Technical Pearls for Swine Lung Transplantation

Video-assisted thoracoscopic surgery simulation and training: a comprehensive literature review

BACKGROUND

Video-assisted thoracic surgery (VATS) has become the standard for lung cancer diagnosis and treatment. However, this surgical technique requires specific and dedicated training. In the past 20 years, several simulator systems have been developed to promote VATS training. Advances in virtual reality may facilitate its integration into the VATS training curriculum. The present review aims to first provide a comprehensive overview of the simulators for thoracoscopic surgery, focused especially on simulators for lung lobectomy; second, it explores the role and highlights the possible efficacy of these simulators in the surgical trainee curriculum.

METHODS

A literature search was conducted in the PubMed, EMBASE, Science Direct, Scopus and Web of Science databases using the following keywords combined with Boolean operators "AND" and "OR": virtual reality, VR, augmented reality, virtual simulation, mixed reality, extended reality, thoracic surgery, thoracoscopy, VATS, video-assisted thoracoscopic surgery, simulation, simulator, simulators, training, and education. Reference lists of the identified articles were hand-searched for additional relevant articles to be included in this review.

RESULTS

Different types of simulators have been used for VATS training: synthetic lung models (dry simulators); live animals or animal tissues (wet simulators); and simulators based on virtual or augmented reality. Their role in surgical training has been generally defined as useful. However, not enough data are available to ascertain which type is the most appropriate.

CONCLUSIONS

Simulator application in the field of medical education could revolutionize the regular surgical training curriculum. Further studies are required to better define their impact on surgeons' training programs and, finally, on patients' quality of care.

Orthotopic Heart Auto-Transplantation in a Swine Model

BACKGROUND AND AIM

The porcine heart bears the best resemblance to the human heart and remains the preferred preclinical model for anatomical, physiological, and medical device studies. In an effort to study phenomena related strictly to ischemia reperfusion and donor preservation protocols, it is essential to avoid the immune responses related to allotransplantation. Orthotopic auto-transplantation is a unique strategy to the field of cardiac transplantation for ex vivo experimentation. Nevertheless, auto-transplantation carries its own technical challenges related to insufficient length of the great vessels that are to be transected and re-anastomosed.

METHODS

A novel method for orthotopic cardiac auto-transplantation in the porcine model was developed and was described herein. Porcine models were used for ex vivo experimentation of a novel device to study ischemia reperfusion injury.

RESULTS

A total of five porcine models were used for ex vivo experimentation of a novel device to mitigate ischemia reperfusion injury and determine effects of donor preservation. Modifications to routine cardiac transplantation protocols to allow for successful auto-transplantation are described.

CONCLUSION

Orthotopic cardiac auto-transplantation in the porcine model is a plausible and technically feasible method for reliable study of ischemia reperfusion injury and donor preservation protocols. Here, we describe methods for both direct orthotopic porcine cardiac auto-transplantations as well as a simplified protocol that can be substituted for full surgical auto-transplantation for the studies of preservation of donor hearts.

Immunosuppressive regimens in porcine transplantation models

Pigs, or Sus scrofa domestica, are commonly used animal models in translational transplantation research due to their anatomical, physiological, and immunological similarities to humans. In solid organ transplantation studies, immunosuppressive medications may be administered to pigs to prevent rejection. We provide an overview of the immunosuppressive regimens used in allogeneic solid organ transplantation in pigs, including heart, lung, kidney, bowel and cotransplanted organs and focus on the use of tacrolimus, mycophenolate mofetil, and corticosteroids.

A novel experimental porcine model to assess the impact of differential pulmonary blood flow on ischemia-reperfusion injury after unilateral lung transplantation

BACKGROUND

Primary graft dysfunction (PGD) remains a major obstacle after lung transplantation. Ischemia-reperfusion injury is a known contributor to the development of PGD following lung transplantation. We developed a novel approach to assess the impact of increased pulmonary blood flow in a large porcine single-left lung transplantation model.

MATERIALS

Twelve porcine left lung transplants were divided in two groups (n = 6, in low- (LF) and high-flow (HF) group). Donor lungs were stored for 24 h on ice, followed by left lung transplantation. In the HF group, recipient animals were observed for 6 h after reperfusion with partially clamping right pulmonary artery to achieve a higher flow (target flow 40-60% of total cardiac output) to the transplanted lung compared to the LF group, where the right pulmonary artery was not clamped.

RESULTS

Survival at 6 h was 100% in both groups. Histological, functional and biological assessment did not significantly differ between both groups during the first 6 h of reperfusion. injury was also present in the right native lung and showed signs compatible with the pathophysiological hallmarks of ischemia-reperfusion injury.

CONCLUSIONS

Partial clamping native pulmonary artery in large animal lung transplantation setting to study the impact of low versus high pulmonary flow on the development of ischemia reperfusion is feasible. In our study, differential blood flow had no effect on IRI. However, our findings might impact future studies with extracorporeal devices and represent a specific intra-operative problem during bilateral sequential single-lung transplantation.

A Simplified Continuous Two-stitch Suture for Bronchial Anastomosis of Left Single Lung Transplant in Dogs

Large animal models are essential to pre-clinical trials of pulmonary transplantation and bronchial anastomosis poses a great technical challenge to the procedure. Presented here is a simplified continuous two-stitch suture technique into bronchial anastomosis during the course of left single lung transplantation in canine. Animals were divided into three groups with each group having 6 animals. Left single lung transplantation in canine was performed to assess the feasibility of using this technique for bronchial anastomosis. In the control groups, all anastomoses were done by using traditional technique. Allograft functions and hemodynamic parameters were monitored during a 3-h reperfusion period. Quality of bronchial healing and airway complications were assessed by bronchoscopic surveillance after transplantation. We successfully completed left lung transplantation in 18 dogs, and all the dogs survived the procedures. The new technique substantially simplified the procedures for bronchial anastomosis and greatly reduced the time for bronchial anastomosis (P<<0.01) and the ischemic time of the grafts (P<0.05) compared to the control group. The continuous two-stitch suture attenuated the tissue injury to allografts and led to better blood gas exchange function as compared to the control group (P<0.05). Good bronchial healing (Grade I) was observed in all the groups. A canine left single lung transplantation model is feasible by using the novel suture technique, and the new technique is as safe as the traditional method. The technique is easy to learn, particularly for less experienced operators. Simpler and time-saving, the technique has great potential to be widely employed in clinical lung transplantation.

TuThor: an innovative new training model for video-assisted thoracic surgery

OBJECTIVES

Video-assisted thoracic surgery (VATS) is a complex technique requiring dedicated surgical training. Platforms for such training are scarce and often rely on the use of live animals, which raises ethical concerns. The objective of this study was to develop a box trainer that is dedicated for VATS training and able to reproduce bleeding scenarios.

METHODS

The developed Tuebingen Thorax Trainer comprises 5 components that are mounted on a human anatomy-like thoracic cavity containing a porcine organ complex. Any standard thoracoscopic instrument can be used. The organ complex is attached to a perfusion module. We assessed the applicability of the system in four 1-day VATS training courses at the Tuebingen Surgical Training Center. Assessment was performed using a questionnaire handed out to all participants.

RESULTS

Forty participants have been trained with the Tuebingen Thorax Trainer at our institution since November 2016. Thirty-five (87.5%) participants stated that the Tuebingen Thorax Trainer is an adequate model for VATS training. The ex vivo organ complex was reported to be realistic with regards to the level of detail and scale (76%). A large proportion of participants (27.5%) were experienced with VATS and reported having performed >50 procedures before taking the training course.

CONCLUSIONS

This new training device allows realistic training for VATS procedures. 'Stagnant hydrostatic perfusion' permits simulation of reproducible bleeding scenarios. The device is low in production costs and offers a strong resemblance to the clinical scenario. It reduces the use of animal models and contributes to the efforts in making surgical skills training for VATS more accessible.

El biomodelo porcino en la investigación médica traslacional: del biomodelo al humano en trasplante pulmonar

Introducción. La anatomía humana y porcina son comparables. En consecuencia, el biomodelo porcino tiene el potencial de ser implementado para entrenar al profesional quirúrgico en áreas como el trasplante de órganos sólidos.Objetivo. Describir los procedimientos y hallazgos obtenidos mediante experimentos de medicina respiratoria traslacional con biomodelos porcinos realizados en un laboratorio de experimentación animal, y hacer una revisión comparativa entre el pulmón humano y el porcino.Materiales y métodos. El experimento se llevó a cabo en nueve cerdos de raza híbrida en un laboratorio de cirugía experimental. Se estudiaron la anatomía y la histología de las vías respiratorias mediante fibrobroncoscopia, biopsia bronquial y lavado broncoalveolar. El lavado broncoalveolar se estudió con citología en base líquida y se evaluó con las coloraciones de Papanicolau y hematoxilina y eosina. Se utilizaron técnicas de patología molecular, como inmunohistoquímica, citometría de flujo y microscopía electrónica. Los cerdos se sometieron a neumonectomía izquierda con posterior implante del injerto en otro cerdo experimental.Resultados. Los estudios histopatológicos y moleculares evidenciaron un predominio de macrófagos alveolares (98 %) y linfocitos T (2 %) en el lavado broncoalveolar porcino. En los estudios del parénquima pulmonar porcino se encontró tejido linfoide hiperplásico asociado a las paredes bronquiales. La microscopía electrónica evidenció linfocitos T dentro del epitelio y el diámetro de las cilias porcinas fue similar al de las humanas.Conclusiones. El biomodelo porcino es viable en la investigación traslacional para el entendimiento de la anatomía del sistema respiratorio y el entrenamiento en trasplante pulmonar. La implementación de este modelo experimental podría fortalecer los grupos que planean implementar un programa institucional de trasplante pulmonar en humanos.

Pig lung transplant survival model

Although lung transplant is a life-saving therapy for some patients, primary graft dysfunction (PGD) is a leading cause of mortality and morbidity soon after a transplant. Ischemia reperfusion injury is known to be one of the most critical factors in PGD development. PGD is by definition an acute lung injury syndrome that occurs during the first 3 d following lung transplantation. To successfully translate laboratory discoveries to clinical practice, a reliable and practical large animal model is critical. This protocol describes a surgical technique for swine lung transplantation and postoperative management for a further 3 d post transplant. The protocol includes the background and rationale, required supplies, and a detailed description of the donor operation, transplant surgery, postoperative care, and sacrifice surgery. A pig lung transplant model is reliably produced in which the recipients survive for 3 d post transplant. This 3-d survival model can be used by lung transplant researchers to assess the development of PGD and to test therapeutic strategies targeting PGD. In total, the protocol requires 5 h for the surgeries, plus ~2 h in total for the postoperative care.

Approaches to Establish Extracardiac Total Cavopulmonary Connections in Animal Models—A Review

Background:

Long-term survival of patients with a single ventricle palliated with a Fontan procedure is still limited. No curative treatment options are available. To investigate the pathophysiology and potential treatment options, such as mechanical circulatory support (MCS), appropriate large animal models are required. The aim of this review was to analyze all full-text manuscripts presenting approaches for an extracardiac total cavopulmonary connection (TCPC) animal model to identify the feasibility and limitations in the acute and chronic setting.

Methods:

A literature search was performed for full-text publications presenting large animal models with extracardiac TCPCs on Pubmed and Embase. Out of 454 reviewed papers, 23 manuscripts fulfilled the inclusion criteria. Surgical procedures were categorized and hemodynamic changes at the transition from the biventricular to the univentricular condition analyzed.

Results:

Surgical procedures varied especially regarding coronary venous flow handling and anatomic shape of the TCPC. In most studies (n = 14), the main pulmonary artery was clamped and the coronary venous flow redirected by additional surgical interventions. Only in five reports, the caval veins were connected to the right pulmonary artery to create a true TCPC shape, whereas in all others (n = 18), the veins were connected to the main pulmonary artery. An elevated pulmonary vascular resistance was identified as a limiting hemodynamic factor for TCPC completion in healthy animals.

Conclusions:

A variety of acute TCPC animal models were successfully established with and without MCS, reflecting the most important hemodynamic features of a Fontan circulation; however, chronic animal models were not reported.

Technique and perioperative management of left pneumonectomy in neonatal piglets

BACKGROUND

Although commonly performed in adult swine, unilateral pneumonectomy in piglets requires significant modifications in the surgical approach and perioperative care because of their smaller size and limited physiological reserve.

METHODS

Nineteen neonatal piglets underwent a left pneumonectomy. They were allowed 5-7 d of preoperative acclimation and nutritional optimization. Preoperative weight gain and laboratory values were obtained before the time of surgery. A "ventro-cranial" approach is adopted where components of the pulmonary hilum were sequentially identified and ligated, starting from the most ventral and cranial structure, the superior pulmonary vein. The principle of gentle ventilation was followed throughout the entire operation.

RESULTS

The median age of the piglets at the time of surgery was 12 (10-12) d. The median preoperative weight gain and albumin level were 20% (16-26%) and 2.3 (2.1-2.4) g/dL, respectively. The median operative time was 59 (50-70) min. Five of the first nine piglets died from complications, two from poor preoperative nutritional optimization (both with <10% weight gain and 2 g/dL for albumin), one from an intubation complication, one from intra-operative bleeding, and one in the postoperative period from a ruptured bulla. No mortality occurred for the next 10 cases.

CONCLUSIONS

Successful outcomes for unilateral pneumonectomy in piglets require special attention to preoperative nutritional optimization, gentle ventilation, and meticulous surgical dissection. Preoperative weight gain and albumin levels should be used to identify appropriate surgical candidates. The "ventro-cranial" approach allows for a technically straightforward completion of the procedure.

Porcine pulmonary auto-transplantation for ex vivo therapy as a model for new treatment strategies

OBJECTIVES

Lung auto-transplantation is the surgical key step in experiments involving ex vivo therapy of severe or end-stage lung diseases. Ex vivo therapy has become a clinical reality because of systems such as the Organ Care System (OCS) Lung, which is the only commercially available portable lung perfusion system. However, survival experiments involving porcine lung auto-transplantation pose special surgical and anaesthesiological challenges. This current study was designed to describe the development of surgical techniques and aneasthesiological management strategies that facilitate lung auto-transplantation survival surgery including a follow-up period of 4 days.

METHODS

Left pneumonectomy was performed in 12 Mini-Lewe miniature pigs. After ex vivo treatment of the harvested lungs within the OCS Lung for 2 h, the lungs were retransplanted into the same animal (auto-transplantation). Four animals were used to develop the optimal techniques and establish an experimental protocol. According to the final protocol, eight additional animals were operated. The follow-up period was 4 days.

RESULTS

There were four severe intraoperative surgical complications [anatomical variant of the superior vena cava (two times), a complication related to the bronchial anastomosis and a complication related to the pulmonary arterial anastomosis]. The major postoperative problems were hyperkalaemia, prolonged recovery from anaesthesia and pulmonary oedema after reperfusion. Establishment of the surgical technique showed that using a pericardial tube to facilitate the anastomosis of the thin left superior pulmonary vein should be considered to prevent thrombosis. However, routine use of the patch technique to construct venous and arterial anastomoses is not necessary. Furthermore, traction on the venous anastomoses can be avoided by performing the bronchial anastomosis first.

CONCLUSIONS

Lung auto-transplantation is a feasible experimental model for ex vivo therapy of lung diseases and is applicable for experimental questions concerning human lung transplantation.

Innovative, simplified orthotopic lung transplantation in rats

BACKGROUND

Various techniques of orthotopic single lung transplantation in rats have been reported; however, their widespread use has been limited owing to the complexity of the procedure. We report a novel microsurgical lung transplantation model in rats with a high survival rate that can be performed by one surgeon alone.

METHODS

A total of 90 left lung allografts were transplanted from Fischer to Wistar Kyoto rats. We developed a triple axis precision system to place and stabilize the vascular clips intrathoracically to clamp the bronchovascular structures, thereby avoiding interference with the heart and contralateral lung movement. A single-suture bronchial anastomosis technique and proximal cuffing approach for vascular anastomosis was used, rendering surgical assistance unnecessary.

RESULTS

In our recent series, both short-term (12 h) and long-term (21 d) survival was 100%. The lungs showed excellent perfusion and ventilation immediately on transplantation. Blood gas samples drawn from the left pulmonary vein and the histologic sections revealed excellent graft function. The donor operation lasted 20 ± 2 min, donor left lung dissection required 20 ± 2 min, and implantation required 90 ± 5 min.

CONCLUSIONS

The present innovative method of left orthotopic single lung transplantation can be performed by one experienced surgeon alone, with excellent results and a high degree of reproducibility.

[Ex situ tracheobronchoplastic operations using the organ care system]

First clinical experiences with the organ care system (OCS) in lung transplantation showed that this device allows perfusion and ventilation of the lungs under practically physiological conditions. Some pulmonary pathologies necessitate ex situ operations, e.g. to avoid pneumonectomy. The objective of this work was to investigate the feasibility of ex situ pulmonary surgery within the OCS.In the first procedure a large tracheobronchial leakage was covered with a pericardial patch. The procedure was authorized by the local committee of animal welfare. In the second surgery a replacement of the distal trachea using an aortic graft was performed after removal of the heart-lung segment from a pig from the slaughterhouse. The postoperative ventilation of both lungs was free of problems. The mean pressure of the pulmonary artery remained steady during the whole experiment. The setup to prevent lung edema was basically successful.Performing thoracic surgery with the OCS is feasible; however, this approach is reserved for very special indications. Further investigations to optimize technical details of the OCS setup for this purpose are necessary.