Which of the Following Patients Should Be Evaluated First

Which of the following patients should be evaluated first?

A) 76-year-old female admitted 3 days ago with pneumonia; most recent blood gases are pH 7.35, PaO₂ of 90, HCO₃ of 35, and PaCO₂ of 29
B) 48-year-old male admitted yesterday with kidney stones complaining of pain of a 5 on a 0-10 scale
C) 52-year-old female admitted yesterday with acute renal failure; most recent lab results are pH of 7.3, PaO₂ of 94, HCO₃ of 15, PaCO₂ of 44, K of 6.1, Na of 148, and osmolality of 369
D) 59-year-old male admitted 2 days ago with stage III bronchogenic carcinoma complaining of nausea and pain of a 6 on a 0-10 scale