Histochemical Alterations in One Lung Ventilation

Pathophysiological profile of non-ventilated lung injury in healthy female pigs undergoing mechanical ventilation

BACKGROUND

Lung regions excluded from mechanical insufflation are traditionally assumed to be spared from ventilation-associated lung injury. However, preliminary data showed activation of potential mechanisms of injury within these non-ventilated regions (e.g., hypoperfusion, inflammation).

METHODS

In the present study, we hypothesized that non-ventilated lung injury (NVLI) may develop within 24 h of unilateral mechanical ventilation in previously healthy pigs, and we performed extended pathophysiological measures to profile NVLI. We included two experimental groups undergoing exclusion of the left lung from the ventilation with two different tidal volumes (15 vs 7.5 ml/kg) and a control group on bilateral ventilation. Pathophysiological alteration including lung collapse, changes in lung perfusion, lung stress and inflammation were measured. Lung injury was quantified by histological score.

RESULTS

Histological injury score of the non-ventilated lung is significantly higher than normally expanded lung from control animals. The histological score showed lower intermediate values (but still higher than controls) when the tidal volume distending the ventilated lung was reduced by 50%. Main pathophysiological alterations associated with NVLI were: extensive lung collapse; very low pulmonary perfusion; high inspiratory airways pressure; and higher concentrations of acute-phase inflammatory cytokines IL-6, IL-1β and TNF-α and of Angiopoietin-2 (a marker of endothelial activation) in the broncho-alveolar lavage. Only the last two alterations were mitigated by reducing tidal volume, potentially explaining partial protection.

CONCLUSIONS

Non-ventilated lung injury develops within 24 h of controlled mechanical ventilation due to multiple pathophysiological alterations, which are only partially prevented by low tidal volume.

Oncological advantage of nonintubated thoracic surgery: Better compliance of adjuvant treatment after lung lobectomy

BACKGROUND

Video-assisted thoracoscopic (VATS) surgery contributes to improved survival, adjuvant chemotherapy delivery and less postoperative complications. Nonintubated thoracic surgery (NITS) VATS procedures improves immunological responses in lung cancer patients; however, there is no data regarding adjuvant chemotherapy delivery effectiveness following NITS lobectomies. In this study, we aimed to compare protocol compliance and toxic complications during adjuvant chemotherapy after intubated and nonintubated VATS lobectomies in non-small cell lung cancer (NSCLC).

METHODS

We retrospectively reviewed the medical records of 66, stage IB-IIIB NSCLC patients who underwent intubated or nonintubated VATS lobectomy and received adjuvant chemotherapy.

RESULTS

A total of 38 patients (17 males, mean age 64 years) underwent conventional VATS and 28 (7 males; mean age 63 years) uniportal VATS NITS. Both groups had comparable demographic data, preoperative pulmonary function, and Eastern Cooperative Oncology Group (ECOG) status. Among the intubated and nonintubated patients, 82% and 75% were diagnosed with adenocarcinoma, respectively. The incidence of adenocarcinoma and squamous cell carcinoma cases were similar in both groups; however, the pathological staging showed significant differences, as 5 (18%) nonintubated patients had stage IB lung cancer, compared with the intubated group (P = 0.01). Further distribution of stages was similar between the groups. We observed significant differences in chest tube duration and operation time in the nonintubated group (P < 0.01). Among nonintubated patients, 92% completed the planned chemotherapy protocol, compared to 71% of the intubated group (P = 0.035). Grade 1/2 toxicity occurred significantly more often in the intubated group (16% vs. 0%, P = 0.03) and there was a lower incidence of grade 4 neutropenia in the nonintubated group (0% vs. 16%, P = 0.03).

CONCLUSIONS

Our results showed that the nonintubated procedure resulted in improved adjuvant chemotherapy compliance and lower toxicity rates after lobectomy.

KEY POINTS

SIGNIFICANT FINDINGS OF THE STUDY: Oncological advantage of the non-intubated thoracic surgery: better compliance with therapy protocol. What this study adds NITS lobectomies contribute to better administration of adjuvant chemotherapy with the planned cycle number and dosage.

Can apneic oxygen insufflation become a novel lung protective ventilation strategy? A randomized, controlled, blinded, single center clinical trial

Objective

The aim of this study was to determine whether a AOI strategy on non-ventilated lung could reduce the regional and systemic proinflammatory cytokine and oxidative stress response associated with esophagectomy, and to evaluate whether AOI can be used as a novel lung protective ventilation strategy. Its impact on oxygenation after OLV, surfactant protein A, B, C (SP-A, B, C), postoperative hospital stay and postoperative pulmonary complications (PPCs) was also evaluated.

Methods

Fifty-four adults (ASA II-III) undergoing esophagectomy with OLV were enrolled in the study. Patients were randomly assigned into 2 groups: control group (group C) and treated group (group T). Group C was treated with traditional OLV mode,while group T was given AOI of 5 L/min oxygen on the non-ventilated lung immediately at the beginning of OLV. Arterial blood gas was analyzed before and after OLV. A bronchoalveolar lavage(BAL) was performed after OLV on the non-ventilated lung. Proinflammatory cytokine, oxidative stress markers(TNF-α, NF-κB,sICAM-1,IL-6,IL-10,SOD,MDA) and SP-A, B, C were analyzed in serum and BALF as the primary endpoint.The clinical outcome determined by PPCs was assessed as the secondary endpoint.

Results

Patients with AOI had better oxygenation in the recovery period, oxygenation index(OI) (394[367–426] and 478[440–497]mmHg, respectively) of group T at T₂ and T₃ were significantly higher than those (332[206–434] and 437[331–512]mmHg, respectively) of group C. OLV resulted in an increase in the measured inflammatory markers in both groups, however, the increase of inflammatory markers upon OLV in the group C was significantly higher than those of group T. OLV resulted in an increase in the measured SP-A, B, C in serum of both groups. However, the levels of SP-A, B, C of group T were lower than those of group C in serum after OLV, and the results in BALF were the opposite. The BALF levels of SOD(23.88[14.70–33.93]U/ml) of group T were higher than those(15.99[10.33–24.16] U/ml) of group C, while the levels of MDA in both serum and BALF of group T(8.60[4.14–9.85] and 1.88[1.33–3.08]nmol/ml, respectively) were all lower than those of group C (11.10[6.57–13.75] and 1.280[1.01–1.83]nmol/ml) after OLV. There was no statistical difference between the two groups in terms of postoperative hospital stay and the incidence of PPCs.

Conclusion

AOI on non-ventilated lung during OLV can improve the oxygenation function after OLV, relieve the inflammatory and oxidative stress response in the systemic and non-ventilated lung after OLV associated with esophagectomy.

Trial registration

ChiCTR-IOR-17011037. Registered on 31 March 2017.

Use of lung-protective strategies during one-lung ventilation surgery: a multi-institutional survey

Background

Limited evidence suggests that intraoperative lung-protective ventilation (LPV) during one-lung ventilation (OLV) may reduce respiratory complications after thoracic surgery. Little is known about LPV practices during OLV. Our purpose was to assess the state of practice/perspectives of anesthesiologists regarding LPV during elective OLV.

Methods

We conducted a multi-institutional cross-sectional survey of anesthesiologists performing OLV at high-volume Canadian tertiary/university centers. The survey was designed, refined and distributed by a multi-disciplinary team using the Dillman method. Univariable and multivariable analyses were used.

Results

Seventy-five (63%) of 120 eligible respondents completed the survey. Although the critical care literature focuses on minimizing tidal volume (TV) as the central strategy of LPV, most respondents (89%, n=50/56) focused on minimizing peak airway pressure (PAP) as their primary strategy of intraoperative LPV. Only 64% (n=37/58) reported actively trying to minimize TV. While 32% (n=17/54) were unsure about the current evidence regarding LPV, 67% (n=36/54) believed that the evidence favoured their use during OLV. Perceived clinical and institutional barriers were the only predictors of reduced attempts to minimize TV on univariate analyses. In multivariable/adjusted analyses, perceived institutional barriers were the only predictors of reduced attempts to minimize TV with adjusted odds ratio of 0.1 (95% CI: 0.03-0.6).

Conclusions

Most anesthesiologists defined low PAP as the primary strategy of LPV during OLV and attempted to minimize it. This study is the first to assess the practice/perspectives of anesthesiologists regarding LPV during OLV and also the first to explore predictors of LPV use. Randomized trials are currently ongoing. However, this study suggests that institutional barriers may subvert future knowledge translation and need to be addressed.

Short-term one-lung ventilation does not influence local inflammatory cytokine response after lung resection

Background

One-lung ventilation (OLV) is a ventilation procedure used for pulmonary resection which may results in lung injury. The aim of this study was to evaluate the local inflammatory cytokine response from the dependent lung after OLV and its correlation to VT. The secondary aim was to evaluate the clinical outcome of each patient.

Methods

Twenty-eight consecutive patients were enrolled. Ventilation was delivered in volume-controlled mode with a VT based on predicted body weight (PBW). 5 cmH₂O positive end-expiratory pressure (PEEP) and FiO₂ 0.5 were applied. Bronchoalveolar lavage (BAL) was performed in the dependent lung before and after OLV. The levels of pro-inflammatory interleukins (IL-1α, IL-1β, IL-6, IL-8), tumor necrosis factor alpha (TNFα), vascular endothelial growth factor (VEGF), endothelial growth factor (EGF), monocyte chemoattractant protein-1 (MCP-1) and anti-inflammatory cytokines, such as interleukins (IL-2, IL-4, IL-10) and interferon (IFN-γ), were evaluated. Subgroup analysis: to analyze the VT setting during OLV, all patients were ventilated within a range of 5-10 mL/kg. Thirteen patients, classified as a conventional ventilation (CV) subgroup, received 8-10 mL/kg, while 15 patients, classified as a protective ventilation (PV) subgroup, received 5-7 mL/kg.

Results

Cytokine BAL levels after surgery showed no significant increase after OLV, and no significant differences were recorded between the two subgroups. The mean duration of OLV was 64.44±21.68 minutes. No postoperative respiratory complications were recorded. The mean length of stay was for 4.00±1.41 days in the PV subgroup and 4.45±2.07 days in the CV group; no statistically significant differences were recorded between the two subgroups (P=0.511).

Conclusions

Localized inflammatory cytokine response after OLV was not influenced by the use of different VT. Potentially, the application of PEEP in both ventilation strategies and the short duration of OLV could prevent postoperative complications.

Immunological and Inflammatory Impact of Non-Intubated Lung Metastasectomy

Background: We hypothesized that video-assisted thoracic surgery (VATS) lung metastasectomy under non-intubated anesthesia may have a lesser immunological and inflammatory impact than the same procedure under general anesthesia. Methods: Between December 2005 and October 2015, 55 patients with pulmonary oligometastases (at the first episode) successfully underwent VATS metastasectomy under non-intubated anesthesia. Lymphocytes subpopulation and interleukins 6 and 10 were measured at different intervals and matched with a control group composed of 13 patients with similar clinical features who refused non-intubated surgery. Results: The non-intubated group demonstrated a lesser reduction of natural killer lymphocytes at 7 days from the procedure (p = 0.04) compared to control. Furthermore, the group revealed a lesser spillage of interleukin 6 after 1 (p = 0.03), 7 (p = 0.04), and 14 (p = 0.05) days. There was no mortality in any groups. Major morbidity rate was significantly higher in the general anesthesia group 3 (5%) vs. 3 (23%) (p = 0.04). The median hospital stay was 3.0 vs. 3.7 (p = 0.033) days, the estimated costs with the non-intubated procedure was significantly lower, even excluding the hospital stay. Conclusions: VATS lung metastasectomy in non-intubated anesthesia had significantly lesser impact on both immunological and inflammatory response compared to traditional procedure in intubated general anesthesia.

A novel method for right one-lung ventilation modeling in rabbits

There is no standard method by which to establish a right one-lung ventilation (OLV) model in rabbits. In the present study, a novel method is proposed to compare with two other methods. After 0.5 h of baseline two-lung ventilation (TLV), 40 rabbits were randomly divided into sham group (TLV for 3 h as a contrast) and three right-OLV groups (right OLV for 3 h with different methods): Deep intubation group, clamp group and blocker group (deeply intubate the self-made bronchial blocker into the left main bronchus, the novel method). These three methods were compared using a number of variables: Circulation by heart rate (HR), mean arterial pressure (MAP); oxygenation by arterial blood gas analysis; airway pressure; lung injury by histopathology; and time, blood loss, success rate of modeling. Following OLV, compared with the sham group, arterial partial pressure of oxygen and arterial hemoglobin oxygen saturation decreased, peak pressure increased and lung injury scores were higher in three OLV groups at 3 h of OLV. All these indexes showed no differences between the three OLV groups. During right-OLV modeling, less time was spent in the blocker group (6±2 min), compared with the other two OLV groups (13±4 min in deep intubation group, P<0.05; 33±9 min in clamp group, P<0.001); more blood loss was observed in clamp group (11.7±2.8 ml), compared with the other two OLV groups (2.3±0.5 ml in deep intubation group, P<0.001; 2.1±0.6 ml in blocker group, P<0.001). The first-time and final success rate of modeling showed no differences among the three OLV groups. Deep intubation of the self-made bronchial blocker into the left main bronchus is an easy, effective and reliable method to establish a right-OLV model in rabbits.

Lung Injury After One-Lung Ventilation: A Review of the Pathophysiologic Mechanisms Affecting the Ventilated and the Collapsed Lung

Lung injury is the leading cause of death after thoracic surgery. Initially recognized after pneumonectomy, it has since been described after any period of 1-lung ventilation (OLV), even in the absence of lung resection. Overhydration and high tidal volumes were thought to be responsible at various points; however, it is now recognized that the pathophysiology is more complex and multifactorial. All causative mechanisms known to trigger ventilator-induced lung injury have been described in the OLV setting. The ventilated lung is exposed to high strain secondary to large, nonphysiologic tidal volumes and loss of the normal functional residual capacity. In addition, the ventilated lung experiences oxidative stress, as well as capillary shear stress because of hyperperfusion. Surgical manipulation and/or resection of the collapsed lung may induce lung injury. Re-expansion of the collapsed lung at the conclusion of OLV invariably induces duration-dependent, ischemia-reperfusion injury. Inflammatory cytokines are released in response to localized injury and may promote local and contralateral lung injury. Protective ventilation and volatile anesthesia lessen the degree of injury; however, increases in biochemical and histologic markers of lung injury appear unavoidable. The endothelial glycocalyx may represent a common pathway for lung injury creation during OLV, because it is damaged by most of the recognized lung injurious mechanisms. Experimental therapies to stabilize the endothelial glycocalyx may afford the ability to reduce lung injury in the future. In the interim, protective ventilation with tidal volumes of 4 to 5 mL/kg predicted body weight, positive end-expiratory pressure of 5 to 10 cm H2O, and routine lung recruitment should be used during OLV in an attempt to minimize harmful lung stress and strain. Additional strategies to reduce lung injury include routine volatile anesthesia and efforts to minimize OLV duration and hyperoxia.

Prophylactic methylprednisolone to reduce inflammation and improve outcomes from one lung ventilation in children: a randomized clinical trial

BACKGROUND

One lung ventilation (OLV) results in inflammatory and mechanical injury, leading to intraoperative and postoperative complications in children. No interventions have been studied in children to minimize such injury.

OBJECTIVE

We hypothesized that a single 2-mg·kg(-1) dose of methylprednisolone given 45-60 min prior to lung collapse would minimize injury from OLV and improve physiological stability.

METHODS

Twenty-eight children scheduled to undergo OLV were randomly assigned to receive 2 mg·kg(-1) methylprednisolone (MP) or normal saline (placebo group) prior to OLV. Anesthetic management was standardized, and data were collected for physiological stability (bronchospasm, respiratory resistance, and compliance). Plasma was assayed for inflammatory markers related to lung injury at timed intervals related to administration of methylprednisolone.

RESULTS

Three children in the placebo group experienced clinically significant intraoperative and postoperative respiratory complications. Respiratory resistance was lower (P = 0.04) in the methylprednisolone group. Pro-inflammatory cytokine IL-6 was lower (P = 0.01), and anti-inflammatory cytokine IL-10 was higher (P = 0.001) in the methylprednisolone group. Tryptase, measured before and after OLV, was lower (P = 0.03) in the methylprednisolone group while increased levels of tryptase were seen in placebo group after OLV (did not achieve significance). There were no side effects observed that could be attributed to methylprednisolone in this study.

CONCLUSIONS

Methylprednisolone at 2 mg·kg(-1) given as a single dose prior to OLV provides physiological stability to children undergoing OLV. In addition, methylprednisolone results in lower pro-inflammatory markers and higher anti-inflammatory markers in the children's plasma.

Limb remote ischemic preconditioning attenuates lung injury after pulmonary resection under propofol-remifentanil anesthesia: a randomized controlled study

BACKGROUND

Remote ischemic preconditioning (RIPC) may confer the protection in critical organs. The authors hypothesized that limb RIPC would reduce lung injury in patients undergoing pulmonary resection.

METHODS

In a randomized, prospective, parallel, controlled trial, 216 patients undergoing elective thoracic pulmonary resection under one-lung ventilation with propofol-remifentanil anesthesia were randomized 1:1 to receive either limb RIPC or conventional lung resection (control). Three cycles of 5-min ischemia/5-min reperfusion induced by a blood pressure cuff served as RIPC stimulus. The primary outcome was PaO2/FIO2. Secondary outcomes included other pulmonary variables, the incidence of in-hospital complications, markers of oxidative stress, and inflammatory response.

RESULTS

Limb RIPC significantly increased PaO2/FIO2 compared with control at 30 and 60 min after one-lung ventilation, 30 min after re-expansion, and 6 h after operation (238 ± 52 vs. 192 ± 67, P = 0.03; 223 ± 66 vs. 184 ± 64, P = 0.01; 385 ± 61 vs. 320 ± 79, P = 0.003; 388 ± 52 vs. 317 ± 46, P = 0.001, respectively). In comparison with control, it also significantly reduced serum levels of interleukin-6 and tumor necrosis factor-α at 6, 12, 24, and 48 h after operation and malondialdehyde levels at 60 min after one-lung ventilation and 30 min after re-expansion (all P < 0.01). The incidence of acute lung injury and the length of postoperative hospital stay were markedly reduced by limb RIPC compared with control (all P < 0.05).

CONCLUSION

Limb RIPC attenuates acute lung injury via improving intraoperative pulmonary oxygenation in patients without severe pulmonary disease after lung resection under propofol-remifentanil anesthesia.

From "awake" to "monitored anesthesia care" thoracic surgery: A 15 year evolution

Although general anesthesia still represents the standard when performing thoracic surgery, the interest toward alternative methods is increasing. These have evolved from the employ of just local or regional analgesia techniques in completely alert patients (awake thoracic surgery), to more complex protocols entailing conscious sedation and spontaneous ventilation. The main rationale of these methods is to prevent serious complications related to general anesthesia and selective ventilation, such as tracheobronchial injury, acute lung injury, and cardiovascular events. Trends toward shorter hospitalization and reduced overall costs have also been indicated in preliminary reports. Monitored anesthesia care in thoracic surgery can be successfully employed to manage diverse oncologic conditions, such as malignant pleural effusion, peripheral lung nodules, and mediastinal tumors. Main non-oncologic indications include pneumothorax, emphysema, pleural infections, and interstitial lung disease. Furthermore, as the familiarity with this surgical practice has increased, major operations are now being performed this way. Despite the absence of randomized controlled trials, there is preliminary evidence that monitored anesthesia care protocols in thoracic surgery may be beneficial in high-risk patients, with non-inferior efficacy when compared to standard operations under general anesthesia. Monitored anesthesia care in thoracic surgery should enter the armamentarium of modern thoracic surgeons, and adequate training should be scheduled in accredited residency programs.

Simvastatin attenuates neutrophil recruitment in one-lung ventilation model in rats

PURPOSE

To investigate the anti-inflammatory effects of simvastatin in rats undergoing one-lung ventilation (OLV) followed by lung re-expansion.

METHODS

Male Wistar rats (n=30) were submitted to 1-h OLV followed by 1-h lung re-expansion. Treated group received simvastatin (40 mg/kg for 21 days) previous to OLV protocol. Control group received no treatment or surgical/ventilation interventions. Measurements of pulmonary myeloperoxidase (MPO) activity, pulmonary protein extravasation, and serum levels of cytokines and C-reactive protein (CRP) were performed.

RESULTS

OLV significantly increased the MPO activity in the collapsed and continuously ventilated lungs (31% and 52% increase, respectively) compared with control (p<0.05). Treatment with simvastatin significantly reduced the MPO activity in the continuously ventilated lung but had no effect on lung edema after OLV. The serum IL-6 and CRP levels were markedly higher in OLV group, but simvastatin treatment failed to affect the production of these inflammatory markers. Serum levels of IL-1β, TNF-α and IL-10 remained below the detection limit in all groups.

CONCLUSIONS

In an experimental one-lung ventilation model pre-operative treatment with simvastatin reduces remote neutrophil infiltration in the continuously ventilated lung. Our findings suggest that simvastatin may be of therapeutic value in OLV-induced pulmonary inflammation deserving clinical investigations.

Application of indigenous continuous positive airway pressure during one lung ventilation for thoracic surgery

During one lung ventilation (OLV) hypoxemia may occur due to ventilation-perfusion mismatch. It can be prevented with application of ventilation strategy that prevents atelectasis while minimally impairing perfusion of the dependant lung. Here, two cases are reported who required OLV and in whom hypoxemia could be prevented with the application of continuous positive airway pressure to the deflated or non-dependant lung, using an indigenous technique. We suggest use of this technique which is easy to be employed during the intraoperative period.

Nitric oxide and endothelin-1 release after one-lung ventilation during thoracoabdominal esophagectomy

One-lung ventilation (OLV) is applied during esophagectomy to improve exposure during the thoracic part of the operation. Collapse of lung tissue, shunting of pulmonary blood flow, and changes in alveolar oxygenation during and after OLV may possibly induce an ischemia-reperfusion response in the lung, which may affect the pulmonary endothelium. Such a reaction might thereby contribute to the frequently occurring respiratory complications among these patients. In this small trial, 30 patients were randomized to either OLV (n= 16) or two-lung ventilation (TLV, n= 14) during esophagectomy. Central venous and arterial plasma samples were taken before and after OLV/TLV for analysis of nitrite and a metabolite of nitric oxide (NO), and also during the 1st, 2nd, 3rd, and 10th postoperative day for analysis of endothelin, another endothelium-derived vasoactive mediator. Lung biopsies were taken before and after OLV or TLV, and analyzed regarding immunofluorescence for isoform of NO synthase, a protein upregulated during inflammatory response and also vascular congestion. No changes in lung isoform of NO synthase immunofluorescence or vascular congestion were registered after neither OLV nor TLV. Plasma nitrite and endothelin levels were similar in the two study groups. We conclude that OLV does not seem to have any influence on key regulators of pulmonary vascular tone and inflammation, i.e. NO and endothelin. From this perspective, OLV seems to be a safe method, which defends its clinical position to facilitate surgical exposure during thoracoabdominal esophagectomy.

Surfactant administration prior to one lung ventilation: physiological and inflammatory correlates in a piglet model

OBJECTIVES

To test the hypothesis that surfactant, when given prophylactically during one lung ventilation (OLV), improves physiological stability and reduces inflammation.

METHODS

Prospective controlled animal study. After 30 min of mechanical ventilation, surfactant was administered to the left lung of the treatment group. Right lung mechanical ventilation continued for 3 hr, after which the left lung was unblocked. Bilateral mechanical ventilation was continued for 30 min thereafter. Physiological parameters and biomarkers of inflammation in plasma, lung tissue homogenates, and bronchoalveolar lavage (BAL) were measured.

MEASUREMENTS AND MAIN RESULTS

Oxygenation improved in the surfactant group, reaching statistical significance at 3 hr of OLV and again after 30 min of bilateral mechanical ventilation following the OLV. Plasma levels of interleukin (IL)-1 β, IL-6, and tumor necrosis factor (TNF)-α showed a trend for reduction. The lung homogenates from the ventilated lungs had significantly lower levels of IL-1 β (P < 0.01) and IL-6 (P < 0.01). The BAL specimen showed an overall reduction in the cytokine levels; IL-1 β was significantly lower in the ventilated lungs (P < 0.01).

CONCLUSIONS

Surfactant administration improves oxygenation and decreases inflammation, as evidenced by a decrease in several inflammatory cytokines both in the plasma and lungs of a piglet model of OLV.

The effects of anesthetic preconditioning with sevoflurane in an experimental lung autotransplant model in pigs

BACKGROUND

Ischemia-reperfusion lung injury is doubly important in thoracic surgery because of the associated ventilation damage to 1 lung. In this study we evaluated the cytoprotective effects of sevoflurane in a pulmonary autotransplant model in pigs.

METHODS

Twenty Large White pigs undergoing pneumonectomy plus lung autotransplant were divided into 2 10-member groups on the basis of the anesthetic received (propofol or sevoflurane). Proinflammatory mediators, oxidative stress, nitric oxide metabolism, and hemodynamic and blood variables were measured at 5 different time points.

RESULTS

There was an increase of oxidative stress markers and proinflammatory mediators in the propofol group, whereas the hemodynamic variables were similar in both groups.

CONCLUSIONS

We demonstrated that sevoflurane decreased the inflammatory response and oxidative stress in a live ischemia-reperfusion lung model.

Human models of acute lung injury

Acute lung injury (ALI) is a syndrome that is characterised by acute inflammation and tissue injury that affects normal gas exchange in the lungs. Hallmarks of ALI include dysfunction of the alveolar-capillary membrane resulting in increased vascular permeability, an influx of inflammatory cells into the lung and a local pro-coagulant state. Patients with ALI present with severe hypoxaemia and radiological evidence of bilateral pulmonary oedema. The syndrome has a mortality rate of approximately 35% and usually requires invasive mechanical ventilation. ALI can follow direct pulmonary insults, such as pneumonia, or occur indirectly as a result of blood-borne insults, commonly severe bacterial sepsis. Although animal models of ALI have been developed, none of them fully recapitulate the human disease. The differences between the human syndrome and the phenotype observed in animal models might, in part, explain why interventions that are successful in models have failed to translate into novel therapies. Improved animal models and the development of human in vivo and ex vivo models are therefore required. In this article, we consider the clinical features of ALI, discuss the limitations of current animal models and highlight how emerging human models of ALI might help to answer outstanding questions about this syndrome.

Does a protective ventilation strategy reduce the risk of pulmonary complications after lung cancer surgery?: a randomized controlled trial

BACKGROUND

Protective ventilation strategy has been shown to reduce ventilator-induced lung injury in patients with ARDS. In this study, we questioned whether protective ventilatory settings would attenuate lung impairment during one-lung ventilation (OLV) compared with conventional ventilation in patients undergoing lung resection surgery.

METHODS

One hundred patients with American Society of Anesthesiology physical status 1 to 2 who were scheduled for an elective lobectomy were enrolled in the study. During OLV, two different ventilation strategies were compared. The conventional strategy (CV group, n=50) consisted of FIO2 1.0, tidal volume (Vt) 10 mL/kg, zero end-expiratory pressure, and volume-controlled ventilation, whereas the protective strategy (PV group, n=50) consisted of FIO2 0.5, Vt 6 mL/kg, positive end-expiratory pressure 5 cm H2O, and pressure-controlled ventilation. The composite primary end point included PaO2/FIO2<300 mm Hg and/or the presence of newly developed lung lesions (lung infiltration and atelectasis) within 72 h of the operation. To monitor safety during OLV, oxygen saturation by pulse oximeter (SpO2), PaCO2, and peak inspiratory pressure (PIP) were repeatedly measured.

RESULTS

During OLV, although 58% of the PV group needed elevated FIO2 to maintain an SpO2>95%, PIP was significantly lower than in the CV group, whereas the mean PaCO2 values remained at 35 to 40 mm Hg in both groups. Importantly, in the PV group, the incidence of the primary end point of pulmonary dysfunction was significantly lower than in the CV group (incidence of PaO2/FIO2<300 mm Hg, lung infiltration, or atelectasis: 4% vs 22%, P<.05).

CONCLUSION

Compared with the traditional large Vt and volume-controlled ventilation, the application of small Vt and PEEP through pressure-controlled ventilation was associated with a lower incidence of postoperative lung dysfunction and satisfactory gas exchange.

TRIAL REGISTRY

Australian New Zealand Clinical Trials Registry; No.: ACTRN12609000861257; URL: www.anzctr.org.au.

Protective ventilation to reduce inflammatory injury from one lung ventilation in a piglet model

OBJECTIVES

To test the hypothesis that protective ventilation strategy (PVS) as defined by the use of low stretch ventilation (tidal volume of 5 ml x kg(-1) and employing 5 cm of positive end expiratory pressure (PEEP) during one lung ventilation (OLV) in piglets would result in reduced injury compared to a control group of piglets who received the conventional ventilation (tidal volume of 10 ml x kg(-1) and no PEEP).

BACKGROUND

PVS has been found to be beneficial in adults to minimize injury from OLV. We designed the current study to test the beneficial effects of PVS in a piglet model of OLV.

METHODS

Ten piglets each were assigned to either 'Control' group (tidal volume of 10 ml x kg(-1) and no PEEP) or 'PVS' group (tidal volume of 5 ml x kg(-1) during the OLV phase and PEEP of 5 cm of H2O throughout the study). Experiment consisted of 30 min of baseline ventilation, 3 h of OLV, and again 30 min of bilateral ventilation. Respiratory parameters and proinflammatory markers were measured as outcome.

RESULTS

There was no difference in PaO2 between groups. PaCO2 (P < 0.01) and ventilatory rate (P < 0.01) were higher at 1.5 h OLV and at the end point in the PVS group. Peak inflating pressure (PIP) and pulmonary resistance were higher (P < 0.05) in the control group at 1.5 h OLV. tumor necrosis factor-alpha (P < 0.04) and IL-8 were less (P < 0.001) in the plasma from the PVS group, while IL-6 and IL-8 were less (P < 0.04) in the lung tissue from ventilated lungs in the PVS group.

CONCLUSIONS

Based on this model, PVS decreases inflammatory injury both systemically and in the lung tissue with no adverse effect on oxygenation, ventilation, or lung function.

Low dose methylprednisolone prophylaxis to reduce inflammation during one-lung ventilation

BACKGROUND

The specific aim of this study was to examine the efficacy of a low dose of methylprednisolone in minimizing inflammatory response in juvenile piglets when given 45-60 min prior to onset of one-lung ventilation.

METHODS

Twenty piglets aged 3 weeks were assigned to either the control group (n = 10) or methylprednisolone group (n = 10). The animals were anesthetized and after 30 min of ventilation, they had their left lung blocked. Ventilation was continued via right lung for 3 h. The left lung was then unblocked. Following another 30 min of bilateral ventilation, the animals were euthanized and both lungs were harvested. The methylprednisolone group had a single dose (2 mg x kg(-1)) of methylprednisolone given i.v. 45-60 min prior to onset of one-lung ventilation. Physiological parameters (PaO2, resistance, and compliance) and markers of inflammation (tumor necrosis factor [TNF]-alpha, interleukin [IL]-1beta, IL-6, and IL-8) were measured at baseline and every 30 min thereafter. Lung tissue homogenates from both collapsed and ventilated lungs were analyzed for TNF-alpha, IL-1beta, IL-6, and IL-8.

RESULTS

The methylprednisolone group had higher partial pressure of oxygen (P = 0.01), lower plasma levels of TNF-alpha (P = 0.03) and IL-6 (P = 0.001) when compared with control group. Lung tissue homogenate in the methylprednisolone group had lower levels of TNF-alpha (P < 0.05), IL-1beta (P < 0.05), and IL-8 (P < 0.05) in both the collapsed and the ventilated lungs.

CONCLUSIONS

In a piglet model of one-lung ventilation, use of prophylactic methylprednisolone prior to collapse of the lung improves lung function and decreases systemic pro-inflammatory response. In addition, in the piglets who received methylprednisolone, there were reduced levels of inflammatory mediators in both the collapsed and ventilated lungs.

Early detection of acute lung injury uncoupled to hypoxemia in pigs using ultrasound lung comets

OBJECTIVE

Oleic acid-induced lung injury is an established experimental model of acute lung injury in pigs and is considered to reproduce the early exudative phase of acute respiratory distress syndrome. Ultrasound lung comets are an echographic sign of extravascular lung water, originating from thickened interlobular septa. The objective of this study was to evaluate the timing and relationship between the number of ultrasound lung comets, the Pao2/Fio2 ratio, and the static respiratory compliance in an experimental model of oleic acid-induced lung injury in pigs.

DESIGN

Laboratory experiment.

SETTING

Research institute.

SUBJECTS

Ten anesthetized pigs.

INTERVENTIONS

Acute lung injury was induced by injection of oleic acid (0.1 mL/kg, intravenously). Ultrasound lung comets, Pao2/Fio2, and static respiratory compliance were measured at baseline and at 15, 30, 60, and 90 mins after the injection of oleic acid. We evaluated ultrasound lung comets by transthoracic echography (7.5-MHz vascular probe), scanning on right and left hemithoraxes at 12 predefined scanning sites.

MEASUREMENTS AND MAIN RESULTS

Acute lung injury/acute respiratory distress syndrome was present in all pigs at 90 mins. The number of ultrasound lung comets increased over time and was consistently earlier than the decrease in Pao2/Fio2. At 15 mins, ultrasound lung comets were markedly increased, but no significant changes in Pao2/Fio2 were observed. Accordingly, static respiratory compliance was dramatically reduced at 15 mins compared with baseline (17.04 +/- 1.82 vs. 34.84 +/- 2.62 mL/cm H2O, p < .05).

CONCLUSIONS

Ultrasound lung comets, assessed by transthoracic echography, detected extravascular lung water accumulation very early in the course of the oleic acid lung injury in pigs, in the presence of a normal Pao2/Fio2. These results suggest that ultrasound lung comets could be a very early, noninvasive, and simple method to detect and quantify pulmonary edema in acute lung injury.

One-lung ventilation: For how long?

OBJECTIVE

Lung injury induced by one-lung ventilation is rare, but it is a condition that may result in high mortality. This study evaluates the effects of one-lung ventilation and occlusion time on collapsed and contralateral lungs.

METHODS

Sprague-Dawley rats were allocated randomly into 7 groups consisting of 6 animals each: sham; O1, 1 hour of occlusion/2 hours of re-expansion; C1, 3 hours of mechanical ventilation control; O2, 2 hours of occlusion/2 hours of re-expansion; C2, 4 hours of mechanical ventilation control; O3, 3 hours of occlusion/2 hours of re-expansion; and C3, 5 hours of mechanical ventilation control groups. In the occlusion groups, the left lung was collapsed by bronchial occlusion. Malondialdehyde activity was determined in the blood, and myeloperoxidase and malondialdehyde activity was determined in the collapsed and contralateral lungs. Lung tissues were also examined histopathologically.

RESULTS

Malondialdehyde and myeloperoxidase levels rose as occlusion duration increased. This increase was greater in the occlusion groups than that in their own control groups. Increases were significant in the O2 compared with the O1 groups (P < .005). Histologically, tissue damage increased as occlusion time rose injury in collapsed and contralateral lungs. Injury was greater in the occlusion groups than injury in their own control groups (P < .005).

CONCLUSIONS

Our findings show that biochemical and histopathologic injury occur in collapsed and contralateral lungs in one-lung ventilation, and this injury increases as occlusion time rises. We believe that occlusion and occlusion time-related injury should be borne in mind in the clinic under conditions requiring the application of one-lung ventilation.