Risk prediction of acute kidney injury in cardiac surgery and prevention using aminophylline

Predictors of acute kidney injury in patients undergoing adult cardiac surgery

Background

Acute kidney injury (AKI) after cardiac surgery (CS) is not uncommon and has serious effects on mortality and morbidity. A majority of patients suffer mild forms of AKI. There is a paucity of Indian data regarding this important complication after CS.

Aims and Objectives

The primary objective was to study the incidence of AKI associated with CS in an Indian study population. Secondary objectives were to describe the risk factors associated with AKI-CS in our population and to generate outcome data in patients who suffer this complication.

Methods

Serial patients (n = 400) presenting for adult CS (emergency/elective) at a tertiary referral care hospital in South India from August 2016 to November 2017 were included as the study individuals. The incidence of AKI-CS AKI network (AKIN criteria), risk factors associated with this condition and the outcomes following AKI-CS are described.

Results

Out of 400, 37 (9.25%) patients developed AKI after CS. AKI associated with CS was associated with a mortality of 13.5% (no AKI group mortality 2.8%, P = 0.001 [P < 0.05]). When AKI was severe enough to need renal replacement therapy, the mortality increased to 75%. Patients with AKI had a mean hospital stay 16.92 ± 12.75 days which was comparatively longer than patients without AKI (14 ± 7.98 days). Recent acute coronary syndrome, postoperative atrial fibrillation, and systemic hypertension significantly predicted the onset of AKI-CS in our population.

Conclusions

The overall incidence of AKI-CS was 9.25%. The incidence of AKI-CS requiring dialysis (Stage 3 AKIN) AKI-CS was lower (2%). However, mortality risks were disproportionately high in patients with AKIN Stage 3 AKI-CS (75%). There is a need for quality improvement in the care of patients with AKI-CS in its most severe forms since mortality risks posed by the development of Stage 3 AKIN AKI is higher than reported in other index populations from high resource settings.

Cardiopulmonary Bypass and AKI: AKI Is Bad, So Let's Get Beyond the Diagnosis

It is now well-established that AKI is a serious and common complication following cardiopulmonary bypass (CPB) in both children and adults, adverse outcomes may occur in the short term as well as long term, with higher incidence of chronic kidney disease, increased healthcare utilization and higher frequency of cardiovascular events in patients who develop post-CPB AKI. Despite the advances in our understanding of the pathogenesis of the disease and the improvement in diagnostic tools, our therapeutic options have remained suboptimal. There are multiple challenges in designing a clinical therapeutic AKI trial, including a multi-factorial etiology, difficulties with accurate diagnosis of AKI, achievement of adequate study power, and determination of appropriate outcomes. We are often left with "supportive" care. Studies have shown some benefit to AKI bundles, but adherence to bundle guidelines may be suboptimal. Current best practices should include maintenance of adequate renal perfusion pressure and avoidance of fluid overload, with consideration of early renal replacement therapy. Finally, multi-center trials of AKI therapies are crucial to finding treatment for this devastating complication of CPB.

Applicability of the Cleveland clinic scoring system for the risk prediction of acute kidney injury after cardiac surgery in a South Asian cohort

Background

Acute kidney injury (AKI) after cardiac surgery is a frequent post-operative complication associated with an increased risk of mortality, morbidity and hospital costs. Preoperative risk scores such as the Cleveland Clinic Scoring Tool (CCST) have been validated in Western population group to identify patients at higher risk of AKI and may facilitate preventive strategies. However, the scoring tool has not been validated systematically in a South Asian cohort. We aimed to evaluate the applicability of the CCST in prediction of AKI after open cardiac surgery in a South–Indian tertiary care center.

Materials and methods

A retrospective study of all patients who underwent elective open cardiac surgery over a 4 year period from Jan 2012 to Dec 2015 at a single centre were included and relevant details extracted from a comprehensive chart review. The primary outcome was AKI as defined by the Kidney Disease Improving Global Outcomes (KDIGO) criteria. Patients were risk stratified as per the CCST to assess for prediction of AKI into low risk (0–2), intermediate risk (3–5) and high risk (>6) groups.

Results

A total of 276 patients underwent open cardiac surgery with mean age of 51.5 ± 13.06 yrs. This included 177 (64.1%) males and 99 females (35.8%). Overall incidence of AKI was 6.88%. Mean age, gender, BMI, preoperative serum creatinine, diabetes mellitus, chronic obstructive pulmonary disease, cardiopulmonary bypass time was similar in patients who developed AKI vs those who did not have AKI postoperatively. The mean CCST scores were 1.6 in those without AKI, 1.5 in stage 1, 3.0 in stage 2 and 3.4 in stage 3 AKI. Higher risk scores predicted greater risk of AKI. A total of 106 patients (38.4%) were on ACE/ARB, 119 patients (43.1%) received beta-blockers, 110 (39.8%) received diuretics while 144(52.1%) had received preoperative statins. Comparison of drug use between the two groups revealed that preoperative use of ACEI/ARB was associated with highest risk of AKI (p = 0.006). Mortality rate was also high at 15.7% in those with AKI compared to 3.1% in non-AKI group (p = 0.04).

Conclusion

The modified CCST was valid in risk identification of patients with severe stage of AKI but did not have strong discrimination for early AKI stages. Preoperative statin use did not protect against AKI in our study, however preoperative ARB/ACEI use was significantly associated with occurrence of postoperative AKI.

Evaluation of the Effect of Aminophylline in Reducing the Incidence of Acute Kidney Injury After Cardiac Surgery

Objectives

Acute renal failure is a common complication of major cardiovascular surgeries (One-third of patients). Adenosine release as a vascular vasodilator increases after cardiac surgery, which reduces renal and glomerular blood flow and subsequently causes kidney ischemic damage. The present study aimed at evaluating the impact of aminophylline as an adenosine receptor antagonist on renal function after cardiac surgery hoping to find an appropriate method to reduce acute kidney injury.

Methods

The patients in the intervention group received 5 mg/kg aminophylline bolus after induction of anesthesia; then, 0.25 mg/kg/hr of the drug was administered intraoperatively and up to 48 hours after surgery in the ICU cardiac surgery. Similar volume of normal saline was injected to the patients of the second group. Serum BUN, Cr, and GFR were measured pre- and postoperatively and 3 days postsurgery. Patients’ 24- hour urine output and RIFLE were also calculated.

Results

Those patients who received medication were extubated earlier (P = 0.018) and received lower amount of inotropic drugs (P < 0001). According to the RIFLE criteria, most of the patients experienced no change or even improved GFR and Cr amounts compared to the control group (p < 0.05). GFR and Cr value of all the patients with Cleveland score, less and more than 6, showed a significant difference between the 2 groups (P = 0.001 and P = 0.01, respectively). According to the RIFLE criteria, most of the patients experienced no change or even improved GFR.

Conclusions

Aminophylline in cardiac surgery can reduce the frequency of acute kidney injury according to RIFLE criteria and could be used in the prevention of AKI as a safe and efficient modality in high-risk patients. Also, the use of this drug may reduce the need for inotropic medication at the time of surgery, intensive care unit stay length, and extubation time.