I had a patient with severe ARDS who had been anuric for 24 hours. She was in a respiratory acidosis, with a PaCO2 of 75 and a bicarb of 18. Her pH was 7.20.The fellow ordered CRRT, but the next day the attending d/c it saying that the pt didn't need CRRT because this was a respiratory acidosis. This didn't make sense to me. First of all, even though the pt's electrolytes were stable, shouldn't anurea itself be an indication for immediately starting dialysis? (She was hypotensive, so she needed CRRT). Also, the bicarb wasn't compensating for the respiratory acidosis. I agreed with the fellow's reasoning which was that by starting dialysis to compensate for the respiratory acidosis we could use lower lung volumes, which would benefit the pt's ARDS. All that made sense to me, but the attending disagreed. I didn't hear his reasoning, but what do you guys think?