![These findings are most consistent with….
a) Metabolic acidosis with compensatory Hypocapnia.
b) Primary metabolic acidosis with
respiratory alkalosis.
c) Acute respiratory alkalosis fully compensated.
d) Chronic respiratory alkalosis fully compensated.
pH 7.39
PCO2 l5mmHg
HCO3 8mmol/L
PaO2 90 mmHg
For metabolic acidosis: FULL COMPENSATION
Expected PaCO2 = (1.5 x [HCO3]) + 8 ) + 2
(Winter’s equation)
PCO 2 ……SHOULD BE 20
Case 6………….
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acid base examples of cases. presentation
- 2. Alveolar-arterial Difference Inspired O2 = 21 % piO2 = (760-45) x . 21 = 150 mmHg O2 CO2 palvO2 = piO2 – pCO2 / RQ = 150 – 40 / 0.8 = 150 – 50 = 100 mm Hg PaO2 = 90 mmHg palvO2 – partO2 = 10 mmHg One click and wait
- 3. Alveolar- arterial Difference O2 CO2 Oxygenation Failure WIDE GAP piO2 = 150 pCO2 = 40 palvO2= 150 – 40/.8 =150-50 =100 PaO2 = 45 D = 100 - 45 = 55 Ventilation Failure NORMAL GAP piO2 = 150 pCO2 = 80 palvO2= 150-80/.8 =150-100 = 50 PaO2 = 45 D = 50 - 45 = 5 PAO2 (partial pres. of O2. in the alveolus.) = 150 - ( PaCO2 / .8 ) 760 – 45 = 715 : 21 % of 715 = 150 No click
- 4. 20 × 5 = 100 Expected PaO2 = FiO2 × 5 = PaO2 Normal situation No click
- 5. The Blood Gas Report: normals… pH 7.40 + 0.05 PaCO2 40 + 5 mm Hg PaO2 80 - 100 mm Hg HCO3 24 + 4 mmol/L The essentials HCO3 No click
- 6. PaCO2 of 10 pH Acute change .08 Chronic change .03 No click
- 7. INTERPRETATION OF A.B.G. FOUR STEP METHOD OF DEOSAT 1) LOOK FOR pH 2) WHO IS THE CULPRIT ? 3) IF RESPIRATORY ACUTE / CHRONIC ? 4) IF METABOLIC / COMP. / ANION GAP CLINICAL CORRELATION No click
- 8. compensation considered complete when the pH returns to normal range Clinical blood gases by Malley No click
- 9. COMPENSION LIMITS METABLIC ACIDOSIS PaCO2 = Up to 10 ? METABOLIC ALKALOSIS PaCO2 = Maximum 6O RESPIRATORY ACIDOSIS BICARB = Maximum 40 RESPIRATORY ALKALOSIS BICARB = Up to 10 No click
- 10. Blood Gas Report Measured 37.0 o C pH 7.523 PaCO2 30.1 mm Hg PaO2 105.3 mm Hg Calculated Data HCO3 act 22 mmol / L O2 Sat 98.3 % PO2 (A - a) 8 mm Hg D PO2 (a / A) 0.93 Entered Data FiO2 21.0 % Case 1 16 year old female with sudden onset of dyspnea. No Cough or Chest Pain Vitals normal but RR 56, anxious. One clicks for answer Acute respiratory alkalosis And why acute ?
- 11. Case 2 6 year old male with progressive respiratory distress Muscular dystrophy . Blood Gas Report Measured 37.0 o C pH 7.301 PaCO2 76.2 mm Hg PaO2 45.5 mm Hg Calculated Data HCO3 act 35.1 mmol / L O2 Sat 78 % PO2 (A - a) 9.5 mm Hg D PO2 (a / A) 0.83 Entered Data FiO2 21 % pH <7.35 :acidemia Res. Acidemia : High PaCO2 and low pH Hypoxemia Normal A-a gradient D CO2 =76-40=36 Expected D pH for ( Acute ) = .08 for 10 Expected ( Acute ) pH = 7.40 - 0.29=7.11 Chronic resp. acidosis Hypoventilation Chronic respiratory acidosis With hypoxia due to hypoventilation Five clicks
- 12. 7.60 20 7.50 30 7.40 40 7.30 50 7.20 60 7.10 70 pH PaCO2 Acute respiratory change Last two digits pH 80 – PaCO2 No click
- 13. Case 3 8-year-old male asthmatic; 3 days of cough, dyspnea and orthopnea not responding to usual bronchodilators. O/E: Respiratory distress; suprasternal and intercostal retraction; tired looking; on 4 L NC. Blood Gas Report Measured 37.0 o C pH 7. 24 PaCO2 49.1 mm Hg PaO2 66.3 mm Hg Calculated Data HCO3 act 18.0 mmol / L O2 Sat 92 % PO2 (A - a) mm Hg D PO2 (a / A) Entered Data FiO2 30 % 153-66= 87 pH <7.35 ; acidemia PaCO2 >45; respiratory acidemia piO2 = 715x.3=214.5 / palvO2 = 214-49/.8=153 Wide A / a gradient Hypoxia WITH INCREASE IN CO2 BICARB MUST RISE ? Bicarbonate is low……… Metabolic acidosis + respiratory acidosis 30 × 5 = 150 D CO2 = 49 - 40 = 9 Expected D pH ( Acute ) = 9/10 x 0.08 = 0.072 Expected pH ( Acute ) = 7.40 - 0.072 = 7.328 Acute resp. acidosis 8-year-old male asthmatic with resp. distress Six clicks
- 14. Case 4 8 year old diabetic with respi. distress fatigue and loss of appetite. Blood Gas Report Measured 37.0 o C pH 7.23 PaCO2 23 mm Hg PaO2 110.5 mm Hg Calculated Data HCO3 act 14 mmol / L O2 Sat % PO2 (A - a) mm Hg D PO2 (a / A) Entered Data FiO2 21.0 % pH <7.35 ; acidemia HCO3 <22; metabolic acidemia Last two digits of pH Correspond with co2 If Na = 130, Cl = 90 Anion Gap = 130 - (90 + 14) = 130 – 104 = 26 Three clicks
- 15. Blood Gas Report Measured 37.0 o C pH 7.46 PaCO2 28.1 mm Hg PaO2 55.3 mm Hg Calculated Data HCO3 act 19.2 mmol / L O2 Sat % PO2 (A - a) mm Hg D PO2 (a / A) Entered Data FiO2 24.0 % Case 5 : 10 year old child with encephalitis pH almost within normal range Mild alkalosis PaCO2 is low , respiratory low by around 10 ( Acute ) by .08 (Chronic ) by .03 BICARBINATURIA Bicarb looks low ? Is it expected ? Four clicks
- 16. These findings are most consistent with…. a) Metabolic acidosis with compensatory Hypocapnia. b) Primary metabolic acidosis with respiratory alkalosis. c) Acute respiratory alkalosis fully compensated. d) Chronic respiratory alkalosis fully compensated. pH 7.39 PCO2 l5mmHg HCO3 8mmol/L PaO2 90 mmHg For metabolic acidosis: FULL COMPENSATION Expected PaCO2 = (1.5 x [HCO3]) + 8 ) + 2 (Winter’s equation) PCO 2 ……SHOULD BE 20 Case 6…………. One click
- 17. Adolescent boy with appendicitis , posted for surgery , he is a known case of SLE. His pre-op ABG shows : Room air pH 7.39 pCO2 l5mmHg paO2 90 mmHg HCO3 8mmol/L These findings are most consistent with…. a) Metabolic acidosis with compensatory Hypocapnia. b) Primary metabolic acidosis with respiratory alkalosis. c) Acute respiratory alkalosis fully compensated. d) Chronic respiratory alkalosis fully compensated. What is the probable cause for the above findings ? Are they OK as far as oxygenation is concerned ? Case 7………. No click
- 18. Patient was hypo volumic , received Normal Saline bolus... Corrected acidosis He was operated ….but post-op became drowsy His ABG…….. FiO2….30% pH 7.38 PaCO2 38 PaO2 60 1) Why hypoxemia ? 2) Were the lungs bad to begin with ? ( Pre OP PaO2 90 mmHg ) 3) Micro atelectesis during surgery ? Anesthetist goofed up the case 4) Pure and simple hypoventilation …..Sedation ? No click
- 19. Why hypoxemia ? Lungs were bad to begin with ? Micro atelectesis during surgery Pure and simple hypoventilation ? sedation PRE OP ….ABG on room air pH 7.39 PaCO2 l5mmHg PaO2 90 mmHg HCO3 8mmol/L Pre OP .....A/a gradient palv O2 = Pi O2 – PaCO2 / RQ = 150 – 15 / 0.8 = 150 – 18 = 132 mm Hg 132 – 90= 42 WIDE A / a gradient Oxygenation status good …..? One click
- 20. Apparently the lungs looked good with PaO2 of 90……. But have a good look at the ABG again With wash out of CO 2 ………. The expected PaO2 should have been more than 90 . This coupled with correction of acidosis ( normalizing PaCO2 ) Lowered the PaO2 …post operatively. Conclusion …….. Lungs were not normal to begin with ( SLE )…….. No click
- 21. Correlate PaO2 with FiO2 But please also correlate with PaCO2 Learning point No click
- 22. Respiratory Alkalosis Is it acute ? What is the Diagnosis Click for answer Case 8,,,,,,,,,,,,,,,,,, pH 7.583 PCO2 19.8 HCO3 18.7
Editor's Notes
- #2: 45 is partial pressure of water vapour Rq resp quotient .8