Bronchial transsection and reanastomosis in pigs with and without bronchial arterial circulation

Airway complications after lung transplantation: benefit of a conservative bronchoscopy strategy

Background

After lung transplantation (LT), between 2% and 25% of bronchial anastomoses develop complications requiring therapeutic intervention. The status of healing of both bronchial anastomoses and downhill airways are well described by the French consensual MDS standardized grading system (Macroscopic, Diameter, Suture). We analyzed risks factors for airway complications (AC) after transplantation and the way we managed them. We report here our challenging method of early rigid bronchoscopic intervention with airway stenting on bronchial healing.

Methods

All single center consecutives LTs were retrospectively analyzed between 2010-2016. Patient-level data (demographic, peri-operative data) and anastomosis-level data (surgical parameters, bronchoscopy findings) were monitored. The incidence and contributive factors of ACs are reported. We also reported modalities of the conservative treatment and outcome.

Results

A total of 121 LTs were performed, 39 single-lung and 82 bilateral sequential LT. Main indication for LT were cystic fibrosis (45%) and emphysema (25%) and 58 were male patients (n=70). After a waiting period of healing, 28 patients presented AC on 41 anastomoses (prevalence: 23%). A multivariate analysis found as contributive factors of ACs, post-operative infection by Aspergillus [odds ratio (OR) 2.7, 95% confidence interval (CI): 1.08-6.75; P=0.033] at the patient level, and at the anastomosis level, emphysema (OR 2.4, 95% CI: 1.02-5.6; P=0.045), early dehiscence (OR 11.2, 95% CI: 1.7-76; P=0.01) and cold ischemia time >264 min (OR 2.45, 95% CI: 1.08-5.6; P=0.03). All the 41 ACs were managed conservatively with rigid bronchoscopy (range, 1-10), 41 stents (21 in silicone and 20 fully-covered Silicone Expandable Metallic Stents) without major complication. Two AC were still under regular bronchoscopic care and silicone stenting for long left bronchus reason. No surgical intervention was needed. The 2-years overall survival rate where not different between AC group and controls, respectively 85% and 81%.

Conclusions

Airway healing after transplantation remains a scalable process and the French consensual MDS classification helped us for therapeutic decisions. Rigid bronchoscopy and safety use of current stenting devices may have the pivotal role in the conservative management of ACs, avoiding perilous situation of surgery for AC. Despite a high rate of AC, their favorable evolution may be explained by the cautious care of airway healing and maybe by the use of the Celsior antioxidant solution.

Anastomotic airway complications after lung transplantation: risk factors, treatment modalities and outcome-a single-centre experience

OBJECTIVES

Anastomotic airway complications give rise to morbidity and mortality after lung transplantation. Knowledge about contributing factors helps in adopting diagnostic and therapeutic strategies. Systematic endoscopic description and classification play a key role.

METHODS

A retrospective analysis of all bronchial anastomoses between 2005 and 2013 was performed to assess anastomotic complications and associated variables. Treatment modalities and outcome of endobronchial and surgical interventions are reported.

RESULTS

The prevalence of anastomotic airway complications in our cohort was 11%. Contributive factors were all recipient-dependent: microbial infection during the first postoperative trimester [odds ratio (OR) 3.4 (2.1-5.5); P < 0.0001], recipient age [OR 3.0 (1.3-7.1); P = 0.01], right-sided anastomosis [OR 2.5 (1.4-3.3); P = 0.001], the presence of microbiological colonization prior to transplantation [OR 1.8 (1.1-3.1); P = 0.02] and [Formula: see text] during the first 72 h after transplantation [OR 1.6 (1.1-2.7); P = 0.04]. Seventy-five percent of cases were managed conservatively, of which 93% evolved clinically favourable during follow-up. Our data support the use of the proposed MDS classification and show that MDS class M3b, D2x, Sxe or higher are associated with an increased intervention rate.

CONCLUSION

Anastomotic airway complications remain an important issue after lung transplantation. The identified risk factors may play a role in the pathophysiology of anastomotic complications. The indication for endobronchial intervention should be carefully considered based on endoscopic classification since most cases resolve or stabilize over time.

Lung transplant infection

Lung transplantation has become an accepted therapeutic procedure for the treatment of end‐stage pulmonary parenchymal and vascular disease. Despite improved survival rates over the decades, lung transplant recipients have lower survival rates than other solid organ transplant recipients. The morbidity and mortality following lung transplantation is largely due to infection‐ and rejection‐related complications. This article will review the common infections that develop in the lung transplant recipient, including the general risk factors for infection in this population, and the most frequent bacterial, viral, fungal and other less frequent opportunistic infections. The epidemiology, diagnosis, prophylaxis, treatment and outcomes for the different microbial pathogens will be reviewed. The effects of infection on lung transplant rejection will also be discussed.

Tissue hypoxaemia causes oedema, inflammation and fibrosis in porcine bronchial transsection

OBJECTIVES

Bronchial artery revascularization in lung transplantation is disputed. This study examined the physiological consequences of porcine bronchial transsection and reanastomosis with and without bronchial artery blood supply with relation to lung transplantation.

DESIGN

Translational, controlled animal study. Twelve pigs were operated through a left lateral thoracotomy. The left bronchus was transsected and reanastomosed. In the control group (n = 6), the bronchial arteries were preserved and in the study group (n = 6) they were severed. Bronchial mucosa blood flow (BMBF) was measured with laser-Doppler velocimetry and bronchial mucosa haemoglobin saturation and concentration with diffuse reflectance spectrophotometry. Measurements were made preoperatively, postoperatively and after 1 week.

RESULTS

In the study group, left postoperative BMBF was significantly lower than preoperatively (115 vs. 210 PU/s, p = 0.0001) and lower than in the control group (115 vs. 205 PU/s, p = 0.002). Repeated measurement ANOVA showed a significant treatment effect depending on time (p = 0.0034). The left mucosal haemoglobin saturation in the study group was significantly reduced postoperatively, 92% versus 61%, with a treatment effect depending on time (p = 0.0080). The reduction in left/right ratio of the mucosal haemoglobin concentration 1 week postoperatively in the study group was insignificant.

CONCLUSION

Bronchial transsection and reanastomosis without bronchial artery blood supply was followed by significant decrease in mucosal blood flow and saturation postoperatively, and also in tissue haemoglobin concentration at section, and provides a physiologic explanation of histological changes.

Topographic anatomy of bronchial arteries in the pig: a corrosion cast study

The anatomy of porcine bronchial circulation has not been fully described. The purpose of this study was to investigate the extrapulmonary topographic anatomy of bronchial arteries in pig. Ten pigs weighing 15-25 kg were studied. Between one and four bronchial arteries were found in each pig. The bronchoesophageal artery (BEA), tracheobronchial artery (TBA), inferior bronchial artery (IBA) and accessory bronchial artery (ABA) were present in 10/10, 8/10, 6/10 and 2/10 animals, respectively. The trunk of BEA had a diameter of about 3 mm, a length of 1-7 mm, and originated from the anterior and medial aspect of the descending thoracic aorta at the level between the 2nd and 4th thoracic vertebrae (T2-T4) in all animals. The extrapulmonary topographic anatomy of bronchial arteries in pigs exhibits similarities to that of humans. BEA is the main blood supplier of the porcine tracheobronchial tree with a relatively constant location of origin and a sufficient size for anastomosis. These characteristics render BEA the ideal vessel for bronchial revascularization in pigs.

Diffuse reflectance spectrophotometry with visible light: comparison of four different methods in a tissue phantom

The purpose of the study was to compare algorithms of four methods (plus two modifications) for spectrophotometric haemoglobin saturation measurements. Comparison was made in tissue phantoms basically consisting of a phosphate buffer, Intralipid and blood, allowing samples to be taken for reference measurements. Three experimental series were made. In experiment A (eight phantoms) we used the Knoefel method and measured specific extinction coefficients with a reflection spectrophotometer. In experiment B (six phantoms) the fully oxygenated phantoms were gradually deoxygenated with baker's yeast, and simultaneous measurements were made with our spectrophotometer and with a reference oxymeter (ABL-605) in 3 min intervals. For each spectrophotometric measurement haemoglobin saturation was calculated with all algorithms and modifications, and compared with reference. In experiment C (11 phantoms) we evaluated the ability of a modification of the Knoefel method to measure haemoglobin concentration in absolute quantities using extinction coefficients from experiment A.Results. Experiment A: with the Knoefel method extinction coefficients (+/-SD) for oxyhaemoglobin at 553.04 and 573.75 nm were 1.117 (+/-0.0396) ODmM(-1) and 1.680 (+/- 0.0815) ODmM(-1), respectively, and for deoxyhaemoglobin 1.205 (+/- 0.0514) ODmM(-1) and 0.953 (+/-0.0487) ODmM(-1), respectively. Experiment B: high correlation with the reference was found in all methods (r = 0.94-0.97). However, agreement varied from evidently wrong in method 3 and the original method 4 (e.g. saturation above 160%) to high agreement in method 2 as well as the modifications of methods 1 and 4, where oxygen dissociation curves were close to the reference method. Experiment C: with the modified Knoefel method the mean haemoglobin concentration difference from reference was 8.3% and the correlation was high (r = 0.91). We conclude that method 2 and the modifications of 1 and 4 were superior to the others, but depended on known values in the same or similar phantoms. The original method 1 was independent of results from the tissue phantoms, but agreement was slightly poorer. Method 3 and the original method 4 could not be recommended. The ability of the modified method 1 to measure haemoglobin concentration is promising, but needs further development.

Evaluation of factors damaging the bronchial wall in lung transplantation

BACKGROUND

Lung transplantation has become important in treating end-stage lung disease; however, bronchial complications are common. Lack of bronchial arterial circulation, ischemic time, and acute rejection episodes may damage the bronchial wall. In this study, we analyzed factors that may hamper bronchial airway healing, requiring intervention after lung transplantation.

METHODS

We collected data from a consecutive series of 81 transplantations performed between 1993 and 2002 and evaluated recipients for bronchial complications. In 30 single and 51 sequential bilateral lung transplantations, a total of 132 anastomoses were performed. Four patients (3 bilateral and 1 single lung transplant recipients who died within the first 14 post-operative days were excluded from the analysis. Finally, 125 lung grafts remained for statistical analysis of factors influencing bronchial complications.

RESULTS

Peri-operative mortality was 8.9%. Eleven patients (14.7%) experienced severe bronchial complications in 16 of 125 evaluated bronchial anastomoses (12.8%) and required surgical treatment or bronchoscopic interventional therapy. In a multivariate logistic regression model, severe reperfusion edema (adjusted odds ratio, 8.3; p = 0.002) and rejection episode within the 1st post-operative month (adjusted odds ratio, 4.1; p = 0.036) were associated with bronchial complications. Using the univariate model, we found that factors such as interleukin-2-antibody induction therapy, immunosuppression, or bronchial anastomotic technique had significant influence on bronchial healing, whereas we could not confirm this when using multivariate anasysis.

CONCLUSIONS

Preventing reperfusion edema with optimized lung preservation and with early and aggressive medical treatment or mechanical hemodynamical support (e.g., veno-arterial extra corporal membrane oxygenation are necessary to avoid prolonged ventilation dependence, which may result in bronchial complications. Furthermore, avoiding early rejection episodes promotes uncomplicated bronchial healing.

Responses of the bronchial and pulmonary circulations to short-term nitric oxide inhalation before and after endotoxaemia in the pig

The physiological responses of the bronchial circulation to acute lung injury and endotoxin shock are largely unexplored territory. This study was carried out to study the responsiveness of the bronchial circulation to nitric oxide (NO) inhalation before and after endotoxaemia, in comparison with the pulmonary circulation, as well as to study changes in bronchial blood flow during endotoxaemia. Six anaesthetized pigs (pre-treated with the cortisol-synthesis inhibitor metyrapone) received an infusion of 10 microg/kg endotoxin during 2 h. Absolute bronchial blood flow was measured via an ultrasonic flow probe around the bronchial artery. The pigs received increasing doses of inhaled NO over 5 min each (0, 0.2, 2 and 20 ppm) before and after 4 h of endotoxaemia. The increase in bronchial vascular conductance during 5 min of inhalation of 20 ppm NO before endotoxin shock was significantly higher (area under curve (AUC) 474.2 +/- 84.5% change) than after endotoxin shock (AUC 118.2 +/- 40.4%, P < 0.05 Mann-Whitney U-test). The reduction of the pulmonary arterial pressure by 20 ppm NO was not different. A short rebound effect of the pulmonary arterial pressure occurred after discontinuation of inhaled NO before endotoxaemia (AUC values above baseline 54.4 +/- 19.7% change), and was virtually abolished after endotoxaemia (AUC 6.1 +/- 4.0%, P = 0.052, Mann-Whitney U-test). Our results indicate that the responsiveness of the bronchial circulation to inhalation of increasing doses of inhaled NO during endotoxin shock clearly differ from the responsiveness of the pulmonary circulation. The reduced responsiveness of the bronchial circulation is probably related to decreased driving pressure for the bronchial blood flow. The absence of the short rebound effect on pulmonary arterial pressure (PAP) after induction of shock could be related to maximum constriction of the pulmonary vessels at 4 h.