1 / 16

Acid – Base Disorders

Acid – Base Disorders. Viyeka Sethi PGY 4 Med-Peds. Four Main Acid-Base Disorders. Normal Values. Step by Step. Determine the primary disturbance: Acidemia or Alkalemia: look at the pH < 7.40 = acidemia > 7.40 = alkalemia Respiratory or Metabolic: look at HCO3 and CO2

colton-stanley
Download Presentation

Acid – Base Disorders

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Acid – Base Disorders Viyeka Sethi PGY 4 Med-Peds

  2. Four Main Acid-Base Disorders

  3. Normal Values

  4. Step by Step • Determine the primary disturbance: • Acidemia or Alkalemia: look at the pH < 7.40 = acidemia > 7.40 = alkalemia • Respiratory or Metabolic: look at HCO3 and CO2 HCO3 = primary metabolic acidosis pCO2 = primary respiratory acidosis and vice versa for alkalosis

  5. Determine acute or chronic for Respiratory Disturbance: Compensation attempts to normalize pH but can be present with an abnormal pH Expected change in pCO2 best used for primary metabolic disturbance and expected change in HCO3 for primary respiratory disturbance

  6. Respiratory Disturbance Compensation

  7. Primary Metabolic Disturbance: Calculate anion gap : Na – (Cl + HCO3) Normal = 12 +/- 2 If gap is >20 then there is primary metabolic acidosis regardless of pH or bicarb. Helps narrow differential with a anion gap or non-anion gap metabolic acidosis

  8. Assess appropriate respiratory compensation for metabolic disorder: Respiratory compensation is fast Winters formula: Expected pCO2 = (1.5 * HCO3) + 8 (+/-2) If measured pCO2 is < expected then co-existing resp. alkalosis > expected then co-existing resp. acidosis

  9. Determine if other metabolic disturbances co-exist with AG metabolic acidosis: Delta gap – accounts for increase in anion gap and shows any variation in HCO3 If no other disorder is present then the calculation should be 24

  10. Delta Gap Corrected HCO3 = measured HCO3 + (AG - 12) • So if corrected HCO3 >24 then metabolic alkalosis co-exists <24 then non-anion gap metabolic acidosis co-exists

  11. Hints • Simple acid base – compensatory response always in direction of primary variable • Compensation is more pronounced with chronic disorders • Normal pH indicates two or more acid-base disorders • If given electrolytes, use them!!!

  12. Pneumonics for pnuemonic lovers

  13. Case 1 • 3 yo boy with diarrhea is evaluated in the ER. Initial ABG shows: ph – 7.23 HCO3 – 10 pCO2 – 23 AG - 13 Expected pCO2 = (1.5 * HCO3) + 8 +/-2 So, Expected pCO2 = (1.5 * 10) + 8 +/-2 =(15) + 8 +/-2 =23 +/- 2 So, we have a metabolic acidosis with respiratory compensation Alkalemia or acidemia? Low pH = acidemia Primary disturbance resp. or metabolic? Low HCO3 = metabolic acidosis Normal AG so no need for Delta gap equation BUT Is there adequate respiratory compensation? (Use Winter’s formula)

  14. Case 2 • 5 yo boy presents to ED with dyspnea for 3 days. ABG shows the following: pH – 7.35 paCO2 – 60 paO2 – 57 HCO3 - 31 Acidemia or alkalemia? Low pH = Acidemia Primary Resp. or Metabolic disturbance? Respiratory Check yourself….using rules for Primary Resp disturbance For every 10 increase in pCO2 - pH decreases by .08 acutely or .03 chronically HCO3 increases by 1 acutely or 3 chronically So, this is a chronic resp. acidosis

  15. Case 3 • 15 yo with 4 days of vomiting and fever. pH- 7.50 Na- 138 pCO2- 42 Cl- 80 pO2- 80 HCO3- 34 Acidemia or alkalemia? High ph = alkalemia Respiratory or Metabolic? High HCO3 = metabolic Anion Gap? 138 – (80 + 34) = 24 Is Resp. compensation appropriate? Exp. pCO2 = (1.5 * HCO3) + 8 +/-2 =(51) + 8 +/-2 =59 +/- 2 So, NO the CO2 is lower so we have a Co-existent resp.alkalosis Checking the Delta gap only useful in a primary metabolic acidosis.

  16. Case 4

More Related