Comparative study of solutions for pulmonary preservation using an isolated rabbit lung model.

At the University of Minnesota, University of Wisconsin (UW), modified Euro-Collins (MEC), and Marshall (M) solutions were compared as agents for pulmonary preservation in an isolated rabbit lung model. Normal saline (NS) was used as a control. The heart-lung blocks of donor rabbits were flushed with, and then preserved in, one of the solutions at 4 degrees C. Five rabbits were studied in each group. After 8 h of cold ischemia, the left lung was ventilated and reperfused with fresh venous blood from donor rabbits for 30 min. Pulmonary function was assessed by serial measurements of oxygen (O2) and carbon dioxide (CO2) tensions in blood obtained from the left atrial appendage. The ratios of wet/dry (W/D) weight of the lungs were calculated to assess the extent of pulmonary edema. After 8 h of preservation followed by 30 min of reperfusion, O2 tension was significantly higher with UW (178.36 + 1.72 mmHg). The calculated P values were UW vs NS, < 0.0001; UW vs MEC, 0.154; and UW vs M, 0.0001. CO2 tension with UW was also lower than the other solutions: UW, 35.8 +/- 0.698 mmHg; NS, 48.5 +/- 0.745 mmHg; MEC, 40.69 +/- 0.749 mmHg; and M, 44.68 +/- 0.697 mmHg. The calculated P value was UW vs NS, 0.0001; UW vs MEC, 0.0003; and UW vs M, 0.0001 using repeated-measures analysis of covariance. The W/D ratio was lower with UW as well; UW, 6.82 +/- 0.19; NS, 8.01 +/- 0.23; MEC, 7.28 +/- 0.10; and M, 7.34 +/- 0.17. The P value was < 0.001 using post-hoc tests. In this model, UW solution preserved the lungs better than the other three solutions tested and therefore warrants further clinical application.

Importance of adaptive stimulation of the latissimus dorsi muscle in cardiomyoplasty.

During cardiac synchronized latissimus dorsi (LD) stimulation, adaptive duration (AD) allows the pulse train length to be set as a percentage of the cardiac cycle. The LD contraction duration adjusts to variations in heart rate (HR). The effects of AD on LD work output and blood flow (BF) were investigated in nine dogs that underwent skeletal muscle ventricle (SMV) construction. The SMVs were stimulated according to the cardiomyoplasty protocol. BF and the pressure increase (delta P) generated during SMV contraction were monitored biweekly for 3 months. SMV contraction time increased significantly after training (P < 0.0001). The trained SMV could only partially contract at duration settings of 25% and 30%. Before training, the increase in mean pressure and BF during 35% AD increased proportionally with increasing HR. After training, BF and mean pressure decreased with increasing HR because of reduced peak pressure generation during partial SMV contractions. When duration was fixed at 200 msec, BF increased with HR to 80 bpm but decreased with additional increases in HR. At high rates and fixed duration, inadequate relaxation between contractions resulted in the inefficient muscle performance and reduced BF. AD did not impair BF and allowed the appropriate autoregulatory response to occur in the trained and untrained LD so that the supply-to-demand ratio did not become compromised over a large range of HR.

Conformational adaptation of muscle: implications in cardiomyoplasty and skeletal muscle ventricles.

In dynamic cardiomyoplasty and other forms of muscle-powered cardiac assist, the stretch that should be applied to the skeletal muscle to obtain optimal resting tension remains unclear. To test the hypothesis that skeletal muscle is capable of conformational adaptation over time, the effect of altered resting tension on the chronic performance of a skeletal muscle ventricle was studied. In 7 mongrel dogs, skeletal muscle ventricles constructed from the lastissimus dorsi muscle were stimulated to contract for 12 weeks against an implantable mock circulation. The preload pressure was altered, thereby varying the resting tension of the latissimus dorsi. One group (group I; n = 5) was maintained at a preload of 80 mm Hg, whereas a second group (group II; n = 2) was maintained at 20 mm Hg. Adaptation to preload was observed. After 12 weeks, the pressure increase generated by the skeletal muscle ventricle at a preload of 20 mm Hg was only 35 +/- 2 mm Hg for group I compared with 44 +/- 5 mm Hg for group II. At a preload of 80 mm Hg, the pressure increase was 61 +/- 4 mm Hg for group I and only 34 +/- 6 mm Hg for group II. Adaptation of the latissimus dorsi to a new resting tension has important implications in the use of skeletal muscle for cardiac assist. Stretching the latissimus dorsi to its in situ length during cardiomyoplasty is not required for future muscle performance to be optimal.

Tracheobronchial obstruction due to silicosis.

Broncholithiasis can result in airway obstruction through the erosion of calcified lymph nodes into the bronchial lumen or by extrinsic compression of the tracheobronchial tree. We report an unusual case of broncholithiasis in a patient with silicosis who developed airway obstruction from endobronchial polypoid masses of granulation tissue adjacent to calcified mediastinal lymph nodes. The production of granulation tissue may have been the result of broncholiths in the early stages of erosion into the tracheobronchial tree. Efforts to ablate the endobronchial polyps using YAG laser phototherapy were only temporarily successful and surgical removal of the calcified mediastinal lymph nodes was required to halt further polyp growth. Surgical specimens grew Mycobacterium avium-intracellulare (MAI), a common pathogen in patients with silicosis. MAI may have contributed to the local inflammatory milieu provoking the exuberant tissue response.

Combined laser phototherapy and growth factor treatment of bronchial obstruction after lung transplantation.

Lung transplantation has resulted in dramatic functional improvement in patients with end-stage pulmonary diseases. Among the complications of lung transplantation are dehiscence and stenosis at the site of the bronchial or tracheal anastomosis. In this case report, we describe a single lung transplant recipient in whom partial bronchial dehiscence, followed by exuberant growth of granulation tissue, resulted in obstruction of the bronchial lumen. After mechanical dilation failed to produce lasting relief of bronchial obstruction, a novel approach to this problem was successfully employed: YAG laser phototherapy was used to remove obstructing granulation tissue, followed by application of a preparation derived from autologous blood platelets to promote epithelialization of the bronchial anastomosis. The bronchus remains patent and fully epithelialized six months after therapy.