Gene expression changes with a 'non-injurious' ventilation strategy

The association between regional transcriptome profiles and lung volumes in response to mechanical ventilation and lung injury

Background

Lung inhomogeneity plays a pivotal role in the development of ventilator-induced lung injury (VILI), particularly in the context of pre-existing lung injury. The mechanisms that underlie this interaction are poorly understood. We aimed to elucidate the regional transcriptomic response to mechanical ventilation (MV), with or without pre-existing lung injury, and link this to the regional lung volume response to MV.

Methods

Adult female BALB/c mice were randomly assigned into one of four groups: Saline, MV, lipopolysaccharide (LPS) or LPS/MV. Lung volumes (tidal volume, Vt; end-expiratory volume, EEV) were measured at baseline or after 2 h of ventilation using four-dimensional computed tomography (4DCT). Regional lung tissue samples corresponding to specific imaging regions were analysed for the transcriptome response by RNA-Seq. Bioinformatics analyses were conducted and the regional expression of dysregulated gene clusters was then correlated with the lung volume response.

Results

MV in the absence of pre-existing lung injury was associated with regional variations in tidal stretch. The addition of LPS also caused regional increases in EEV. We identified 345, 141 and 184 region-specific differentially expressed genes in response to MV, LPS and LPS/MV, respectively. Amongst these candidate genes, up-regulation of genes related to immune responses were positively correlated with increased regional tidal stretch in the MV group, while dysregulation of genes associated with endothelial barrier related pathways were associated with increased regional EEV and Vt when MV was combined with LPS. Further protein–protein interaction analysis led to the identification of two protein clusters representing the PI3K/Akt and MEK/ERK signalling hubs which may explain the interaction between MV and LPS exposure.

Conclusion

The biological pathways associated with lung volume inhomogeneity during MV, and MV in the presence of pre-existing inflammation, differed. MV related tidal stretch induced up-regulation of immune response genes, while LPS combined with MV disrupted PI3K/Akt and MEK/ERK signalling.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-01958-2.

The Society for Translational Medicine: clinical practice guidelines for mechanical ventilation management for patients undergoing lobectomy

Patients undergoing lobectomy are at significantly increased risk of lung injury. One-lung ventilation is the most commonly used technique to maintain ventilation and oxygenation during the operation. It is a challenge to choose an appropriate mechanical ventilation strategy to minimize the lung injury and other adverse clinical outcomes. In order to understand the available evidence, a systematic review was conducted including the following topics: (I) protective ventilation (PV); (II) mode of mechanical ventilation [e.g., volume controlled (VCV) versus pressure controlled (PCV)]; (III) use of therapeutic hypercapnia; (IV) use of alveolar recruitment (open-lung) strategy; (V) pre-and post-operative application of positive end expiratory pressure (PEEP); (VI) Inspired Oxygen concentration; (VII) Non-intubated thoracoscopic lobectomy; and (VIII) adjuvant pharmacologic options. The recommendations of class II are non-intubated thoracoscopic lobectomy may be an alternative to conventional one-lung ventilation in selected patients. The recommendations of class IIa are: (I) Therapeutic hypercapnia to maintain a partial pressure of carbon dioxide at 50-70 mmHg is reasonable for patients undergoing pulmonary lobectomy with one-lung ventilation; (II) PV with a tidal volume of 6 mL/kg and PEEP of 5 cmH₂O are reasonable methods, based on current evidence; (III) alveolar recruitment [open lung ventilation (OLV)] may be beneficial in patients undergoing lobectomy with one-lung ventilation; (IV) PCV is recommended over VCV for patients undergoing lung resection; (V) pre- and post-operative CPAP can improve short-term oxygenation in patients undergoing lobectomy with one-lung ventilation; (VI) controlled mechanical ventilation with I:E ratio of 1:1 is reasonable in patients undergoing one-lung ventilation; (VII) use of lowest inspired oxygen concentration to maintain satisfactory arterial oxygen saturation is reasonable based on physiologic principles; (VIII) Adjuvant drugs such as nebulized budesonide, intravenous sivelestat and ulinastatin are reasonable and can be used to attenuate inflammatory response.

Does Paravertebral Blockade Facilitate Immediate Extubation after Totally Endoscopic Robotic Mitral Valve Repair Surgery?

Objective

Immediate extubation of select patients in the operating room after cardiac surgery has been shown to be safe and may result in improved hemodynamics and decreased cost perioperatively. The aim of this study was to evaluate whether the addition of paravertebral blockade (PVB) to general anesthesia facilitates extubation in the operating room in patients undergoing totally endoscopic robotic mitral valve repair (TERMR).

Methods

A review of 65 consecutive patients who underwent TERMR between January 2012 and June 2013 at a single institution was conducted. Patients were divided into two groups, one group that received PVB and general anesthesia and a second group that received general anesthesia alone. The data analyzed included quantities of anesthetic administered during surgery and the location of extubation after surgery.

Results

A total of 34 patients received PVB and general anesthesia, whereas 31 received general anesthesia alone. The two groups had similar demographic and surgical data. Patients in the PVB and general anesthesia group were more likely to be extubated in the operating room (67.6%, n = 23 vs 41.9%, n = 13, P = 0.048) and required less intraoperative fentanyl (3.41 μg/kg vs 4.90 μg/kg, P = 0.006). There were no adverse perioperative events in either group related to PVB or extubation.

Conclusions

The addition of PVB to general anesthesia for perioperative pain control facilitated extubation in the operating room in patients undergoing TERMR. Paravertebral blockade allowed for lower intraoperative fentanyl dosing, which may account for the increased incidence of immediate extubation. A detailed prospective study is warranted.

Positive end-expiratory pressure and variable ventilation in lung-healthy rats under general anesthesia

Objectives

Variable ventilation (VV) seems to improve respiratory function in acute lung injury and may be combined with positive end-expiratory pressure (PEEP) in order to protect the lungs even in healthy subjects. We hypothesized that VV in combination with moderate levels of PEEP reduce the deterioration of pulmonary function related to general anesthesia. Hence, we aimed at evaluating the alveolar stability and lung protection of the combination of VV at different PEEP levels.

Design

Randomized experimental study.

Setting

Animal research facility.

Subjects

Forty-nine male Wistar rats (200–270 g).

Interventions

Animals were ventilated during 2 hours with protective low tidal volume (V_T) in volume control ventilation (VCV) or VV and PEEP adjusted at the level of minimum respiratory system elastance (Ers), obtained during a decremental PEEP trial subsequent to a recruitment maneuver, and 2 cmH₂O above or below of this level.

Measurements and Main Results

Ers, gas exchange and hemodynamic variables were measured. Cytokines were determined in lung homogenate and plasma samples and left lung was used for histologic analysis and diffuse alveolar damage scoring. A progressive time-dependent increase in Ers was observed independent on ventilatory mode or PEEP level. Despite of that, the rate of increase of Ers and lung tissue IL-1 beta concentration were significantly lower in VV than in VCV at the level of the PEEP of minimum Ers. A significant increase in lung tissue cytokines (IL-6, IL-1 beta, CINC-1 and TNF-alpha) as well as a ventral to dorsal and cranial to caudal reduction in aeration was observed in all ventilated rats with no significant differences among groups.

Conclusions

VV combined with PEEP adjusted at the level of the PEEP of minimal Ers seemed to better prevent anesthesia-induced atelectasis and might improve lung protection throughout general anesthesia.

Tidal volume in animal models of hemorrhagic and endotoxic shock

The aim of this study was to examine the characteristics of lung, kidney and small intestine injury caused by early resuscitation from hemorrhagic shock (HS) and endotoxic shock (ES) when ventilating with different tidal volumes (Vts). The study also considered the determination of the appropriate Vt for use in mechanical ventilation (MV) during treatment for shock. Resuscitated rabbits were ventilated with varying Vts for 120 min following 60 min of HS or ES. The histopathology, ultrastructure and apoptotic index (AI) of the lung, kidney and small intestine were then measured. Organs from the high-Vt groups (VT=12-15 ml/kg) showed the highest pathological scores (PSs; P<0.05). For HS, the renal PS and AI of the HS-M group (Vt=8-10 ml/kg)were lower than those of the HS-L group (Vt=4-6 ml/kg) and the lung PS and AI of the HS-C (control) group were lower compared with those of the HS-M group. For ES, the lung PS of the ES-L group was lower compared with that of the ES-M group (Vt=8-10 ml/kg) and the lung AI of the ES-C (control) group was lower compared with that of the ES-L group (Vt=4-6 ml/kg). When ventilated with the same Vt, ES resulted in higher PSs in the lung and intestine and a lower renal PS (P<0.05) than HS. MV was not recommended for either shock type. When it was necessary for MV to be applied, low Vt (4-6 ml/kg) protected the lung in ES. Moderate Vt (8-10 ml/kg) may be relatively safe to use for HS.

Perioperative lung protection strategies in cardiothoracic anesthesia: are they useful?

Patients are at risk for several types of lung injury in the perioperative period. These injuries include atelectasis, pneumonia, pneumothorax, bronchopleural fistula, acute lung injury, and acute respiratory distress syndrome. Anesthetic management can cause, exacerbate, or ameliorate most of these injuries. Lung-protective ventilation strategies using more physiologic tidal volumes and appropriate levels of positive end-expiratory pressure can decrease the extent of this injury. This review discusses the effects of mechanical ventilation and its role in ventilator-induced lung injury with specific reference to cardiothoracic anesthesia.

Pro: early extubation in the operating room following cardiac surgery in adults

There is growing evidence that the general current approach in many centers of continued mechanical ventilation following cardiac surgery has evolved through historical experience rather than having a strong physiological basis in current practice. There is evidence going back several decades supporting very early (in the operating room [OR]) extubation in pediatric cardiac anesthesia. The authors provide evidence from numerous sources showing that extubation in the OR or shortly after arrival in the ICU is safe and cost-effective and is not prevented by the type of cardiac surgery or the use of cardiopulmonary bypass. They query if the paradigm should not be reversed and very early extubation be the routine unless contraindicated. Like any anesthetic technique, appropriate patient selection is called for, but this technique is widely appropriate.

Lung protective strategies in anaesthesia

Patients are at risk for several types of lung injury in the perioperative period including atelectasis, pneumonia, pneumothorax, acute lung injury, and acute respiratory distress syndrome. Anaesthetic management can cause, exacerbate, or ameliorate these injuries. This review examines the effects of perioperative mechanical ventilation and its role in ventilator-induced lung injury. Lung protective ventilatory strategies to specific clinical situations such as cardiopulmonary bypass and one-lung ventilation along with newer novel lung protective strategies are discussed.