Renal failure after cardiac surgery: Pathophysiology, prevention and treatment

Acute renal failure is common after cardiac surgery and is associated with a high mortality. There are many causes, but renal ischaemia associated with low cardiac output and hypotension, nephrotoxins and sepsis are the most common. Most patients who develop renal failure continue to pass an adequate volume of urine, so urine output is a poor indicator of renal function. Prevention should be based on maintaining circulating blood volume, which requires close haemodynamic monitoring and optimisation of renal oxygen delivery by maintaining an adequate arterial oxygen saturation, haemoglobin concentration, cardiac output and perfusion pressure. Nephrotoxic agents such as gentamicin, vancomycin and indomethacin should be avoided, particularly in patients at increased risk of renal failure. Sepsis must be detected early and treated appropriately. Renal failure requires aggressive nutritional support and careful fluid, electrolyte and acid-base management. This is best done with a continuous form of renal replacement therapy such as venovenous haemofiltration.