Objective: To investigate the relationship between changes in serum thyroid hormone levels and postoperative acute kidney injury (AKI) as well as the severity of AKI in patients with acute type A aortic dissection (ATAAD), and to evaluate their predictive value for in-hospital mortality.
Methods: A retrospective study was conducted. Patients who underwent surgery for ATAAD and received treatment in the Department of Intensive Care Medicine of Nanjing Hospital Affiliated to Nanjing Medical University from January 2021 to December 2023 were enrolled. General information, thyroid function, biochemical indicators, blood routine, procalcitonin, coagulation function and other data were collected. Patients were divided into AKI group and non-AKI group based on whether AKI occurred after surgery. In addition, patients were divided into NTIS group and non-NTIS group based on whether they developed non-thyroidal illness syndrome (NTIS). The factors associated with AKI and the impact of thyroid hormone levels on the stage of AKI were analyzed. The predictive value of thyroid hormone and serum creatinine (SCr) for in-hospital mortality was analyzed using the receiver operator characteristic curve (ROC curve).
Results: A total of 176 postoperative ATAAD patients were enrolled. AKI occurred in 105 patients (59.7%), including 46 cases (26.1%) of stage 1 AKI, 32 cases (18.2%) of stage 2 AKI, and 27 cases (15.3%) of stage 3 AKI. NTIS occurred in 113 patients (64.2%), the incidence of NTIS in the non-AKI group and in patients with stage 1, stage 2, and stage 3 AKI was 54.9% (39/71), 56.5% (26/46), 84.4% (27/32), and 77.8% (21/27), respectively. Compared with the non-AKI group, the AKI group had higher body mass index, proportion of vasopressors and cardiac stimulants used, incidence of pulmonary infection and NTIS, blood transfusion, reoperation, and continuous renal replacement therapy (CRRT), higher predicted mortality and actual mortality, as well as longer total hospital stay and the length of intensive care unit stay, and lower levels of free tri-iodothyronine (FT3), total tri-iodothyronine (TT3), and free thyroxine (FT4), and there were statistically significant differences in SCr, uric acid, blood sodium, alanine transaminase, aspartate transaminase, creatine kinase, MB isoenzyme of creatine kinase, white blood cell count, procalcitonin, platelet count, prothrombin time, activated partial thromboplastin time, and fibrinogen between the two groups (all P<0.05). The NTIS group had higher postoperative day 1, 3, and 5 SCr levels, overall AKI incidence, and incidences of stage 2 and stage 3 AKI than the non-NTIS group (all P<0.05). FT3, TT3, FT4, and total thyroxine (TT4) decreased with increasing severity of AKI stage (all P<0.05), while TSH slightly increased with increasing severity of AKI stage (P>0.05). ROC curve analysis showed that the area under the curve (AUC) and 95% confidence interval (95%CI) of FT3, TT3, and postoperative day 1 SCr for predicting in-hospital mortality were 0.770 (0.636-0.904), 0.812 (0.708-0.916), and 0.719 (0.597-0.840), respectively. The combination of the three had the highest AUC, which was 0.838 (0.732-0.944).
Conclusions: The incidence of AKI is relatively high in patients following ATAAD surgery. The decline in FT3 and FT4 levels may contribute to the occurrence and progression of AKI. The lower the thyroid hormone levels, the more severe AKI and the worse the prognosis. FT3 and TT3 combined with postoperative day 1 SCr may serve as auxiliary predictors of in-hospital mortality in ATAAD patients.