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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 31, No 4, July/August 2020
AFRICA
205
Cardiac surgery-associated acute kidney injury:
pathophysiology and diagnostic modalities and
management
Gontse Leballo, Palesa Motshabi Chakane
Abstract
Acute kidney injury is a disease spectrum that can present
with from mild renal dysfunction to complete renal fail-
ure that would require renal replacement therapy. Cardiac
surgery-associated acute kidney injury is a complication that
carries a grave disease burden. Risk factors are identified as
being either modifiable or non-modifiable. This literature
review aims to define the pathophysiology of cardiac surgery-
associated acute kidney injury, the current definition and clas-
sification of acute kidney injury and the available diagnostic
modalities, especially the use of biomarkers.
Keywords:
cardiac surgery-associated acute kidney injury, cardio-
pulmonary bypass, acute renal failure, renal replacement thera-
py, kidney disease improved global outcomes
Submitted 30/9/19, accepted 21/11/19
Published online 12/6/20
Cardiovasc J Afr
2020;
31
: 205–212
www.cvja.co.zaDOI: 10.5830/CVJA-2019-069
Cardiac surgery presents with postoperative complications,
particularly when cardiopulmonary bypass (CPB) is utilised.
1
Acute kidney injury (AKI) is still one of the most common
complications with deleterious effects following cardiac surgery.
2
Over two million cardiac surgical procedures are performed
around the world each year.
3
A recent systematic review and a
meta-analysis found the total incidence of AKI in adult patients
after cardiac surgery to be 22.3%.
4
AKI is a broad clinical
syndrome,
5
presenting small changes in renal function markers
and progressing to a need for renal replacement therapy (RRT).
6
The incidence of AKI in patients undergoing cardiac surgery in
the African population is not documented.
The risk of postoperative death in patients undergoing cardiac
surgery ranges from 5 to 30% when serum creatinine levels are
≥ 1.5 mg/dl, which makes serum creatine an independent risk
factor for morbidity and mortality following cardiac surgery.
7
In a retrospective evaluation of adult patients in a cardiac
intensive care unit (ICU) following coronary artery bypass
graft (CABG) or valvular surgery by Machado
et al
.,
7
using
the Kidney Disease Improving Global Outcomes (KDIGO)
criteria in a group of patients who presented with elevated
serum creatinine levels pre-operatively, patients with an elevated
serum creatinine in the pre-operative period associated with high
EuroSCORE values and an increased length of CPB and ICU
stay, developed cardiac surgery-associated AKI (CSA-AKI).
7
In
this cohort of 918 patients, 391 (43%) developed CSA-AKI. The
diagnosis of AKI using the KDIGO criteria was shown to be a
powerful predictor of 30-day mortality.
7
Using the AKIN criteria to diagnose CSA-AKI, Vellinga
et al
.
8
found 14.7% of patients to have developed AKI. These
patients were of advanced age, had low pre-operative estimated
glomerular filtration rate (eGFR), chronic kidney disease and
presented for emergency surgery. The patients who developed
AKI were also found to have received loop diuretics and had
received blood transfusion in the postoperative period.
8
Bastin
et al
.
9
assessed 1 881 patients using the Risk Injury
Failure End Stage, Kidney Disease (RIFLE), Acute Kidney
Injury Network (AKIN) and KDIGO criteria in defining the
epidemiology of AKI following cardiac surgery and compared
the outcome of patients requiring RRT in the same population.
The AKIN and KDIGO criteria were found to be comparable
in predicting the incidence and outcome of AKI. An increase in
age, low pre-operative eGFR, longer duration of CPB, increased
length of ICU and hospital stay, and repeat surgery correlated
with an increased risk of CSA-AKI.
9
A total of 122 (6.5%)
patients required RRT: 117 patients within seven days and
five patients seven days after surgery.
9
Their hospital mortality
rate decreased from 82.9% previously to 53.8%, and this was
attributed to more patients being started on RRT before their
serum creatinine level was > 30 mmol/l.
9
In a review article by Rosner and Okusa,
10
the incidence of
AKI correlated with the type of surgery. Combined CABG and
valvular surgery had an AKI incidence of 4.6% with 3.3% of the
patients requiring RRT.
10
CABG alone had the lowest incidence of
AKI of 2.5%, while valvular surgery had an incidence of 2.8%.
10
O’Neal
et al
.
11
divided risk factors into pre-, intra- and
postoperative risks. An increase in age, female gender and
co-morbid diseases such as hypertension, diabetes mellitus,
chronic kidney disease, hyperlipidaemia, peripheral vascular
disease, anaemia and smoking were contributing factors in the
pre-operative period.
11
CPB was an intra-operative risk factor
Department of Anaesthesiology, University of the
Witwatersrand, Charlotte Maxeke Johannesburg Academic
Hospital, Johannesburg, South Africa
Gontse Leballo, MB BCh, BSc, DA (SA),
gleballomothibi@gmail.comPalesa Motshabi Chakane, MB ChB, BSc, DA (SA), FCA (SA)
Review Article