acid base examples of cases. presentation

acid base disorders

1. Alveolar-arterial Difference Inspired O 2 = 21 % p i O 2 = (760-45) x . 21 = 150 mmHg O 2 CO 2 p alv O 2 = p i O 2 – pCO 2 / RQ = 150 – 40 / 0.8 = 150 – 50 = 100 mm Hg PaO 2 = 90 mmHg p alv O 2 – p art O 2 = 10 mmHg One click and wait

2. Alveolar- arterial Difference O 2 CO 2 Oxygenation Failure WIDE GAP p i O 2 = 150 pCO 2 = 40 p alv O 2 = 150 – 40/.8 =150-50 =100 PaO 2 = 45 D = 100 - 45 = 55 Ventilation Failure NORMAL GAP p i O 2 = 150 pCO 2 = 80 p alv O 2 = 150-80/.8 =150-100 = 50 PaO 2 = 45 D = 50 - 45 = 5 PAO 2 (partial pres. of O 2 . in the alveolus.) = 150 - ( PaCO 2 / .8 ) 760 – 45 = 715 : 21 % of 715 = 150 No click

3. 20 × 5 = 100 Expected PaO 2 = FiO 2 × 5 = PaO 2 Normal situation No click

4. The Blood Gas Report: normals… pH 7.40 + 0.05 PaCO 2 40 + 5 mm Hg PaO 2 80 - 100 mm Hg HCO 3 24 + 4 mmol/L O2 Sat >95 Always mention and see FIO2 The essentials HCO3 No click

5. PaCO 2 of 10 pH Acute change .08 Chronic change .03 No click

6. INTERPRETATION OF A.B.G. FOUR STEP METHOD OF DEOSAT LOOK FOR pH WHO IS THE CULPRIT ? IF RESPIRATORY ACUTE / CHRONIC ? IF METABOLIC / COMP. / ANION GAP CLINICAL CORRELATION No click

7. compensation considered complete when the pH returns to normal range Clinical blood gases by Malley No click

8. 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

9. Blood Gas Report Measured 37.0 o C pH 7.523 PaCO 2 30.1 mm Hg PaO 2 105.3 mm Hg Calculated Data HCO 3 act 22 mmol / L O 2 Sat 98.3 % PO 2 (A - a) 8 mm Hg D PO 2 (a / A) 0.93 Entered Data FiO 2 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 ?

10. Case 2 6 year old male with progressive respiratory distress Muscular dystrophy . Blood Gas Report Measured 37.0 o C pH 7.301 PaCO 2 76.2 mm Hg PaO 2 45.5 mm Hg Calculated Data HCO 3 act 35.1 mmol / L O 2 Sat 78 % PO 2 (A - a) 9.5 mm Hg D PO 2 (a / A) 0.83 Entered Data FiO 2 21 % pH <7.35 :acidemia Res. Acidemia : High PaCO 2 and low pH Hypoxemia Normal A-a gradient D CO 2 =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

11. 7.60 20 7.50 30 7.40 40 7.30 50 7.20 60 7.10 70 pH PaCO 2 Acute respiratory change Last two digits pH 80 – PaCO 2 No click

12. 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 PaCO 2 49.1 mm Hg PaO 2 66.3 mm Hg Calculated Data HCO 3 act 18.0 mmol / L O2 Sat 92 % PO 2 (A - a) mm Hg D PO 2 (a / A) Entered Data FiO 2 30 % 153-66= 87 pH <7.35 ; acidemia PaCO 2 >45; respiratory acidemia p i O 2 = 715x.3=214.5 / p alv O 2 = 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 CO 2 = 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

13. 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 HCO 3 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

14. Blood Gas Report Measured 37.0 o C pH 7.46 PaCO2 28.1 mm Hg PaO2 55.3 mm Hg Calculated Data HCO 3 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 PaCO 2 is low , respiratory low by around 10 ( Acute ) by .08 (Chronic ) by .03 BICARBINATURIA Bicarb looks low ? Is it expected ? Four clicks

15. 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 PCO 2 l5mmHg HCO 3 8mmol/L PaO 2 90 mmHg For metabolic acidosis: FULL COMPENSATION Expected PaCO 2 = (1.5 x [HCO3]) + 8 ) + 2 (Winter’s equation) PCO 2 ……SHOULD BE 20 Case 6…………. One click

16. Adolescent boy with appendicitis , posted for surgery , he is a known case of SLE. His pre-op ABG shows : Room air pH 7.39 pCO 2 l5mmHg paO 2 90 mmHg HCO 3 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

17. Patient was hypo volumic , received Normal Saline bolus... Corrected acidosis He was operated ….but post-op became drowsy His ABG…….. FiO 2 ….30% pH 7.38 PaCO 2 38 PaO 2 60 1) Why hypoxemia ? 2) Were the lungs bad to begin with ? ( Pre OP PaO 2 90 mmHg ) 3) Micro atelectesis during surgery ? Anesthetist goofed up the case 4) Pure and simple hypoventilation …..Sedation ? No click

18. 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 PaCO 2 l5mmHg PaO 2 90 mmHg HCO 3 8mmol/L Pre OP .....A/a gradient p alv O 2 = P i O 2 – PaCO 2 / RQ = 150 – 15 / 0.8 = 150 – 18 = 132 mm Hg 132 – 90= 42 WIDE A / a gradient Oxygenation status good …..? One click

19. Apparently the lungs looked good with PaO 2 of 90……. But have a good look at the ABG again With wash out of CO 2 ………. The expected PaO 2 should have been more than 90 . This coupled with correction of acidosis ( normalizing PaCO 2 ) Lowered the PaO 2 …post operatively. Conclusion …….. Lungs were not normal to begin with ( SLE )…….. No click

20. Correlate PaO 2 with FiO 2 But please also correlate with PaCO 2 Learning point No click

21. Respiratory Alkalosis Is it acute ? What is the Diagnosis Click for answer Case 8,,,,,,,,,,,,,,,,,, pH 7.583 PCO2 19.8 HCO3 18.7