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The Siggaard-Andersen acid-base chart. Radiometer Medical ApS, Åkandevej 21, DK-2700 Brønshøj, Tel: +45 38 27 38 27, www.radiometer.com. The Siggaard-Andersen Acid-Base Chart. Illustrating p CO 2 pH standard base excess, SBE, c Base(ecf) Tool for fast interpretation of acid-base status
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The Siggaard-Andersen acid-base chart Radiometer Medical ApS, Åkandevej 21, DK-2700 Brønshøj, Tel: +45 38 27 38 27, www.radiometer.com
The Siggaard-Andersen Acid-Base Chart • Illustrating • pCO2 • pH • standard base excess, SBE, cBase(ecf) • Tool for fast interpretation of acid-base status • illustrates metabolic and respiratory conditions • differentiates between acute and chronic cases • gives a reading of SBE
Use of the Siggaard-Andersen Chart • Acid-base balance is maintained by • respiratory regulation • metabolic regulation • Difficult to establish the underlying cause for a disturbance • SBE indicates the metabolic acid-base status • is practically unaffected by respiratory changes • indicates the level of “missing buffer capacity” • Slopes have been experimentally determined by CO2 inhalation or hyperventilation
Chronic resp. acidosis Acute resp. acidosis Chronic metab. alkalosis Acute metab. acidosis Acute resp. alkalosis Chronic metab. acidosis Chronic resp. alkalosis
Case: 56-year-old man • A 56-year-old man was admitted to hospital because ofdyspnea and cyanosis • A BG sample is drawn
pO2 35.2 mmHg pCO2 99 mmHg sO2 62% • Chronic hypercapnia with an acute exacerbation • A chest X-ray revealed emphysema and fibrosis
Patient result
Treatment • On suspicion of pulmonary infection antibiotic treatment was started and supplemental oxygen was administered by one liter per minute nasally • Because of the chronic hypercapnia, oxygen treatment might cause risk of further deterioration due to hypoventilation • The second arterial blood gas results were collected 30 minutes after start of oxygen treatment:
pO2 45 mmHg pCO2 91.5 mmHg sO2 77% • Slight improvement
Patient result
Treatment • The oxygen supply was increased to two liters per minute • Another 30 minutes later the third blood gas status was measured:
pO2 69.8 mmHg pCO2 106.5 mmHg sO2 91% • This revealed that the oxygen therapy had caused hypoventilation and acute hypercapnia
Patient result
Treatment • The oxygen flow was therefore decreased to one liter per minute again • During the next hours the arterial blood gas status gradually improved • Six hours after admission, the patient’s blood gas status turned out to be:
pO2 57.0 mmHg pCO2 82.5 mmHg sO2 88%
Patient result
Conclusion - Acid-Base Chart • This case shows the importance of fast and correct interpretation of the acid-base status • If the chronic component of the initial arterial blood gas status had been misjudged, the patient would have been given more supplemental oxygen, and this could have caused severe hypoventilation or even respiratory arrest
Radiometer Medical ApS, Åkandevej 21, DK-2700 Brønshøj, Tel: +45 38 27 38 27, www.radiometer.com