Part Ⅱ Incidence And Risk Factors Of Acute Kidney Injury After Femoral Neck Fracture in Elderly Patients: A Retrospective Case-control Study

Results

1. Patient characteristics

Comparisons of the demographic characteristics between the AKI and non-AKI groups are shown in Table 1. A total of 308 elderly patients with femoral neck fractures, including 216 (70.1%) females and 92 (29.9%) males with a mean age of 79.06±7.3 years, were recruited in this study. The overall incidence of postoperative AKI was 12% (37 cases). There were no significant differences in age or sex between the two groups, nor were there differences in other characteristics, such as preoperative comorbidities, BMI, or surgical time.

2. Potential risk factors

The potential risk factors for postoperative AKI are presented in Table 2. The early postoperative level of serum albumin, hemoglobin changes, and intraoperative hypotension were identified as significant risk factors for AKI (p < 0.01). Compared to the non-AKI group, the AKI group exhibited more intraoperative blood loss (p=0.036). There were no significant differences in preoperative creatinine levels, preoperative albumin levels, preoperative hemoglobin levels, preoperative mean arterial pressure (MAP), anesthesia methods, surgical methods, surgical time, blood transfusion history, or postoperative complications between the two groups. After adjusting for age, intraoperative blood loss, and BMI, early postoperative albumin levels, hemoglobin changes, and intraoperative hypotension were found to be independent risk factors for postoperative AKI (Table 3).

3. ROC curves for the significant risk factors

Figure 1 shows the ROC curves of hemoglobin changes predicting AKI. The area under the curve (AUC) was 0.789. The cut-off value of the hemoglobin change was > 22.5 g/L with a sensitivity of 64.9% and a specificity of 97.8%. Fig. 2 shows the ROC curves of postoperative albumin levels predicting AKI. The area under the curve (AUC) was 0.859. The cut-off value of postoperative albumin levels was <29.6 g/L with a sensitivity of 78.2% and a specificity of 83.8%. Based on the beta factors of the previous binary logistic regression, we proposed a formula for predicting the risk of postoperative AKI: model=3.207 + 0.128* hemoglobin change (g/L) -0.463* postoperative albumin level (g/L) +2.609* intraoperative hypotension (Yes, 1; No, 0). The ROC curves of the model and the other three independent risk factors are shown in Fig. 3. Te model was significantly superior to the postoperative albumin level (p=0.011) and other independent risk factors.

4. 1‑year cumulative mortality

At the 1-year follow-up, the overall cumulative mortality was 26.0%. The patients with any AKI had a significantly higher mortality of 40.5% than those without AKI (24.0%, p < 0.001, Fig. 4). Most of these deaths occurred within three months after surgery.

Discussion

In our study population, the incidence of postoperative AKI was 12%, slightly lower than the 11.8%-28.4% reported by previous studies for hip fracture patients. These differences can be attributed to various factors, such as the varied definitions of AKI, varied monitoring periods, and heterogeneity of the selected patients. However, we do agree that elderly patients with hip fractures or femoral neck fractures are at a greater risk of postsurgical AKI. Compared with previous studies, we focused only on patients with femoral neck fractures, rather than all types of hip fractures.

Shin et al.’s findings [7–9, 16] suggested that postoperative hypoalbuminemia, substantial blood loss, and intraoperative hypotension are associated with postoperative AKI in patients with hip fractures. The conclusions of our study were consistent with previous studies to some extent, but we found no significant differences in preoperative albumin levels, preoperative hemoglobin levels, preoperative MAP, or other baselines between the two groups. Therefore, we can boldly conclude that the occurrence of postoperative AKI in patients with femoral neck fractures is mainly related to intraoperative and postoperative blood for hypoperfusion. Of course, there are maybe other possible reasons for postoperative AKI caused by hypoalbuminemia and anemia9. Therefore, we recommend timely treatment for patients with postoperative albumin levels lower than 29.6 g/L or postoperative hemoglobin decreases greater than 22.5 g/L.

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Some studies [17–19] have reported that blood transfusion is also a risk factor for postoperative AKI in hip fracture patients. As a result, we seem to be caught in a paradoxical dilemma. The cause of AKI caused by blood transfusion is not clear. Some studies suggest that it may be caused by immunological responses induced by blood transfusions. Therefore, we are more inclined to believe that the association between blood transfusions and AKI may be the expression of the patient’s primary disease, such as anemia and hypotension, rather than the blood transfusion itself causing AKI. Therefore, we recommend blood transfusion for patients who meet transfusion indications.

Many other risk factors for AKI after hip surgery, such as age, preoperative albumin levels, BMI, preoperative complications, and postoperative complications, have been reported [18, 20, 21]. In this study, these indicators were not found to be significantly different between the AKI and no-AKI groups. These outcomes could be attributed to differences in the populations for different studies. We cannot deny that these factors are high-risk factors for postoperative AKI in patients with femoral neck fractures. Therefore, they should be taken into account in clinical work to prevent AKI. More prospective large sample studies are needed to confirm these possible risk factors.

The proposed prediction formula was confirmed by the ROC curve. Its predictive ability was superior to that of hemoglobin changes, early postoperative hypoalbuminemia, and intraoperative hypotension alone. The AUG of the model was significantly larger than the AUG of postoperative albumin levels and hemoglobin changes, indicating that the model could find the optimal solution to balance sensitivity and specificity in predicting postoperative AKI. Using this formula, we intend to demonstrate that multiple factors should be integrated and analyzed to evaluate patients’ risk for postoperative AKI.

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By clarifying the risk factors for postoperative AKI in patients with femoral neck fractures, clinical work can be better guided to avoid the occurrence of postoperative AKI. Good intraoperative blood pressure control and the timely correction of hypoalbuminemia and anemia during the perioperative period can effectively prevent the occurrence of AKI. At the same time, we can use more advanced and accurate markers for the early diagnosis of AKI in patients to achieve early treatment, such as retinol-binding protein, neutrophil gelatinase-associated lipocalin, and cystatin C which have been proven sensitive for the early detection of AKI [22, 23]. For some patients with high-risk factors for AKI, we should pay more attention to the regular test results of patients, and if necessary, use preventive drugs for AKI.

The limitations of this study are as follows. First, it was a retrospective study; therefore, it is necessary to perform a large-scale prospective study to confirm our findings. Second, since this was a retrospective study, the long-term follow-up of patients was not possible to observe changes in long-term creatinine levels and patient survival. Third, due to the limited sample size, staging and related studies of postoperative AKI were not performed. Fourth, sCr levels can be influenced by volume overload, nutrition, steroids, and muscle trauma [24]. The immediate postoperative period sCr concentrations can be lower than at baseline as a result of hemodilution after massive fluid administration and fluid shifts. Biomarkers for the early detection of AKI [22, 23] should be evaluated in future studies.

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Conclusion

The incidence of postoperative AKI in elderly patients with femoral neck fractures was 12%. Independent risk factors for postoperative AKI included perioperative hemoglobin changes, early postoperative hypoalbuminemia, and intraoperative hypotension. At the same time, postoperative AKI significantly increased mortality in elderly patients with femoral neck fractures. Taking multiple possible factors into consideration can better predict the possibility of elderly patients developing AKI after surgery

The effect of Cistanche extract on acute kidney injury after femoral neck fracture in elderly patients

The incidence of acute kidney injury (AKI) is relatively high among elderly patients following femoral neck fracture surgeries. Recently, researchers have explored the potential benefits of Cistanche extract on AKI development in these patients.

Cistanche extract contains biologically active compounds capable of reducing inflammation and oxidative stress on renal function, promoting tissue regeneration, and reducing cell apoptosis. A growing body of evidence suggests that Cistanche extract may possess protective abilities against AKI by mitigating risk factors associated with this condition.

In particular, studies have revealed that Cistanche extract administration can significantly reduce serum creatinine levels and decrease the occurrence of AKI postoperatively in elderly patients with femoral neck fractures. This finding highlights the potential therapeutic value of Cistanche extract as a complementary treatment in managing the onset and progression of AKI following surgery. Moving forward, greater research will help establish standard dosage, formulation, administration methods, and safety of use for Cistanche extract in this specific population.

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Author Details

Sizheng Zhan1,2, Wenyong Xie1,2, Ming Yang1,2, Dianying Zhang1,3 and Baoguo Jiang1,2

1 Department of Orthopedics, Peking University People’s Hospital, No.11 Xizhimen South Street, Xicheng District, Beijing 100044, China.

2 Ministry of Education Key Laboratory of trauma treatment and nerve regeneration, Peking University People’s Hospital, Beijing 100044, China.

3 Department of Orthopedics, Peking University Binhai Hospital, Tianjin 300450, China.