretion of HCO3 to try to even out the acid-base balance. (
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Does respiratory alkalosis have anything to do with urinary incontinence in women?
no it does not ... respiratory alkalosis is primarily a dysfunction in breathing ... specifically ... hyperventilation (
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why does rapid breathing at high altitudes results to respiratory alkalosis?
Lower Po2 at high altitudes increases the respiratory rate and the heart rate. When you increase the respiratory rate you blow off more CO2 resulting in less acid in your blood. This is a respiratory alkalosis. If you bring supplemental oxygen with you this can be prevented.
God bless.
PS I should have told you that as you gain altitude the barometric pressure decreases and if the FIO2 (the fractional concentration of oxygen) remains the same then you are breathing in less oxygen and become hypoxemic. (
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when a patient is in respiratory alkalosis how do you increase their paco2 levels?
If they are conscious and breathing spontaneously you get them to breathe into a paper bag. This helps retain CO2 instead of blowing off to much.
If they are unconsious and on a vent then you need to decrease the minute ventilation. You can do this by either lowering their mandatory rate or decreasing their tidal volume.
Have a great day! (
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What are the preventions against Respiratory Alkalosis?
Anxiety, fever, stimulant drugs, pain, sepsis(a toxic condition resulting from infection), hypobarism (high altitude), and any other condition in which ventilatory elimination of C02 exceeds it's production. Basically you are hyperventilating! These are all causes of respiratory alkalosis, so if you can manage to avoid all of these you should be okay. (
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why does prolonged crying results to respiratory alkalosis?
Because of the prolonged sobbing which is similar to sighing. This increases your minute ventilation and blows off CO2 resulting in the respiratory alkalosis. (
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