Arterial blood gas

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Arterial blood gas

• Dr. Basu MD

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(Acid) The Respiratory System

• ? ventilation "blow off" CO2 (acid) ?? CO2
  (acid) ? Alkalosis.
• ? ventilation ? retain CO2 (acid) ? ? CO2 (acid)
  ? Acidosis.

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(Base) The Renal System

• Acidosis ? H and low HCO3 (base)
• Compensation
• Kidney excreting H and retaining HCO3 (base).
• Lung increasing ventilation to blow off CO2
  (acid) and decrease the Acidosis.

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(Base) The Renal System

• Alkalosis ? H and excess HCO3 (base).
• Compensation
• Kidney excrete HCO3 and retain H
• Lung hypoventilation to retain CO2 (acid) to
  decrease the Alkalosis.

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Normal value

• pH 7.35-7.45,
• pCO2 of 35-45 mmHg
• HCO3 22-26 mmol/L

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How to reads the data

• First, look at pH. (Normal 7.35-7.45)
• pH is lt 7.35 ACIDOSIS. pH is gt 7.45
  ALKALOSIS.

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look at pH again

• If -- 7.35-7.45 (normal) COMPENSATED.
• If pH is lt7.35 or gt7.45 UNCOMPENSATED.

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Metabolic or respiratory

• CO2 is lt35 or gt45 RESPIRATORY.
• HCO3 is lt22 or gt26 METABOLIC.

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?

• pH 7.55 ,  CO2 40,  HCO3 30
• pH 7.35,  CO2 45,  HCO3 20

If it is 7.35-7.45 (normal) COMPENSATED. If
the pH is lt7.35 or gt7.45 UNCOMPENSATED.
CO2 is lt35 or gt45 RESPIRATORY. HCO3 is lt22 or
gt26 METABOLIC
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CO2 is lt35 or gt45 RESPIRATORY. HCO3 is lt22 or
gt26 METABOLIC
pH 7.50 PaCO2 45 HCO3 33 Uncomp. Met. Alk.
pH 7.44 PaCO2 47 HCO3 28 Com Met alka.
pH 7.20 PaCO2 36 HCO3 14 Uncomp. Met acidosis
pH 7.35 PaCO2 31 HCO3 18.1 Com. Met acidosis
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pH 7.50 PaCO2 29 HCO3 22 Uncomp Resp. alka
pH 7.43 PaCO2 32 HCO3 21 pH 7.42 PaCO2 32 HCO3 20 Com Resp alka
pH 7.23 PaCO2 59 HCO3 22 Uncomp Resp acidosis
pH 7.36 PaCO2 56 HCO3 31.4 pH 7.38 PaCO2 70 HCO3 42 Com Resp acidicosis
CO2 is lt35 or gt45 RESPIRATORY. HCO3 is lt22 or
gt26 METABOLIC
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Respiratory Acidosis

• ? pCO2 .
• Compensation ? HCO3
• Cause
• Chronic obstructive pulmonary disease (COPD)
• Electrolyte deficiencies (K, P04 - )

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Initial value / after Compensation

• Without Compensation
• pH (lt7.35)
• PaCO2 (gt47 mm Hg)
• HCO3 20-26 mmol/L

• WithCompensation
• pH ( 7.35)
• PaCO2 (gt47 mm Hg)
• HCO3 32mmol/L ( acute)
• HCO3 44mmol/L ( chronic)

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Respiratory alkalosis

• arterial pCO2 falls
• Compensation ? bicarbonate slightly.
• Hyperventilation
• Pneumonia
• Shock/decreased cardiac output

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Respiratory alkalosis

• pH (gt 7.45)
• PaCO2 ( 20 mm Hg)
• HCO3 28 mmol/L

• pH ( 7.35)
• PaCO2 ( 20 mm Hg)
• HCO3 18 mmol/L

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Metabolic acidosis

• ? in fixed acids in the blood.
• Compensation hyperventilation gt ? pCO2
• Cause
• Diarrhea
• Alcoholism (ethanol)
• Ketoacidosis

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Metabolic acidosis ketoacidosis

• Glucose gt 250
• pH 7.00 to 7.24
• HCO3 10 to lt 15
• PaCO2 ( 25 mm Hg)
• Anion gap gt11
• Increased electrolytes

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Metabolic alkalosis

• Plasma bicarbonate increases
• Compensation hypoventilation gt CO2 retention.
• Cause
• Gastric fluid loss Vomiting

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Metabolic alkalosis

• pH 7.58
• pCO2 21 mmHg
• HCO3  40 mmol/l
• gt 26
• pO2  154 mmHg

• pH  7.50
• pCO2 60 mmHg
• HCO3  40 mmol/l
• pO2  154 mmHg

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Thank you