The results suggest that the patients undergoing unilateral radical nephrectomy and CPB-assisted inferior vena cava thrombectomy have a high AKI rate. Age is associated with the occurrence of AKI in such patients.
Renal cancer complicated with cancer-associated thrombosis in the inferior vena cava or even the atrium is challenging 7–10. In the early days, targeted therapy was used in most cases. In recent years, some large surgical centers in China have been performing radical nephrectomy and inferior vena cava thrombectomy with the emergence of more advanced surgical instruments, anesthetic, and surgical techniques 10,14−17. Compared with other therapies, radical nephrectomy combined with thrombectomy can significantly extend patients’ overall survival and improve their 5-year survival rate 18. Cancer-associated embolism is graded according to the five-grade rating method of the Mayo Clinic, and the surgery is performed according to the grade. Grade 0 cancer-associated thrombosis can be removed without blocking the inferior vena cava. Grades I and II cancer-associated thrombosis can be removed by only blocking the proximal and distal inferior vena cava and the contralateral renal vein momentarily. For grades III and IV cancer-associated thrombosis, it is suggested to perform CPB to control the hemodynamics and cause deep hypothermic circulatory arrest (DHCA). Cancer-associated thrombosis in the right atrium should be completely removed, requiring CPB and DHCA 19. About 38% of the patients undergoing surgery have postoperative complications, and 4%-10% die during the perioperative period 20. According to the literature, postoperative complications are mainly related to the grade of cancer-associated thrombosis. Specifically, the incidence of postoperative complications in patients with grade I cancer-associated thrombosis is 18% and increases to 20% in grade II, 26% in grade III, and 47% in grade IV 21. Bleeding, pulmonary embolism, incision infection, and acute renal failure are common postoperative complications in patients with grade IV cancer-associated thrombosis, as reported in the literature 7–10, 22.
The occurrence of postoperative AKI might be related to the surgical procedures, such as the use of CPB, great blood pressure fluctuations due to poor control of intraoperative blood pressure, and use of colloids during surgery, so after the CPB-aided surgery for renal cancer complicated with cancer-associated thrombosis, in which one kidney is removed, the nephron number drops by half, and the patient is more prone to AKI. However, our results indicated that there was no obvious significant difference in CPB duration between patients with AKI or not.
For anesthesia during radical nephrectomy and CPB-aided inferior vena cava thrombectomy, the main difficulties are the risks of intraoperative bleeding and embolism due to detachment of the cancer-associated thrombosis when it is being removed during surgery, as well as instability of the circulatory system after vessel blocking, which would cause severe fluctuations and ischemic injury of vital organs 7–10, 23. Before surgery, the surgeon should have full access to the tumor’s location and should grade the cancer-associated thrombosis and determine the specific surgical procedures. As the right renal vein is shorter than the left renal vein, renal cancer complicated with cancer-associated thrombosis in the inferior vena cava on the right is more common than on the left, and surgery for cancer-associated thrombosis of grade ≥ II on the left is more difficult than that on the right. Moreover, sufficient amounts of blood products should be prepared before surgery because blood loss during the surgery for grade III cancer-associated thrombosis can be up to 2000 mL, and the blood loss during surgery for grade IV cancer-associated thrombosis can be up to 4000 mL. For patients needing CPB, plasma, fibrinogen, and platelets should also be prepared 24. DHCA should be provided during the CPB-assisted surgery for grade IV cancer-associated thrombosis, but CPB and hypothermia can have a higher risk of acute renal failure 25. The patient should be given appropriate volume enlargement before CPB and be given vasoactive drugs to maintain the central venous pressure at the higher normal value, to avoid a sharp drop in the volume of returned blood and the blood pressure after blocking. During blocking, the fluid infusion should be limited, and α-receptor agonists and venous dilators should be given to maintain the CVP at the lower normal value, to avoid acute heart failure or pulmonary edema due to a great volume of returned blood when the inferior vena cava is opened 15. In this study, the difference in anesthesia duration between the two groups was not statistically significant, suggesting that anesthesia duration was not significantly related to postoperative renal function impairment or renal failure. Moreover, our research also demonstrated that surgical trauma in patients may have no obvious difference in non-AKI group and AKI group. Patients with renal cancer are older, have decreased physical functions and comorbidities, and have poorer glomerular filtration than young people, which causes a higher incidence of AKI 17. Results of this study corroborated such a conclusion since age was the only associated risk factor. Our results suggest that more attention should be paid to older patients after surgery.
This study has limitations. It was a retrospective study with a small sample size from a single center. This study carries all the biases inherent to retrospective analyses.
In conclusion, patients undergoing unilateral radical nephrectomy and CPB-assisted thrombectomy in the inferior vena cava or atrial pulmonary artery are at risk of postoperative AKI. Of such patients, older ones are at a higher risk of postoperative AKI.