Paradigm Shift of Interventional Strategies and Outcomes for Acute Limb Ischemia Post-Pandemic

PURPOSE

We performed a large-scale comparison of patients treated for acute limb ischemia (ALI) in the pre-COVID (2017-2019) and COVID (2020-2022) eras to evaluate changes in interventional strategies and compare factors associated with adverse outcomes. We sought to characterize patient outcomes in an evolving ALI treatment algorithm in response to pandemic-associated presentation delays and rapid technological advancements in mechanical thrombectomy (MT).

METHODS

Using the TriNetX global research network, we conducted a multicenter query across 80 health care organizations (HCOs) spanning 4 countries for patients treated for ALI. Propensity score matching was performed to account for comorbidities. Risk of adverse outcomes within 30 days was calculated for each era, including re-intervention (RI30), major/minor amputation, and death. Patients were then stratified by initial intervention: open revascularization (OR), MT, or catheter-directed thrombolysis and adjunctive endovascular procedures alone (CDT/EP). Risk of adverse outcomes was compared between treatment groups of the same era.

RESULTS

After propensity score matching, the pre-COVID era and COVID era cohorts included 7344 patients each. COVID era patients experienced a statistically significant higher risk of 30-day mortality (RR=1.211, p=0.027). Mechanical thrombectomy interventions were performed more frequently in the COVID era (RR=1.314, p<0.0001). Comparing outcomes between treatment groups, MT patients required RI30 more than OR patients (pre-COVID: RR=2.074, p=0.006; COVID: RR=1.600, p=0.025). Open revascularization patients had higher 30-day mortality (pre-COVID: RR=2.368, p<0.0001; COVID: RR=2.013, p<0.0001) and major amputations (pre-COVID: RR=2.432, p<0.0001; COVID: RR=2.176, p<0.0001) than CDT/EP. Pre-COVID CDT/EP patients were at higher risk for RI30 (RR=1.449, p=0.005) and minor amputations (RR=1.500, p=0.010) than OR. The MT group had higher major amputation rates than CDT/EP (pre-COVID: RR=2.043, p=0.019; COVID: RR=1.914, p=0.007). COVID-era MT patients had greater 30-day mortality (RR=1.706, p=0.031) and RI30 (RR=1.544, p=0.029) than CDT/EP.

CONCLUSION

Significant shifts toward an MT-based approach have been observed in the last 3 years. Although MT required more RI30 than OR, there was no associated consequence of mortality and limb salvage. The increased mortality seen among COVID-era patients could be explained by delayed presentation, as well as poorly understood pro-thrombogenic or pro-inflammatory mechanisms related to the first waves of COVID. More research is necessary to determine an optimal treatment algorithm.

CLINICAL IMPACT

Comorbid risk factors and severity of ischemia must be carefully considered before selecting an interventional strategy to prevent adverse outcomes and maximize limb salvage. Open revascularization strategies are associated with increased mortality and limb loss compared to less-invasive thrombolytic therapy alone. Mechanical thrombectomy (MT)-based approaches have been increasingly used in the last 3 years. Patients receiving MT are more likely to require reintervention within 30 days.

Giant 20 × 35 cm brachial artery pseudoaneurysm after fistulogram treated with surgical resection of pseudoaneurysm and patch angioplasty of brachial artery

Brachial artery pseudoaneurysms are a rare entity, which can occur secondary to infectious, traumatic, or iatrogenic causes. We present a 78-year-old female with end-stage renal disease on hemodialysis via a right brachio-basilic arteriovenous fistula. She had previously undergone numerous fistulograms and endovascular interventions for right upper extremity swelling due to prolonged bleeding following dialysis. After a recent fistulogram she developed recurrent arm swelling. Duplex showed a large hematoma without any evidence of vascular flow. However, intraoperatively, she was noted to have a giant 20 × 35 cm pseudoaneurysm of the brachial artery. Therapeutic options include endovascular stenting, embolization, thrombin injection, ultrasound-guided compression, and surgery. We elected to perform resection of the large pseudoaneurysm and arteriovenous fistula ligation due to the large size. Given her end-stage renal disease status and lacking quality autogenous vein, we were able to perform a patch angioplasty repair of her brachial artery without requiring a bypass.

Endovascular Coil Embolization of an Enlarging Gastroduodenal Artery Aneurysm

Gastroduodenal artery aneurysms are a rare type of visceral aneurysm that can lead to rupture and death. We present a 75-year-old male with history of hypertension, diabetes, and hyperlipidemia with an incidental finding of a 3.2 × 3.7 cm gastroduodenal aneurysm found on abdominal computed tomography angiography (CTA). After refusing surgical intervention, he was seen two years later and presented with an enlarged gastroduodenal aneurysm, now 5.0 × 5.1 cm, visible on a repeat abdominal CTA. Upon his continued refusal for an open surgery, we elected for endovascular repair of this GDA aneurysm via coil embolization.

Sex-Related Disparities in Acute Limb Ischemia Treatment Outcomes

BACKGROUND

Although a substantial impetus behind disparities research in healthcare exists, those that are sex-related within vascular surgery outcomes are largely unexplored. Consequently, published guidelines lack specificity when it comes to treating male and female patients with vascular disease. Disparities related to patients suffering from chronic limb-threatening ischemia have been broached, although no extensive studies assessing disparities in acute limb ischemia treatment outcomes have come to the forefront. In this study, our aim is to identify and quantify sex-related disparities as they pertain to interventions for acute limb ischemia.

METHODS

Using the TriNetX global research network, we conducted a multicenter query across 48 healthcare organizations spanning 5 countries for patients treated for acute limb ischemia. We determined the number of male and female patients that received one of the following interventions: open revascularization, percutaneous mechanical thrombectomy, or catheter-directed thrombolysis and/or adjunctive endovascular procedures. Propensity score matching was performed to account for comorbidities. Risk of adverse outcomes within 30 days was calculated for each sex, including reintervention, major amputation, and death. Risk of adverse outcomes was then compared between treatment groups of the same sex and between sexes. Type-I errors were reduced through utilization of the Holm-Bonferroni method to correct P values.

RESULTS

Within our study, we noted several important findings. Females were more likely to receive catheter-directed thrombolysis and/or adjunctive endovascular procedures (P = 0.001) than males. There were no significant differences in the rates of open revascularization or percutaneous mechanical thrombectomy between males and females. Overall, females were more likely to die within 30 days (P < 0.0001) and greater number of males required reintervention within 30 days (P < 0.0001). Analyzing outcomes within individual treatment groups, females undergoing open revascularization or catheter-directed thrombolysis and/or adjunctive endovascular intervention demonstrated a profound increase in mortality within 30 days of intervention (P = 0.0072 and P = 0.0206, respectively), but these differences were not reflected in the percutaneous mechanical thrombectomy group. Limb salvage rates in females were higher than males overall although there were no significant sex differences within any treatment groups specifically.

CONCLUSIONS

In conclusion, there was a significantly higher risk of death in females across all treatment groups in the studied timeframe. Limb salvage rates were higher for females in the open revascularization (OR) treatment group, while males were more likely to require a reintervention across all treatment groups. By evaluating these disparities, we can provide greater insight into personalized treatment for patients presenting with acute limb ischemia.

MYOSIN LIGHT CHAIN KINASE DELETION WORSENS LUNG PERMEABILITY AND INCREASES MORTALITY IN PNEUMONIA-INDUCED SEPSIS

ABSTRACT

Increased epithelial permeability in sepsis is mediated via disruptions in tight junctions, which are closely associated with the perijunctional actin-myosin ring. Genetic deletion of myosin light chain kinase (MLCK) reverses sepsis-induced intestinal hyperpermeability and improves survival in a murine model of intra-abdominal sepsis. In an attempt to determine the generalizability of these findings, this study measured the impact of MLCK deletion on survival and potential associated mechanisms following pneumonia-induced sepsis. MLCK -/- and wild-type mice underwent intratracheal injection of Pseudomonas aeruginosa . Unexpectedly, survival was significantly worse in MLCK -/- mice than wild-type mice. This was associated with increased permeability to Evans blue dye in bronchoalveolar lavage fluid but not in tissue homogenate, suggesting increased alveolar epithelial leak. In addition, bacterial burden was increased in bronchoalveolar lavage fluid. Cytokine array using whole-lung homogenate demonstrated increases in multiple proinflammatory and anti-inflammatory cytokines in knockout mice. These local pulmonary changes were associated with systemic inflammation with increased serum levels of IL-6 and IL-10 and a marked increase in bacteremia in MLCK -/- mice. Increased numbers of both bulk and memory CD4 + T cells were identified in the spleens of knockout mice, with increased early and late activation. These results demonstrate that genetic deletion of MLCK unexpectedly increases mortality in pulmonary sepsis, associated with worsened alveolar epithelial leak and both local and systemic inflammation. This suggests that caution is required in targeting MLCK for therapeutic gain in sepsis.

The RIPK3 Scaffold Regulates Lung Inflammation During Pseudomonas Aeruginosa Pneumonia

RIPK3 (receptor-interacting protein kinase 3) activity triggers cell death via necroptosis, whereas scaffold function supports protein binding and cytokine production. To determine if RIPK3 kinase or scaffold domains mediate pathology during Pseudomonas aeruginosa infection, control mice and those with deletion or mutation of RIPK3 and associated signaling partners were subjected to Pseudomonas pneumonia and followed for survival or killed for biologic assays. Murine immune cells were studied in vitro for Pseudomonas-induced cytokine production and cell death, and RIPK3 binding interactions were blocked with the viral inhibitor M45. Human tissue effects were assayed by infecting airway epithelial cells with Pseudomonas and measuring cytokine production after siRNA inhibition of RIPK3. Deletion of RIPK3 reduced inflammation and decreased animal mortality after Pseudomonas pneumonia. RIPK3 kinase inactivation did neither. In cell culture, RIPK3 was dispensable for cell killing by Pseudomonas and instead drove cytokine production that required the RIPK3 scaffold domain but not kinase activity. Blocking the RIP homotypic interaction motif (RHIM) with M45 reduced the inflammatory response to infection in vitro. Similarly, siRNA knockdown of RIPK3 decreased infection-triggered inflammation in human airway epithelial cells. Thus, the RIPK3 scaffold drives deleterious pulmonary inflammation and mortality in a relevant clinical model of Pseudomonas pneumonia. This process is distinct from kinase-mediated necroptosis, requiring only the RIPK3 RHIM. Inhibition of RHIM signaling is a potential strategy to reduce lung inflammation during infection.

TIGIT modulates sepsis-induced immune dysregulation in mice with preexisting malignancy

TIGIT is a recently identified coinhibitory receptor that is upregulated in the setting of cancer and functionally contributes to the impairment of antitumor immunity. However, its role during sepsis is unknown. Because patients with cancer are 10 times more likely to die of sepsis than previously healthy (PH) patients with sepsis, we interrogated the role of TIGIT during sepsis in the context of preexistent malignancy. PH mice or cancer (CA) mice inoculated with lung carcinoma cells were made septic by cecal ligation and puncture (CLP). We found that sepsis induced TIGIT upregulation predominantly on Tregs and NK cells in both PH and CA mice. Anti-TIGIT Ab improved the 7-d survival of CA septic mice but not PH mice after CLP. Treatment of CA septic animals but not PH septic animals with anti-TIGIT mAb significantly reversed sepsis-induced loss of CD4+ T cells, CD8+ T cells, Foxp3+ Treg, and CD19+ B cells in the spleen, which was the result of decreased caspase-3+ apoptotic cells. In sum, we found that anti-TIGIT Ab reversed sepsis-induced T cell apoptosis in CA septic mice and led to a significant survival benefit, suggesting its use as a potential immunotherapy to improve outcomes in septic patients with cancer.

The IL-27 receptor regulates TIGIT on memory CD4+ T cells during sepsis

Sepsis is a leading cause of morbidity and mortality associated with significant impairment in memory T cells. These changes include the upregulation of co-inhibitory markers, a decrease in functionality, and an increase in apoptosis. Due to recent studies describing IL-27 regulation of TIGIT and PD-1, we assessed whether IL-27 impacts these co-inhibitory molecules in sepsis. Based on these data, we hypothesized that IL-27 was responsible for T cell dysfunction during sepsis. Using the cecal ligation and puncture (CLP) sepsis model, we found that IL-27Rα was associated with the upregulation of TIGIT on memory CD4⁺ T cells following CLP. However, IL-27 was not associated with sepsis mortality.

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Numbers of IL-27Rα⁺ memory T cells are decreased following cecal ligation and puncture

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TIGIT is expressed on more IL-27Rα⁺ versus IL-27Rα⁻ memory CD4⁺ T cells during sepsis

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Il27ra^−/− and WT T cells exhibit similar effector function and apoptosis during sepsis

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IL-27 signaling does not impact sepsis mortality

Early- and Late-Onset Bloodstream Infections in the Intensive Care Unit: A Retrospective 5-Year Study of Patients at a University Hospital in China

BACKGROUND

Limited data are available regarding the current microbiological characteristics of bloodstream infections (BSIs) in intensive care units (ICUs) in China. This retrospective study aimed to determine the epidemiology of early- and late-onset BSIs in our ICU.

METHODS

We retrospectively collected data about ICU patients with BSI from 2013 to 2017. The patients were divided into the early- and late-onset BSI groups according to if BSI occurred within or beyond 48 hours after ICU admission. Univariate and multivariate logistic regression analyses were used to assess the risk factors for infection with multidrug resistant organisms (MDROs).

RESULTS

Of 5474 ICU admissions, 486 (8.9%) patients with BSIs and with 500 microorganisms were included in this study, 246 (50.6%) of whom had early-onset BSIs. Two hundred and seventy patients were infected with MDROs. The proportion of MDRO infections was significantly higher among patients with late-onset BSIs than among those with early-onset BSIs (57.9% vs. 41.5%, P = .017). The ICU mortality rate was significantly higher in the late-onset BSI group (44.6% vs. 33.8%, P = .014) and early and appropriate antimicrobial treatment significantly improved the survival rate among patients with BSI (P < .001).

CONCLUSIONS

MDROs affected more than half of patients with BSI in the ICU. Early appropriate empirical antimicrobial therapy could improve clinical outcome of patients with BSIs.

Preexisting malignancy abrogates the beneficial effects of CXCR4 blockade during sepsis

Patients with cancer are at an increased risk of developing and dying from sepsis. We previously reported that blockade of the chemokine receptor CXCR4 resulted in decreased CD4⁺ T cell exhaustion and improved survival in a model of polymicrobial sepsis in previously healthy mice. Here, we sought to determine whether CXCR4 blockade could improve mortality and immune dysregulation during sepsis complicated with malignancy. Results in animals inoculated with a lung cancer cell line and subjected to CLP 3 weeks later indicated that CXCR4 was up-regulated on naïve and central memory T cells following sepsis. Of note, and in contrast to results in previously healthy mice, CXCR4 blockade failed to improve survival in cancer septic animals; instead, it actually significantly worsened survival. In the setting of cancer, CXCR4 blockade failed to result in T cell egress from the bone marrow, reverse lymphopenia in the spleen, or reverse T cell exhaustion. Mechanistically, elevated expression of CD69 on naïve T cells in the bone marrow of cancer septic animals was associated with their inability to egress from the bone marrow in the setting of CXCR4 blockade. In conclusion, these results illuminate the differential impact of CXCR4 blockade on sepsis pathophysiology in the setting of cancer and highlight the need for personalized therapy during sepsis.

Critical illness and the role of the microbiome

The number of microbes living within the intestinal lumen is similar to the number of all cells of human origin in the host. Although historically little attention has been paid to the massive microbial community residing inside each of us, the last few years have witnessed an explosion of information related to the role of the microbiome in the maintenance of health and in the pathogenesis of disease. Here, we review data suggesting that the microbiome is converted into a pathobiome in critical illness and potential strategies for targeting the microbiome for therapeutic gain in the intensive care unit.

Increased mortality in CD43-deficient mice during sepsis

CD43 is a large transmembrane protein involved in T cell activation. Previous studies of CD43^-/- mice in viral models have demonstrated a role for CD43 in Th1/Th2 skewing, activation of Foxp3+ Treg, and T cell apoptosis. However, the role of CD43 during sepsis has never been tested. Thus, we interrogated the role of CD43 during sepsis using a murine cecal ligation and puncture (CLP) model, and found that CD43^-/- mice demonstrated significantly worsened mortality compared to B6 mice following CLP. Phenotypic analysis of splenocytes isolated 24 h after septic insult revealed significantly increased apoptosis of central memory cells in both CD4⁺ and CD8⁺ T cell compartments in CD43^-/- septic mice compared to WT septic mice. Furthermore, CD43^-/-septic mice exhibited a prominent Th2 skewing following sepsis relative to WT septic mice, as evidenced by a significant decrease in the frequency of IL-2⁺ CXCR3⁺ T_H1 cells as a significant increase in the frequency of IL-4⁺ CCR4⁺ T_H2 cells. Finally, septic CD43^-/- animals contained significantly fewer CD25⁺ Foxp3⁺ T_Reg cells as compared to WT septic animals. Importantly, depleting CD25⁺ Treg eliminated the increased mortality observed in CD43^-/- mice. Taken together, these data demonstrate an important role of CD43 in modulating immune dysregulation and mortality following sepsis.