Mecanismos biofísicos, celulares y modulación de la lesión pulmonar inducida por la ventilación mecánica

Effects of ABCDE Bundle on Hemodynamics in Patients on Mechanical Ventilation

BACKGROUND Mechanical ventilation is an important part of advanced life support in the intensive care unit (ICU). This study aimed to investigate the effects of ABCDE bundle on hemodynamics in patients on mechanical ventilation (MV). MATERIAL AND METHODS This study used a cross-sectional overall controlled approach in which 143 patients on mechanical ventilation were divided into 2 groups. In the pre-ABCDE bundle group (n=70), conventional sedation and analgesia strategy were used. In the post-ABCDE bundle group (n=73), ABCDE bundle was used. Changes in hemodynamics parameters and related prognostic indicators were monitored at various time points before (T0) and at 1 d (T1), 3 d (T3), 5 d (T5), and 7 d (T7) after implementation of the 2 strategies. RESULTS Mean arterial blood pressure (MAP), central venous pressure (CVP), heart rate (HR), and oxygenation index (PaO2/FiO2) in the bundle group were improved more significantly than those in the pre-ABCDE bundle group (P<0.05). For comparison between various monitoring time points in the same group, compared with before intervention, MAP, CVP, HR, and PaO2/FiO2 changed significantly in the bundle group at 3 d, 5 d, and 7 d after intervention, and the difference was statistically significant (P<0.05). Compared with before intervention, differences in all hemodynamics indicators were statistically significant in the pre-ABCDE bundle group at 5 d and 7 d after intervention (P<0.05). Compared with the pre-ABCDE bundle group, differences in prognostic indicators in the post-ABCDE bundle were statistically significant (P<0.05). CONCLUSIONS ABCDE bundle is safe and effective for patients on mechanical ventilation, and can improve hemodynamics and enhance oxygenation index. ABCDE bundle might be helpful in reducing 28-d mortality and improving prognosis.

Effects on lung stress of position and different doses of perfluorocarbon in a model of ARDS

We determined whether the combination of low dose partial liquid ventilation (PLV) with perfluorocarbons (PFC) and prone positioning improved lung function while inducing minimal stress. Eighteen pigs with acute lung injury were assigned to conventional mechanical ventilation (CMV) or PLV (5 or 10 ml/kg of PFC). Positive end-expiratory pressure (PEEP) trials in supine and prone positions were performed. Data were analyzed by a multivariate polynomial regression model. The interplay between PLV and position depended on the PEEP level. In supine PLV dampened the stress induced by increased PEEP during the trial. The PFC dose of 5 ml/kg was more effective than the dose 10 ml/kg. This effect was not observed in prone. Oxygenation was significantly higher in prone than in supine position mainly at lower levels of PEEP. In conclusion, MV settings should take both gas exchange and stress/strain into account. When protective CMV fails, rescue strategies combining prone positioning and PLV with optimal PEEP should improve gas exchange with minimal stress.

Emerging drugs for acute lung injury

INTRODUCTION

Acute respiratory distress syndromes (ARDS) are devastating disorders of overwhelming pulmonary inflammation and hypoxemia, resulting in high morbidity and mortality.

AREAS COVERED

The main pharmacological treatment strategies have focused on the attempted inhibition of excessive inflammation or the manipulation of the resulting physiological derangement causing respiratory failure. Additionally, such interventions may allow reduced occurence mechanical ventilation injury. Despite promising preclinical and small clinical studies, almost all therapies have been shown to be unsuccessful in large-scale randomized controlled trials. The evidence for pharmacological treatment for ARDS is reviewed. Potential future treatments are also presented.

EXPERT OPINION

We suggest for future clinical trials addressing prevention and early intervention to attenuate lung injury and progression to respiratory failure.

Effects of mechanical ventilation with different tidal volume on oxidative stress and antioxidant in lung

Purpose

The aim of this study was to investigate the changes in oxidative stress and antioxidants in lung tissue under different tidal volume ventilation conditions.

Methods

Forty-eight male Wistar rats were randomized into four groups, namely, group C, the control group, which was not ventilated, and groups C1, C2 and C3, the treatment groups, which were ventilated for 2 h with tidal volumes of 8, 30 and 42 ml/kg, respectively. The right middle lobe was assayed for malondialdehyde (MDA), the right posterior lobe was assayed using Western blotting for Nrf2, GCLm and SrX1 and the left lobe was assayed for Nrf2, GCLm and SrX1 mRNA.

Results

The MDA levels were increased in the three treatment groups, with MDA levels highest in group C3 and lowest in group C1 (C3 > C2 > C1) (all P < 0.05). The mRNA expression of Nrf2, GCLm and SrX1 was highest in group C3 and lowest in group 1 (C3 > C2 > C1) (all P < 0.05). No significant difference was observed between group C1 and group C (P > 0.05). A Western blot analysis showed that Nrf2, GCLm and SrX1 expression was highest in group C3 and lowest in group C1 (C3 > C2 > C1) (all P < 0.05). No significant difference was observed between group C1 and group C (P > 0.05).

Conclusions

Oxidative stress and antioxidant enzyme levels in the lungs of rats were positively associated with the tidal volumes of mechanical ventilation, suggesting that higher tidal volumes cause more severe oxidative stress and increased antioxidant responses.

Antioxidant effect of human adult adipose-derived stromal stem cells in alveolar epithelial cells undergoing stretch

INTRODUCTION

Alveolar epithelial cells undergo stretching during mechanical ventilation. Stretch can modify the oxidative balance in the alveolar epithelium. The aim of the present study was to evaluate the antioxidant role of human adult adipose tissue-derived stromal cells (hADSCs) when human alveolar epithelial cells were subjected to injurious cyclic overstretching.

METHODS

A549 cells were subjected to biaxial stretch (0-15% change in surface area for 24h, 0.2Hz) with and without hADSCs. At the end of the experiments, oxidative stress was measured as superoxide generation using positive nuclear dihydroethidium (DHE) staining, superoxide dismutase (SOD) activity in cell lysates, 8-isoprostane concentrations in supernatant, and 3-nitrotyrosine by indirect immunofluorescence in fixed cells.

RESULTS

Cyclically stretching of AECs induced a significant decrease in SOD activity, and an increase in 8-isoprostane concentrations, DHE staining and 3-nitrotyrosine staining compared with non-stretched cells. Treatment with hADSCs significantly attenuated stretch-induced changes in SOD activity, 8-isoprostane concentrations, DHE and 3-nitrotyrosine staining.

CONCLUSION

These data suggest that hADSCs have an anti-oxidative effect in human alveolar epithelial cells undergoing cyclic stretch.

[Lung-brain interaction in the mechanically ventilated patient]

Patients with acute lung injury or acute respiratory distress syndrome (ARDS) admitted to the ICU present neuropsychological alterations, which in most cases extend beyond the acute phase and have an important adverse effect upon quality of life. The aim of this review is to deepen in the analysis of the complex interaction between lung and brain in critically ill patients subjected to mechanical ventilation. This update first describes the neuropsychological alterations occurring both during the acute phase of ICU stay and at discharge, followed by an analysis of lung-brain interactions during mechanical ventilation, and finally explores the etiology and mechanisms leading to the neurological disorders observed in these patients. The management of critical patients requires an integral approach focused on minimizing the deleterious effects over the short, middle or long term.

[Lung-brain interaction in the mechanically ventilated patient]

Patients with acute lung injury or acute respiratory distress syndrome (ARDS) admitted to the ICU present neuropsychological alterations, which in most cases extend beyond the acute phase and have an important adverse effect upon quality of life. The aim of this review is to deepen in the analysis of the complex interaction between lung and brain in critically ill patients subjected to mechanical ventilation. This update first describes the neuropsychological alterations occurring both during the acute phase of ICU stay and at discharge, followed by an analysis of lung-brain interactions during mechanical ventilation, and finally explores the etiology and mechanisms leading to the neurological disorders observed in these patients. The management of critical patients requires an integral approach focused on minimizing the deleterious effects over the short, middle or long term.

Fatores associados à displasia broncopulmonar em prematuros sob ventilação mecânica precoce

OBJETIVOS: descrever os fatores neonatais e de assistência ventilatória associados à displasia broncopulmonar (DBP), e verificar sua frequência em recém-nascidos prematuros submetidos à ventilação mecânica (VM) na primeira semana de vida. MÉTODOS: coorte retrospectiva, realizada em Unidade de Terapia Intensiva Neonatal. Foram analisados prontuários de 86 prematuros, sob VM na primeira semana de vida e registrados dados neonatais, parâmetros da VM e sua relação com a DBP. Para verificar a associação entre as variáveis do estudo e a DBP utilizou-se o teste do qui-quadrado e o Exato de Fisher quando indicado. O teste t e o Kruskal Wallis foram utilizados para a comparação das médias das variáveis contínuas. RESULTADOS: a DBP ocorreu em 17,4%. Foram relacionados à doença: menor peso ao nascer e idade gestacional, Apgar <7 no 1º e 5º minutos, maior tempo sob antibioticoterapia, nutrição parenteral e VM, valores elevados de fração inspirada de oxigênio (FiO2), VM como primeiro suporte respiratório, menor volume de nutrição enteral e ganho ponderal . Não houve diferença nos níveis de pressão positiva inspiratória, pressão positiva expiratória final e diferença de pressão. CONCLUSÕES: a ocorrência da DBP foi baixa e relacionada ao manejo clínico e nutricional e VM precoce e prolongada. Excetuando-se a FiO2 média não foi encontrada relação entre a doença e os demais parâmetros ventilatórios.

[Transfusion-related acute lung injury]

The term Transfusion-Related Acute Lung Injury (TRALI) was coined in 1985. It is a relatively rare, life-threatening clinical syndrome characterized by acute respiratory failure and non-cardiogenic pulmonary edema during or following a blood transfusion. Although its true incidence is unknown, a rate 1 out of every 5000 transfusions has been quoted. TRALI has been the most common cause of transfusion-related fatalities during three years in the USA. Two different etiologies have been proposed. The first is a single antibody-mediated event involving the transfusion of anti-HLA or antigranulocyte antibodies into patients whose leukocytes express the cognate antigens. The second is a two-event model: the first event is related to the clinical condition of the patient (sepsis, trauma, etc.) resulting in pulmonary endothelial activation and neutrophil sequestration, and the second event is the transfusion of a biologic response modifier that activates these adherent polymorphonuclear leukocytes resulting in endothelial damage and capillary leak. The patient management is support as needed based on the severity of the clinical picture and strategies to prevent TRALI are focused on: donor-exclusion policies, product management strategies and avoidance of unnecessary transfusions.

[Survival of rats subjected to different levels of pulmonary injury]

OBJECTIVE

To determine a pulmonary injury model in rats that is associated with moderate mortality after extubation.

DESIGN AND SETTING

An experimental study in an animal model of ventilator-induced lung injury in the animal research laboratory in Virgen de las Nieves University Hospital.

SUBJECTS AND METHOD

A total of 45 male Wistar-Kyoto rats weighing 250-300g received food and water ad libitum. The rats were anesthetized and a tracheotomy was performed by insertion of endotracheal tube by tracheotomy.

INTERVENTIONS

Pulmonary injury due to mechanical ventilation was maintained for 60 min with high tidal volume (25 ml/kg) combined with intratracheal instillation of different doses of 0,9% saline solution. Rats were randomly distributed into 3 groups (15 animals in each group) with different amounts of instilled saline solution: group I, 0.5 ml/250 g body weight; group II, 1 ml/250 g body weight, and group III, 1.5 ml/250 g body weight.

MAIN MEASUREMENTS

Survival of animals after extubation was recorded every 5 min for the first 40 min and then at 3 h, 24 h, 72 h, and 7 days.

RESULTS

Survival in rats that received 0.5, 1 and 1.5 ml/250 g of intratracheal saline solution was 60%, 43% and 0% respectively, with statistically significant differences between groups receiving 0.5 and 1.5 ml/250 g (p = 0.003).

CONCLUSIONS

Survival in rats mechanically ventilated with high moderate volume is influenced by increased doses of intratracheal saline solution and this is important to design studies that analyze the effect the interventions on mortality.