Care of the acute kidney injury patient

The primary purpose of the urinary system is to regulate the body's fluid balance, acid-base, electrolytes and regulate blood pressure. The kidneys also have a role in the excretion of metabolic waste and toxins, as well as in the secretion and metabolism of hormones.

Acute kidney injury is characterised by renal parenchymal injury. This represents an abrupt decline in glomerular filtration rate characterised by increased serum and plasma creatinine concentrations, uraemia (when severe enough) and, often, changes to urine output (Haskey, 2019). It is associated with decreased renal function, fluid, electrolyte and acid-base imbalances and retention of uraemic waste products (Bar-Nathan et al, 2022).

There are four phases of acute kidney injury based on pathophysiology (Monaghan et al, 2012):

The causes of acute kidney injury can be divided into three categories:

This occurs when renal blood flow is compromised due to certain conditions or situations such as dehydration, shock or congestive heart failure. It is important to remember the kidneys receive 20–25% of cardiac output (Waxman, 2020). In response, the kidneys conserve water and sodium, resulting in a reduction of urine output known as ‘physiological oliguria’. Local production of prostaglandins helps maintain renal blood flow, but this can be affected by drugs, including non-steroidal anti-inflammatories, and potentially lead to renal ischaemia. If left untreated, this can cause acute tubular necrosis and intrinsic renal failure. Therefore, it is crucial to recognise pre-renal failure promptly, identify and address the underlying cause and carefully choose drugs to avoid initiation.