Acute kidney injury (AKI) is a deadly and incompletely understood disorder in which sudden impairment of kidney function occurs secondary to one or more of a variety of underlying conditions. Mortality associated with AKI is very high and treatment is unsatisfactory. The condition primarily affects acutely ill and injured patients and disproportionably affects the elderly. Many of those that survive have permanent kidney failure and other long-term morbidities, which may include cardiovascular disease and immune dysfunction. While the term 'acute kidney injury' dates back to the early 20th century, when it was used in reference to acute mercury poisoning, it has only recently been applied to describe impaired kidney function in the setting of critical illness. In 2002, during an Acute Dialysis Quality Initiative (ADQI) conference held in Vicenza, AKI was defined using the now widely accepted consensus criteria known as RIFLE (Risk, Injury, Failure, Loss, End-Stage Kidney Disease). AKI replaced the term acute renal failure in part because of the recognition that acute impairment in renal function, even when relatively mild and far less than frank failure, was associated with worse clinical outcomes. Criteria for AKI were therefore set at small changes in serum creatinine or urine output. Thanks to consensus criteria for AKI, we now know that this condition is very common, occurring in as many as two thirds of ICU patients and about 2,100 per million population, and is associated with dramatic reductions in survival -as much as a 3-to 8-fold decrement at hospital discharge compared to controls without AKI.
Although there is some evidence that mortality rates may have decreased in recent years, the incidence of sepsis is increasing so that overall deaths from this disease are increasing. Improved diagnostic techniques and classification may help target therapies more rapidly and more appropriately.
The respiratory system is key to the management of patients with respiratory, as well as haemodynamic, compromise and should be monitored. The ventilator is more than just a machine that delivers gas; it is a true respiratory system monitoring device, allowing the measurement of airway pressures and intrinsic positive end-expiratory pressure and the plotting of pressure/volume curves. For effective and reliable monitoring, it is necessary to keep in mind the physiology, such as the alveolar gas equation, heart-lung interactions, the equation of movement, etc. Monitoring the respiratory system enables adaptation of not only respiratory management, but also haemodynamic management.
