Early action saves kidneys. The principles of treatment are as follows:
• Treat any life-threatening hyperkalaemia first.
• Correct hypovolaemia and establish an effective circulating volume.
• Treat hypoperfusion.
• Exclude obstruction as soon as possible.
• Treat the underlying cause.
In acute renal failure, early restoration of volume may be all that is required. Sometimes, volume replacement fails to restore blood pressure (for example, in severe sepsis or acute cardiac failure) in which case vasoactive drugs are required to improve renal perfusion. Bicarbonate should not be given to treat a metabolic acidosis that is due to hypoperfusion. After
UTI plus obstructive uropathy
Bacterial tubulo-interstitial nephritis (pyelonephritis)
ACUTE RENAL FAILURE
Figure 8.3 Acute renal failure caused by urinary tract infection (UTI). There is evidence to suggest a direct effect on the kidney by endotoxins. Dehydration owing to vomiting and NSAID use also contribute. Pre-existing renal impairment or diabetes increases risk. Reprinted with permission of Oxford University Press (Advanced Renal Medicine, by AEG Raine, 1992)
volume restoration, fluid may be restricted to measurable plus insensible losses to avoid volume overload in oliguric patients. Frusemide is often used at his point. If the patient fails to respond to restoration of volume and perfusion, renal replacement therapy (RRT) is the next step. Patients require RRT for an average of 13 days and around 36% patients with acute renal failure require this. Only 3% require RRT long term. Liaison with a renal specialist is important.
Non-obstructive urinary tract infection is an important cause of acute renal failure, sometimes overlooked, and should be aggressively treated (Figure 8.3).
Many treatments improve urine output but have no effect on outcome in established ARF:
• high dose loop diuretics (bolus or infusion)
Frusemide is said to cause a reduction in renal oxygen demand and mannitol is thought to scavenge free radicals -theoretical benefits that are not borne out in clinical practice. However, loop diuretics can help convert oliguric renal failure to non-oliguric renal failure and thus avoid problems with volume overload.
There are many potential treatments that have been tried in the prevention of ARF and have been found to be ineffective:
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