Page 502 - ACCCN's Critical Care Nursing

Support of Renal Function 18

Ian Baldwin
Gavin Leslie

function to deteriorate are not, however, always ischaemic
Learning objectives or necrotic in origin, and a syndrome with degrees of
failure is often evident. Therefore a new consensus defini-
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After reading this chapter, you should be able to: tion and classification system has been established. This
● summarise the physiology of urine production approach describes staging of ARF severity and embraces
● describe the most likely causes of renal failure in the the concept of acute kidney injury (AKI) where, like other
critically ill adult organs of the body, a dynamic spectrum is found, from
● differentiate between acute and chronic renal failure small indiscrete changes in function that are immediately
● outline treatment approaches in managing renal failure in reversible, through to gross signs and irreversible organ
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critical illness failure.
● appreciate historical developments in dialysis Acute renal failure is defined by a rapid deterioration in
● describe the indications for renal replacement therapy in renal function (hours to days), which is easily detected
critical care by commonly measured markers of kidney performance,
● understand the principles and challenges associated with including blood urea nitrogen, serum creatinine, and a
nursing management of continuous renal replacement failed ability to adequately regulate electrolytes, sodium
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therapy in critical care. and water balance. While generally reversible, ARF
can be life-threatening in the critically ill patient if acid–
base balance, electrolyte levels (particularly potassium)
or fluid overloads are not effectively diagnosed and
managed.
The preferred serum marker of renal function is the serum
Key words creatinine level. The exact level of serum creatinine that
is considered excessive is disputed; however, a doubling
urine production of the baseline serum creatinine or levels in excess of 200
acute renal failure µmol/L is commonly agreed on as being indicative of
acute kidney injury ARF. Urine output is also a key factor in determining the
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continuous renal replacement therapy (CRRT) severity of ARF. It is well established that oliguric renal
dialysis history failure, that is, a urine output of less than 0.5 mL/kg/h in
adults and 1 mL/kg/h in infants, is associated with poorer
patient outcome than the non-oliguric form. 4

Acute renal failure is reported to occur in 20–25% of
intensive care patient admissions, much higher than the
INTRODUCTION broader hospital rate of 5%. 5,6,7 In critical care, ARF often
forms part of the multiple organ dysfunction syndrome,
Sudden deterioration of kidney function, to the point
where there is retention of nitrogenous wastes, or acute whose cause has often been associated with sepsis,
renal failure (ARF), is a common manifestation of critical trauma, pneumonia or cardiovascular dysfunctions (see
illness and is often associated with failure of other organs. Chapter 21). Mortality in intensive care ARF is high, with
Acute renal failure is a syndrome with numerous causes, those patients requiring renal replacement therapy (RRT)
including glomerulonephritis, prerenal azotaemia, having worse outcomes than those patients who can be
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urinary tract obstruction and vasculitis. Acute tubular managed without this intervention.
necrosis (ATN) is a collective term commonly used to This chapter focuses on the underlying causes and man-
describe acutely deteriorating renal function, reflecting agement of ARF in critical care, with particular emphasis
pathological changes from various renal insults of a on nursing perspectives for managing patients with this
nephrotoxic or ischaemic origin. Factors that cause renal life-threatening organ system failure. 479