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