I can tell you why metric: It is much, much easier.One liter of water weighs one kilo. If you come in 2.4 kilos over your dry weight you'd need 2.4 liters of fluid removed (net, in the event you'd add in prime and rinse back).If you looked at the same situation as being 4.8 pounds over your dry weight ... how many ounces is that, that you'd need removed?
As for the sodium bicarb--your blood was probably too acidic due to changes in your electrolye balance so the MD ordered the bicarb to make it more alkaline. Many dialysis patients take it. I took it to keep my blood more alkaline because my body likes to make uric acid kidney stones and by taking it I have had no more stones formed.