Determination of the value of glycated hemoglobin HbA_1c and fructosamine in assessing the risk of perioperative complications after cardiac surgery in patients with type 2 diabetes

Introduction

Diabetes, in particular type 2, is a condition which significantly increases the risk of development and progression of atherosclerosis [1, 2]. It is estimated that 60% of patients hospitalized with coronary artery disease have varying degrees of impaired glucose tolerance [3, 4]. Metabolic disorders in diabetes can cause coagulation disorders, hypertension, dyslipidemia, and synthesis of free radicals [5]. They can worsen the perioperative course and prognosis in patients undergoing cardiac surgery [6]. According to the recommendations of the Polish Association of Diabetes, metabolic preparation of the patient for surgery includes normalization of blood glucose [7]. The measure of glycemic control is the determination of the concentration of glycated hemoglobin (HbA_1c). It is assumed that the patient eligible for surgery should have a balanced glucose level of HbA_1c < 7%. Remember, however, it should be that the concentration of glycated hemoglobin reflects the alignment within 3 months preceding the mark [8]. In a situation where the patient is eligible for the procedure, and does not meet the metabolic control (HbA_1c < 7%), it is necessary to intensify hypoglycemic therapy that will lead to the normalization of the blood glucose profile. There remains the situation where the patient has a normal blood glucose daily profile and still maintains elevated glycosylated hemoglobin, which according to the recommendations disqualifies a patient from the planned surgery.
The process of non-enzymatic glycation, which is the product of glycated hemoglobin, is a reaction that includes all proteins. It consists of a combination of a glucose molecule with the free amino group of the polypeptide chain [9]. The protein albumin is subject to glycation and as a result of this process produces fructosamine, a somewhat forgotten parameter that determines the glycemic control. Given the life of albumin, the concentration of fructosamine determines glycemic control during the 3–4 weeks prior to the measurement [10]. It seems, therefore, that determination of fructosamine can be a useful study determining the metabolic alignment, especially the situation of hypoglycemic treatment and the need to verify the information factors.

Aim

Glycemic control is necessary in patients with diabetes subjected to cardiac surgery. Evaluation of alignment is based on the determination of the percentage of glycated hemoglobin A1c, which reflects the alignment of the preceding 3 months. The open issue is whether the determination of the concentration of fructosamine reflecting alignment in the previous 3 weeks will be a comparable parameter. The aim of the study is to evaluate metabolic control by the concentration of fructosamine and the percentage of HbA_1c with respect to the occurrence of postoperative complications in diabetic patients undergoing coronary artery bypass grafting.

Material and methods

We analyzed the results of off-pump coronary artery bypass (OPCAB) and coronary artery bypass graft (CABG) procedures performed in 105 patients with type 2 diabetes in 2014–2015. The mean age was 65.7 ±7.3.
Diabetes duration was 9.2 ±2.3 years. In all subjects, the concentration of fructosamine and HbA_1c was designated. The analysis included postoperative complications. We analyzed the following complications: delirium, stroke, prolonged respiratory therapy > 24 h, slow wound healing, visceral ischaemia, death.

Statistical analysis

The results were statistically analyzed. Average value ± SD and events of interest were calculated. Comparisons between selected groups were made using the χ2 test with Yates correction for continuity.

Results

Mean HbA_1c level in the study group was 7.23 ±1.2% and fructosamine concentration was 261 ±43.8 mmol/l. Figure 1 shows the correlation between the percentage of glycated hemoglobin A1c and fructosamine. There was a significant correlation between these parameters (r = 0.597, p < 0.001).
In the total study group of 105 patients perioperative complications occurred in 9 (8.5%) patients. There was a higher, though not significantly, value of the tested parameters of glycemic control in diabetic patients with perioperative complications compared to patients with an uncomplicated course (Tab. I).
Next we calculated percentages of patients who experienced perioperative complications depending on the HbA_1c and the corresponding concentration of fructosamine. As the cut-off point for HbA_1c we adopted HbA_1c 7% – a reference value for optimal glycemic control during the perioperative period [7]. Complications occurred in 4 (3.8%) patients with HbA_1c < 7%, and 5 (4.8%) patients with HbA_1c ≥ 7% (n.s.). For fructosamine the figures were 6 (5.7%) patients with a concentration of < 285 μmol/l and 3 (2.9%) at a concentration ≥ 285 μmol/l (n.s.).

Discussion

In the present study, we found that the percentage of HbA_1c as much as the concentration of fructosamine defines the risk of perioperative complications in patients undergoing cardiac surgery. The analysis includes only those complications that are potentially associated with the environment hyperglycemia [11].
First, an analysis of the correlation between HbA_1c and fructosamine was performed. There was a high, statistically significant correlation, indicating that both of these parameters to a comparable extent describe the metabolic control of patients.
Subsequently we rated interdependent incidence of perioperative complications and concentrations of the test parameters. Noteworthy is the fact that the incidence of complications in the study group is small, not different from their appearance in our center [12]. This is due to the fact that one of the elements taken into account to qualify for the surgery is the degree of metabolic control.
Glycemic control plays an important role in the prognosis after cardiac surgery [13, 14]. Zerr et al. analyzing a database including 8910 patients, including 1585 patients with diabetes, found that the implementation of procedures of treatment, enabling one to obtain blood glucose during the perioperative period of less than 200 mg%, reduces the incidence of deep wound infection from 2.4% to 1.5% (p < 0.02). We noted a similar percentage of deep wound infection in our study, where one of the elements of the qualification is to assess glycemic control. In the present analysis, the percentage of patients with delayed wound healing was 2.17% in the group with HbA_1c < 7%, and 1.69.% for HbA_1c ≥ 7% and the corresponding concentration of fructosamine.

Conclusions

The HbA_1c and fructosamine levels to a similar extent define the risk of perioperative complications in patients undergoing cardiac surgery. Given the dynamics of temporal changes in the concentrations of these substances in the event of a rapid normalization of blood glucose, one should consider including designation of fructosamine panel tests performed before surgery, especially in patients in whom there is a need to quickly compensate for elevated blood glucose.

Disclosure

Authors report no conflict of interest.

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