lecture 12.docx

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University of Manitoba
Biochem. and Medical Genetics
BGEN 3020
Jason Leboe- Mcgowan

Lecture 12 Acid-base and Blood Gas Acidosis – increase in H ions, therefore decrease in pH + Alkalosis – decrease in H ions, therefore increase in pH New equation for acid/base physio by Goljan: pH = [HCO ] / p3O 2 Increase in bicarb = increase pH = metabolic alkalosis Decrease in bicarb = decrease pH = metabolic acidosis Increase pCO = dec2ease pH = respiratory acidosis Decrease pCO = incr2ase pH = respiratory alkalosis Compensation = bodies attempt to try to maintain a normal pH (which it never does). So if you want to keep pH roughly normal (assuming you could). 1. Example: if you have metabolic alkalosis (increase in bicarb: which is in the numerator), then have to increase denominator (pCO ) to2keep it normal, therefore, compensation is due to respiratory (pCO )2acidosis. A nice way of memorizing it is what is the opposite of metabolic? Respiratory and what is the opposite of acidosis? Alkalosis, and vice versa. 2. Example: if you have metabolic acidosis (decrease bicarb) what do we have to do with the pCO 2 We have to get rid of it. If we decrease the nominator, we have to decrease the dominator in order for the equation to stay the same. Therefore, we have to blow off the CO 2 (hyperventilation). 3. Ventilation is a CO2term! Hyperventilation = Increase in respiratory rate allows for the blowing off of CO , therefore 2 results in respiratory alkalosis. For the treatment of respiratory alkalosis is to give the pt a paper bag and ask to breath in it, b/c then they are re-breathing their own CO . 2 Hypoventilation = Decrease in respiratory rate allows for the retention of CO , th2refore results in respiratory acidosis. Full compensation does not exist; you never bring back the pH to the normal range. There is one exception: chronic respiratory alkalosis in high altitude; ie mountain sickness (ie peru). Respiratory conditions: acidosis and alkalosis 1. Things that deal with CO :2 a) Respiratory center is in medulla oblongata, which controls the breathing rate b) Upper airways – if obstructed, there will be a problem getting rid of CO . 2 c) Chest bellows – most imp muscle of respiration is diaphragm. On inspiration: the diaphragm goes down, the negative intrathroacic pressure increases, and air is sucked into the lungs and blood is sucked into the right side of the heart (this is why neck veins collapse on inspiration). Negative vacuum sucks blood and air into your chest. On expiration, there is a “+” intrathrocic pressure, pushing things out. It helps the left heart to push blood out and it also helps the lungs by pushing out air. Examples: (a) Barbiturates or any drug that depresses the respiratory center will leads to respiratory acidosis (b) CNS injury to medulla oblongata – resp acidosis (c) Anxiety = MCC resp alkalosis. When you take a test, sometimes you feel strange, and get numb and tingly, especially around mouth and on the tips of fingers, and become twitchy (b/c you are in tetany) its all caused by being alkalotic and ionizing calcium level gets lower and you really are getting tetany. Therefore you become twitchy and paresthesias (ie carpal pedal sign or trousseau’s sign are both signs of tetany). All due to tetany b/c of breathing too fast from anxiety. (d) Pregnant woman have resp alkalosis b/c estrogen and p
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