OXYGEN

Scenario 4 Solution

A 78 year old male is admitted with a six month history of shortness of breath, ankle edema, orthopnea, a productive cough, hoarseness and 30-40lb weight loss. He has a palpable mass in his abdomen, which turns out to be colonic cancer. As part of his preoperative work up, a blood gas is performed: pH 7.42 PaCO₂ 36 PaO₂ 41 SaO2 78%. He is put on 100% oxygen, has a chest x-ray performed, which is normal, and a spiral CT of his thorax, which also appears normal. His blood gas on 100% oxygen is: pH 7.46, PaCO₂ 36, PaO₂ 42, SaO₂ 78%.

What do you think is wrong with this patient?

Hypoxemia refractory to oxygen therapy is a right to left shunt until otherwise proven. This patient underwent echocardiography which showed a markedly enlarged right ventricle with reduced right ventricular function; there was reduced global left ventricular function. On cardiac catheterization this patient had a patent foramen ovale, a right to left shunt (with Eisenmenger physiology), and equalization of pulmonary and systemic blood pressures. Of his 8 liter cardiac output, 6 litres were shunting right to left. He was unsuitable for surgery.

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