The association of post-lung transplant acute kidney injury with mortality is independent of primary graft dysfunction: A cohort study

Interorgan communication networks in the kidney-lung axis

The homeostasis and health of an organism depend on the coordinated interaction of specialized organs, which is regulated by interorgan communication networks of circulating soluble molecules and neuronal connections. Many diseases that seemingly affect one primary organ are really multiorgan diseases, with substantial secondary remote organ complications that underlie a large part of their morbidity and mortality. Acute kidney injury (AKI) frequently occurs in critically ill patients with multiorgan failure and is associated with high mortality, particularly when it occurs together with respiratory failure. Inflammatory lung lesions in patients with kidney failure that could be distinguished from pulmonary oedema due to volume overload were first reported in the 1930s, but have been largely overlooked in clinical settings. A series of studies over the past two decades have elucidated acute and chronic kidney-lung and lung-kidney interorgan communication networks involving various circulating inflammatory cytokines and chemokines, metabolites, uraemic toxins, immune cells and neuro-immune pathways. Further investigations are warranted to understand these clinical entities of high morbidity and mortality, and to develop effective treatments.

Postoperative Acute Kidney Injury and Long-Term Outcomes After Lung Transplantation

BACKGROUND

This study sought to characterize perioperative risk factors of acute kidney injury (AKI) and report outcomes associated with its development in the immediate postoperative setting after lung transplantation.

METHODS

Study investigator performed a retrospective analysis of all adult patients undergoing primary lung transplantation at a single institution from January 1, 2011 to December 31, 2021 AKI was defined using Kidney Disease: Improving Global Outcomes (KDIGO) criteria after lung transplantation and was stratified on the basis of whether patients required renal replacement therapy (RRT; AKI-no RRT vs AKI-RRT).

RESULTS

Of the 754 patients included, 369 (48.9%) any AKI developed in the postoperative period (252 AKI-no RRT vs 117 AKI-RRT). Risk factors for postoperative AKI included higher preoperative creatinine levels (odds ratio [OR], 5.15; P < .001), lower preoperative estimated glomerular filtration rate (OR, 0.99; P < 0.018), delayed chest closure (OR, 2.72; P < .001), and higher volumes of postoperative blood products (OR, 1.09; P < .001) in the multivariable analysis. On univariate analysis, both AKI groups were also associated with higher rates of pneumonia (P < .001), reintubation (P < .001), mortality on index admission (P < 0.001), longer ventilator duration (P < .001), longer intensive care unit length of stay (P < .001), and longer hospital length of stay (P < .001), with the highest rates in the AKI-RRT group. In a multivariable survival analysis, postoperative AKI-no RRT (hazard ratio [HR], 1.50; P = .006) and AKI-RRT (HR, 2.70; P < .001) were associated with significantly worse survival independent of severe grade 3 primary graft dysfunction at 72 hours (HR, 1.45; P = .038).

CONCLUSIONS

The development of postoperative AKI was associated with numerous preoperative and intraoperative factors. Postoperative AKI remained significantly associated with poorer posttransplantation survival. Severe cases of AKI necessitating RRT portended the worst survival after lung transplantation.

Future Directions in Optimizing Anesthesia to Reduce Perioperative Acute Kidney Injury

BACKGROUND

Perioperative acute kidney injury (AKI) is common in surgical patients and is associated with high morbidity and mortality. There are currently few options for AKI prevention and treatment. Due to its complex pathophysiology, there is no efficient medication therapy to stop the onset of the injury or repair the damage already done. Certain anesthetics, however, have been demonstrated to affect the risk of perioperative AKI in some studies. The impact of anesthetics on renal function is particularly important as it is closely related to the prognosis of patients. Some anesthetics can induce anti-inflammatory, anti-necrotic, and anti-apoptotic effects. Propofol, sevoflurane, and dexmedetomidine are a few examples of anesthetics that have protective association with AKI in the perioperative period.

SUMMARY

In this study, we reviewed the clinical characteristics, risk factors, and pathogenesis of AKI. Subsequently, the protective effects of various anesthetic agents against perioperative AKI and the latest research are introduced.

KEY MESSAGE

This work demonstrates that a thorough understanding of the reciprocal effects of anesthetic drugs and AKI is crucial for safe perioperative care and prognosis of patients. However, more complete mechanisms and pathophysiological processes still need to be further studied.

Pulmonary, circulatory and renal considerations in the early postoperative management of the lung transplant recipient

Lung transplantation volumes and survival rates continue to increase worldwide. Primary graft dysfunction (PGD) and acute kidney injury (AKI) are common early postoperative complications that significantly affect short-term mortality and long-term outcomes. These conditions share overlapping risk factors and are driven, in part, by circulatory derangements. The prevalence of severe PGD is up to 20% and is the leading cause of early death. Patients with pulmonary hypertension are at a higher risk. Prevention and management are based on principles learned from acute lung injury of other causes. Targeting the lowest effective cardiac filling pressure will reduce alveolar edema formation in the setting of increased pulmonary capillary permeability. AKI is reported in up to one-half of lung transplant recipients and is strongly associated with one-year mortality as well as long-term chronic kidney disease. Optimization of renal perfusion is critical to reduce the incidence and severity of AKI. In this review, we highlight key early post-transplant pulmonary, circulatory, and renal perturbations and our center's management approach.

Primary graft dysfunction grade correlates with acute kidney injury stage after lung transplantation

BACKGROUND

Primary graft dysfunction (PGD) and acute kidney injury (AKI) are major early complications of lung transplantation and are associated with increased mortality. Lung injury after PGD can contribute to renal dysfunction; however, the association between PGD and AKI severity has not been thoroughly investigated. We analyzed the association between PGD grading and AKI staging, and the impact of AKI on subsequent changes to chronic kidney disease (CKD), including glomerular filtration rate (GFR), over time.

METHODS

This was a retrospective review of a single-center lung transplantation database between January 2018 and June 2022. AKI and GFR categories were classified according to the Kidney Disease: Improving Global Outcomes criteria. Spearman's and Kaplan-Meier tests were used to compare disease severity and assess survival.

RESULTS

In a total of 206 patients: 119 (57.8%), 25 (12.1%), 34 (16.5%), and 28 (13.6%) had PGD grades 0, 1, 2, and 3, respectively; 96 (46.6%), 47 (22.8%), 27 (13.1%), and 36 (17.5%) had AKI stages 0, 1, 2, and 3, respectively. Twenty-one of the 28 patients (75.0%) with PGD grade 3 had AKI stage 3. There was a significant correlation between PGD grade and AKI stage (P<0.001). There was also a significant correlation between AKI stage and GFR category of CKD at 3, 6, 9, and 12 months after lung transplantation (all P<0.001). For all AKI stages, GFR categories worsened with postoperative time.

CONCLUSIONS

PGD grade was significantly correlated with AKI stage, and AKI stage was correlated with GFR categories of CKD.

Longitudinal assessment of renal function after lung transplantation for cystic fibrosis: transition from post-operative acute kidney injury to acute kidney disease and chronic kidney failure

INTRODUCTION

The clinical trajectory of post-operative acute kidney injury (AKI) following lung transplantation for cystic fibrosis is unknown.

METHODS

Incidence and risk factors for post-operative AKI, acute kidney disease (AKD) and chronic kidney disease (CKD) were retrospectively analyzed in cystic fibrosis patients undergoing lung transplantation. Logistic regressions, Chi-square, Cuzick rank tests, and Cox-proportional hazard models were used.

RESULTS

Eighty-three patients were included. Creatinine peaked 3[2-4] days after transplantation, with 15(18%), 15(18%), and 20(24%) patients having post-operative AKI stages 1, 2, and 3, while 15(18%), 19(23%) and 10(12%) developed AKD stage 1, stage 2 and 3, respectively. Higher AKI stage was associated with worsening AKD (p = 0.009) and CKD (p = 0.015) stages. Of the 50 patients with AKI, 32(66%) transitioned to AKD stage > 0, and then 27 (56%) to CKD stage > 1. Female sex, extracorporeal membrane oxygenation support as a bridge to lung transplant and at the end of the surgery, the use of intraoperative blood components, and cold-ischemia time were associated with increased risk of post-operative AKI and AKD. Higher AKI stage prolonged invasive mechanical ventilation (p = 0.0001), ICU stay (p = 0.0001), and hospital stay (p = 0.0001), and increased the incidence of primary graft dysfunction (p = 0.035). Both AKI and AKD stages > 2 worsened long-term survival with risk ratios of 3.71 (1.34-10.2), p = 0.0131 and 2.65(1.02-6.87), p = 0.0443, respectively.

DISCUSSION

AKI is frequent in cystic fibrosis patients undergoing lung transplantation, it often evolves to AKD and to chronic kidney disease, thereby worsening short- and long-term outcomes.

Extracellular vesicles from lung tissue drive bone marrow neutrophil recruitment in inflammation

Extracellular vesicles (EVs) are single-membrane vesicles that play an essential role in long-range intercellular communications. EV investigation has been explored largely through cell-culture systems, but it remains unclear how physiological EVs exert homeostatic or pathological functions in vivo. Here, we report that lung EVs promote chemotaxis of neutrophils in bone marrow through delivery of double stranded DNA (dsDNA). We have identified and characterized EVs containing dsDNA collected from both human and murine lung tissues using newly developed approaches. Our analysis of EV proteomics together with single-cell RNA sequencing data reveals that type II alveolar epithelial cells are the main source of the lung EVs. Furthermore, we demonstrate that the lung EVs accumulate in bone marrow and enhance neutrophil recruitment under inflammation conditions. Moreover, lung EV-DNA stimulates neutrophils to release the chemokines CXCL1 and CXCL2 via DNA-TLR9 signalling. Our findings establish a molecular basis of lung EVs in enhancement of host immune response to bacterial infection and provide new insights into understanding of vesicle-mediated systematic communications.

Incidence and Perioperative Risk Factors of Acute Kidney Injury Among Lung Transplant Recipients

BACKGROUND

Acute kidney injury (AKI) is a significant burden in an early postoperative period after lung transplantation (LT). The development of severe AKI, including a need for continuous renal replacement therapy (CRRT), is associated with increased mortality among lung transplant recipients. Evaluation of AKI incidence and predictive factors related to the development of severe AKI and with the use of CRRT in the early postoperative period after LT.

METHODS

Retrospective study of 73 consecutive patients after LT operated between 2015 and 2018 in our center. We noted the stage of AKI according to KDIGO guidelines in the 7 postoperative days.

RESULTS

We noted AKI among 62 lung transplant recipients (84.9%). We recognized the first and second stages of AKI in 21 patients (28.8%) and 19 patients 26%, respectively (group A). We identified severe AKI (group C) in 22 recipients (30.1%), 9 of whom needed CRRT postoperatively. There was a nonsignificant difference between groups in baseline serum creatinine (0.69 ± 0.22 mg/dL vs 0.84 ± 0.34; P = .073). Group C subjects statistically more often suffered from pulmonary hypertension (P < .001) and diabetes (P < .001). In both groups, the duration of the procedure was comparable, but, among patients with severe AKI, procedures were performed more often with the use of extracorporeal circulation (50% vs 68%; P = .194) CONCLUSIONS: Pulmonary hypertension and diabetes could be significant risk factors of high-grade AKI development after LT. Identification of factors modifying renal insufficiency development in lung transplant recipients needs further investigations.

Interorgan crosstalk mechanisms in disease: the case of acute kidney injury-induced remote lung injury

Homeostasis and health of multicellular organisms with multiple organs depends on interorgan communication. Tissue injury in one organ disturbs this homeostasis and can lead to disease in multiple organs, or multiorgan failure. Many routes of interorgan crosstalk during homeostasis are relatively well known, but interorgan crosstalk in disease still lacks understanding. In particular, how tissue injury in one organ can drive injury at remote sites and trigger multiorgan failure with high mortality is poorly understood. As examples, acute kidney injury can trigger acute lung injury and cardiovascular dysfunction; pneumonia, sepsis or liver failure conversely can cause kidney failure; lung transplantation very frequently triggers acute kidney injury. Mechanistically, interorgan crosstalk after tissue injury could involve soluble mediators and their target receptors, cellular mediators, in particular immune cells, as well as newly identified neuro-immune connections. In this review, I will focus the discussion of deleterious interorgan crosstalk and its mechanistic concepts on one example, acute kidney injury-induced remote lung injury.

Inhaled Pulmonary Vasodilator Therapy in Adult Lung Transplant: A Randomized Clinical Trial

Importance

Inhaled nitric oxide (iNO) is commonly administered for selectively inhaled pulmonary vasodilation and prevention of oxidative injury after lung transplant (LT). Inhaled epoprostenol (iEPO) has been introduced worldwide as a cost-saving alternative to iNO without high-grade evidence for this indication.

Objective

To investigate whether the use of iEPO will lead to similar rates of severe/grade 3 primary graft dysfunction (PGD-3) after adult LT when compared with use of iNO.

Design, Setting, and Participants

This health system-funded, randomized, blinded (to participants, clinicians, data managers, and the statistician), parallel-designed, equivalence clinical trial included 201 adult patients who underwent single or bilateral LT between May 30, 2017, and March 21, 2020. Patients were grouped into 5 strata according to key prognostic clinical features and randomized per stratum to receive either iNO or iEPO at the time of LT via 1:1 treatment allocation.

Interventions

Treatment with iNO or iEPO initiated in the operating room before lung allograft reperfusion and administered continously until cessation criteria met in the intensive care unit (ICU).

Main Outcomes and Measures

The primary outcome was PGD-3 development at 24, 48, or 72 hours after LT. The primary analysis was for equivalence using a two one-sided test (TOST) procedure (90% CI) with a margin of 19% for between-group PGD-3 risk difference. Secondary outcomes included duration of mechanical ventilation, hospital and ICU lengths of stay, incidence and severity of acute kidney injury, postoperative tracheostomy placement, and in-hospital, 30-day, and 90-day mortality rates. An intention-to-treat analysis was performed for the primary and secondary outcomes, supplemented by per-protocol analysis for the primary outcome.

Results

A total of 201 randomized patients met eligibility criteria at the time of LT (129 men [64.2%]). In the intention-to-treat population, 103 patients received iEPO and 98 received iNO. The primary outcome occurred in 46 of 103 patients (44.7%) in the iEPO group and 39 of 98 (39.8%) in the iNO group, leading to a risk difference of 4.9% (TOST 90% CI, -6.4% to 16.2%; P = .02 for equivalence). There were no significant between-group differences for secondary outcomes.

Conclusions and Relevance

Among patients undergoing LT, use of iEPO was associated with similar risks for PGD-3 development and other postoperative outcomes compared with the use of iNO.

Trial Registration

ClinicalTrials.gov identifier: NCT03081052.

Postoperative acute kidney injury and renal replacement therapy after DCD lung transplantation

Acute kidney injury (AKI) after lung transplantation (LTx) is a common complication. We aimed to assess whether donation after circulatory death (DCD) is associated with an increased risk of AKI and renal replacement therapy (RRT) in the early postoperative period compared to the donation after brain death (DBD). Retrospective data on a cohort (N = 95) of LTx patients (DCD n = 17, DBD n = 78) characterized by no use of ex-vivo lung perfusion were analyzed for the incidence of AKI within 30 postoperative days and incidence of RRT within 7 and 30 days. After optimal full matching, an imbalance remained between the DCD and DBD patients in respect to intraoperative use of cardiopulmonary bypass (CPB). Therefore, a further subset (n = 77) was defined that excluded CPB patients, and matching was repeated (DCD n = 13 vs. DBD n = 63) resulting in a fair balance on a range of preoperative characteristics and intraoperative use of ECMO. In both matched subsets, DCD was associated with around twice higher risk of AKI and RRT within 7 and 30 postoperative days. In conclusion, data suggest that DCD could be associated with worse early renal outcomes in a subset of LTx patients and justify further studies on the topic in order to refine further renal care pathways perioperatively.

Calcineurin Inhibitor-Based Maintenance Immunosuppression in Lung Transplant Recipients: Optimal Serum Levels for Managing Acute Rejection and Renal Function

BACKGROUND

Although effective for curtailing alloimmune responses, calcineurin inhibitors (CNIs) have an adverse-effect profile that includes nephrotoxicity. In lung transplant (LTx) recipients, the optimal serum levels of the CNI tacrolimus necessary to control alloimmune responses and minimize nephrotoxicity are unknown.

METHODS

This retrospective, single-center study reviewed tacrolimus whole blood trough levels (BTLs), grades of acute cellular rejection (ACR), acute rejection scores, and creatinine clearance (CrCl) obtained in LTx recipients within the first year after their transplant procedure. Comparisons were made between the first 90 days post LTx (when tacrolimus BTLs were maintained >10 µg/L) and the remainder of the post-LTX year (when BTLs were <10 µg/L).

RESULTS

Despite tacrolimus mean BTLs being higher during the first 90 days post LTx compared with the remainder of the first post-LTx year (10.4 ± 0.3 µg/L vs 9.5 ± 0.3 µg/L, P < .0001) there was no association with lower grades of ACR (P = .24). The intensity of ACR (as determined by acute rejection scores) did not correlate with tacrolimus mean BTLs at any time during the first posttransplant year (P = .79). During the first 90 days post LTx there was a significant decline in CrCl and a correlation between increasing tacrolimus mean BTLs and declining CrCl (r = -0.26, P = .03); a correlation that was not observed during the remainder of the year (r = -0.09, P = .52).

CONCLUSIONS

In LTx recipients, maintaining BTLs of the CNI tacrolimus >10µg/L did not result in superior control of acute rejection responses but was associated with declining renal function.

Acute kidney injury after lung transplantation: a narrative review

Acute kidney injury (AKI) is a commonly recognized complication after lung transplantation (LT) and is related to increased mortality and morbidity. With the improvement of survival after LT and the increasing number of lung transplant recipients, the detrimental impact of current management on renal function has become increasingly apparent. Multifarious risk factors in the perioperative setting contribute to the development of AKI, including the preoperative status and complications of the recipient, complex perioperative problems especially hemodynamic fluctuation, and exposure to nephrotoxic agents, mainly calcineurin inhibitors (CNIs) and antimicrobial drugs. Identification and minimization of the effects of these risk factors can relieve AKI severity and incidence in high-risk patients. Close monitoring of urine output and serum creatinine (sCr) levels and of specific biomarkers may promote early recognition of AKI and rapid nephrology intervention to improve outcomes. This review summarizes advances in the epidemiology, diagnostic criteria, biological markers of AKI, and further recommends appropriate treatment strategies for the long-term management of AKI related manifestations in lung transplant recipients. Future work will need to focus on developing more accurate measures of renal function and identifying patients before the occurrence of early renal damage. Combining renal protection strategies with the use of new biomarkers to develop early kidney risk identification and protection protocols is a promising idea that requires further investigation.

The Effect of Monthly Anti-CD25+ Treatment with Basiliximab on the Progression of Chronic Renal Dysfunction after Lung Transplantation

BACKGROUND

Chronic renal dysfunction (CRD), as predominantly related to calcineurin-inhibitor (CNI) nephrotoxicity, is associated with increased morbidity and mortality after lung transplantation (LTx). Basiliximab (BSX), a recombinant chimeric monoclonal antibody against CD25⁺ on activated T-lymphocytes, although often employed as an "induction immunosuppression" after solid organ transplantation, may further allow for reduction in CNI exposure with monthly administration and amelioration of CRD.

OBJECTIVE

To determine the effect of monthly anti-CD25⁺ treatment with basiliximab on the progression of chronic renal dysfunction after lung transplantation.

METHODS

Post-LTx recipients with stages IIIB-V CRD were treated with monthly intravenous infusion of BSX 20 mg. They were analyzed for creatinine clearance at 1, 3, 6, and 12 months; rate of the change in the clearance (the slope of the regression line) and FEV₁/month; de novo HLA class I or II DSA; and infectious events (IE). Tacrolimus (TAC) trough levels were concurrently targeted at 2-4 ng/mL during BSX therapy. The criteria for BSX discontinuation included acute lung allograft rejection, acute respiratory infection, and progression to end-stage renal disease (ESRD).

RESULTS

9 LTx recipients were treated with BSX for ≥6 months. The median time past after their LTx was 1853 (range: 75-7212) days; the mean±SD age was 64.3±11.3 years; the male:female ratio was 7:2. The baseline mean±SD creatinine clearance 1-3 months prior to BSX initiation was 22.8±5.14 mL/min/1.73 m² (CI: 3.95) consistent with CRD stages-IIIB (2), IV (6), and V (1). Prior to BSX treatment, all 9 patients had established CLAD-obstructive-phenotype (BOS, n=4) and restrictive-phenotype (RAS, n=5). During the course of BSX treatment, the aggregate creatinine clearance mean slope increased by a mean±SD of 0.747±0.467 mL/min/1.72 m²/month (CI: 0.359), consistent with "stabilization" of renal function in 7 patients; deterioration occurred in 2 with transition to chronic hemodialysis. Spirometric stability in lung allograft function was observed in 5 patients with a mean±SD aggregate FEV₁ slope of -1.49±1.08 mL/month (CI: 2.50). 3 deaths occurred due to the following conditions during BSX treatment-HFpEF/Sepsis + CLAD/Parainfluenza type 2 bronchiolitis + CLAD. 2 recipients developed "weak MFI" HLA class II DSA; no HLA class I DSA was detected during the treatment.

CONCLUSION

Renal sparing therapy with monthly BSX infusion with concurrent reduction in CNI exposure (TAC = 2-4 ng/mL) for stages IIIB-V CRD was associated with stability in creatinine clearance in 78% of patients over a treatment course of 6-12 months. Pre-existing CLAD afflicting all patients and inherent variability in progression of chronic rejection, limits our assessment of BSX efficacy in this context. We detected an infrequent de novo HLA class II DSA during BSX therapy.

Acute Kidney Injury after Lung Transplantation: A Systematic Review and Meta-Analysis

Background: Lung transplantation has been increasingly performed worldwide and is considered an effective therapy for patients with various causes of end-stage lung diseases. We performed a systematic review to assess the incidence and impact of acute kidney injury (AKI) and severe AKI requiring renal replacement therapy (RRT) in patients after lung transplantation. Methods: A literature search was conducted utilizing Ovid MEDLINE, EMBASE, and Cochrane Database from inception through June 2019. We included studies that evaluated the incidence of AKI, severe AKI requiring RRT, and mortality risk of AKI among patients after lung transplantation. Pooled incidence and odds ratios (ORs) with 95% confidence interval (CI) were obtained using random-effects meta-analysis. The protocol for this meta-analysis is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42019134095). Results: A total of 26 cohort studies with a total of 40,592 patients after lung transplantation were enrolled. Overall, the pooled estimated incidence rates of AKI (by standard AKI definitions) and severe AKI requiring RRT following lung transplantation were 52.5% (95% CI: 45.8–59.1%) and 9.3% (95% CI: 7.6–11.4%). Meta-regression analysis demonstrated that the year of study did not significantly affect the incidence of AKI (p = 0.22) and severe AKI requiring RRT (p = 0.68). The pooled ORs of in-hospital mortality in patients after lung transplantation with AKI and severe AKI requiring RRT were 2.75 (95% CI, 1.18–6.41) and 10.89 (95% CI, 5.03–23.58). At five years, the pooled ORs of mortality among patients after lung transplantation with AKI and severe AKI requiring RRT were 1.47 (95% CI, 1.11–1.94) and 4.79 (95% CI, 3.58–6.40), respectively. Conclusion: The overall estimated incidence rates of AKI and severe AKI requiring RRT in patients after lung transplantation are 52.5% and 9.3%, respectively. Despite advances in therapy, the incidence of AKI in patients after lung transplantation does not seem to have decreased. In addition, AKI after lung transplantation is significantly associated with reduced short-term and long-term survival.