• SOM 4th Yr Curriculum

• CLERKSHIP INFORMATION
• Introduction / Goals and Objectives
• Rotations
  • HMC
  • UWMC
  • VAMC
• Seminars
• Faculty Only
• PULMONARY EDUCATION
• Pulmonary Med Library
• Arterial Blood Gases
• Cardiopulmonary Exercise Testing
• Mechanical Ventilation
• Pulmonary Function Testing
• Pleural Effusion
• Radiology

Arterial Blood Gas

Case 1 Answers

A 24 year-old woman is found down in Pioneer Square by some bystanders. The medics are called and, upon arrival, find her with an oxygen saturation of 88% on room air and pinpoint pupils on exam. She is brought into the Harborview ER where a room air arterial blood gas is performed and reveals: pH 7.25, PCO₂ 60, PO₂ 65 HCO₃- 26, Base Excess 1. Her chemistry panel shows: sodium 137, chloride 100, bicarbonate 26.

Acid-base status:

• The patient has a low pH (acidemia)
• The PCO₂ is high (respiratory acidosis) and the bicarbonate is at the upper end of normal. The low pH and high PCO₂ imply that the respiratory acidosis is the primary process
• The anion gap is 10 and is, therefore, normal. The patient does not have an elevated anion gap acidosis.
• There is no compensatory process. Although the measured bicarbonate is just above normal, the base excess of 1 tells us that there is no metabolic alkalosis
• The delta gap is 10 -12 = -2 and the delta-delta is -2 + 27 = 25. There is, therefore, no metabolic process.
• Summary: An acute, uncompensated respiratory acidosis leading to acidemia.

Alveolar-arterial oxygen difference:

The alveolar-arterial difference is 10 mmHg, a normal value, which tells us that her hypoxemia is entirely due to hypoventilation.

Explanation for the clinical picture:

The respiratory acidosis implies that the patient is hypoventilating. This fact, in combination with the pinpoint pupils suggests the patient is suffering from an acute narcotic overdose. In this case, the narcotic is most likely heroin.

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