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									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
 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        2
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        3
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        4
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        5
RULE #1



     THE PH




               (c) 2006 Dr. B. Al-Saigh - Regina
               General Hospital - Department of
                   Academic Family Medicine        6
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        7
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        8
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        9
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        10
RULE #2



     THE ANION GAP




                      (c) 2006 Dr. B. Al-Saigh - Regina
                      General Hospital - Department of
                          Academic Family Medicine        11
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        12
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        13
PATIENT V



     OF COURSE NOT!




                       (c) 2006 Dr. B. Al-Saigh - Regina
                       General Hospital - Department of
                           Academic Family Medicine        14
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        15
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        16
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        17
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        18
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        19
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        20
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        21
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        22
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        23
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        24
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        25
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        26
PATIENT V



            WHO IS THIS PATIENT?




              (c) 2006 Dr. B. Al-Saigh - Regina
              General Hospital - Department of
                  Academic Family Medicine        27
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        28
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        29
PATIENT W



     PH = 7.5

     THUS, THIS PERSON IS ALKALOTIC




                      (c) 2006 Dr. B. Al-Saigh - Regina
                      General Hospital - Department of
                          Academic Family Medicine        30
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        31
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        32
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        33
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        34
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        35
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        36
PATIENT W




               WHO IS PATIENT W?




                (c) 2006 Dr. B. Al-Saigh - Regina
                General Hospital - Department of
                    Academic Family Medicine        37
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        38
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        39
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        40
               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        41
                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        42
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        43
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        44
PATIENT X



               WHO IS PATIENT X?




                (c) 2006 Dr. B. Al-Saigh - Regina
                General Hospital - Department of
                    Academic Family Medicine        45
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        46
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        47
ANSWER



    ONE CANNOT BOTH HYPER AND HYPOVENTILATE!!!!




                     (c) 2006 Dr. B. Al-Saigh - Regina
                     General Hospital - Department of
                         Academic Family Medicine        48
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        49
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        50
PATIENT Y



     PATIENT Y HAS A RESPIRATORY ACIDOSIS, AN AG M.
      ACIDOSIS AND A M. ALKALOSIS




                      (c) 2006 Dr. B. Al-Saigh - Regina
                      General Hospital - Department of
                          Academic Family Medicine        51
PATIENT Y



               WHO IS PATIENT Y?




                (c) 2006 Dr. B. Al-Saigh - Regina
                General Hospital - Department of
                    Academic Family Medicine        52
PATIENT Y



     THEY ARE A KNOWN DIABETIC THAT WENT INTO DKA,
      BEGAN VOMITTING SHORTLY THEREAFTER AND
      PRESENTED TO THE ER IN AN OBTUNDED STATE




                      (c) 2006 Dr. B. Al-Saigh - Regina
                      General Hospital - Department of
                          Academic Family Medicine        53
QUESTIONS TO PONDER ON :



     1. ANALYZE THE FOLLOWING ABG AND RENAL PANEL
      DATA: 7.1 / 15 / 5 / 140 / 110? WHAT CLINICAL SCENARIO
      WILL PRODUCE THESE RESULTS?

     2. WHAT CAUSES A LOW ANION GAP METABOLIC
      ACIDOSIS?




                         (c) 2006 Dr. B. Al-Saigh - Regina
                         General Hospital - Department of
                             Academic Family Medicine          54
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

								
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