Data were expressed as Median (25-75 median percentiles) or frequency
(%) as appropriate. Stage I of AKI: Increase ≥0.3 mg/dL (≥26.4 mmol/L),
or Increase ≥150-200% (1.5-2-fold) from baseline. Stage II of AKI:
Increase >200-300% (2-3-fold) from baseline. Stage III of
AKI: Increase > 300% (>3-fold) from baseline,
or SCr to ≥4 mg/dL (≥354 mmol/L) with an acute increase ≥0.5 mg/dL (≥44
mmol/L).
Discussion
This study uniquely focuses on both pediatrics and adults to identify
CSA-AKI risk factors to help in prevention. GFR is the best measure of
kidney function, but it lacks specificity and sensitivity as a biomarker
and SCr had been the main method to detect AKI. The main CSA-AKI
predictive risk factors include age, perioperative GFR, lactate
dehydrogenase (LDH), prothrombin time (PT), history of surgery,
transfusion, cardiac arrhythmia, coronary heart disease (CHD), or
chronic kidney disease (CKD), calcium channel blocker (CCB), proton pump
inhibitors (PPI), non-steroidal anti-inflammatory drugs (NSAID),
antibiotic or statin before surgery12. Obesity is an
independent risk factor and oxidative stress may partially mediate this
association13. Our study showed that younger age is a
protective factor against CSA-AKI. The incidence in the pediatric
patients was (20.07%) compared to 28.68% in adults.
The reported incidence varies, according to AKI definition, between
1%-30%. We chose strict criteria that define AKI by increasing in SCr
≥ 0.3 mg/dL above baseline, thus justifying the high incidence in our
study 28.68% compared to others. CSA-AKI pathophysiology is not fully
understood. it can be related to impaired renal reserve or decrease
renal perfusion, reperfusion, inflammation, oxidative stress, toxins and
hemolysis. Hemoglobin induced pigment nephropathy is another factor.
Prophylactic sodium bicarbonate might help in
prevention14. Many studies showed that CSA-AKI is
significantly related to the female gender, presence of Chronic
obstructive pulmonary disease (COPD), diabetes mellitus (DM), peripheral
vascular disease, renal impairment and congestive heart failure (CHF),
valve surgery, case urgency, cardiogenic shock requiring intra-aortic
balloon, left coronary insufficiency, length of ACX and CPB, off-pump
versus on-pump surgery, non-pulsatile flow, hemolysis, and
hemodilution12,15-17. Park and colleagues showed that
off pump surgery has similar incidence of CSA-AKI to on
pump18.
Urgency was not an important risk factor in our study.
Our study showed insignificant relation to female gender, DM, type of
surgery and case urgency. Age and hypertension were significant risk
factors in our adults. In our study, the age group 60-69 years was the
high-risk group.
In addition to morbidity burden, 30 days mortality or death within
indexed hospitalization is significantly associated with CSA-AKI. in our
study, this was 13.1% slightly lower than the reported literature
between 15%-30%18,19. CSA-AKI is the most expensive
complication especially when using RRT20,21. Our study
like others showed that stage 1 is the most common type (68.2%). Jiang
and colleagues reported high mortality of CSA-AKI-RRT and recommend
adjustment of the modifiable predictors to help in
prevention21.
In pediatric group the incidence was 20.07% as per AKIN criteria.
Krawczeski and colleagues reported an incidence of 42% using the same
criteria22. The majority of our pediatric cases that
developed CSA-AKI (63.2%) were in the age group > 30 days-
≤2 years. This age group is at greater risk of renal failure because of
their limited physiological GFR before 2 years of
age22,23. Our study showed that lower preoperative SCr
in pediatric patients is a predictive risk factor. This might be due to
age, bad nutrition, and smaller body weight.
Prevention
Nowadays, there is no pharmacological or nonpharmacological treatment of
CSA-AKI. The available and approved management is confined to
hemodynamic manipulations, intravenous resuscitation, balanced-salt
fluid administration. Perioperative administration of sodium bicarbonate
for the prevention of CSA-AKI is debated25.
Identification of high-risk group and prevention is the best and optimal
strategy12-18,26,27.
Post cardiac surgery hyperglycemia is a common complication and is
reported in 33.7–74% in non-diabetic patients after cardiac
surgery27. Novel biomarkers of kidney injury such as
neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18
(IL-18), cystatin C (CysC), have the potential to facilitate the early
diagnosis of CSA-AKI29.
Fenoldopam,
a short acting dopamine A1 receptor agonist, may reduce RRT and
mortality in critically ill patients and in patients undergoing
cardiovascular surgery30.
We adopted a simple protocol for all our cardiac surgery patients to
help in prevention table 4.
Table4