A total of 730 consecutive patients with TA-AAD in our hospital from January 2014 to December 2018 were retrospectively analyzed. Previous approval was obtained from the institutional research ethics committee, which waived the need for individual informed consent. Aortic dissection was diagnosed by computed tomography angiography at either our institution or the referring hospital. Patients with a history of chronic renal failure (CRF) or with intraoperative and postoperative death within 24 hours were excluded. Patients were divided into the control group (601 cases) and the CRRT group (111 cases) according to whether they received CRRT after surgery. The basic clinical data of the two groups are shown in Table 1.
Demographic variables included age, gender, body mass index (BMI), previous medical history (hypertension, diabetes, cardiac surgery, coronary artery disease, cerebrovascular disease), aortic dissection features (blood supply of renal artery) and pericardial effusion. Operation-related variables were the duration of cardiopulmonary bypass (CPB) and aortic cross-clamping, extracorporeal circulation assist, the duration of deep hypothermic circulatory arrest (DHCA). Laboratory variables included preoperative serum creatinine (sCr) and serum blood urea nitrogen (BUN) levels. Postoperative variables included drainage volume 24 hours after surgery, duration of mechanical ventilation, ICU and hospital stay, and 30-day mortality.
Criteria for the initiation and termination of CRRT after severe AKI is referred to the guidelines for the clinical practice of AKI from the global organization for the improvement of renal prognosis: Kidney Disease Improving Global Outcomes (KDIGO)[9]. When patients have severe AKI after surgery, that is, within 48 h after surgery, when the increase in sCr was greater than 26.5umol/L or the urine volume was less than 0.5 ml/kg/h lasting for 6 h and serum K + > 6.0 mmol/L or blood HCO3− <10 mmol/L were observed, CRRT may be considered. During treatment, the corresponding CRRT mode and treatment amount were set according to the individual situation of the patient. CRRT termination criteria: the increase in sCr within 48 hours after surgery is less than 26.5umol/L or the urine volume is more than 0.5 ml/kg/h lasting for 6 h, and serum K + < 6.0 mmol/L or HCO3− >10 mmol/L. Within 48 h after the last CRRT treatment, without CRRT support, the results of two sCr tests decreased by a range of > 50umol/L (the sampling interval is greater than 12 h) or urine volume > 0.5 ml/kg/h within 12 h, and CRRT treatment could be considered for termination when serum K + < 5.5 mmol/L and HCO3− >18 mmol/L in the latest blood gas test [10].
CRRT was performed in our department, using the 11.5f double-chamber dialysis catheter, the AV600S polysulfone membrane blood filter and the connection pipeline of blood filtration, infusion pump, and syringe pump. The internal jugular vein or femoral vein or subclavian vein was selected to place a single double-chamber blood filter catheter. The hemodynamic force is provided by the blood pump. 1000 ml heparin brine was pre-flushed before using the filter to empty the air bubbles in the filter and pipeline. We then placed the sterile collecting bag 30-50cm below the filter, and recorded the flow of liquid in and out every hour. In the early postoperative patients after aortic dissection, local anticoagulation of prefilter citrate was used to reduce bleeding. The replacement solution was 0.9% normal saline and 5% glucose solution, with a ratio of 3:1. Additionally, 250 ml 5% sodium bicarbonate was added for q4h or q6h to timely supplement the physiological needs and nutrients lost by blood filtration. The input method is pre or post-dilution method, which can balance the fluid and adjust the infusion speed according to the amount of filtrate and input. The filter is usually replaced after a blockage or when the filtrate drops, and the continuous veno-venous hemofiltration (CVVH) blood flow should be 100–150 ml/min.
Surgical Procedure
The median sternal incision was used in all surgeries under general anesthesia and DHCA. All patients were treated with Terumo inlet membrane lung, no pre-rinse containing sugar was used in extracorporeal circulation, ultrafiltration and autologous blood recovery devices were routinely used. Extracorporeal circulation was established by a routine femoral artery or right axillary artery and right atrial intubation. When the nasopharyngeal temperature dropped to 34℃, the ascending aorta was blocked and cardiac arrest fluid was injected to complete the operation of the proximal end of the aorta. When the nasopharyngeal temperature dropped to 18 ~ 20℃ and the bladder temperature to 22 ~ 24℃, systemic circulatory was arrested, and the flow was reduced to 3 ~ 5 ml· kg− 1·min− 1 to complete the operation of the aortic arch and descending arch. All patients returned to the ICU for routine monitoring and treatment.
Statistical Analysis
SPSS 25.0 software was used for statistical analysis. Univariate analysis was performed for each variable. Data were compared using the Student t test or non- parametric Wilcoxon Mann-Whitney U test for continuous variables and the chi-squared or Fisher's exact test for categorical variables before matching; The multivariate model included variables that were significant on univariate analysis. Baseline characteristics (Demographic variables, previous medical history, aortic dissection features and pericardial effusion) were matched for propensity scores. We performed one-to-one pair matching using nearest neighbor matching without replacement within 0.02 standard deviations of the logit of the propensity score as caliper width.
Kaplan-Meier curves were generated to provide survival estimates at postoperative points in time. Differences between the 2 groups were determined by log-rank tests. For all analyses, a probability value of less than 0.05 was considered statistically significant.