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THE ACIDIC TRUTH AND THE BASIC FACTS

THE ACIDIC TRUTH AND THE BASIC FACTS. A SUGGESTED APPROACH TO RAPID ANALYSIS OF MIXED A/B DISORDERS DR. AL-SAIGH REGINA GENERAL HOSPITAL DEPARTMENT OF ACADEMIC FAMILY MEDICINE. RESOURCES. Based on discussion taken from: A Practical Approach to Acid-Base Disorders

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THE ACIDIC TRUTH AND THE BASIC FACTS

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  1. THE ACIDIC TRUTH AND THE BASIC FACTS A SUGGESTED APPROACH TO RAPID ANALYSIS OF MIXED A/B DISORDERS DR. AL-SAIGH REGINA GENERAL HOSPITAL DEPARTMENT OF ACADEMIC FAMILY MEDICINE

  2. RESOURCES Based on discussion taken from: A Practical Approach to Acid-Base Disorders West J Med. 1991 August; 155(2): 146–151 Richard J. Haber, MD (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  3. PRESENTATION OVERVIEW • DIAGNOSING PRIMARY A/B D/O • DIAGNOSING MIXED A/B D/O • ATTRIBUTING THE RIGHT CLINICAL SCENARIO TO THE UNDERLYING A/B DISTURBANCE (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  4. GENERAL POINTERS • A/B D/O ARE THE FINAL COMMON PATHWAY OF CERTAIN MEDICAL CONDITIONS • YOU CAN USE YOUR DX OF MIXED A/B D/O TO GENERATE A DDX OR TO STRENGTHEN YOUR SUSPICION FOR A GIVEN MEDICAL CONDITION (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  5. GENERAL POINTERS • CAUSES OF THE FOUR A/B D/O ARE INCLUDED IN THE WORKBOOK • TIME WILL NOT PERMIT TO GO OVER THEM IN DETAIL • ALWAYS KEEP THEM IN MIND AND USE THEM TO GENERATE YOUR DDX (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  6. RULE #1 • THE PH (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  7. RULE #1 • ALWAYS BEGIN BY CHECKING FOR THE PH • A PRIMARY A/B DISTURBANCE WILL CAUSE EITHER AN ACIDOTIC OR ALKALOTIC STATE (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  8. RULE #1 • IF AND WHEN THE BODY COMPENSATES FOR THIS DISTURBANCE, IT NEVER EVER OVERCOMPENSATES • I.E. A D/O MANIFESTING AS ACIDOSIS WILL NEVER OVERCOMPENSATE AND PUT YOU IN AN ALKALOTIC STATE (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  9. RULE #1 • NEXT, LOOK AT THE CO2 AND HCO3 VALUES • FIRST, DETERMINE IF, AT ALL, THEY ARE CHANGED FROM NORMAL • THEN, DETERMINE THE DIRECTION OF CHANGE (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  10. RULE #1 • FINALLY, ASK YOURSELF IF THAT DIRECTION OF CHANGE EXPLAINS THE PH • USUALLY, IN A PRIMARY A/B D/O, ONE VALUE WILL EXPLAIN THE PH AND THE OTHER WILL BE NORMAL OR IN A DIRECTION THAT TRIES TO COMPENSATE FOR THAT CHANGE IN PH (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  11. RULE #2 • THE ANION GAP (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  12. RULE #2 • HOW CAN I CONVINCE YOU TO ALWAYS LOOK FOR THE AG? • TAKE THE FOLLOWING EXAMPLE OF PATIENT V (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  13. PATIENT V • ABG OF PATIENT V IS 7.4 / 40 / 24 • SOLELEY BASED ON THE ABG RESULTS, DOES THIS PATIENT HAVE A PRIMARY A/B D/O? (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  14. PATIENT V • OF COURSE NOT! (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  15. PATIENT V • YOU NEED TO LOOK AT THE RENAL PANEL AND SPECIFICALLY AT THE NA AND CL LEVELS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  16. THE AG • WHAT IS AN ANION GAP? • CATIONS - ANIONS • CATIONS : NA AND K • ANIONS : CL, HCO3 AND PROTEINS • THE COMMONLY MEASURED CATIONS ARE NA. K IS NEGLIGABLE EXTRACELLULARLY (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  17. THE AG • THE COMMONLY MESURED ANIONS ARE CL AND HCO3. PROTEINS ARE NOT MEASURED REGULARLY • THUS, THE AG IS THE DIFFERENCE IN MESURED ANIONS FROM CATIONS • IT IS ROUGHLY 8-12 MMOL/L (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  18. THE AG • DOES THAT MEAN THAT WE ARE WALKING AROUND WITH A NET POSITIVE CHARGE? (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  19. THE AG • NO! • THE UNMEASURED ANIONS MUST EXCEED THE UNMEASURED CATIONS IN ORDER TO ESTABLISH ELECTRICAL NEUTRALITY (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  20. PATIENT V • BACK TO OUR EXAMPLE: • WE NOW NEED TO CHECK FOR THE AG • OUR NA IS 145 / OUR CL IS 100 • THUS, THE AG IS 21 (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  21. RULE #2 • WHICH BRINGS US TO THE SECOND RULE. HOW DO WE INTERPRET THE AG? • FOLLOW ON (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  22. RULE #2 • IF THE AG IS > 20, WE ALSO HAVE AN AG METABOLIC ACIDOSIS, REGARDLESS OF PH (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  23. PATIENT V • THUS, IN THIS NORMAL APPEARING PATIENT V, WE HAVE AN AG METABOLIC ACIDOSIS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  24. RULE #3 • CALCULATE THE Δ AG + HCO3 • IF ABOVE > 26 : METABOLIC ALKALOSIS • IF BELOW < 22 : NON AG METABOLIC ACIDOSIS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  25. PATIENT V • IN OUR EXAMPLE OF PATIENT V, THE AG = 21 • Δ AG = 21 - 12 = 9 • HCO3 = 24 • 9 + 24 = 33 • 33 > 26 • THUS, THIS PATIENT ALSO HAS METABOLIC ALKALOSIS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  26. PATIENT V • PATIENT V, WHO PRESENTED WITH AN ABG OF 7.4 / 40 / 24, AND LYTES OF NA 145 / CL OF 100 HAS AG METABOLIC ACIDOSIS AND METABOLIC ALKALOSIS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  27. PATIENT V WHO IS THIS PATIENT? (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  28. PATIENT V • A CHRONIC RENAL FAILURE PATIENT WHO DEVELOPED UREMIA AND LATER VOMITTED (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  29. PATIENT W • PATIENT W PRESENT TO THE ER WITH THE FOLLOWING ABG AND RENAL PANEL PERTINENT RESULTS: • 7.5 / 20 / 15 / 140 / 103 • LET US WORK OUR THIS PATIENT’S A/B STATUS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  30. PATIENT W • PH = 7.5 • THUS, THIS PERSON IS ALKALOTIC (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  31. PATIENT W • CO2 IS 20. THIS IS LOWER THAN NORMAL • A LOW CO2 IS COMPATIBLE WITH ALKALOSIS • HCO3 IS 15. THIS IS LOWER THAN NORMAL • A LOW HCO3 IS COMPATIBLE WITH ACIDOSIS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  32. PATIENT W • IS PATIENT W IN RESPIRATORY ALKALOSIS WITH METABOLIC COMPENSATION? OR • IS PATIENT W UNDERGOING A MIXED A/B D/O? (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  33. PATIENT W • REMAIN SYSTEMATIC: • CALCULATE THE AG: • AG = 140 – (103 + 15) = 22 • 22 > 20 • THUS, THERE IS ALSO AN AG METABOLIC ACIDOSIS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  34. PATIENT W • MOVE ON TO RULE NUMBER 3: • ∆ AG = 22 – 12 = 10 • 10 + 15 = 25 • 25 IS WITHIN THE NL OF THE HCO3 CONCENTRATION (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  35. PATIENT W • PATIENT W THUS HAS A RESPIRATORY ALKALOSIS AND AN AG METABOLIC ACIDOSIS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  36. PATIENT W • TAKE HOME LESSON FROM PATIENT W: • IF YOU DID NOT CALCULATE THE AG, YOU WOULD HAVE MISSED THE AG METABOLIC ACIDOSIS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  37. PATIENT W • WHO IS PATIENT W? (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  38. PATIENT W • THEY ARE A PATIENT WHO INGESTED A LARGE AMOUNT OF ASA AND DISOLAYED THE CENTRALLY MEDIATED RESP. ALKALOSIS AND THE AG METABOLIC ACIDOSIS ASSOCIATED WITH SALICYLATE POISONING (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  39. PATIENT X • PATIENT X PRESENTS TO THE ER WITH THE FOLLOWING PERTINENT A/B AND RENAL PANEL VALUES: • 7.5 / 20 / 15 / 145 / 100 (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  40. PATIENT X • THE PH IS 7.5 • THIS PATIENT IS ALKALOTIC (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  41. PATIENT X • THE CO2 IS 20. IT IS DEPRESSED • THAT CAN ACCOUNT FOR THE ALKALOSIS • THE HCO3 IS 15. IT IS DEPRESSED • THAT CANNOT ACCOUNT FOR THE ALKALOSIS BUT IT CAN BE A COMPENSATION FOR THE ALKALOSIS OR AN INDICATION OF ANOTHER A/B DISTURBANCE • THUS, THE PRIMARY DISTURBANCE IS A RESPIRATORY ALKALOSIS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  42. PATIENT X • AG = 30 THUS AN AG METABOLIC ACIDOSIS • ∆ AG + HCO3 = 33 THUS A METABOLIC ALKALOSIS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  43. PATIENT X • PATIENT X IS THUS UNDERGOING 3 A/B DISTURBANCES AT ONCE: A RESP. ALKALOSIS, AN AG METABOLIC ACIDOSIS AND A METABOLIC ALKALOSIS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  44. PATIENT X • TAKE HOME MESSAGE FROM PATIENT X: ANALYZING 3 PRIMARY A/B DISTURBANCES IN ONE PATIENT IS REDICULOUSLY SIMPLE! (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  45. PATIENT X • WHO IS PATIENT X? (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  46. PATIENT X • THIS PERSON HAD A HX OF VOMITTING (M. ALKALOSIS) EVIDENCE OF ALCOHOLIC KETOACIDOSIS (AG M. ACIDOSIS) AND FINDING COMPATIBLE WITH A BACTERIAL PNEUMONIA (RESP. ALKALOSIS) (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  47. QUESTION : • WHY CAN THERE NOT BE 4 A/B DISTURBANCES IN ONE PATIENT AT THE SAME TIME? (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  48. ANSWER • ONE CANNOT BOTH HYPER AND HYPOVENTILATE!!!! (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  49. PATIENT Y • PATIENT Y PRESENT TO THE ER WITH THE FOLLOWING PERTINENT ABG AND RENAL PANEL VALUES: • 7.1 / 50 / 15 / 145 / 100 (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

  50. PATIENT Y • PH IS 7.1 : THIS PATIENT IS ACIDOTIC • CO2 IS RAISED; HCO3 IS DEPRESSED • THIS IS A RESPIRATORY ACIDOSIS • AG = 30 : THIS PT. HAS AG M. ACIDOSIS • 30 – 12 = 18 ; 18 + 15 = 33 • 33 > 26 : THIS PATIENT HAS A M. ALKALOSIS (c) 2006 Dr. B. Al-Saigh - Regina General Hospital - Department of Academic Family Medicine

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