Discussion
At the end of this study we determined that the creatinine levels of
diabetic patients receiving insulin medication with normal creatinine
and microalbuminuria increased significantly on the post-op 3rd day,
when compared to the patients having oral antidiabetic medication.
It is known that cardiac surgery, which has been performed for many
years in the world, is a risky and difficult discipline in mortality and
morbidity compared to other surgical disciplines (16). Diabetes mellitus
is accepted as an independent risk factor especially for coronary
atherosclerosis, which concerns a wide age group(17). It is known that
diabetes alone increases mortality and morbidity in coronary artery
disease, both at younger ages and with more widespread involvement(18),
and in coronary artery bypass operations(19). The following can be
considered as main reasons for poor prognosis during and after surgery
due to diabetes: Severe cardiac disease, subclinical insufficiency in
renal functions in accompany, dehydration and electrolid disorders due
to hyperglycemia, arrhythminogenic, and increased fatty acids that
decrease myocardial oxygen demand(20,21). Since the effect of diabetes
on coronary bypass surgery is known to increase mortality and morbidity,
in our study, we aimed to investigate on type 2 diabetic patients using
insulin and taking oral antidiabetics in terms of kidney functions and
morbidity.
Today, most of the coronary artery bypass surgeries are performed
on-pump. We have done all the operations we have performed on-pump. It
is known that on-pump coronary artery bypass operations alone cause an
increase in renal functions and are an important cause of morbidity(22).
Loss of renal functions causes cardiac dysfunction, lung function
impairment, wound healing problems, and prolongation of stay intensive
care and hospital stays(23).
While microalbuminuria is seen as a marker of complications that develop
in diabetic patients, it is considered a sign of diabetic
nephropathy(24) and it is also known to increase early mortality in
these patients(25). It is accepted as a marker of atherosclerosis, which
is the cause of ischemic heart diseases in patients without
diabetes(26).
While clinical studies investigating the effects of microalbuminuria on
mortality and heart failure in cardiovascular diseases were previously
conducted we aimed to investigate diabetic patients using insulin and
taking oral antidiabetics(27). Studies on patients who had undergone
coronary artery bypass surgery were generally compared on patient groups
with and without microalbuminuria(28). In a study conducted by Kristina
S. and al. in 2015, patients with microalbuminuria who have type 2
diabetes were compared with non-diabetic patients(29). In our searches
we did not find a previous study comparing type 2 diabetes patients
receiving insulin medication and taking oral antidiabetics.
In our study, we aimed to compare patients who underwent coronary artery
bypass surgeries with type 2 diabetes patients receiving insulin
treatments and patients taking oral antidiabetics all with normal
creatinine values of microalbuminuria, which is one of the poor
prognostic factors.
According to the results we obtained there were no statistically
significant difference between the preoperative demographic data,
preoperative microalbuminuria levels and perioperative cross clamp
times, total pump times and bypass numbers of both groups.
When the postoperative durations of stay on the ventilator compared,
there was no statistically significant difference between the groups
although the durations were longer in the diabetic group receiving
insulin treatment. There was no statistically significant difference
between the amount of drainage. When the length of stay in intensive
care unit and hospital stays were compared, there was no statistically
significant difference, although the average of the diabetic group
receiving insulin treatment was high.
No postoperative early mortality observed in both patient groups.
Mediastinitis developed in one patient who was in the diabetic group
receiving insulin treatment. Mediastinitis is generally seen with a rate
of 1-4%, and it is known that rates of non-healing wounds and
mediastinitis are higher in diabetic patients receiving insulin
treatment (30). In our study, the rate of mediastinitis was calculated
as 1.25%. When only the group receiving insulin treatment was
considered, the rate was found as 2.38%. When we evaluated this result,
we thought that diabetes treatment with insulin may have a facilitating
role for mediastinitis rather than microalbuminuria.
When the postoperative data are examined, it is seen that the most
important difference is on renal functions. The mean preoperative
creatine level of diabetic group taking oral antidiabetics was 0.88 ±
0.16, and the mean creatine level was 1.01 ± 0.18 on the postoperative
3rd day. The increase in between was found to be statistically
significant (P <0.001). The mean preoperative creatine levels
of diabetic group receiving insulin treatment were 0.93 ± 0.21, the mean
postoperative day 3 creatine levels were found to be 1.33 ± 0.46, and
the increase in creatine levels was also statistically significant (P
<0.001). These two data showed that there was a significant
increase in creatine levels after on-pump coronary artery bypass surgery
of the type 2 diabetes patients using insulin and taking oral
antidiabetics, with microalbuminuria.
When the preoperative creatinine values of both groups were compared,
there was no statistically significant difference. When the increases in
creatinine levels on the postoperative 3rd day were compared between the
groups, there was a much higher increase in the diabetic group using
insulin compared to the diabetic group taking oral antidiabetics, which
was statistically significant (P <0.001). Acute renal failure
developed in only one patient in the diabetic group using insulin who
returned to normal with the treatment, without any need for dialysis.
This shows us that creatine levels of diabetic patients receiving
insulin treatment with microalbuminuria have a significant increase when
compared to ones taking oral antidiabetics, and these patients even have
the risk of acute renal failure.
As the conclusion of this study, we think that the presence of
microalbuminuria in patients causes impairment in renal functions in the
early postoperative period of on-pump coronary artery bypass operations,
and this deterioration is much more severe in type 2 diabetes patients
receiving insulin treatment. In addition, we think that the surgery of
patients with microalbuminuria can be performed safely, since there is
no difference between the durations of stay on the ventilator, the
length of stay in intensive care unit and hospital stay, and the
impairment of kidney functions can be treated with an effective
intensive care treatment without the need for dialysis.
The number of patients included seems to be sufficient because only the
patient group with microalbuminuria was determined as the target for our
study however, we think that a larger patient group should be studied
and the results should be compared with another study including patients
with low ejection fraction.