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Acid Base Balance Cases

Acid Base Balance Cases. Dr Svitlana Zhelezna Clinical Teaching Fellow UHCW NHS Trust svitlana.zhelezna@uhcw.nhs.uk 2013/2014 academic year. Acid-base balance. Maintenance of normal ECF [H + ] (pH) depends on the balance between: carbon dioxide production and excretion

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Acid Base Balance Cases

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  1. Acid Base Balance Cases Dr Svitlana Zhelezna Clinical Teaching Fellow UHCW NHS Trust svitlana.zhelezna@uhcw.nhs.uk 2013/2014 academic year

  2. Acid-base balance Maintenance of normal ECF [H+] (pH) depends on the balance between: carbon dioxide production and excretion hydrogen ion production and excretion Imbalances are dealt with by buffering Compensation But reversed usually only by correction of the underlying disorder

  3. Case 1 73 yr old man COAD/COPD Acute exacerbation, SOB, fever BaselineNormal Range pH 7.28 7.35-7.45 pCO2 9.7 4.5-6.0 kPa pO2 8.3 12-15 kPa Bicarb 34 22-28 mmol/L

  4. Respiratory acidosis Cause hypoventilation leading to CO2 retention Correction restore normal gas exchange Compensation increased renal acid excretion Features acutely: low pH, high [H+], n[HCO3-], high pCO2 chronically: low pH, high [H+], high [HCO3-], high pCO2

  5. Case 2 49 y. o. woman T1DM at A&E 2/7 drowsiness O/E: dehydrated, rapid deep breathing pH 7.12 (7.35-7.45) pCO2 2.2 kPa (4.5-6.0) pO2 15.3 kPa (12-15) bicarb 9 mmol/L (22-28)

  6. Case 3 62 yr old woman T2DM 2/7 increasing drowsiness, breathing rapidly and deeply Sodium 148 mmol/L 135-145 Potassium 6.1 mmol/L 3.5-5.0 Chloride 109 mmol/L 98-107 Bicarbonate 12 mmol/L 22-28 Urea 60 mmol/L 2.5-8.0 Creatinine 256 umol/L 60-110 pH 7.16 7.35-7.45 pCO2 2.9 4.5-6.0 kPa pO2 11.9 12-158 kPa Bicarb 11 22-28 mmol/L

  7. Metabolic acidosis Causes increased acid formation acid ingestion bicarbonate loss/AKI reduced metabolism/excretion Correction primary cause increased renal acid excretion Initial Compensation: hyperventilation, hence low pCO2 Features Acutely: low pH, high [H+], low [HCO3-], low pCO2 Chronically: low pH, high [H+], low [HCO3-], Normal pCO2

  8. Case 4 47-year old woman – vomiting persistently Previously treated for DU, dehydrated, hypotensive, RR 9 Sodium 142 mmol/L 135 -145 Potassium 2.9 mmol/L 3.5 - 5.0 Chloride 85 mmol/L 98 -107 Bicarbonate 44 mmol/L 22 - 28 Urea 24.3 mmol/L 2.5 - 8.0 Creatinine 150 mmol/L 60 -110 pH 7.55 7.35-7.45 pCO2 8.1 4.5-6.0 kPa pO2 13.2 12-158 kPa Bicarb 42 22-28 mmol/L

  9. Metabolic alkalosis (1) Cause loss of gastric acid increased renal H+ excretion e.g. in hypokalaemia Correction primary cause increased renal bicarbonate excretion Compensation hypoventilation with CO2 retention Features high pH, low [H+], high [HCO3-], N/high pCO2

  10. Metabolic alkalosis (2) Limit to compensation CO2 is respiratory stimulant Limits to correction Hypochloraemia thus increased bicarbonate reabsorption with sodium Hypovolaemia thus increased distal sodium reabsorption but potassium depletion (GI loss) so increased acid excretion (paradoxically acid urine)

  11. Thank you! Any questions?

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