Acute Kidney Injury
Fluids and Prevention of Acute Kidney Injury Andrew Smyth1
and Donal N Reddan2
1. Research Fellow, HRB Clinical Research Facility Galway, Department of Medicine, National University of Ireland and Specialist Registrar, Department of Nephrology, Galway University Hospitals; 2. Consultant Nephrologist, Department of Medicine, National University of Ireland and Department of Nephrology, Galway University Hospitals
Abstract
Acute kidney injury (AKI) is associated with increased in-hospital mortality and future risk of chronic kidney disease. A key component of the management of sepsis, which accounts for 50 % of cases of AKI, is fluid administration. Crystalloid or colloid therapies can be used to minimise hypoperfusion and tissue hypoxia, but there is uncertainty as to which is superior. Multiple trials, systematic reviews and meta-analyses have reported conflicting findings, but at present the consensus is that crystalloids should be used for resuscitation, as they are less expensive and have similar efficacy to colloids. Hyperoncotic starch solutions are associated with increased risk of AKI and mortality. Contrast-induced AKI, where administration of iodinated radiocontrast media results in iatrogenic kidney injury, is predictable and preventable. Volume expansion is the mainstay of prevention and intravenous therapy is superior to oral hydration. Despite multiple trials and meta-analyses, there is no evidence to strongly recommend intravenous isotonic saline over isotonic bicarbonate, as both are effective.
Keywords Resuscitation, crystalloid, colloid, acute kidney injury, chronic kidney disease
Disclosure: The authors have no conflicts of interest to declare. Received: 19 December 2011 Accepted: 18 January 2012 Citation: European Nephrology, 2012;6(1):30–2 Correspondence: Donal N Reddan, Department of Nephrology, Merlin Park University Hospital, Merlin Park, Galway, Ireland. E:
donal.reddan@
hse.ie
Acute kidney injury (AKI) is characterised by a reduction in kidney function resulting in failure to maintain fluid, electrolyte and acid-base homeostasis. HKI complicates 5–15 % of hospitalisations, is associated with increased in-hospital mortality and extended length of stay, and may have long-term adverse effects, including an increased risk of end-stage kidney disease1 disease (CKD).2
and an increased risk of chronic kidney An estimated 5–20 % of critically ill patients experience
AKI and 4–9 % of all admissions to intensive care units (ICUs) require renal replacement therapy.3 AKI4
Sepsis accounts for up to 50 % of cases of and fluid administration is frequently necessary to stabilise patients.
The transition to serious illness occurs during critical ‘golden hours’, when treatment may provide maximal benefit. The timing of fluid administration is therefore a key component of early goal-directed therapy;6
Early goal-directed therapy has arisen as an appropriate strategy for managing critically ill patients, as global tissue hypoxia, due to hypoperfusion, is a key development preceding multi-organ failure and death.5
and important physiological goals of such therapy include mean arterial pressure ≥65 mmHg, central venous pressure 8–12 cm water, improved blood lactate, central venous oxygen ≥70 % and urine output ≥0.5 ml/kg/hour. The primary resuscitation goal is to restore tissue perfusion and cellular oxygenation, and maintain end-organ function through volume resuscitation.
Fluids for Resuscitation
Fluids for resuscitation include both crystalloids and colloids. Crystalloids are classified as hypotonic, isotonic or hypertonic. Generally, only hypertonic or isotonic fluids should be used for resuscitation, as hypotonic fluids are not as effective in increasing
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However, albumin is expensive, does not restore the interstitial space and has been associated with anaphylaxis.9
Non-protein
colloids include starches (e.g., 6 % hentastarch, 10 % pentastarch) and dextrans. They are equivalent to albumin as resuscitation fluids, but are expensive, may cause a dose-related coagulopathy10
cross-matching of blood products.14 Which Fluid is Best?
Both crystalloids and colloids have advantages and disadvantages (see Table 1), with no obvious superiority of either regimen. There have been a number of comparative studies considering the ‘colloid versus crystalloid’ question. The largest of these was the Saline versus albumin fluid evaluation (SAFE) study, a multicentre randomised controlled trial of 16 ICUs (n=6,997) comparing 4 % albumin to 0.9 %
© TOUCH BRIEFINGS 2012 and may
occasionally cause anaphylaxis. Starch molecules have been implicated as a cause of AKI11–13
and may interfere with antigen detection during
Colloids are fluid solutions that contain protein and non-protein molecules. Protein colloids include, human serum albumin (5 % and 25 %), gelatin solutions and others. Albumin remains intravascular for longer than crystalloids, therefore allowing rapid plasma volume expansion with less volume. Albumin may be associated with a lower risk of pulmonary oedema than crystalloids, as dilutional hypoalbuminaemia does not occur.8
intravascular volume. Crystalloids are inexpensive and readily available, and promote urinary output through resuscitation of both the intravascular and interstitial space.7
However, they may result in
oedema formation in patients with increased capillary permeability, and there may be a need for increased volumes to achieve resuscitation compared with colloids.
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