Most complications of arteriovenous hemofiltration (Tabie.3) are attributable to the arterial access. Likewise, inadequate azotemia control only applies to the spontaneous arteriovenous techniques. Azotemia control with pump-driven continuous hemofiltration compares favorably with intermittent hemodialysis and, for the same amount of therapy (product of clearance and time), continuous techniques remove more urea because of their access to the total distribution volume. Balancing errors are reduced by the use of automated balancing devices. Extracorporeal losses have to be taken into account when planning nutritional support and drug dosing.
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Table 3 Disadvantages and limitations of CRRT
One of the major disadvantages of CRRT is the need for continuous anticoagulation. CRRT leads to patient immobilization and hypothermia. Prevention of disconnection with disastrous bleeding requires the use of Luer lock connections and sensible pressure monitoring. CRRT requires the presence of medical and nursing expertise within the ICU and increases the workload for intensive care nurses.
An improved outcome compared with conventional dialysis has yet to be conclusively demonstrated. Indications
Uncomplicated acute renal failure can be treated with intermittent dialysis, but almost 90 per cent of intensive care patients with acute renal failure have associated failure of other organs (TabJe...4). In these patients continuous therapy should be used, particularly when fluid removal is the primary indication or when there is cerebral edema, hemodynamic instability, or the need for aggressive nutritional support.
Most of these patients present with a systemic inflammatory response syndrome where circulating mediators are involved in the pathogenesis. Although many of these mediators have been shown to be present in the ultrafiltrate, a reduction of plasma level has only been demonstrated for some secondary mediators (complement activation products, arachidonic acid metabolites, interleukin 6, interleukin 8, elastase, myocardial depressant factor) and not for the proinflammatory cytokines tumor necrosis factor and interleukin 1. However, experimental and (to a lesser extent) clinical studies have shown a beneficial effect of hemofiltration on hemodynamic and respiratory status and even suggest an improved outcome in septic subjects.
Finally, other possible indications of CRRT are severe electrolyte and acid-base disturbances.
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