Daily Anesthesiology Research Analysis

RATIONALE: Conventional monitoring of acute respiratory distress syndrome (ARDS) relies on global parameters, e.g., tidal volume, airway pressure, and driving pressure. These parameters do not capture regional stress heterogeneity within the lung. OBJECTIVES: To develop and validate a novel technique, lung stress mapping visualizing regional lung stress throughout the lung, and to evaluate its biological and clinical relevance. METHODS: Lung stress mapping combines esophageal pressure and plateau pressure with CT-derived pleural pressure gradients to generate spatially resolved maps of inspiratory transpulmonary pressure. Accuracy was tested in pigs by surgically inserted pleural sensors. Biological relevance was assessed in rabbits by correlating lung stress mapping-derived parameters with regional proinflammatory cytokine expression. Clinical feasibility and associations with outcome were evaluated in 20 consecutive ARDS patients enrolled in a prospective study. MEASUREMENTS AND MAIN RESULTS: Good correlation and agreement between sensor-derived and mapping-derived lung stress were confirmed. In rabbits, lung inflammation predominantly occurred in nondependent lung regions where lung stress was higher, and overall inflammation correlated with lung stress mapping-derived parameters. In ARDS patients, all received lung-protective ventilation. Non-survivors had significantly higher lung stress mapping-derived maximum and mean lung stress than survivors, despite similar global ventilatory parameters. Exploratory ROC analyses showed stronger associations of lung stress mapping-derived parameters with 90-day mortality than driving pressure. CONCLUSIONS: Lung stress mapping accurately quantified regional transpulmonary stress and revealed biologically and clinically meaningful heterogeneity. This technique may help identify patients with ARDS at increased risk of ventilator-induced lung injury who would not be recognized through conventional respiratory monitoring.

BACKGROUND: Cardiac output assessment in perioperative and intensive care settings can be challenging in patients with congenital heart disease. Capnodynamic monitoring is a minimally invasive method enabling estimation of effective pulmonary blood flow (EPBF), which corresponds to cardiac output in the absence of significant intrapulmonary shunts. In the setting of cardiac shunts, however, it is unclear if the capnodynamic method represents systemic or pulmonary blood flow. Clinically, separating systemic from pulmonary blood flow may aid in the hemodynamic care of patients with congenital heart disease. Thus, the aim of the current study was to evaluate whether EPBF represents systemic or pulmonary blood flow in an animal model of aorto-pulmonary left-to right shunt. METHODS: An artificial aorto-pulmonary shunt was constructed in ten mechanically ventilated pigs. Measurements of hemodynamic parameters including EPBF, as well as systemic and pulmonary blood flow were performed at different fractions of shunt flow. Simultaneous recordings of EPBF, systemic and pulmonary blood flow were done and examined for agreement to investigate what EPBF represents in the presence of left -to right shunt. RESULTS: With open shunt, bias between EPBF and systemic blood flow was 0.24 L/min, limits of agreement -0.74 (95%CI -1.51 to -0.40) to 1.22 (95% CI 0.88 to 1.99) L/min, mean percentage error of 30%. Corresponding values for EPBF and pulmonary blood flow were bias -1.28 L/min, limits of agreement -3.13 (95% CI -4.14 to -2.63) to 0.56 (95% CI 0.06 to 1.57) L/min, mean percentage error of 38%. Mixed-effects models with animal-level random intercepts demonstrated positive associations between EPBF and both Qs and Qp, with EPBF increases of 1.00 L/min corresponding to increases of 1.00 L/min in Qs and 1.86 L/min in Qp (marginal R2 = 0.69 and 0.76; conditional R2 = 0.86 and 0.89). Lin's concordance correlation coefficient for EPBF vs systemic and pulmonary blood flow were 0.79 (95% CI 0.68 to 0.86) and 0.43 (95% CI 0.32 to 0.52) respectively with open shunt. CONCLUSION: In this experimental model of left-to-right shunt, EPBF more closely reflected systemic blood flow (Qs) than pulmonary blood flow (Qp). This alignment with systemic output, is clinically relevant for monitoring and hemodynamic care, as systemic blood flow is one of the determinants of oxygen delivery.

OBJECTIVES: To explore how early mechanical reperfusion impacts outcomes in high-risk pulmonary embolism (PE) patients supported by veno-arterial extracorporeal membrane oxygenation (V-A ECMO). METHODS: This retrospective international study included adult patients treated with V-A ECMO for high-risk PE at 39 ECMO centers (2014-2024). Early mechanical reperfusion was defined as catheter-directed therapy or surgical embolectomy within 48 hours of ECMO initiation. Patients dying within 12 hours or receiving delayed reperfusion were excluded. The primary outcome was 90-day mortality, assessed using propensity-matched groups. MEASUREMENTS AND MAIN RESULTS: Among 492 patients on V-A ECMO (median age 53), 69% had cardiac arrest, and 28% received early mechanical reperfusion. After propensity matching, 137 patients were compared in each group. Ninety-day mortality was 32% with early mechanical reperfusion on ECMO versus 39% with ECMO stand-alone (HR 0.68; 95% CI, 0.45-1.03; p = 0.07). Overall, ECMO duration and weaning rates were similar; however, early mechanical reperfusion improved ECMO weaning in patients without prior thrombolysis (sHR 1.56; 95% CI, 1.03-2.36; p = 0.04). Bleeding occurred in 50% of patients, with no significant difference between groups. CONCLUSION: In this large international cohort of patients with high-risk PE on V-A ECMO, early mechanical reperfusion therapy was not associated with a reduction in 90-day mortality or ECMO duration. These findings may support a stepwise, individualized approach favoring initial ECMO stand-alone support, although a certain clinical benefit from early mechanical reperfusion in selected patients cannot be excluded.