Managing patients with lactic acidosis, especially the type A variety, is really hard! Usually they have multiple problems, are septic, hypotensive, often on multiple machines and the lactate keeps going up. The choices are between giving soda bicarb, carbicarb or dichloroacetate. The main purpose is to avoid some of complications of severe acidosis such arrhythmias, decreased response to cathechloamines, or reduced contractility. Bicarbonate therapy is a double-edged sword, however, because of the several side-effects such as decreased cardiac output, reduced ionized cardiac output, increased CO2 generation, volume overload and increased lactate generation. Paradoxically, it can also worsen intracellular acidosis.
Staff managing these patients think that it would be great to simply clear it out using an extracorporeal therapy, such as hemodialysis or CRRT.
Unfortunately it usually does not work. Lactate clearance by dialysis is only 3% of the overall clearance, most of which is in the tissue. In one study, they evaluated the utility of continuous venovenous hemofiltration with dialysis, to calculate lactate clearance by the hemofilter in 10 critically ill patients with acute renal failure and stable blood lactate concentrations. They found that the median blood lactate concentration increased despite renal replacement therapy. The median total plasma lactate clearance was 1379 ml/min (range, 754 to 1881 ml/min), and the median filter lactate clearance was 24 ml/min (range, 7 to 36 ml/min). The authors concluded that continuous venovenous hemofiltration with dialysis cannot meet lactate overproduction.
Moreover, the generation of lactic acid is at least order of magnitude greater than the clearance.
The only situation where dialysis has been helpful in management of lactic acidosis is when it is secondary to metformin therapy – even there opinions are divided.
This is not to say extracorporeal therapies are not indicated in patients with lactic acidosis: it can help by volume management, cytokine removal and other mechanisms that can indirectly reduce lactic acid production.