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Saudi Journal of Kidney Diseases and Transplantation
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ORIGINAL ARTICLE  
Year : 2015  |  Volume : 26  |  Issue : 6  |  Page : 1177-1182
Profile of acute kidney injury after open heart surgeries in a tertiary care hospital


1 Department of Cardiology, Sher-I-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India
2 Department of Nephrology, Sher-I-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India
3 Department of Cardiovascular and Thoracic Surgery, Sher-I-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir, India

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Date of Web Publication30-Oct-2015
 

   Abstract 

Our objective is to determine the incidence, etiology, risk factors and outcome of acute kidney injury (AKI) after open heart surgery. A prospective study was conducted on 62 patients who underwent open heart surgery and were followed-up for the development of AKI and to determine its incidence, etiology and outcome. Post-operative AKI was considered when the post-operative serum creatinine was >1.5 mg/dL or there was doubling of serum creatinine above the baseline (pre-operative) with a prior normal renal function. The incidence of AKI in the post-operative period in our study was 17.7%. The common etiological factors for AKI in our study were sepsis, hypotension, prolonged need for ventilator and inotropic support and drugs given in the post-operative period. The important risk factors for the development of AKI in the post-operative period were hypertension, diabetes mellitus, gout, prolonged total bypass time and prolonged aortic cross-clamp time. The overall mortality in our study subjects was 11.3% (seven of 62 died) and the mortality in the patients who developed post-operative AKI was 71.4%.

How to cite this article:
Rather FA, Najar SM, Malla HA, Ahangar A G, Bhat HM, Wani IA. Profile of acute kidney injury after open heart surgeries in a tertiary care hospital. Saudi J Kidney Dis Transpl 2015;26:1177-82

How to cite this URL:
Rather FA, Najar SM, Malla HA, Ahangar A G, Bhat HM, Wani IA. Profile of acute kidney injury after open heart surgeries in a tertiary care hospital. Saudi J Kidney Dis Transpl [serial online] 2015 [cited 2021 Dec 8];26:1177-82. Available from: https://www.sjkdt.org/text.asp?2015/26/6/1177/168601

   Introduction Top


Acute kidney injury (AKI) is characterized by the sudden impairment of kidney function resulting in the retention of nitrogenous and other waste products; this was previously known as acute renal failure. AKI represents a heterogeneous group of conditions that share common diagnostic features including an increase in the plasma or serum creatinine (SCr) concentration and/or an increase in the blood urea nitrogen (BUN) concentration often associated with a reduction in urine volume. [1]

AKI complicates approximately 5% of hospital admissions. The surgical setting accounts for about 18-47% of all cases of AKI, [2] and it occurs in up to 30% of all patients who undergo cardiac surgery. [3] Approximately 1% of these AKI patients require dialysis. [4] The development of AKI is generally associated with a high mortality, a more complicated hospital course and a higher risk for infectious complications. [5] Mortality and morbidity associated with AKI have not markedly changed in the last decade in spite of advances in bypass techniques, intensive care and delivery of hemodialysis. [6]

The incidence of AKI following cardiac surgeries depends on the particular type of cardiopulmonary bypass surgery. Typical coronary artery bypass grafting (CABG) has the lowest incidence of AKI (2.5%), followed by valvular surgery (2.8%), and highest in combined CABG/valvular surgery with an incidence of AKI of 4.6%. [7]

Various studies have examined the risk factors associated with the development of AKI after cardiopulmonary bypass. These include female gender, diabetes, peripheral vascular disease, chronic obstructive airway disease and reduced left ventricular function, or the presence of congestive heart failure (CHF), pre-operative use of an aortic balloon pump, the need for emergency surgery and an elevated pre-operative serum creatinine. [8]

Other factors may be important and potentially modifiable, including those related to the bypass procedure itself, such as cross-clamping, [9] the duration of cardiopulmonary bypass, [10] normo-thermic versus hypothermic bypass, [11] pulsatile versus non-pulsatile bypass flow [12] and on-versus off-pump coronary artery bypass (OPCAB) surgery. [13] A lower incidence of AKI has been reported in off-pump CABG, which eliminates the need for cardiopulmonary bypass. [14]


   Materials and Methods Top


The present study was a prospective study conducted over a period of two years from December 2009 to November 2011 and included 62 patients who underwent open heart surgery in the form of mitral valve replacement (MVR), aortic valve replacement (AVR), double valve replacement (DVR), CABG, tetrology of Fallot (TOF) repair, repair of atrial septal defect (ASD) and ventricular septal defect (VSD), etc. in the Department of Cardiovascular and Thoracic Surgery over a period of two years. These patients were monitored for the development of AKI and to determine its incidence, etiology and outcome.

Post-operative AKI was considered when the post-operative serum creatinine was >1.5 mg/ dL or doubling of serum creatinine above the baseline (pre-operatively) occurred with prior normal renal function.

Exclusion criteria: Pre-operative acute renal injury of any etiology

The following variables were considered: Age, sex, type of surgery, nature of surgery (elective/emergency), total bypass time (TBT)/ aortic cross-clamp time (ACCT), pre-operative co-morbid conditions, clinical condition post-operatively and etiology of post-operative AKI.

In the intra-operative period, a record of TBT and ACCT was made.

In the post-operative period, various clinical and laboratory parameters were monitored during the hospital stay. The clinical parameters monitored were post-operative hypotension, urine output, need for inotropic support, need for ventilatory support and signs and symptoms of sepsis. The laboratory parameters monitored in the post-operative period were blood urea, serum creatinine, complete blood count, venous blood gas and electrolytes and body fluid cultures.


   Statistical analysis Top


Data were described as mean ± SD and percentage. Inter-group comparison of metric data was carried out using the Student t-test, whereas the Mann-Whitney U-test was used for non-parametric data. Additionally, intragroup variants were analyzed by the Fredman test at a confidence interval of 95%. MS Excel, SPSS and Minitab software were used for data analysis.


   Results Top


A total of 62 patients who underwent open heart surgery were included in the study. The mean age of our patients was 28.9 ± 13.9 years, with a range of 2-65 years. Most of our patients were in the age-group of 21-30 years (27.4%). There were 34 females (54.8%) and 28 males (45.2%).

In our study, most of the patients had valvular heart disease that was predominantly rheumatic in origin. Among the valvular lesions, mitral stenosis/mitral regurgitation was predominant and only one patient had post-percutaneous trans mitral commissurotomies (PTMC) acute MR. Among the congenital heart diseases, ASD was common.

Associated co-morbidities were seen in 24.2% of the patients. The common co-morbidities were hypertension (11.3%), diabetes mellitus (3.2%) and hyper-bilirubinemia, chronic atrial fibrillation and infective endocarditis (3.2% each). There was a history of nephrotoxic drug intake in one patient.

In this study, most of the patients were operated on an elective basis (98.4%) and the on-pump technique was commonly used (83.9%). MVR was the common procedure performed (33.9%), followed by ASD repair (19.4%) and VSD repair (12.9%). The mean TBT was 98.9 ± 51.0 min (range 26-270 min) and the mean ACCT was 72.2 ± 37.4 min (range 19-180 min).

Nearly 30 patients developed hypotension in the post-operative period, 54 required ventilatory support and 59 patients received inotropic support in the form of noradrenaline, dopamine and/or dobutamine in the postoperative period.

A total of 11 patients (17.7%) developed AKI in the post-operative period. Most of the patients developed AKI on Day 1 of the postoperative period. Among the studied subjects who developed AKI in the post-operative period, majority were in the age-group of >40 years, and all were electively operated. The on-pump technique was commonly associated with AKI [Table 1]. Among the associated comorbidities in these patients, diabetes mellitus was present in two patients and both developed AKI and seven patients had hypertension and only three developed AKI. Amikacin was used in 54 patients in the post-operative period and nine of these patients (16.7%) developed post-operative AKI.
Table 1: Acute kidney injury in relation to surgery, techniques and procedures performed in the study subjects.

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Among 30 patients who had post-operative hypotension, 11 developed AKI. Among 54 patients who needed ventilatory support in the post-operative period, 11 developed AKI. Similarly, among 59 patients who needed inotropic support, 11 developed AKI [Table 2]. Among the 11 studied subjects who developed AKI in the post-operative period, five had blood culture-proven sepsis. Pseudomonas aeuroginosa was grown in two patients and Staphylococcus aureus, Kleibsella pneumonae and Acinetobacter in one each.
Table 2: Acute kidney injury in relation to hypotension and ventilatory and inotropic support.

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Among the surgical procedures, AKI occurred in three of five TOF repairs, in all CABG patients and two DVR and three MVR cases [Table 1].

The ACT and TBT had a statistically significant correlation with the development of AKI. Among the patients who had AKI, the mean TBT was 152.9 ± 49.4 min vs 87.4 ± 43 min in the patients who had no AKI. Similarly, the mean ACT in AKI patients was 108.2 ± 35.8 min vs 63.4 ± 32.6 min in those without AKI [Table 1].

In our study, of the 11 patients who developed post-operative AKI, dialysis was performed in only one patient (9.09%). In this patient, peritoneal dialysis was performed to correct hyperkalemia. Among the 62 patients studied, seven died in the post-operative period. The associated events with death were AKI, sepsis and hyperkalemia [Table 3].
Table 3. Mortality status of the studied subjects.

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   Discussion Top


A total of 62 patients who underwent open heart surgery were evaluated for the development of AKI in the post-operative period. The main surgical procedures performed were MVR, AVR, DVR, CABG, repair of TOF, ASD and VSD, etc.

The incidence of AKI in the post-operative period in our study was 17.7% (11 of 62). Most of the patients developed AKI on Day 1 of the post-operative period. Yeboah et al [15] in a retrospective study of 428 open heart operations found the incidence of mild and severe renal failure to be up to 26% and 4.7%, respectively. Abel et al [5] in a prospective study of 500 consecutive patients surviving the first 24-h following cardiac surgical procedures found that 7% developed moderate to severe renal failure and 20.4% developed mild azotemia.

The common etiological factors for AKI in our study were sepsis, hypotension, need for ventilator support and drugs given in the post-operative period. Culture-proven sepsis was found to attribute to AKI in five patients (45.4% of patients who developed AKI). Charuhas et al [16] in a retrospective analysis of 24,660 patients undergoing open-heart surgery from 1993 to 2000 found that the overall incidence of infections after open-heart surgery was 3.3%; regarding post-operative AKI, the frequency of infections was 58.5% in patients requiring dialysis versus 23.7% in those with AKI not requiring dialysis.

Post-operative hypotension was an important etiological factor for the development of AKI, and, among the patients who had postoperative hypotension, 36.7% developed AKI. Other etiological factors for AKI were prolonged ventilatory support (20.4%) and prolonged use of inotropes, especially noradrenaline (18.6%). Sural et al [17] in a multivariate analysis of all patients who developed postoperative AKI found that the different etiological factors for AKI were peri-operative hypotension (67.1%), sepsis (63.6%) and exposure to nephrotoxic drugs (29.3%). The lower percentage in our study is likely due to small sample size (62 vs 140 patients). Ascione et al [18] in their study in 2001 identified the following risk factors for AKI: Cardiopulmonary bypass, serum creatinine level 60 h post-operatively, inotropic requirement, need for intraaortic balloon pump, transfusion of packed cells and hours of ventilation.

The important risk factors for the development of AKI in our patients were hypertension, diabetes mellitus, gout, prolonged TBT and prolonged ACCT. Bahar et al [19] in a study on patients undergoing open-heart surgery between January 1991 and May 2001 found the following risk factors associated with post-operative AKI: Advanced age, diabetes mellitus, hypertension, high pre-operative serum creatinine levels, impaired left ventricular function, urgent operation or reoperation, prolonged cardiopulmonary bypass and aortic cross-clamp periods, level of hypothermia, concomitant procedures, low cardiac output state, re-exploration for bleeding or pericardial tamponade and deep sternal or systemic infection.

Surgical technique also had an important bearing on AKI in the post-operative period. Among the 11 patients who developed postoperative AKI in our series, 10 were operated by the on-pump technique and one patient by the beating heart technique. Parwis Massoudy et al [20] in their study of 201 consecutive adult patients found that 100 were operated by the OPCAB technique and 101 by the on coronary artery bypass (ONCAB) technique. Significantly fewer OPCAB patients developed AKI compared with ONCAB (14.0 vs 27.7%; P = 0.03). Additionally, OPCAB was associated with milder stages of AKI, while ONCAB patients had more severe AKI.

In our study, dialysis for post-operative AKI was performed in only one patient (9.09%). In 2003, Thakar et al [21] found that the overall frequency of AKI requiring dialysis after open-heart surgery was 1.82% and the frequency was greater in women (2.36%) than in men (1.60%). The frequency of AKI requiring dialysis in our study is not consistent with the above-mentioned study, and we presume it to be due to a smaller study sample.

The overall mortality in our study was 11.3%, and the mortality in patients who developed post-operative AKI was 71.4%. Our mortality rate is consistent with the study by Ponsa et al [22] in 1997 on adult patients subjected to open heart surgery. They found that the overall crude mortality rate was 10.9% and varied among centers (range, 2.8-14.8%). In 1979, Hilberman et al [23] in a prospective sixmonth study of 204 patients requiring cardiac operations found that patients who developed AKI had a mortality rate of 65%.

Conflict of interest: None declared.

 
   References Top

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Correspondence Address:
Hilal A Malla
Department of Nephrology, Sher-I-Kashmir Institute of Medical Sciences, Srinagar, Jammu and Kashmir
India
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DOI: 10.4103/1319-2442.168601

PMID: 26586056

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