Storage.googleapis.com



Acid Base Disturbances Mike Clark, M.D.How do you determine the type of acid base disturbance?First look at the pH of the person’s arterial blood.What to look for? Is it out of normal range or in normal range? If within normal range, in most cases, the person does not have an acid/base problem. Sometimes they do and the reason it is in normal range is for strong compensation for a problem.If the pH is out of range, is it acidic or basic?If it is acidic (less than 7.35), is it a respiratory problem or a metabolic problem. If the pH is alkalotic (greater than 7.45), then is it a respiratory alkalosis or a metabolic alkalosis. How to determine that? Look at the PaCO2 and the HCO3-. If the PaCO2 is elevated; it is a respiratory acidosis. If the PaCO2 is decreased, it is a metabolic acidosis. In a respiratory acidosis, the PaCO2 is elevated; it is the problem. This elevation causes an increase in the amount of carbonic acid formed. If it is a respiratory acidotic cause, the HCO3- is generally elevated; if the kidneys are trying to help, they will decrease the urinating of HCO3-. The alkaline bicarbonate is trying to neutralize some of the fixed acids, to decrease total H+ concentration. An example of this is an asthma attack or a COPD (emphysema, bronchitis) attack or someone trying to suffocate someone. The person cannot blow off enough CO2.pH = pKa (6.1) + Log [HCO3- ] / .03 x [PaCO2 ]pH – Low PaCO2 high (cause) and HCO3- elevated to compensateIn a metabolic acidosis, there is some increase in the amount of fixed acids; that is the cause for the acidosis. The PaCO2 is decreased, because the person is breathing fast and deep to compensate for the increase in fixed acids by blowing off more volatile (carbonic) acid. The HCO3- is decreased. It is decreased because it is being consumed up in order to neutralize the massive increase in fixed acids, such as lactic acid or hydrochloric acid or others. An example of this is diabetic ketoacidosis, where there is an increase in acetic ketone bodies (acetate, acetoacetate, beta hydroxybutyrate) due to extensive burning of fat instead of glucose. In diabetes, glucose cannot enter the cell due to insulin problems. pH = pKa (6.1) + Log [HCO3- ] / .03 x [PaCO2 ]pH – Low HCO3- low (that is the cause) PaCO2 decreased to compensateIn a respiratory alkalosis, the PaCO2 is decreased; it is the cause of the alkalosis. Thus, the level of volatile acid (carbonic acid) is too low in the blood. As a compensatory action, the kidneys will try to urinate out more bicarbonate and hold on to more fixed acids. Bottom line, the blood bicarbonate level goes down some. The kidney’s effort to urinate out base and hold onto acid assists in holding the pH as close to normal range despite the decrease in carbonic acid (the volatile acid). An example of this is hyperventilation. It could be caused by anxiety or certain medication side effects or other causes. pH = pKa (6.1) + Log [HCO3- ] / .03 x [PaCO2 ]pH – High PaCO2 decreased (that is the cause) HCO3- decreased to compensateIn a metabolic alkalosis, the fixed acid amounts are low; this is the cause for the alkalosis. This could be caused by over consumption of basic substances or kidney problems, in which too much acid is urinated or too much base is retained. It can also be caused by severe vomiting or taking certain diuretics. The PaCO2 is increased in order for the lungs to compensate for the decreased fixed acids.. Thus, the level of volatile acid (carbonic acid) is elevated in the blood. pH = pKa (6.1) + Log [HCO3- ] / .03 x [PaCO2 ]pH – High HCO3- elevated (that is the problem) PaCO2 elevated to compensate ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download