What would cause dark fluid drained from both lungs, having also a severe blood infection?

The infection itself: Very hard to answer with just the details given but if there was a pneumonia with the bloodstream infection, it could have been a parapneumonic effusion which is inflammatory fluid between the lungs and the chest wall (the pleural space). In sepsis and bloodstream infections, if large amounts of IV fluids are given, it is very common for fluid to accumulate in the pleural space. Hope this helps.