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BLOOD GAS ANALYSIS REVISION. SHARON HARVEY 5/10/04. PaO 2 PaCO 2 pH. Partial pressure of oxygen normal 10.8 –13.0 kpa Partial pressure of carbon dioxide normal 4.0 – 6.0 kpa Normal 7.35 – 7.45. REVISION. HCO 3 BE. Concentration of bicarbonate normal 22-26 mmol l -1
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BLOOD GAS ANALYSIS REVISION SHARON HARVEY 5/10/04
PaO2 PaCO2 pH Partial pressure of oxygen normal 10.8 –13.0 kpa Partial pressure of carbon dioxide normal 4.0 – 6.0 kpa Normal 7.35 – 7.45 REVISION
HCO3 BE Concentration of bicarbonate normal 22-26 mmol l-1 Base excess – the quantity of strong acid or base required to restore pH to normal. Normal range +2mmol l-1 to – 2mmol l-1 a positive BE indicates an excess of base while a negative value indicates a deficit of base. REVISION
QUESTIONS TO ASK YOURSELF • ASSESS OXYGENATION Is the patient hypoxic? • DETERMINE STATUS OF THE pH pH> 7.45 = alkalosis pH< 7.35 = acidosis • DETERMINE RESPIRATORY COMPONENT PaCO2 > 6.0 kpa = respiratory acidosis PaCO2 < 4.0 kpa = respiratory alkalosis • DETERMINE METABOLIC COMPONENT HCO3 < 22 mmol l-1 = metabolic acidosis HCO3 > 26 mmol l-1 = metabolic alkalosis
BLOOD GAS ANALYSIS • A 60 year old man is admitted with exacerbation of chronic obstructive pulmonary disease. His arterial blood gases on air showed:- • pH = 7.29 • PaCO2 = 8.5 kpa • PaO2 = 8.0 kpa • HCO3 = 30.5 mmol l-1 • What is the acid-base disturbance and what is the medical management of this patient?
BLOOD GAS ANALYSIS • Answer • This patient has an acidosis wit a high PaCO2 and normal HCO3. This is common in exacerbation of COPD. Treatment would usually involve nebulisers, steroids and antibiotics and possible non-invasive ventilation
BLOOD GAS ANALYSIS • A 30 year old man is admitted with status epilepticus. He is given intravenous diazepam. Arterial blood gases on 15 l/min via a reservoir bag mask showed:- • pH = 7.05 • PaCO2 = 8 kpa • PaO2 = 15 kpa • HCO3 = 16 mmol l-1 • What is his acid-base disturbance and why?
BLOOD GAS ANALYSIS • Answer • The patient has an acidosis with both a high PaCO2 and a high HCO3. The PaO2 is lower than expected because the patient was breathing around 70% oxygen. He has a lactic acidosis from prolonged fitting and a respiratory acidosis from intravenous diazepam.