Renal Replacement in Critical Care

Dr Jonathon Goodall, Consultant Intensivist, Salford

Renal Replacement in Critical Care

Acute renal failure (ARF) is a common in the unwell critical care patient. The kidney has very high metabolic activity, and is therefore particularly susceptible to consequences of low blood pressure and under perfusion. Although ARF is usually found in the context of multi-organ dysfunction, occasionally a single identifiable event can precipitate acute renal failure, such as a period of hypoxia or drug toxicity.

Management of ARF

The management of ARF can be divided into several important stages:

Prevention of Renal Failure

By early identification of the patient at risk of ARF: patients with pre-existing renal disease & chronic renal impairment, diabetic patients, patients taking potentially nephrotoxic drugs, many episodes of ARF may be avoided. Management includes careful fluid balance, meticulous cardiovascular support (with rapid expansion of intravascular volume and use of vasopressors or inotropes when indicated), avoidance of nephrotoxins and aggressive treatment of sepsis. Constant monitoring of renal function is vital.

Renal Supportive Strategies

Early in the course of renal dysfunction, patients should be managed as outlined in the preventative measures. Optimisation of circulating volume and restoration of renal perfusion is essential. Management of electrolyte disturbances will also help in some cases. If these methods fail to restore renal function, there is little evidence to suggest that use of diuretics (such as frusemide or mannitol) alter the course of the ARF, although these may be used in some circumstances.

Blood Purification (Renal Replacement) Strategies

In general it is better to start renal replacement early in the course of an episode of ARF. This allows for control of electrolyte and acid base disturbance, and also supports effective nutrition. Several renal replacement options are available, as outlined in Table 1.

Table 1. Methods of Renal Replacement used on Intensive Care

The presentation will expand on the principles of renal replacement, an some of the advantages and disadvantages of each these techniques.

CVVHD (continuous venovenous hemodialysis)