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    Add as FriendInterpretation of arterial blood gases

    by: Vishram

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    1 :
    2 : ABG MADE EASY ………A Simplified Approach Dr Vishram Buche Om Child Trust Hospital NAGPUR
    3 : pH PCO2 HCO3 PO2
    4 : H a 1 pH H+ nmoles /L. pH 20 7.60 30 7.50 40 7.40 50 7.30 60 7.20 0 14 H+ = 80- last two digits of pH OH ion H+ ion Alkaline Acidic
    5 : 40 nmols/L pH = Power of Hydrogen
    6 : Getting a“ feel ” of Blood Gases
    7 : Primary lesion compensation pH HCO3 CO2 METABOLIC ACIDOSIS HYPER VENTILATION BICARB CHANGES pH in same direction LOW HCO3 LOW pH LOW pCO2 Low Alkali
    8 : Primary lesion compensation pH HCO3 CO2 METABOLIC ALKALOSIS HYPO VENTILATION BICARB CHANGES pH in same direction HIGH HCO3 HIGH pH HIGH CO2 High Alkali
    9 : CO 2 CHANGES pH in opposite direction Primary lesion compensation pH CO 2 BICARB Respiratory acidosis HIGH pCO2 LOW pH HIGH HCO3 High CO2
    10 : Primary lesion compensation pH CO 2 BICARB Respiratory alkalosis Low CO2 CO 2 CHANGES pH in opposite direction LOW pCO2 HIGH pH LOW HCO3
    11 : Body’s physiologic response to Primary disorder in order to bring pH towards NORMAL limit Full compensation Partial compensation No compensation…. (uncompensated) BUT never overshoots, If overcompensation is there, Take it granted it is a MIXED disorder Compensation….
    12 : Remember……. Respiratory compensation is always FAST …12-24 hrs Metabolic compensation is always SLOW...5 -7 days
    13 : How to identify the type of compensation…..? pH HCO3 CO2 7.20 15 40 7.27 15 30 7.37 15 20 Un Compensated Partially Compensated Fully Compensated
    14 : COMPENSATION LIMITS
    15 : Now that I have this data, what does it mean? ----- XXXX Diagnostics ------ Blood Gas Report 248 05:36 Jul 22 2000 Pt ID 2570 / 00 Measured 37.0o C pH 7.463 pCO2 44.4 mm Hg pO2 113.2 mm Hg Corrected 38.6o C pH 7.439 pCO2 47.6 mm Hg pO2 123.5 mm Hg Calculated Data HCO3 act 31.1 mmol / L HCO3 std 30.5 mmol / L BE 6.6 mmol / L O2 CT 14.7 mL / dl O2 Sat 98.3 % ct CO2 32.4 mmol / L pO2 (A - a) 32.2 mm Hg pO2 (a / A) 0.79 Entered Data Temp 38.6 oC ct Hb 10.5 g/dl FiO2 30.0 % output
    16 : The Anatomy of a Blood Gas Report -----XXXX Diagnostics----- Blood Gas Report 328 03:44 Feb 5 2006 Pt ID 3245 / 00 Measured 37.0 0C pH 7.452 pCO2 45.1 mm Hg pO2 112.3 mm Hg Corrected 38.6 0C pH 7.436 pCO2 47.6 mm Hg pO2 122.4 mm Hg Calculated Data HCO3 act 31.2 mmol / L HCO3 std 30.5 mmol / L B E 6.6 mmol / L O2 ct 15.8 mL / dl O2 Sat 98.4 % ct CO2 32.5 mmol / L pO2 (A -a) 30.2 mm Hg ? pO2 (a/A) 0.78 Entered Data Temp 38.6 0C FiO2 30.0 % ct Hb 10.5 gm/dl Measured values… most important Temperature Correction : Is there any value to it ? Calculated Data : Which are useful one? Entered Data : Important
    17 : Uncorrected pH & pCO2 are reliable reflections of in-vivo acid base status Temperature correction of pH & pCO2 do not affect calculated bicarbonate “ There is no scientific basis ... for applying temperature corrections to blood gas measurements…” Shapiro BA, OTCC, 1999. pCO2 reference points at 37o C are well established as a reliable reflectors of alveolar ventilation Reliable data on DO2 and oxygen demand are unavailable at temperatures other than 37o C ……Measured values should be considered And …..Corrected values should be discarded
    18 : Bicarbonate is calculated on the basis of the Henderson equation: [H+] = 24 pCO2 / [HCO3-] or for the Mathematically inclined… Act Bicarbonate: -----XXXX Diagnostics----- Blood Gas Report 328 03:44 Feb 5 2006 Pt ID 3245 / 00 Measured 37.0 0C pH 7.452 pCO2 45.1 mm Hg pO2 112.3 mm Hg Corrected 38.6 0C pH 7.436 pCO2 47.6 mm Hg pO2 122.4 mm Hg Calculated Data HCO3 act 31.2 mmol / L HCO3 std 30.5 mmol / L B E 6.6 mmol / L O2 ct 15.8 mL / dl O2 Sat 98.4 % ct CO2 32.5 mmol / L pO2 (A -a) 30.2 mm Hg ? pO2 (a/A) 0.78 Entered Data Temp 38.6 0C FiO2 30.0 % ct Hb 10.5 gm/dl
    19 : -----XXXX Diagnostics----- Blood Gas Report 328 03:44 Feb 5 2006 Pt ID 3245 / 00 Measured 37.0 0C pH 7.452 pCO2 45.1 mm Hg pO2 112.3 mm Hg Corrected 38.6 0C pH 7.436 pCO2 47.6 mm Hg pO2 122.4 mm Hg Calculated Data HCO3 act 31.2 mmol / L HCO3 std 30.5 mmol / L B E 6.6 mmol / L O2 ct 15.8 mL / dl O2 Sat 98.4 % ct CO2 32.5 mmol / L pO2 (A -a) 30.2 mm Hg ? pO2 (a/A) 0.78 Entered Data Temp 38.6 0C FiO2 30.0 % ct Hb 10.5 gm/dl
    20 : Oxygenation Parameters: ………limitations O2 Content of Blood: Remember Haemoglobin To Know the severity of Hypoxemia Oxygen Saturation: ( remember this is calculated ) Alveolar / arterial gradient: ( classify resp.failure) Arterial / alveolar ratio: Proposed to be less variable Same limitations as A-a gradient -----XXXX Diagnostics----- Blood Gas Report 328 03:44 Feb 5 2006 Pt ID 3245 / 00 Measured 37.0 0C pH 7.452 pCO2 45.1 mm Hg pO2 112.3 mm Hg Corrected 38.6 0C pH 7.436 pCO2 47.6 mm Hg pO2 122.4 mm Hg Calculated Data HCO3 act 31.2 mmol / L HCO3 std 30.5 mmol / L B E 6.6 mmol / L O2 ct 15.8 mL / dl O2 Sat 98.4 % ct CO2 32.5 mmol / L pO2 (A -a) 30.2 mm Hg ? pO2 (a/A) 0.78 Entered Data Temp 38.6 0C FiO2 30.0 % ct Hb 10.5 gm/dl
    21 : Alveolar-arterial O2 Difference * When FiO2 = 21 % : PiO2 = (760-45) x .21= 150 mmHg O2 CO2 PAO2 = 150 – 1.2 (PCO2) = 150 – 1.2 ? 40 = 150 – 50 = 100 mm Hg PaO2 = 90 mmHg ………..PAO2 – PaO2 = ? PAO2 = PiO2* -(PCO2/0.8) PAO2 – PaO2 = 10 mmHg PaO2 PAO2 Classify Respiratory Failure Ventilation–perfusion mismatch
    22 : Alveolar-arterial Difference O2 CO2 Alveolar – arterial G. 100 - 45 = 55 ……………….Wide A-a Oxygenation Failure Wide Gap PCO2 = 40 PaO2 = 45 PAO2 = 150 – 1.2 (40) = 150 - 50 = 100 Ventilation Failure Normal Gap PCO2 = 80 PaO2 = 45 PAO2 = 150-1.2(80) = 150-100 = 50 Alveolar arterial G. 50 – 45 = 5 …………….Normal A-a
    23 : Expected PaO2 = Normal FiO2 x 5 = PaO2 20 x 5 = 100
    24 : Always mention and see… FiO2 ct Hb -----XXXX Diagnostics---- Blood Gas Report Measured 37.0 0C pH 7.452 pCO2 45.1 mm Hg pO2 112.3 mm Hg Calculated Data HCO3 act 31.2 mmol / L O2 Sat 98.4 % O2 ct 15.8 pO2 (A -a) 30.2 mm Hg ? Entered Data FiO2 % Ct Hb gm/dl The essentials of Blood gas…
    25 : A Systematic and Pointed ………. approach
    26 : Steps for Successful Blood Gas Analysis 7
    27 : 1. 2. Look at pH? 3. Who is the culprit ?...Metabolic / Respiratory 4. If respiratory…… acute and /or chronic 5. If metabolic acidosis, Anion gap ?ed and/or normal or both? Is more than one disorder present? Correlate clinically Consider the clinical settings! Anticipate the disorder 7 steps to analyze ABG
    28 : Step 2 Look at the pH Is the patient acidemic pH < 7.35 or alkalemic pH > 7.45 If pH = 7.4 …… Normal Mixed or Fully compensated
    29 : Step 3 ……. CULPRIT? HCO3…… METABOLIC > 26 ….. Met. Alkalosis < 22 ……Met. Acidosis PCO2 ……RESPIRATORY > 45 …… Resp. Acidosis < 35 …… Resp. Alkalosis HCO3 = Base Normal…22-26 CO2 = ACID Normal…35-45
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