Experimental study on size matching in a canine living-donor lobar lung transplant model

Lung transplantation in children

Lung transplantation is a well-established treatment for children facing advanced lung disease and pulmonary vascular disorders. However, organ shortage remains highest in children. For fitting the small chest of children, transplantation of downsized adult lungs, lobes, or even segments were successfully established. The worldwide median survival after pediatric lung transplantation is currently 5.7 years, while under consideration of age, underlying disease, and peri- and posttransplant center experience, median survival of more than 10 years is reported. Timing of referral for transplantation, ischemia-reperfusion injury, primary graft dysfunction, and acute and chronic rejection after transplantation remain the main challenges.

Living-donor lobar lung transplantation

Living-donor lobar lung transplantation (LDLLT) is indicated for critically ill patients who would not survive the waiting period in the case of severe brain-dead donor shortage. It is essential to confirm that potential donors are willing to donate without applying psychological pressure from others. In standard LDLLT, the right and left lower lobes donated by 2 healthy donors are implanted into the recipient under cardiopulmonary support. LDLLT can be applied to various lung diseases including restrictive, obstructive, infectious, and vascular lung diseases in both adult and pediatric patients if size matching is acceptable. Functional size matching by measuring donor pulmonary function and anatomical size matching by 3-dimensional computed tomography volumetry are very useful. When 2 donors with ideal size matching are not available, various transplant procedures, such as single lobe, segmental, recipient lobe-sparing, and inverted lobar transplants are valuable options. There seems to be immunological advantages in LDLLT as compared to cadaveric lung transplantation (CLT). Unilateral chronic allograft dysfunction is a unique manifestation after bilateral LDLLT, which may contribute to better prognosis. The growth of adult lung graft implanted into growing pediatric recipients is suggested by radiologic evaluation. Although only 2 lobes are implanted, postoperative pulmonary function is equivalent between LDLLT and CLT. The long-term outcome after LDLLT is similar to or better than that after CLT. The author has performed 164 LDLLTs resulting in 71.6% survival rate at 10 years. All living-donors returned to their previous life styles. Because of possible serious morbidity in donors, LDLLT should be applied only for critically ill patients.

Living-related lung transplantation

Living-donor lobar lung transplantation (LDLLT) was developed to deal with the severe shortage of brain dead door for patients who would not survive the long waiting period. In standard LDLLT, right and left lower lobes removed from two healthy donors are implanted into a recipient after right and left pneumonectomies using cardiopulmonary bypass (CPB). The number of LDLLT has decreased in the USA due to the recent change in allocation system for cadaveric donor lungs. For the past several years, most of the reports on LDLLT have been from Japan, where the average waiting time for a cadaveric lung is exceeding 800 days. LDLLT has been performed both for adult and pediatric patients suffering from various end-stage lung diseases including restrictive, obstructive, vascular and infectious lung diseases. Since only two lobes are implanted, size matching is a very important issue. Functional size matching by measuring donor pulmonary function and anatomical size matching by three-dimensional computed tomography (3D-CT) volumetry are very useful. For oversize graft, we have employed several techniques, including single lobe transplantation, delayed chest closure, downsizing the graft, and middle lobe transplantation. In cases of undersize mismatch, native upper lobe sparing transplant or right-left inverted transplant was performed. The 5-, 10- and 15-year survivals were 80.8%, 72.6% and 61.7%, respectively. There was no difference in survival between standard LDLLT and non-standard LDLLT such as single, sparing and inverted transplant. All donors have been discharged without any restrictions. LDLLT is a viable option for very ill patients who would not survive a long waiting time for cadaveric lungs. We have successfully developed various surgical techniques to overcome size mismatching with favorable outcome.

Outcomes of various transplant procedures (single, sparing, inverted) in living-donor lobar lung transplantation

OBJECTIVES

In standard living-donor lobar lung transplantation (LDLLT), the right and left lower lobes from 2 healthy donors are implanted. Because of the difficulty encountered in finding 2 donors with ideal size matching, various transplant procedures have been developed in our institution. The purpose of this retrospective study was to compare outcomes of nonstandard LDLLT with standard LDLLT.

METHODS

Between June 2008 and January 2016, we performed 65 LDLLTs for critically ill patients. Functional size matching was performed by estimating graft forced vital capacity based on the donor's measured forced vital capacity and the number of pulmonary segments implanted. For anatomical size matching, 3-dimensional computed tomography volumetry was performed. In cases of oversize mismatch, single-lobe transplant or downsizing transplant was performed. In cases of undersize mismatch, native upper lobe sparing transplant or right-left inverted transplant was performed. In right-left inverted transplants, the donor's right lower lobe was inverted and implanted into the recipient's left chest cavity.

RESULTS

Twenty-nine patients (44.6%) received nonstandard LDLLT, including 12 single-lobe transplants, 7 native upper lobe sparing transplants, 6 right-left inverted transplants, 2 sparing + inverted transplants, and 2 others. Thirty-six patients (57.4%) received standard LDLLT. Three- and five-year survival rates were similar between the 2 groups (89.1% and 76.6% after nonstandard LDLLT vs 78.0% and 71.1% after standard LDLLT, P = .712).

CONCLUSIONS

Various transplant procedures such as single, sparing and inverted transplants are valuable options when 2 donors with ideal size matching are not available for LDLLT.

Cadaveric lobar lung transplantation: technical aspects

BACKGROUND

The use of lobar transplantation and other size reduction techniques has allowed larger donor lungs to be utilized for smaller recipients who tend to have longer waiting times for transplantation. However, despite these advantages, the techniques have not been widely adopted. We outline the surgical and sizing issues associated with this technique.

METHODS

A retrospective review of 23 consecutive patients who received lung transplantation with anatomic lobar reduction was performed, focusing on surgical technique and outcomes.

RESULTS

All 23 patients received an anatomic lobar reduction of between 1 and 3 lobes. Survival analysis showed no difference between the lobar reduction cohort and the other historically comparable lung transplant patients from our institution (p=0.115). Percent predicted forced vital capacity and forced expiratory volume in 1 second at 3 months correlated with transplanted donor to recipient total lung capacity ratio, confirming the importance of correct sizing.

CONCLUSIONS

Anatomic lobar reduction in lung transplantation is a safe and effective means of transplanting pediatric and small adult recipients, and urgently listed patients.

Computed tomography measurement of lung volume in preoperative assessment for living donor lung transplantation: volume calculation using 3D surface rendering in the determination of size compatibility

The objective of this study was to describe the use of CT volume quantification assessment of candidates for LLDLT. Six pediatric candidates for LDLLT and their donors were investigated with helical chest CT, as part of the preoperative assessment. The CT images were analyzed as per routine and additional post-processing with CT volume quantification (CT densitovolumetry) was performed to assess volume matching between the lower lobes of the donors and respective lungs of the receptors. CT images were segmented by density and region of interest, using post-processing software. Size matching was also assessed using the FVC formula. Compatible volumes were found in three cases. The other three cases were considered incompatible. All three recipients with compatible sizes survived the procedure and are alive and well. One patient with incompatible size was submitted to the procedure and died because of complications attributed to the incompatible volumes. One patient with incompatible size has subsequently grown and new measurements are to be taken to check the current volumes. Different donors are being sought for the remaining patient whose lung volumes were considered too big for the prospective transplant donor lobes. Under FVC formula criteria, all cases were considered compatible. CT volume quantification is an easy to perform, non-invasive technique that uses CT images for the preassessment of candidates for LDLLT, to compare the volume of the lower lobes from the donors with volume of each lung in the prospective recipients. Size matching based on CT densitovolumetry and FVC may differ.

Pediatric lung transplantation: perspectives for the pathologist

Lung transplantation offers life-saving and life-extending treatment for children and adolescents with congenital and acquired forms of pulmonary and pulmonary vascular disease, for whom medical therapy is ineffective or insufficient for sustained response. This review summarizes the pathology related to lung transplantation for the practicing pediatric pathologist and also highlights aspects of lung transplantation unique to the pediatric population. Clinical issues related to availability of organs, candidate eligibility, surgical technique, and postoperative monitoring are discussed. Pathologic evaluation of routine surveillance transbronchial biopsies requires attention to acute cellular rejection, opportunistic infection, and other forms of acute and resolving lung injury. These findings are correlated in some cases with endobronchial biopsies and bronchoalveolar lavage as adjunctive tools in surveillance. Open or thoracoscopic biopsies also have diagnostic utility in cases with acute or chronic graft deterioration of uncertain etiology. Future challenges in pediatric lung transplantation are similar to those in the adult population, with continued efforts focused on prolonging graft survival, prevention of bronchiolitis obliterans syndrome due to chronic cellular rejection, and evaluation of humoral rejection.

Ultrafiltration attenuates cardiopulmonary bypass-induced acute lung injury in a canine model of single-lung transplantation

OBJECTIVE

The purpose of this study was to investigate the effects of cardiopulmonary bypass and ultrafiltration on graft function in a canine single-lung transplantation model.

METHODS

Fifteen left single-lung transplantations were done in weight-mismatched canine pairs. The animals were divided into 3 groups: group 1, in which transplantation was done without cardiopulmonary bypass; group 2, in which transplantation was done with cardiopulmonary bypass and in which the cardiopulmonary bypass flow was decreased slowly with controlled pulmonary artery pressure; and group 3, in which transplantation was done with cardiopulmonary bypass and ultrafiltration. Hemodynamic parameters and lung function were monitored for 6 hours after reperfusion. The grafts were harvested for histologic studies, myeloperoxidase assay, and real-time quantitative reverse transcription-polymerase chain reaction of mRNA encoding interleukin 6.

RESULTS

The hemodynamic parameters were similar among the 3 groups. In group 1 PaO2 and alveolar to arterial gradient for O2 levels were excellent throughout the 6-hour observation period, but in group 2 they progressively deteriorated. However, ultrafiltration significantly (P = .02) improved the PaO2 level in group 3. On histology, interstitial edema and polynuclear cell infiltration were most marked in group 2 and significantly worse than in groups 1 and 3. Myeloperoxidase assay and real-time quantitative reverse transcription-polymerase chain reaction showed increased myeloperoxidase activity and interleukin 6 gene expression in group 2 grafts compared with group 1 grafts. Myeloperoxidase activity and interleukin 6 gene expression were suppressed with ultrafiltration.

CONCLUSIONS

Cardiopulmonary bypass had negative effects on the graft, but ultrafiltration attenuated acute lung dysfunction by reducing the inflammatory response.

Bilateral native lung–sparing lobar transplantation in a canine model

OBJECTIVE

Bilateral living-donor lobar lung transplantation has become an accepted approach in response to the cadaveric lung donor shortage. Because only one lobe is implanted in each chest cavity, this procedure is usually confined to patients of small size. The purpose of this study was to develop a technique of bilateral native lung-sparing lobar transplantation that can be applied to large adult patients.

METHODS

Bilateral native lung-sparing lobar transplantation was performed in 12 pairs of dogs. In donor animals the right middle, lower, and cardiac lobes were separated as a right graft, and the left lower lobe was separated as a left graft. In recipient animals these 2 grafts were implanted in the natural anatomic position with sparing native right upper, left upper, and middle lobes. In an acute study (n = 6), transplanted graft function was assessed for 3 hours after ligation of the pulmonary artery branches to the native spared lobes. In a chronic study (n = 6) the immunosuppressed recipients were observed for 3 weeks to assess the quality of bronchial healing and long-term pulmonary function.

RESULTS

Morphologic adaptation of the 2 grafts was found to be excellent. All 6 animals in the acute study showed excellent pulmonary function. Five of 6 animals in the chronic study survived for 3 weeks, with excellent pulmonary function and satisfactory bronchial healing.

CONCLUSION

Bilateral native lung-sparing lobar transplantation was technically possible and associated with excellent pulmonary function and good bronchial healing in a canine experimental model.

Anastomosis of an anomalous segmental vein with the azygos vein in living-donor lobar lung transplantation

We report the case of a living-donor lobar lung transplantation in which we found an abnormal segmental vein in the right lower lobe of the donor lung. The abnormal vein was anastomosed to the azygos vein of the recipient so that lung edema and congestion could be avoided. This alternative technique is effective in living-donor lobar lung transplantation when the superior segmental vein in the right lower lobe of the donor drains into the superior vein.

How to predict forced vital capacity after living-donor lobar-lung transplantation

BACKGROUND

Living-donor lobar-lung transplantation (LDLLT) has evolved from a rarely performed experimental procedure to an accepted therapy for selected patients who are unlikely to survive the long wait for cadaveric lungs. However, a convincing study has not been performed that shows the effects of small grafts and of pre-operative variables in predicting functional outcome of recipients after LDLLT.

METHODS

From October 1998 to March 2002, 2 male and 11 female patients underwent LDLLT. Mean age was 27.3 years (range, 8-53 years). Diagnoses included primary pulmonary hypertension (n = 5), idiopathic interstitial pneumonia (n = 2), bronchiolitis obliterans (n = 2), bronchiectasis (n = 2), lymphangioleiomyomatosis (n = 1), and cystic fibrosis (n = 1). Donors included 12 men and 14 women with a mean age of 40 years. Given that the right lower lobe consists of 5 segments, the left lower lobe of 4, and the whole lung of 19, we estimated the graft forced vital capacity (FVC) based on the donor's measured FVC and compared this with the recipient's FVC measured after LDLLT.

RESULTS

Currently, all patients are alive, with a mean follow-up of 22.2 months (range, 10-51 months). The recipients' FVC measured at 6 months (1,813 +/- 86 ml) correlated well with the graft FVC (1,803 +/- 70 ml), estimated based on the donors' measured FVC (r = 0.802, p = 0.00098).

CONCLUSIONS

Recipient FVC after LDLLT can be predicted by measuring donor FVC before surgery regardless of the diagnosis of the recipient.

The technique of unilateral double lobar lung transplantation in a canine model

OBJECTIVE

Bilateral living-donor lobar lung transplantation has become an accepted alternative to cadaveric lung transplantation. Because only one lobe is implanted in each chest cavity, this procedure seems to be best suited for children and small adults. The purpose of this study was to develop a technique of unilateral double lobar lung transplantation that can be applied to large adult patients.

METHODS

Unilateral double lobar lung transplantation was performed in 6 weight-matched pairs of dogs. In donor animals the right middle, lower, and cardiac lobes were separated as a right graft, and the left lower lobe was separated as a left graft. In recipient animals these 2 grafts were implanted in the right hemithorax after right pneumonectomy. The left graft was implanted as a right upper lobe, having been rotated 180 degrees along the vertical axis and then 180 degrees along the horizontal axis. The right graft was implanted in the natural anatomic position. Function of the transplanted grafts was assessed for 3 hours after ligation of the left main pulmonary artery while the animals were ventilated with 100% oxygen.

RESULTS

Morphologic adaptation of the 2 grafts in the right hemithorax was found to be excellent. All 6 animals survived the assessment period with excellent pulmonary function. At the end of the 3-hour assessment period, the arterial oxygen tension was 519 +/- 31 mm Hg, and the mean pulmonary artery pressure was 30.5 +/- 1.7 mm Hg.

CONCLUSIONS

Unilateral double lobar lung transplantation was technically possible and associated with satisfactory early pulmonary function in a canine experimental model.