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Laboratoy Diagnostics: Arterial Blood Gas – Acidosis and Alkidosis (Step 3-5)

by Carlo Raj, MD
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    Finally, with dealing with the gases, this puts us into yet another formula and this is one in which you cannot... you can’t... there is no way you can circumvent this topic. A-a gradient is what we are looking at and it is a big A that you are paying attention to and the little A. Literally. Have to. The big A represents PAO2. In another words, this is the oxygen in your alveoli and then you subtract from this, the oxygen that is in your little “a” and that then represents the artery. If you take a look at the first bullet point here, you have, PaO2 and from hence forth, you are not going to hear me say PaO2 anymore. I am just going to refer to as being PO2, but to make sure that we are clear and that our teaching points are coming across. The PaO2 is a partial pressure of oxygen in the artery and you will tell me that is approximately PO2, there you go, of 100. 95, depending on the little bit of shunt. Now, the PAO2 would be the alveoli and that is obtained from the alveoli, obviously, but more importantly, let’s just talk about what A-a gradient means to you. What does that gradient even refer to, the gradient coming out of the alveoli or going into the alveoli? Put yourself in the alveoli right now. There you are. You are sitting in that sack. Are you there? Nice to see you. Okay, now, in that sack, you are trying to get that oxygen through the alveolar membrane, through the interstitium and into the pulmonary capillary. That is the gradient. Who are you? Oxygen, okay. So, the gradient there should normally be, well how much? What is your PO2 in the...

    About the Lecture

    The lecture Laboratoy Diagnostics: Arterial Blood Gas – Acidosis and Alkidosis (Step 3-5) by Carlo Raj, MD is from the course Pulmonary Diagnostics. It contains the following chapters:

    • Step 3
    • Step 3: cont'd
    • Step 3: a
    • Step 4: AGMA
    • Step 5: Review Differential Dx.

    Included Quiz Questions

    1. Immediate respiratory compensation that will not correct pH
    2. Delayed respiratory compensation that will correct the pH
    3. Immediate metabolic compensation that will not correct pH
    4. Immediate respiratory compensation that will correct the pH
    5. Delay metabolic compensation that will correct the pH
    1. Bicarbonate binds to H+ ions and acts as a buffer
    2. Bicarbonate is excreted faster in acidic environments
    3. Metabolic acidosis leads to decreased production of bicarbonate
    4. Bicarbonate is lost, either through diarrhea or vomitting
    5. Acidic pH denatures bicarbonate
    1. Metabolic acidosis
    2. Respiratory acidosis
    3. Metabolic alkalosis
    4. Respiratory alkalosis
    5. PCO2 does not effect pH
    1. PCO2 = 1.5 x [HCO3-] + 8
    2. PCO2 = 15 x [HCO3-] + 8
    3. PCO2 = 0.9 x [HCO3-] + 9
    4. PCO2 = 0.9 x [HCO3-] + 16
    5. PCO2 = 0.9 x [HCO3-] + 8
    1. 60mmHg
    2. 10mmHg
    3. 40mmHg
    4. 80mmHg
    5. 30mmHg
    1. Respiratory acidosis with chronically increased bicarbonate
    2. Respiratory acidosis with acutely increased bicarbonate
    3. Respiratory alkalosis with chronically increased bicarbonate
    4. Metabolic alkalosis due to acute increased bicarbonate
    5. Respiratory acidosis due to chronically decreased bicarbonate
    1. Increased pH, decreased PCO2, decreased bicarbonate
    2. Decreased pH, decreased PCO2, decreased bicarbonate
    3. Increased pH, decreased PCO2, increased bicarbonate
    4. Increased pH, increased PCO2, decreased bicarbonate
    5. Increased pH, increased PCO2, increased bicarbonate
    1. 10-14
    2. 12-18
    3. 1-5
    4. 3-7
    5. 16-22
    1. 7-11
    2. 10-14
    3. 13-17
    4. 11-15
    5. 7-14
    1. Is not effected by levels of K or Mg in the body
    2. Anion gap = unmeasured anions - unmeasured cations
    3. Anion gap = Na - (Cl + HCO3)
    4. May include organic anions and proteins
    5. Is influenced by the levels of albumin in the serum
    1. 22
    2. 10
    3. 42
    4. 12
    5. 24
    1. Ketones
    2. Lactic acid
    3. Pyruvate
    4. Salicylic acid
    5. Hydrochloric acid
    1. Measured osmolality - calculated osmolality
    2. Urine osmolality - serum osmolality
    3. Calculated osmolality - measured osmolality
    4. Measured osmolality - (ketones + BUN)
    5. Na + glucose/2 + BUN
    1. Osmolal gap > 10
    2. Negative toxin screen
    3. Elevated ketones in urine
    4. Increased BUN
    5. Anion gap > 20
    1. Change in HCO3 = change in anion gap
    2. Change in HCO3 > change in anion gap
    3. Change in HCO3 < change in anion gap
    4. Change in delta gap = change in anion gap
    5. Change in delta gap > change in anion gap
    1. Bicarbonate being lower than expected in relation to the unmeasured anions calculated from the anion gap
    2. Normal anion gap with increased unmeasured anions above that expected due to change in bicarbonate
    3. Change in bicarbonate is lower than expected when compared to measured anions
    4. Change in bicarbonate equals change in anion gap
    5. Change in delta gap equals change in anion gap
    1. The acidosis is caused by loss of bicarbonate at the level of the kidney
    2. The acidosis is due to ingestion of an exogenous substance
    3. The acidosis is due to an increased production of bicarbonate at the level of the kidney
    4. The patient is compensating for the acidosis by secreting bicarbonate in the urine
    5. The acidosis has an extrarenal etiology
    1. Acetazolamide
    2. Spironolactone
    3. Addison's Disease
    4. Secondary Hypoaldosteronism
    5. RTA type IV
    1. Respiratory acidosis
    2. Respiratory alkalosis
    3. Metabolic alkalosis
    4. Anion gap metabolic acidosis
    5. Non-anion gap metabolic acidosis
    1. Diuretics
    2. Cushing's syndrome
    3. Exogenous alkali load
    4. Gitelman's syndrome
    5. Black licorice ingestion

    Author of lecture Laboratoy Diagnostics: Arterial Blood Gas – Acidosis and Alkidosis (Step 3-5)

     Carlo Raj, MD

    Carlo Raj, MD


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