Effects of Intra-operative Cardiopulmonary Variability On Post-operative Pulmonary Complications in Major Non-cardiac Surgery: A Retrospective Cohort Study.

Intraoperative cardiopulmonary variables are well-known predictors of postoperative pulmonary complications (PPC), traditionally quantified by median values over the duration of surgery. However, it is unknown whether cardiopulmonary instability, or wider intra-operative variability of the same metrics, is distinctly associated with PPC risk and severity. We leveraged a retrospective cohort of adults (n = 1202) undergoing major non-cardiothoracic surgery. We used multivariable logistic regression to evaluate the association of two outcomes (1)moderate-or-severe PPC and (2)any PPC with two sets of exposure variables- (a)variability of cardiopulmonary metrics (inter-quartile range, IQR) and (b)median intraoperative cardiopulmonary metrics. We compared predictive ability (receiver operating curve analysis, ROC) and parsimony (information criteria) of three models evaluating different aspects of the intra-operative cardiopulmonary metrics: Median-based: Median cardiopulmonary metrics alone, Variability-based: IQR of cardiopulmonary metrics alone, and Combined: Medians and IQR. Models controlled for peri-operative/surgical factors, demographics, and comorbidities. PPC occurred in 400(33%) of patients, and 91(8%) experienced moderate-or-severe PPC. Variability in multiple intra-operative cardiopulmonary metrics was independently associated with risk of moderate-or-severe, but not any, PPC. For moderate-or-severe PPC, the best-fit predictive model was the Variability-based model by both information criteria and ROC analysis (area under the curve, AUCVariability-based = 0.74 vs AUCMedian-based = 0.65, p = 0.0015; AUCVariability-based = 0.74 vs AUCCombined = 0.68, p = 0.012). For any PPC, the Median-based model yielded the best fit by information criteria. Predictive accuracy was marginally but not significantly higher for the Combined model (AUCCombined = 0.661) than for the Median-based (AUCMedian-based = 0.657, p = 0.60) or Variability-based (AUCVariability-based = 0.649, p = 0.29) models. Variability of cardiopulmonary metrics, distinct from median intra-operative values, is an important predictor of moderate-or-severe PPC.

Inflammatory Activity in Atelectatic and Normally Aerated Regions During Early Acute Lung Injury.

RATIONALE AND OBJECTIVES: Pulmonary atelectasis presumably promotes and facilitates lung injury. However, data are limited on its direct and remote relation to inflammation. We aimed to assess regional 2-deoxy-2-[18F]-fluoro-D-glucose (18F-FDG) kinetics representative of inflammation in atelectatic and normally aerated regions in models of early lung injury. MATERIALS AND METHODS: We studied supine sheep in four groups: Permissive Atelectasis (n = 6)-16 hours protective tidal volume (VT) and zero positive end-expiratory pressure; Mild (n = 5) and Moderate Endotoxemia (n = 6)- 20-24 hours protective ventilation and intravenous lipopolysaccharide (Mild = 2.5 and Moderate = 10.0 ng/kg/min), and Surfactant Depletion (n = 6)-saline lung lavage and 4 hours high VT. Measurements performed immediately after anesthesia induction served as controls (n = 8). Atelectasis was defined as regions of gas fraction <0.1 in transmission or computed tomography scans. 18F-FDG kinetics measured with positron emission tomography were analyzed with a three-compartment model. RESULTS: 18F-FDG net uptake rate in atelectatic tissue was larger during Moderate Endotoxemia (0.0092 ± 0.0019/min) than controls (0.0051 ± 0.0014/min, p = 0.01). 18F-FDG phosphorylation rate in atelectatic tissue was larger in both endotoxemia groups (0.0287 ± 0.0075/min) than controls (0.0198 ± 0.0039/min, p = 0.05) while the 18F-FDG volume of distribution was not significantly different among groups. Additionally, normally aerated regions showed larger 18F-FDG uptake during Permissive Atelectasis (0.0031 ± 0.0005/min, p < 0.01), Mild (0.0028 ± 0.0006/min, p = 0.04), and Moderate Endotoxemia (0.0039 ± 0.0005/min, p < 0.01) than controls (0.0020 ± 0.0003/min). CONCLUSION: Atelectatic regions present increased metabolic activation during moderate endotoxemia mostly due to increased 18F-FDG phosphorylation, indicative of increased cellular metabolic activation. Increased 18F-FDG uptake in normally aerated regions during permissive atelectasis suggests an injurious remote effect of atelectasis even with protective tidal volumes.

Lung Perfusion and Ventilation During Cardiopulmonary Bypass Reduces Early Structural Damage to Pulmonary Parenchyma.

BACKGROUND: It is unclear whether maintaining pulmonary perfusion and ventilation during cardiopulmonary bypass (CPB) reduces pulmonary inflammatory tissue injury compared with standard CPB where the lungs are not ventilated and are minimally perfused. In this study, we tested the hypothesis that maintenance of lung perfusion and ventilation during CPB decreases regional lung inflammation, which may result in less pulmonary structural damage. METHODS: Twenty-seven pigs were randomly allocated into a control group only submitted to sternotomy (n = 8), a standard CPB group (n = 9), or a lung perfusion group (n = 10), in which lung perfusion and ventilation were maintained during CPB. Hemodynamics, gas exchanges, respiratory mechanics, and systemic interleukins (ILs) were determined at baseline (T0), at the end of 90 minutes of CPB (T90), and 180 minutes after CPB (T180). Bronchoalveolar lavage (BAL) ILs were obtained at T0 and T180. Dorsal and ventral left lung tissue samples were examined for optical and electron microscopy. RESULTS: At T90, there was a transient reduction in PaO2/FIO2 in CPB (126 ± 64 mm Hg) compared with the control and lung perfusion groups (296 ± 46 and 244 ± 57 mm Hg; P < 0.001), returning to baseline at T180. Serum ILs were not different among the groups throughout the study, whereas there were significant increases in BAL IL-6 (P < 0.001), IL-8 (P < 0.001), and IL-10 (P < 0.001) in both CPB and lung perfusion groups compared with the control group. Polymorphonuclear counts within the lung tissue were smaller in the lung perfusion group than in the CPB group (P = 0.006). Electron microscopy demonstrated extrusion of surfactant vesicles into the alveolar spaces and thickening of the alveolar septa in the CPB group, whereas alveolar and capillary histoarchitecture was better preserved in the lung perfusion group. CONCLUSIONS: Maintenance of lung perfusion and ventilation during CPB attenuated early histologic signs of pulmonary inflammation and injury compared with standard CPB. Although increased compared with control animals, there were no differences in serum or BAL IL in animals receiving lung ventilation and perfusion during CPB compared with standard CPB.

Aplicaçäo de análise multivariável ao estudo do teste de lavagem de nitrogênio com respiraçäo única / Application of multivariate analysis to the study of the single-breath nitrogen washout test

O presente trabalho trata da aplicaçäo de método numérica à análise de testes de funçäo pulmonar. Objetiva-se investigar preliminarmente a utilizaçäo de técnicas de análise de múltiplas variáveis aos dados obtidos no teste de lavagem de nitrogênio com respiraçäo única (TN2-RU). O teste foi realizado com uso de sistema experimental baseado em computador. Parâmetros do TN2-RU foram obtidos em 18 voluntários, classificados de acordo com questionário de sintomas respiratórios. Através de análise discriminante obtiveram-se equaçöes cujas variáveis independentes säo parâmetros do TN2-RU. Essas equaçöes permitiram separar, com significância estatística, grupos de sintomáticos e näo sintomáticos (p < 0,05) e tabagistas e näo tabagistas (p < 0,05). Tais resultados indicam a utilidade de métodos de análise de múltiplas variáveis na análise de dados de testes de funçäo pulmonar, possibilitando a objetivaçäo de condutas e estudos clínicos