Citations

Abstract Rationale Premature infants exposed to supplemental oxygen are at increased risk of developing airway diseases such as bronchopulmonary dysplasia (BPD) and asthma, making it important to understand how oxygen detrimentally impacts developing airways. Even in moderation, hyperoxia promotes bronchial airway hyperresponsiveness (AHR) through effects on fetal airway smooth muscle (fASM), a cell type involved in impaired bronchodilation and remodeling. Iron dysregulation has been implicated in adult airway diseases such as asthma, COPD, and hyperoxic lung injury (HLI). Immature antioxidant systems in neonates and their increased susceptibility to iron-induced oxidative stress may lead to ferroptosis, contributing to pathologies observed in subsequent airway disease. The role of impaired iron metabolism, mediated by hyperoxia, remains largely unexplored in fetal airways. This study investigated the effects of increasing oxygen levels on antioxidant systems, iron metabolism, and lipid peroxidation in human fASM. Methods fASM from 18-20 week gestational age (canalicular stage; Mayo IRB exempt) were isolated and exposed to normoxia (21% O2) or increasing levels of hyperoxia (50%, 70%, and 90% O2) and treated with iron chelator, deferoxamine (DFO) [100uM] or reactive oxygen species (ROS) scavenger ferrostatin (Fer-1) [10uM] for 48h. Levels of intracellular iron (Fe2+) were determined using ferroOrange. Cell lysates were examined for protein expression of antioxidant markers (GPX4, SLC7A11, CBS, NRF2, KEAP1, and FSP1) and iron metabolism markers (TfR1, FTH1, and NCOA4). 4-HNE (lipid radical) expression was determined by immunofluorescence staining. Results Hyperoxia decreased SLC7A11, CBS, NRF2, KEAP1 (redox regulators), and iron storage (FTH1) at all concentrations. Iron influx (TfR1) increased under 50% and 70% O2 but not 90% O2. Cytosolic iron levels increased under hyperoxia in a dose-dependent manner and decreased with iron chelator, DFO. DFO further decreased FTH1 expression under 90% O2. 4-HNE (lipid radical) increased under 90% O2 and was reduced by ROS scavenger, Fer-1. Conclusion Our findings suggest that hyperoxia simultaneously impairs antioxidant systems and iron metabolism in fASM. Specifically, hyperoxia dose-dependently increases the labile iron pool which exhausts anti-ferroptotic mechanisms: effects which can be reduced by DFO and Fer-1. This implies the presence of a redox threshold tightly regulating iron accumulation in fASM. Overall, antioxidant impairment and iron metabolism dysfunction synergistically can contribute to pediatric airway disease: mechanisms which allow for the development of targetable strategies to blunt the impact of supplemental oxygen in the premature lung. This abstract is funded by: National Institutes of Health

Abstract Rationale Asthma in the elderly (AIE) is characterized by hyperreactive and thickened, fibrotic airways (remodeling) that are not adequately addressed by current therapies. Thus, understanding mechanisms that drive AIE becomes important. Here, airway smooth muscle (ASM) cells play important roles in normal airway physiology and asthma pathophysiology. Recent discoveries have highlighted the significance of mechanosensitive Piezo (Pz)-Piezo1 and Piezo2 in the lung. While Pz channels are highly expressed, their specific contributions to ASM function remains largely unexplored. Moreover, Pz channels play essential roles in regulating the intracellular calcium homeostasis, which further drives mitochondrial dynamics. Whether Pz signaling influences mitochondrial structure and function-a key determinant of ASM energetics and contractility is unknown and therefore of significant interest. In the present study, we hypothesize that Pz1 channel activation regulates mitochondrial structure and function via an increase in intracellular calcium in ASM, leading to metabolic changes and remodeling, characteristic of AIE. Methods Primary human ASM cells were isolated from lungs of young (<45y) and AIE (≥65y) individuals obtained post-surgery (Mayo Clinic IRB approved). Cells were exposed to mechanical stretch (mimicking breathing) in the presence of either Yoda1/Jedi2 (agonist) or GsMTx4 (inhibitor) for 24 hrs. Mitochondrial fractionation was performed, and protein expression evaluated for mitochondrial dynamics targets (MFN1, MFN2, OPA1, DRP1 and FIS1) and transcriptional markers (mt-Cox1, mt-Cox2, ATP5b and TFAM). The colocalization of mitochondria and Pz channels was observed by immunofluorescence staining. Mitochondrial morphology was examined with MitoTracker staining while function was assessed using Seahorse XF analysis. Intracellular calcium ([Ca2+]i) and mitochondrial calcium ([Ca2+]m) were measured using 5µM Fura-2/AM and 1µM Rhod-2 AM respectively with fluorescence microscopy. Results Confocal microscopy revealed that Piezo1 localizes to mitochondria in ASM. Pz1 activation promoted mitochondrial fission, evidenced by an upregulation of DRP1/FIS1 and downregulation of MFN1/OPA1, confirming a fission-dominant phenotype. Pz1 activation also increased mitochondrial branching while reducing branch length, indicating enhanced fragmentation, particularly in AIE ASM. Yoda1 treatment reduced mitochondrial oxygen consumption rates, suggesting a lower energy demand. Furthermore, Yoda1 increased both [Ca2+]i and [Ca2+]m responses to histamine (10µM), with a more pronounced effect in AIE ASM. Conclusion Overall, our findings suggest that mechanotransduction through Pz channels, particularly Pz1 regulates intracellular calcium regulation and mitochondrial structure and function in ASM, linking extracellular mechanical forces to intracellular energy homeostasis. This mechanism may contribute to the altered energetics and remodeling observed in AIE airway pathophysiology. This abstract is funded by: 24POST1241979 (NAB), R01- HL056470 (YSP), R01-HL177837 (CMP)

Abstract Rationale Extracorporeal membrane oxygenation (ECMO) is an increasingly utilized form of life support for patients with cardiac and/or respiratory failure. Fungal infections remain a serious challenge in patients supported by ECMO, with an estimated prevalence of up to 10% and high morbidity and mortality. While routine antifungal prophylaxis is uncommon in ECMO centers and widely debated, its impact on incidence, pathogenic organisms, resistance patterns, and outcomes has not been described. Methods This was a ten-year experience study of fungemia in patients receiving ECMO where most patients received antifungal prophylaxis. Institutional protocol was to prescribe prophylactic fluconazole based on risk stratification, substituted with echinocandins if indicated. Adults (18 years and older) with ECMO runs between 2014-2024 were screened for fungal organism growth on culture, then narrowed to those with positive blood cultures drawn in the window from 24 hours after cannulation through 72 hours after decannulation. Clinical, microbiological, and outcomes data were descriptively summarized. Institutional review board approved with a waiver of informed consent. Results Among 1,039 adult ECMO runs (979 patients), thirteen patients with fungemia were identified for a calculated incidence rate of 1.29 per 1000 ECMO days (95% CI 0.75 to 2.23). Twelve patients (92%) received antifungal prophylaxis; 85% had echinocandin and 38% azole exposure, with some overlap. Median duration of antifungal exposure was 14 days prior to positive culture. Seven patients (54%) had an open sternum at the time of ECMO cannulation, while 11 (85%) had femoral ECMO access. Four patients (31%) had Candida species isolated from other sources prior to fungemia (mediastinum and respiratory system). Candida parapsilosis (31%), C. albicans (23%), and C. guilliermondii (15%) were the most common isolates. The most likely sources were vascular access catheters (38%) and mediastinum (31%). Seven patients (54%) had suspected or confirmed seeding of ECMO hardware after positive blood cultures, though only two circuit exchanges were performed. Four patients (31%) showed evidence of non-susceptibility to their prophylactic antifungal class (Table 1), with a median 35-day exposure prior to positivity among those patients. Only 62% of patients demonstrated blood culture clearance (median 3 [IQR 2.5-7.75] days). Nearly all patients (92%) died within the hospital stay, including all patients with resistant organisms. Conclusions In an ECMO center with routine antifungal prophylaxis practices, the rate of fungemia identified during ECMO support was low. When fungemia developed, there was a high proportion of drug resistance and mortality. This abstract is funded by: None

Abstract Rationale Longer duration and severity of acute brain dysfunction (ABD), including delirium and coma, have been associated with worse clinical outcomes in critically ill adults. Examining ABD trajectories over time may offer deeper insights into understanding its heterogeneity. This study aimed to characterize ABD trajectories and examine its relationship with clinical characteristics and 30-day mortality. Methods We analyzed data from the multicenter BRAIN-ICU and MIND-ICU prospective cohort study, which included adults with acute respiratory failure and/or shock. Delirium presence and severity were determined twice daily for 7 days using the CAM-ICU-7. A score of 0 indicates no delirium, 1-2 indicates subsyndromal delirium, 3-5 indicates mild-to-moderate delirium, and 6-7 indicates severe delirium. Patients with a RASS of -4 or -5, indicating coma, were assigned a CAM-ICU-7 score of 7. We applied group-based trajectory modeling of CAM-ICU-7 to identify ABD severity trajectory patterns and compared demographics, clinical characteristics, and 30-day mortality among trajectory groups. Results The 1035 patients analyzed had a median age of 62 [IQR, 53-72] years, 61% were male, and 91% were White. Overall, patients had a median Charlson Comorbidity Index of 2 (1-4) and SOFA score at enrollment of 6 (4-9). 731 patients (70.6%) had delirium at some point during the study. Five ABD severity trajectories were identified as the optimal model fit based on global fit indices and clinical interpretability: T1 was associated with mild and persistent ABD, while T2-T5 were characterized by severe ABD early during critical illness with different resolution patterns (Figure). Trajectory membership varied by patient clinical characteristics. T1 had lighter levels of sedation (median RASS score: -2) in the 24 hours surrounding ICU admission than T2-T5 (median RASS scores: -3, -3, -4, and -3, respectively) (p<.001). At enrollment, T1 and T2 had lower modified SOFA scores (median scores: 6) compared to T5 (median score: 7) (p<.001). Trajectory membership independently predicted 30-day mortality, with T5 having the highest 30-day mortality and T2, which had the fastest resolution of ABD, the lowest (p<.001). Conclusions We identified five trajectories of ABD severity over the first week of a patient’s ICU stay. These trajectories were differentially associated with mortality and clinical characteristics, suggesting trajectory-based approaches may enable more nuanced risk stratification and support the tailoring of interventions and clinical trial designs to specific ABD trajectory patterns. Future work should validate these trajectories in independent cohorts, explore whether they modify treatment effects, and determine if they represent distinct mechanistic pathways. This abstract is funded by: NIH/NIA

Abstract Rationale Propofol-based sedation in the intensive care unit (ICU) is associated with clinically significant hemodynamic instability, including hypotension. Previous studies have identified hypotension as a key predictor of adverse outcomes in critically ill patients. However, no validated tools currently exist to systematically predict this risk. Therefore, this study aimed to develop and externally validate machine-learning (ML) models for predicting the risk of hypotension in ICU patients receiving propofol sedation. Methods We developed ML models using retrospective data from adult, mechanically ventilated ICU patients who received propofol infusion for at least 24 hours across four Mayo Clinic sites between 2018 and 2024. The primary outcome was hypotension, defined as ≥ 2 consecutive MAP readings ≤60 mmHg within 15 minutes during the first 6 hours of propofol sedation. The MIMIC-IV dataset was used for external validation. Features were selected using a union of Boruta and LASSO-penalised logistic regression. Four algorithms (elastic net-penalised logistic regression, random forest, LightGBM, and multilayer perceptron) were tuned using Bayesian optimization to minimize cross-entropy loss during leave-one-site-out cross-validation (LOSO-CV). The algorithm with the lowest cross-entropy loss during LOSO-CV was chosen as the best-performing algorithm. Classification thresholds were selected to target sensitivity ≥80%. Model performance was evaluated using area under the receiver operating characteristic curve (AUC-ROC), calibration slope and intercept, sensitivity, and specificity. Feature importance was evaluated using SHapley Additive exPlanations (SHAP). Results The development cohort included 16,361 patients from Mayo Clinic, of whom 3,482 (21.3%) developed hypotension. The external validation cohort comprised 4,684 patients from MIMIC-IV, with 115 (2.5%) experiencing hypotension. Patient characteristics included age, admission Sequential Organ Failure Assessment (SOFA) scores, starting propofol dose, ICU admission source, and comorbidities. The best-performing algorithm was LightGBM. The average AUC-ROC during LOSO-CV was 0.70 (95% confidence interval [CI] 0.68-0.71), versus 0.64 during external validation. The average calibration slope and intercept during LOSO-CV was 1.08 (95% CI 0.89-1.27) and 0.08 (95% CI -0.25-0.41), respectively, versus 0.78 and -2.07 during external validation. The average sensitivity and specificity during LOSO-CV was 0.81 (95% CI 0.79-0.83) and 0.47 (95% CI 0.42-0.52), respectively, versus 0.54 and 0.65 during external validation. Conclusions We developed and externally validated an ML-based classifier that demonstrates moderate discrimination for predicting propofol-induced hypotension in mechanically ventilated ICU patients. This tool may facilitate early identification of high-risk patients and enable proactive hemodynamic management strategies. Further prospective validation and assessment of clinical impact are warranted. This abstract is funded by: None

Abstract Background Ventilated patients in the intensive care unit are often complex and require multiple care team members including bedside nurses, respiratory therapists, advanced practice providers, and physicians. A Quality Improvement initiative was created to address any barriers in communication. Spontaneous breathing trials (SBT) are often used as a surrogate for multidisciplinary communication. Both Respiratory therapist (RT) and provider led spontaneous breathing trial protocols are often performed but not necessarily documented or communicated appropriately. Our primary aim was to increase spontaneous breathing trial documentation from a baseline of 12% to 80% with a counterbalance of not increasing the 24-hour reintubation rate. Methods Using the DMAIC framework, we defined the gap in quality by getting baseline patient data for 3 months including SBT completion rate, SBT documentation rate, time to first SBT, total time on ventilator, 24-hour reintubation rate, and total ICU days. All care team members including providers, RTs, and nurses completed a 10-questions Likert 5-scale survey regarding their views of multidisciplinary communication and SBT completion. We identified the lack of documentation of SBTs and implemented a standardized respiratory therapy shift summary note which included SBT details and major ventilator changes. We then collected the same data over 3 months after implementation. Results Post intervention analysis revealed documentation of daily spontaneous breathing trials improved from 12% to 79%. Pre and post intervention means for patient focused outcomes were statistically unchanged for time to first SBT 26 hours vs 32 hours (p = 0.16), Total ventilator time 5.6 vs 5.4 (p = 0.83), total ICU days 1.9 days vs 2.7 days (p = 0.11), and reintubation rate 14% vs 15%.Survey results showed that there was a statistically significant improvement in overall satisfaction regarding multidisciplinary communication, satisfaction regarding ventilator management discussion on rounds, and if documentation amount was appropriate. Also, there was a significant improvement in the percentage of care team members that were aware of daily SBTs occurring. Conclusion The implementation of RT shift summary greatly improved staff member satisfaction, multidisciplinary discussion during rounds, and awareness of SBT occurrence among providers, RTs, and nurses. While patient centered outcomes were statistically unchanged over this very brief period of observation, having better staff satisfaction and communication may eventually lead to improved outcomes over time and can lead to further analysis to avoid mishaps that can arise from miscommunication. This abstract is funded by: None

Abstract Rationale Hypophosphatemia affects about one-third of intensive care unit (ICU) patients and is linked to longer hospital stays, illness severity and poor outcomes, yet guidelines for monitoring and correction remain unclear. Studies show a strong association between hypophosphatemia and both prolonged invasive mechanical ventilation (IMV) and weaning failure in patients with respiratory failure, due to reduced adenosine triphosphate generation and weakened respiratory muscle performance. Although phosphate abnormalities correlate with higher mortality in sepsis and septic shock, their impact on IMV duration in this population remains unclear. Therefore, we aimed to evaluate the independent association between hypophosphatemia during ICU stay and the duration of IMV in patients with septic shock. Methods We studied adult patients with septic shock admitted to the medical ICU at Mayo Clinic, Rochester, between March 1, 2006, and April 17, 2018. A retrospective analysis was conducted to examine the association between hypophosphatemia—defined as any serum phosphate level < 2.5 mg/dL during the ICU stay—and the duration of IMV in hours. The following linear regression models were used: 1, unadjusted; 2, adjusted for baseline demographics (age, sex, weight); 3, adjusted for baseline respiratory comorbidities and Charlson Comorbidity Index (CCI); and 4, adjusted for illness severity (using APACHE III and SOFA scores) and oxygenation (minimum PaO2/FiO2 score during ICU stay). For each model, the β-coefficient was reported, which represents additional hours of IMV associated with hypophosphatemia, along with 95% confidence intervals and p-values. Results The study included 1082 patients, among them 653 (60.4%) required IMV. 53.6% (n = 350) developed hypophosphatemia during their ICU stay. The mean duration of IMV was significantly longer in patients with hypophosphatemia compared with those without (184 ± 218 h vs 100 ± 126 h; p < 0.001; 95% CI 56-112). This association persisted across all multivariable linear regression models. After adjustment for baseline demographics, hypophosphatemia remained significantly associated with longer IMV duration (β = 79.8 h; 95% CI 51.8-107.8; p < 0.001). Further adjustment for respiratory comorbidities and CCI yielded similar results (β = 81.8 h; 95% CI 54.2-109.4; p < 0.001). After controlling for illness severity and oxygenation status, hypophosphatemia remained independently associated with prolonged IMV duration (β = 69.2 h; 95% CI 39.9-98.4; p < 0.001). Conclusion Hypophosphatemia was independently associated with longer duration of IMV in patients with septic shock, which prolongs ICU level care and delays rehabilitation. This highlights the need for updates on guidelines for maintaining optimal serum phosphate levels in patients who are mechanically ventilated. This abstract is funded by: None

Abstract Introduction Sedation is routinely administered to facilitate comfort and tolerance of life support for critically ill adults dependent on invasive mechanical ventilation. Isoflurane, a widely used anesthetic during surgery, has properties that may also benefit ICU patients requiring continuous sedation. However, efficacy as a sedative and safety in this population is not well established. Methods We conducted two identically designed multicenter randomized trials, INSPIRE ICU1 and INSPIRE ICU2, at hospitals across the US. Ventilator-dependent adults were randomly assigned in a 1.5:1 ratio to receive either inhaled isoflurane or intravenous propofol as the first-line sedative for up to 48 ± 6 hours, targeting a sedation depth between Richmond agitation-sedation scale (RASS) -1 (drowsy) to -4 (responsive only to physical stimuli). Isoflurane was administered via an anesthetic conserving device (Sedaconda ACD-S). In both arms, opioids were permitted at the lowest dose required to achieve freedom from pain. The primary outcome was the percentage of time at target sedation level, assessed as a noninferiority outcome with pre-specified margin of 15%. Secondary outcomes included opioid exposure, wake-up time after end of treatment, time to extubation, and proportion of time with spontaneous breathing effort. Results A total of 470 combined participants were included in the two trials. In each trial, 142 patients were randomly assigned to isoflurane and 93 to propofol. In INSPIRE ICU1, percentage of time within target sedation depth was 77.1 [53.2, 89.9] % with isoflurane and 80.9 [58.2, 96.4] % with propofol (difference -1.5 [-8.9, >99] %; p < 0.01 for noninferiority). In INSPIRE ICU2, percentage of time within target sedation depth was 72.6 [66.4, 78.9] % with isoflurane and 74.5 [67.5, 81.5] % with propofol (difference -1.9 [-9.4, >99] %; p < 0.01 for noninferiority). In both trials, patients assigned to isoflurane received significantly less opioid, measured as fentanyl equivalents, during the treatment period. In INSPIRE ICU2, participants receiving isoflurane were significantly likelier to exhibit spontaneous breathing efforts, but this finding was not replicated in INSPIRE ICU1. There were no significant differences in time to wake-up or time to extubation between groups in either trial. No episodes of malignant hyperthermia or propofol infusion syndrome were reported. Adverse events were comparable in type and frequency between groups. Conclusions In two US multicenter trials, isoflurane was noninferior to propofol for maintaining target sedation depth in adults undergoing invasive ventilation, and was associated with significantly lower opioid exposure. (NCT05327296, NCT05312385) This abstract is funded by: Sedana Medical

Abstract Rationale Propofol sedation in mechanically ventilated patients often causes clinically significant hypotension. While we concurrently developed and validated a machine-learning (ML) classifier to predict hypotension risk, accurately estimating the timing of hemodynamic deterioration could enable more precise, proactive interventions. This study aimed to develop and externally validate ML models that predict not only whether hypotension will occur, but also when it is likely to develop after propofol initiation. Methods ML models were developed using retrospective data from adult, mechanically ventilated ICU patients who received propofol infusion for ≥24 hours across four Mayo Clinic sites from 2018 to 2024 and developed hypotension (≥2 consecutive MAP readings ≤60 mmHg within 15 minutes) during the first 6 hours of sedation. The MIMIC-IV dataset was used for external validation. Features were selected using a union of Boruta and LASSO-penalised quantile regression. Two quantile algorithms (LASSO-penalised quantile regression and LightGBM) were trialed to predict the conditional median and interquartile range (IQR) of time to hypotension. In addition, two probabilistic algorithms (NGBoost and Mixture Density Network) were trialed to predict the full conditional distribution. The quantile models were tuned via Bayesian optimisation to minimise pinball loss during leave-one-site-out cross-validation (LOSO-CV), whereas probabilistic models were tuned to minimise the Continuous Ranked Probability Score. The algorithm with the lowest average pinball loss was deemed the best-performing algorithm. Model performance was evaluated using median absolute error (MAE), IQR coverage, and IQR width. Feature importance was evaluated using SHapley Additive exPlanations (SHAP). Results We included 3482 patients from the Mayo Clinic for model development, with 115 patients from the MIMIC-IV dataset used for external validation. Patient characteristics in the modeling dataset included age, sex, admission SOFA scores, weight, ICU admission source, and initial propofol dose. The best-performing algorithm was LightGBM-based quantile regression. The average MAE during LOSO-CV was 4.11 hours (95% confidence interval [CI] 3.98-4.23), versus 4.83 hours during external validation. The average IQR coverage and width during LOSO-CV was 0.49 (95% CI 0.48-0.49) and 7.12 (6.89-7.35), respectively, versus 0.07 and 6.51 during external validation. Conclusions We developed and externally validated a quantile regression model that predicts both the timing and uncertainty of propofol-induced hypotension in mechanically ventilated ICU patients. This model provides clinicians with actionable time estimates that may facilitate preemptive hemodynamic interventions and optimize sedation management. Prospective validation, expanded predictors and clinical impact assessment are warranted. This abstract is funded by: None

Abstract Rationale Postoperative pulmonary complications (PPCs) importantly contribute to postoperative morbidity and mortality, particularly for American Society of Anesthesiologists (ASA) physical status III patients. It remains unclear whether risk factors for PPCs depend on sex. We hypothesised that sex modifies the relationship between perioperative risk factors and PPCs in ASA III patients undergoing noncardiothoracic surgery with general anesthesia. Methods We performed a secondary analysis of prospective data from 1,202 ASA III patients undergoing non-cardiothoracic surgery. Data consisted of preoperative demographics, comorbidities, intraoperative physiology, medications, and procedure information. The primary outcome was a composite of PPCs by postoperative day 7. Mixed-effects linear models incorporated sex as main effect and interaction with covariates. Results Age, chronic obstructive pulmonary disease, upper abdominal surgery, surgical duration, and emergency surgery significantly increased the odds of ≥ 1 PPC by postoperative day 7. Male patients presented a higher rate of ≥ 3 PPCs, and mechanical ventilation was less protective in female patients. Yet, sex did not significantly modify the relationship between perioperative factors and the primary outcome (no p<0.05 for the interaction effect with sex). In the secondary analysis, gastroesophageal reflux disease affected atelectasis more strongly in male than female patients (relative odds-ratios for female versus male =0.27; 95% CI 0.13 to 0.57). Conclusions In ASA III patients undergoing non-cardiothoracic surgery with general anesthesia, perioperative factors are predominantly not significantly modified by sex in their relationship to PPCs. GERD’s association with atelectasis in male patients could be explored in future prospective studies as a target for reducing pulmonary complications. This abstract is funded by: NHLBI - UH3 HL140177