Study design:
This retrospective, single-center study was conducted to report the 12-month outcomes of coronary bypass grafting specifically in patients with compromised renal function. The study aimed to provide valuable insights into the long-term outcomes of this surgical intervention in this particular patient population.
Ethical Considerations:
After obtaining approval from the Health Science University Eskisehir Hospital Clinical Trials Ethics Committee, we proceeded to establish a de-identified database for the study. Adhering to the guidelines outlined by the committee and in accordance with ethical principles, we ensured the protection of patient privacy and confidentiality. The de-identification process involved removing any personally identifiable information from the dataset to maintain anonymity and uphold the highest standards of data security. By implementing these measures, we aimed to safeguard patient confidentiality while conducting a rigorous and ethically sound investigation. The Approval number is: " ESH/GOEK 2023/2”.
Patients:
This study included a total of 58 patients who underwent on-pump coronary artery bypass grafting surgery for complete myocardial revascularization. The surgeries were performed between the years 2020 and 2022.
Disease Definitions:
The diagnoses of the diseases selected as variables in this research were determined through a comprehensive examination of the patients' medical records and reports by the respective medical specialties. The diagnoses of conditions such as carotid disease (CD), acute myocardial infarction (AMI), previous myocardial infarction (PMI), structural heart disease (SHD), previous atrial fibrillation (AFib), type 2 diabetes mellitus (T2DM), chronic obstructive pulmonary disease (COPD), malignancy, anaemia, obesity, and severe renal impairment were established based on echocardiography reports, cardiology records, internal medicine records, pulmonology records, nephrology records, and consultations with relevant medical specialists. Additionally, consultations with nephrology and neurology specialists were sought for post-operative acute kidney injury (AKI) and stroke cases, and infectious disease specialists were consulted for the diagnosis of infections.
Complete Revascularization Definition:
In this study, complete revascularization was defined as the successful revascularization of all identified significant lesions. The determination of significant lesions was based on a diameter stenosis of 50% or more in vessels with a reference diameter of 2.0 mm or larger. However, it is important to highlight that in instances of stenosis in the posterior descending artery (PLV) or posterior descending artery (PDA), bypass was performed to vessels with a reference diameter exceeding 1.5 mm. This approach ensured the comprehensive revascularization of all significant lesions, including those in the PLV and PDA, to optimize revascularization outcomes (8).
Estimated Glomerular Filtration Rate Calculation:
In this study, the glomerular filtration rate (GFR) was calculated using the MRDR4 formula. The equation used was as follows:
eGFR = 175 x (SCr)^(-1.154) x (age)^(-0.203) x 0.742 [if female] x 1.212 [if Black]
This formula took into account the serum creatinine level (SCr) and the age of the patients. Additionally, adjustments were made based on gender (0.742 for females) and race (1.212 for individuals of Black ethnicity). The calculated eGFR values provided an estimation of the patients' glomerular filtration rate, which was used as a measure of their renal function in the study.(9)
Procedures of Renal Protection:
Conventional Ultrafiltration:
During the study, the group employed conventional ultrafiltration (CUF) as a technique from the rewarming stage until the completion of cardiopulmonary bypass (CPB). For modified ultrafiltration, a simplified arteriovenous technique was utilized. This technique involved the use of specialized equipment, including a 0.25-inch tubing line and a polysulfone hemofilter. To facilitate the process, a three-way connector was employed at the free end to connect both the inlet and outlet of the hemofilter to the 0.25-inch tubing(10).
In the case of conventional ultrafiltration (CUF), the inlet tubing of the hemofilter was connected to the arterial line, originating from the 40-μm arterial line filter. On the other hand, the outlet tubing of the hemofilter was connected to the venous reservoir through a three-way connector. This setup allowed for the effective removal of excess fluid and solutes during the bypass procedure, contributing to the overall success and efficiency of the cardiopulmonary bypass process (10).
Preoperatively Haemodialysis:
Within this study, three patients who had an estimated glomerular filtration rate (eGFR) below 45 mL/min were undergoing preoperative hemodialysis. These patients required additional renal support due to their compromised kidney function. The preoperative hemodialysis was performed through arteriovenous fistulas, which were pre-existing in these patients. By undergoing hemodialysis prior to the surgery, the aim was to optimize their renal status and ensure better management of their kidney function during the subsequent surgical procedure.
Surgical Procedure
A combination of inhaled and intravenous balanced anaesthesia, selected by the anaesthetist, was administered to the patients. The surgical procedure involved a traditional median sternotomy, followed by cannulation of the ascending aorta and right atrium using a biphasic cannula. Extracorporeal circulation was established using an adult membrane oxygenator, with a nasopharyngeal temperature maintained at 32°C. Warm anterograde blood cardioplegia was utilized. Distal anastomoses were performed by clamping the aorta, and upon completion, the clamp was released. Subsequently, the aorta was laterally clamped to perform proximal anastomoses in the ascending aorta. Meanwhile, the blood was gradually warmed to reach the body's physiological temperature. For patients with impaired renal function (GFR < 60), during this warming process (approximately 30 minutes), ultrafiltration at a rate of 30-50 cc per minute was applied. Once all anastomoses were completed and the patient was adequately warmed, they were removed from the extracorporeal circulation.
Graft Conduits:
All patients in the study underwent LIMA to LAD anastomosis. To achieve complete revascularization, the saphenous vein, obtained through open harvesting, was carefully prepared and anastomosed to the predetermined coronary branches.
Data Collection:
Data for this study was collected from various reliable sources. Preoperative data were obtained by meticulously examining medical records from relevant departments, including cardiology, internal medicine, pulmonology, and nephrology. These records provided a comprehensive overview of variables such as age, BMI, gender, HT history, carotid artery disease, AMI, PMI, SHD, previous atrial fibrillation, T2DM, COPD, malignancy, anaemia, obesity, severe renal impairment, LVEF, eGFR, creatinine levels, HB, albumin, HCT, AST, ALT, HDL, LDL, and FEV1/FVC. Intraoperative data were meticulously collected by reviewing surgical records. This involved documenting critical information such as the number of distal anastomoses, cardiopulmonary bypass time, aortic cross-clamp time, instances of low cardiac output syndrome, prolonged bleeding, and any unfortunate occurrences of intraoperative death.
Postoperative data were gathered from both ICU and general ward records, in addition to consulting the national electronic health system records. This comprehensive approach allowed for the recording of vital variables including cardiopulmonary resuscitation, graft occlusion, stroke, bleeding, transfusion requirements (including FFP and PRBC), acute kidney injury, wound site infection, sternal dehiscence, Po HCT, Po Creatinine, intubation time, ICU duration, length of stay, and mortality. Furthermore, 12-month outcomes were meticulously evaluated using data extracted from the national electronic health system records. This analysis provided insights into significant factors such as the need for redo revascularization, renal replacement therapy, cardiac mortality, and all-cause mortality at the end of the 12-month follow-up period.
Data Analysis:
The categorical data in this study were presented as percentages, which represent the proportion of individuals in each category. On the other hand, numerical data were presented as mean values and standard deviations (SD). To assess overall survival, Kaplan-Meier with the log-rank test was conducted for statistical analysis.