Single-lung ventilation and oxidative stress: a different perspective on a common practice

An optimal protective ventilation strategy in lung resection surgery: a prospective, single-center, three-arm randomized controlled trial

Protective ventilation reduces ventilator-induced acute lung injury postoperatively; however, the optimal strategy for one-lung ventilation (OLV) remains unclear. This study compared three protective ventilation strategies with a postoperative partial pressure of oxygen (PaO2)/fraction of inspired oxygen (FiO2) ratio to reduce the incidence of immediate postoperative pulmonary complications (PPCs) in patients undergoing lung resection surgery. Eighty-seven patients with ASA physical status I-III requiring OLV for lung resection surgery were randomized into three groups according to the applied ventilation strategies: low tidal volume (VT) of 4 mL/kg of predicted body weight (PBW) (LV group), medium VT of 6 mL/kg of PBW (MV group), and high VT of 8 mL/kg of PBW (HV group). All patients received 5 cmH2O of positive end-expiratory pressure (PEEP). The primary outcome was the mean difference of PaO2/FiO2 ratio after surgery. The radiologic findings of acute lung injuries were also evaluated. The incidence of immediate PPCs was determined by PaO2/FiO2 ratio of < 300 mmHg and/or newly developed radiological findings within 72 h after surgery. The MV group showed the highest PaO2/FiO2 ratio at 6 h postoperatively (P = 0.010). There were no significant among-group differences in radiological findings in 3 postoperative days. The MV group showed the lowest incidence of immediate PPCs among the three groups (P = 0.007). During OLV in lung resection surgery, protective ventilation at a VT of 6 mL/kg with PEEP of 5 cmH2O may achieve a higher postoperative PaO2/FiO2 ratio, reducing the incidence of immediate PPCs.

Association between inspired oxygen fraction and development of postoperative pulmonary complications in thoracic surgery: a multicentre retrospective cohort study

BACKGROUND

Limited data exist to guide oxygen administration during one-lung ventilation for thoracic surgery. We hypothesised that high intraoperative inspired oxygen fraction during lung resection surgery requiring one-lung ventilation is independently associated with postoperative pulmonary complications (PPCs).

METHODS

We performed this retrospective multicentre study using two integrated perioperative databases (Multicenter Perioperative Outcomes Group and Society of Thoracic Surgeons General Thoracic Surgery Database) to study adult thoracic surgical procedures using one-lung ventilation. The primary outcome was a composite of PPCs (atelectasis, acute respiratory distress syndrome, pneumonia, respiratory failure, reintubation, and prolonged ventilation >48 h). The exposure of interest was high inspired oxygen fraction (FiO2), defined by area under the curve of a FiO2 threshold > 80%. Univariate analysis and logistic regression modelling assessed the association between intraoperative FiO2 and PPCs.

RESULTS

Across four US medical centres, 141/2733 (5.2%) procedures conducted in 2716 patients (55% female; mean age 66 yr) resulted in PPCs. FiO2 was univariately associated with PPCs (adjusted OR [aOR]: 1.17, 95% confidence interval [CI]: 1.04-1.33, P=0.012). Logistic regression modelling showed that duration of one-lung ventilation (aOR: 1.20, 95% CI: 1.03-1.41, P=0.022), but not the time-weighted average FiO2 (aOR: 1.01, 95% CI: 1.00-1.02, P=0.165), was associated with PPCs.

CONCLUSIONS

Our results do not support limiting the inspired oxygen fraction for the purpose of reducing postoperative pulmonary complications in thoracic surgery involving one-lung ventilation.

Down-regulating lncRNA KCNQ1OT1 relieves type II alveolar epithelial cell apoptosis during one-lung ventilation via modulating miR-129-5p/HMGB1 axis induced pulmonary endothelial glycocalyx

OBJECTIVE

Endothelial glycocalyx (EG) maintains vascular homeostasis and is destroyed after one-lung ventilation (OLV)-induced lung injury. Long noncoding RNAs (lncRNAs) are critically involved in various lung injuries. This study aimed to investigate the role and regulatory mechanism of KCNQ1 overlapping transcript 1 (KCNQ1OT1) in OLV-induced lung injury and LPS-induced type II alveolar epithelial cell (AECII) apoptosis.

METHODS

The rat OLV model was established, and the effects of KCNQ1OT1 on OLV-induced ALI in vivo were explored. Bax and Caspase-3 expression in rat lung tissues was measured by immunochemistry (IHC). AECIIs were isolated from rat lungs and treated with LPS or normal saline (control) for in vitro analysis. The expression of KCNQ1OT1, miR-129-5p, and HMGB1 was measured by quantitative real-time PCR (qRT-PCR) or Western blot (WB). Cell proliferation and apoptosis were examined by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide (MTT) and flow cytometry. The downstream targets of KCNQ1OT1 were predicted by bioinformatics, and the binding relationship between KCNQ1OT1 and miR-129-3p was verified by dual-luciferase reporter assays. The potential target of miR-129-5p was further explored on the Targetscan website and revealed to target HMGB1. Enzyme-linked immunosorbent assay (ELISA) or WB was adopted to determine the levels of IL-1β, TNF-α, MDA, SOD, heparanase (HPA), matrix metalloproteinase 9 (MMP9), heparan sulfate (HS) and syndecan-1 (SDC-1).

RESULTS

KCNQ1OT1 and HMGB1 were up-regulated during OLV-induced lung injury, and their expression was positively correlated. KCNQ1OT1 knockdown reduced OLV-induced pulmonary edema and lung epithelial cell apoptosis, increased vascular permeability, reduced IL-1β, TNF-α, MDA, and SOD levels and glycocalyx markers by targeting miR-129-5p or upregulating HMGB1. Overexpressing KCNQ1OT1 promoted cell apoptosis, reduced cell proliferation, aggravated inflammation and oxidative stress, and up-regulated HMGB1, HPA and MMP9 in LPS-treated AECIIs, while the HMGB1 silencing showed the opposite effects. MiR-129-5p mimics partially eliminated the KCNQ1OT1-induced effects, while recombinant HMGB1 restored the effects of miR-129-5p overexpression on AECIIs. Additionally, KCNQ1OT1 was demonstrated to promote the activation of the p38 MAPK/Akt/ERK signaling pathways in AECIIs via HMGB1.

CONCLUSION

KCNQ1OT1 knockdown alleviated AECII apoptosis and EG damage during OLV by targeting miR-129-5p/HMGB1 to inactivate the p38 MAPK/Akt/ERK signaling. The findings of our study might deepen our understanding of the molecular basis in OLV-induced lung injury and provide clues for the targeted disease management.

Effects of epidurally administered dexmedetomidine and dexamethasone on postoperative pain, analgesic requirements, inflammation, and oxidative stress in thoracic surgery

The aim of this study was to compare the effects of dexmedetomidine and dexamethasone as adjuvants to preoperative epidural administration of local anesthetic (ropivacaine) in thoracic surgery on the postoperative level of pain, use of analgesics, inflammation, and oxidative stress. The study enrolled 42 patients who underwent elective thoracic surgery in a one-year period at the University Hospital Dubrava (Zagreb, Croatia). Based on a computer-generated randomization list the patients were assigned to the dexmedetomidine (n = 18) or dexamethasone (n = 24) group. Postoperatively, patients of dexmedetomidine group reported lower pain (VAS value 1 h post surgery, 3.4 ± 2.7 vs. 5.4 ± 1.8, dexmedetomidine vs. dexamethasone, p < 0.01) and had lower anal-gesic requirements in comparison with dexamethasone group. Thus, dexmedetomidine in comparison with dexamethasone was more efficient in lowering pain and analgesia requirements 24 h after the surgery. On the contrary, dexamethasone had better anti-inflammatory properties (CRP level 24 h post surgery, 131.9 ± 90.7 vs. 26.0 ± 55.2 mg L-1, dexmedetomidine vs. dexamethasone, p < 0.01). Both dexmedetomidine and dexamethasone exhibited antioxidant effects, however, their antioxidant properties should be further explored. The results of this study improve current knowledge of pain control in thoracic surgery.

Unrecognized Pulmonary Hypertension in Non-Cardiac Surgical Patients: At-Risk Populations, Preoperative Evaluation, Intraoperative Management and Postoperative Complications

Pulmonary hypertension is a well-established independent risk factor for perioperative complications after elective non-cardiac surgery. Patients undergoing cardiac surgery are routinely evaluated for the presence of pulmonary hypertension in the preoperative period. Better monitoring in the postoperative critical care setting leads to more efficient management of potential complications. Data among patients with pulmonary hypertension undergoing elective non-cardiac surgery are scant. Moreover, the condition may be unidentified at the time of surgery. Also, monitoring after non-cardiac surgery can be very limited in the PACU setting, as opposed to the critical care setting. All these factors can result in a higher postoperative complication rate and poor outcomes.

Muscular tissue desaturation and pneumonia in patients receiving lung cancer surgery: a cohort study

BACKGROUND

Post-operative pneumonia (POP) is a common complication of lung cancer surgery, and muscular tissue oxygenation is a root cause of post-operative complications. However, the association between muscular tissue desaturation and POP in patients receiving lung cancer surgery has not been specifically studied. This study aimed to investigate the potential use of intra-operative muscular tissue desaturation as a predictor of POP in patients undergoing lung cancer surgery.

METHODS

This cohort study enrolled patients (≥55 years) who had undergone lobectomy with one-lung ventilation. Muscular tissue oxygen saturation (SmtO 2 ) was monitored in the forearm (over the brachioradialis muscle) and upper thigh (over the quadriceps) using a tissue oximeter. The minimum SmtO 2 was the lowest intra-operative measurement at any time point. Muscular tissue desaturation was defined as a minimum baseline SmtO 2 of <80% for >15 s. The area under or above the threshold was the product of the magnitude and time of desaturation. The primary outcome was the association between intra-operative muscular tissue desaturation and POP within seven post-operative days using multivariable logistic regression. The secondary outcome was the correlation between SmtO 2 in the forearm and that in the thigh.

RESULTS

We enrolled 174 patients. The overall incidence of muscular desaturation (defined as SmtO 2 < 80% in the forearm at baseline) was approximately 47.1% (82/174). The patients with muscular desaturation had a higher incidence of pneumonia than those without desaturation (28.0% [23/82] vs. 12.0% [11/92]; P  = 0.008). The multivariable analysis revealed that muscular desaturation was associated with an increased risk of pneumonia (odds ratio: 2.995, 95% confidence interval: 1.080-8.310, P  = 0.035) after adjusting for age, American Society of Anesthesiologists status, Assess Respiratory Risk in Surgical Patients in Catalonia score, smoking, use of peripheral nerve block, propofol, and study center.

CONCLUSION

Muscular tissue desaturation, defined as a baseline SmtO 2 < 80% in the forearm, may be associated with an increased risk of POP.

TRIAL REGISTRATION

No. ChiCTR-ROC-17012627.

Perioperative cardiovascular pathophysiology in patients undergoing lung resection surgery: a narrative review

Although thoracic surgery is understood to confer a high risk of postoperative respiratory complications, the substantial haemodynamic challenges posed are less well appreciated. This review highlights the influence of cardiovascular comorbidity on outcome, reviews the complex pathophysiological changes inherent in one-lung ventilation and lung resection, and examines their influence on cardiovascular complications and postoperative functional limitation. There is now good evidence for the presence of right ventricular dysfunction postoperatively, a finding that persists to at least 3 months. This dysfunction results from increased right ventricular afterload occurring both intraoperatively and persisting postoperatively. Although many patients adapt well, those with reduced right ventricular contractile reserve and reduced pulmonary vascular flow reserve might struggle. Postoperative right ventricular dysfunction has been implicated in the aetiology of postoperative atrial fibrillation and perioperative myocardial injury, both common cardiovascular complications which are increasingly being appreciated to have impact long into the postoperative period. In response to the physiological demands of critical illness or exercise, contractile reserve, flow reserve, or both can be overwhelmed resulting in acute decompensation or impaired long-term functional capacity. Aiding adaptation to the unique perioperative physiology seen in patients undergoing thoracic surgery could provide a novel therapeutic avenue to prevent cardiovascular complications and improve long-term functional capacity after surgery.

Olmesartan Attenuates Single-Lung Ventilation Induced Lung Injury via Regulating Pulmonary Microbiota

Single-lung ventilation (SLV) associated acute lung injury is similar to ischemia reperfusion (IR) injury which is usually occurred during lung surgery. Olmesartan (Olm), a novel angiotensin receptor blocker (ARB), has been reported to ameliorate organ IR injury. Several recent studies have shown that lung microbiota may be involved in pulmonary diseases, but the effect of pulmonary microbiota in SLV-induced lung injury has not been reported. This study aims to determine the mechanism of how Olm attenuates SLV induced lung injury. Our data showed that 7 days Olm treatment before modeling markedly alleviated SLV-induced lung injury by suppressing inflammation and reactive oxygen species. Bronchoalveolar lavage fluid samples from the injured side were collected for 16S rRNA gene-based sequencing analysis and 53 different bacteria at the genus and species levels were identified. Furthermore, the injured lung samples were collected for metabolomics analysis using liquid chromatography-mass spectrometry analyses to explore differential metabolites. The Kyoto Encyclopedia of Genes and Genomes (KEGG) was applied to analyze the correlation between differential metabolites and lung microbiota. A total of 38 pathways were identified according to differential metabolites and 275 relevant pathways were enriched via analyzing the microbial community, 24 pathways were both identified by analyzing either metabolites or microbiota, including pyrimidine metabolism, purine metabolism, aminoacyl-tRNA biosynthesis and ATP-binding cassette transporter. Besides classical blockage of the renin-angiotensin II system, Olm could also alleviate SLV-induced lung injury by rewiring the interaction between pulmonary microbiota and metabolites.

Perioperative Pulmonary Atelectasis: Part I. Biology and Mechanisms

Pulmonary atelectasis is common in the perioperative period. Physiologically, it is produced when collapsing forces derived from positive pleural pressure and surface tension overcome expanding forces from alveolar pressure and parenchymal tethering. Atelectasis impairs blood oxygenation and reduces lung compliance. It is increasingly recognized that it can also induce local tissue biologic responses, such as inflammation, local immune dysfunction, and damage of the alveolar-capillary barrier, with potential loss of lung fluid clearance, increased lung protein permeability, and susceptibility to infection, factors that can initiate or exaggerate lung injury. Mechanical ventilation of a heterogeneously aerated lung (e.g., in the presence of atelectatic lung tissue) involves biomechanical processes that may precipitate further lung damage: concentration of mechanical forces, propagation of gas-liquid interfaces, and remote overdistension. Knowledge of such pathophysiologic mechanisms of atelectasis and their consequences in the healthy and diseased lung should guide optimal clinical management.

Protective effects of dexmedetomidine on lung in rats with one-lung ventilation

Protective effect of dexmedetomidine (DEX) on the lungs of one-lung ventilation (OLV) rat model and its effect on inflammatory factors were investigated. Ninety-two rats were selected and divided into groups A, B, C and D (n=23) according to the principle of similar body weight. OLV rat model was established. Before modeling (15 min), rats in group C were injected with sodium chloride. Rats in group D were injected with DEX at a speed of 5 µg/kg/h. Group A rats were ventilated in both lungs for 2 h. Rats in groups B and C (0.9% sodium chloride injection + OLV) and in group D (DEX + OLV) were subjected to OLV for 2 h and bilateral ventilation for 10 min. Concentrations of interleukin (IL)-6, IL-10 and tumor necrosis factor-α (TNF-α) in lung tissue of rats were detected by ELISA. The malondialdehyde (MDA) concentration and superoxide dismutase (SOD) activity in rat lung tissue were detected by radioimmunoassay. Wet weight (W)/dry weight (D) of lung tissue was calculated and indexes of the four groups of rats were compared. Compared with group A, IL-6, TNF-α and MDA concentrations and W/D of lung tissue of rats in groups B, C and D were significantly increased (p<0.05); SOD activity and IL-10 concentration were significantly decreased (p<0.01). Compared with groups B and C, the concentrations of IL-6, TNF-α and W/D in rats of group D were significantly decreased (p<0.01), but IL-10 significantly increased (p<0.01). Compared with groups B and C, the MDA concentration in lung tissue of rats in group D was significantly decreased (p<0.01), but SOD activity significantly increased (p<0.01). DEX can inhibit the production of inflammatory factors in the development and progression of pulmonary inflammation. It can inhibit lipid peroxidation, relieve pulmonary edema, and reduce lung injury after OLV, sin order to protect the lung.