With the aging population, the prevalence of
coronary artery disease has been increasing all around
the world recently. As the aging population increases,
the number of CABG operations also increases.[
7]
The CABG is still the gold-standard technique for
the treatment of coronary artery disease. Mortality
rate varies between 2.5 and 26%.[
7] Renal damage is a
frequent complication after CABG and is usually seen
as a mild creatinine increase. However, in some cases,
creatinine increase may be high or AKI may complicate prognosis in patients with high comorbidities, leading
to the increased mortality.[
8]
Hemodialysis need after cardiac surgery ranges
between 1 and 7%. Mortality rate in patients with
renal failure is 60%.[9,10] There is also the increased rate
of infection and prolonged hospital stay in patients who
have CPB-related AKI.[11] Therefore, postoperative
renal dysfunction is an important complication
due to its relation with postoperative mortality and
morbidity.[12,13] The main causes of CPB-related AKI
are decreased perfusion pressure, nephrotoxic agents,
and CPB-related inflammatory response.[14-16] The
main goal of CPB is to maintain tissue perfusion.
Perfusionist regulates this process by coordinating the
mean arterial pressure and CPB flow rate.
Extracorporeal circulation with CPB produces
systemic inflammatory response. As the CPB time
increases, the risk of systemic inflammatory response
syndrome (SIRS) also increases.[17] There are many
studies showing that a CPB time longer than 80 min
poses a significant risk for SIRS.[18] Review of the
literature also reveals that there is a relation between
AKI and CPB, as described previously before a
relation between CBP and SIRS. Zhiwei et al.[19]
concluded that prolonged perfusion time was related
to AKIN Stage ≥2 renal damage and it was a major
risk factor for postoperative AKI. In our study, we
analyzed patients according to CPB time. We showed
that the increased CPB time was strongly related to
AKI as follows: Group 1, 4% (n=4); Group 2, 10%
(n=10), and Group 3, 17.6% (n=9). The AKIN scores
were higher in Groups 2 and 3, compared to Group 1
(p<0.05). We found that one (1%) patient in Group 1,
two (2%) patients in Group 2, and four (7.8%) patients
in Group 3 had AKIN ≥ Stage 2, respectively.
In another study including acute renal failure
patients after cardiac surgery, Bove et al.[12] included
5,068 patients and they found that 171 patients had
AKI after cardiac surgery. In addition, 94 patients
needed renal replacement therapy and patients who
needed renal replacement therapy had a longer mean
CPB time (116±51.2 min) compared to those who did
not (82±31.7). They concluded that decreased CPB
time also decreased the CPB-related AKI. In our
study, 16 patients needed postoperative hemodialysis
(Group 2, n=8, 8%; Group 3, n=8, 15.7%). The need
for hemodialysis was significantly higher in Groups
2 and 3, compared to Group 1; however, there
was no statistically significant difference between Groups 2 and 3. The main goal of the intraoperative
patient management in terms of CPB is to manage
optimal perfusion pressure, flow rate, hemodilution,
and CPB time. Therefore, managing CPB time in
an appropriate level would reduce the AKI risk,
postoperative morbidity, and mortality.[20]
In a study by Elmanday et al.,[21] CPB time had a
statistically significant importance for the development
of postoperative AKI. They found that postoperative
creatinine and BUN levels were significantly higher
and eGFR levels were significantly lower in the AKI
group, compared to non-AKI group. In our study,
there was no significant difference in the preoperative
creatinine, BUN, and eGFR values. However,
postoperative creatinine and BUN levels were higher
in Groups 2 and 3, compared to Group 1. Also, the
eGFR levels were significantly lower in Groups 2
and 3, compared to Group 1. Perioperative anemia is
another important indicator of postoperative AKI.[22,23]
In our study, we showed that there was no statistically
significant difference in the hemoglobin levels among
the groups.
Patients with left ventricular dysfunction have
an increased AKI risk.[22] Low cardiac output and
the need for inotropic or mechanical support after
cardiac surgery are also major risk factors for AKI.[22]
In our study, three (3%) patients in Group 1, nine
(9%) patients in Group 2, and eight (15.7%) patients
in Group 3 needed IABP. The need for IABP in
Group 3 was significantly higher, compared to
Group 1. Ortega-Loubon et al.[24] performed a study
about AKI-related ICU stay and mortality after
CABG in 435 patients. The mean ICU stay for their
patients with and without AKI was 7.4±9.3 days and
2.7±2.2 days, respectively. The 30-day mortality rate
was 18.5% and 3.1% in patients with and without
AKI, respectively. In our study, we found that
the ICU stay and in-hospital stay were higher in
Group 3, compared to the other groups. There was no
significant difference between Groups 1 and 2. The
mortality rate in Group 3 was significantly higher
compared to Group 1. In the literature, there is
a limited number of studies regarding AKI and
neurological complications after cardiac surgery. A
study by Ryden et al.[25] showed that postoperative
neurological complication in patients with AKI were
higher compared to those without postoperative AKI.
In our study, there was no significant difference
among the groups (p>0.05).
The main limitations of this study include its
single-center, retrospective design with a relatively
small sample size. In addition, only creatinine and
eGFR values were used for the AKIN classification;
however, there are many other sensitive parameters
such as renal-specific proteins to calculate renal
function and eGFR. Screening of the risk factors along
with the measurement of novel biomarkers may enable
early diagnosis of patients who are susceptible to AKI
and may be helpful to tailor the appropriate treatment
protocol.
In conclusion, the incidence of CPB-related AKI is
still high in our surgical practice. The most important
way to reduce the risk of CPB-related AKI is to
manage the modifiable risk factors for patients and
extracorporeal circulation technique. It is a good
option to prefer off-pump techniques for patients who
have a high postoperative AKI risk. Furthermore,
decreasing the inflammatory response and CPB time
for on-pump procedures may also contribute to prevent
AKI.
Declaration of conflicting interests
The authors declared no conflicts of interest with respect
to the authorship and/or publication of this article.
Funding
The authors received no financial support for the research
and/or authorship of this article.