Development of an Anti-Adhesive Membrane for Use in Video-Assisted Thoracic Surgery

Lung Volume Reduction Surgery Before Lung Transplantation: A Propensity-Matched Analysis

BACKGROUND

Lung volume reduction surgery (LVRS) is treatment option for chronic obstructive pulmonary disease, the second most common indication for lung transplantation (LTx) in the United States. Lung volume reduction surgery before LTx is controversial. Single-institution studies report contradicting results, and the impact of undergoing LVRS before LTx on outcomes after LTx is unclear.

METHODS

We reviewed the United Network for Organ Sharing database for all adults (aged more than 18 years) who underwent first-time LTx for chronic obstructive pulmonary disease in the lung allocation score era. We used patient demographic and clinical characteristics and lung allocation score to propensity match patients who did and patients who did not undergo LVRS before LTx. The primary exposure was prior LVRS. The primary outcome was graft failure after LTx. Unadjusted Kaplan-Meier and adjusted Cox proportional hazards models were used to assess outcomes.

RESULTS

A total of 4905 patients with chronic obstructive pulmonary disease underwent LTx between May 2005 and March 2017. Of them, 107 patients (2.2%) underwent LVRS before LTx. Propensity matching generated 212 matches (106 LVRS+LTx, and 106 LTx only). Median survival was significantly longer in the LTx only cohort (6.5 vs 3.4 years, P = .034). Lung volume reduction surgery before lung transplantation was associated with significantly increased risk of graft failure after lung transplant (hazard ratio 1.72; 95% confidence interval, 1.13 to 2.60; P = .01).

CONCLUSIONS

In this national, propensity-matched analysis of LVRS before LTx, we show that LVRS is associated with a significantly increased risk of graft failure. Patients who undergo LVRS and remain in need of LTx should be carefully assessed and followed postoperatively.

Intrathoracic retention of insoluble hyaluronic acid and its absorption process in rats

BACKGROUND

Post-thoracotomy adhesions are frequent postoperative complications. It has been reported that insoluble hyaluronic acid may prevent adhesions.

MATERIALS AND METHODS

This study had two objectives: first, to determine the in vivo degradation and absorption process, as well as the intrathoracic retention, of solid insoluble hyaluronic acid membrane; and second, to elucidate the association between postoperative intrathoracic retention and the morphological changes of insoluble hyaluronic acid in 12 Wistar rats. Insoluble hyaluronic acid membranes were cut into 2.0 cm × 1.0 cm rectangles in a dry state. After weighing, the test membranes were soaked and washed with saline to be implanted after pericardiotomy via thoracotomy. At Days 4, 7, 10, 14, and 28 after implantation, the rats were euthanized, the chest was opened, and the condition and implantation site of the inserted test membrane were examined.

RESULTS

Although approximately 10 days were required for the test membrane to decrease to half in the thoracic cavity, the intrathoracic remnant decreased to a mean of ~2% just 4 days later.

CONCLUSION

This study clarified the time-dependent degradation process and remnants of insoluble hyaluronic acid in the thoracic cavity. A close relationship between the intrathoracic remnant of insoluble hyaluronic acid and its morphological change associated with degradation was demonstrated.

Elucidation of the time-dependent degradation process in insoluble hyaluronic acid formulations with a controlled degradation rate

Degradation rate of hyaluronic acid to prolong its stability in vivo would be beneficial. We investigated a potential solution for prolonging the stability of hyaluronic acid within the body. We focused on decreasing the swelling ratio to slow the degradation rate of hyaluronic acid by insolubilizing sodium hyaluronate without using potentially harmful substances such as crosslinkers or modifiers. Hyaluronic acid formulations were created with three different swelling ratios and time-dependent morphological changes in hyaluronic acid formulations and were scored based on each swelling ratio. In vivo degradation was modeled in simulated body fluid and the extent of decay of test membranes were monitored over time. Results showed that, by adjusting the swelling ratio, the degradation rate of hyaluronic acid formulation could be controlled. Our research could lead to improvements in many products, not only preventive materials for postoperative adhesions, but also pharmaceutical products such as osteoarthritis treatments and cosmetic medicines.

Assessment of the subcutaneous degradation process of insoluble hyaluronic acid in rats

Insoluble hyaluronic acid (IHA) may prevent adhesions by forming a physical barrier during the period when postoperative adhesions form. This study was performed to verify the changes that a solid IHA membrane undergoes as it is degraded in vivo, and to ascertain the swelling rate of IHA required for it to function as a physical barrier during the postoperative adhesion formation period. Nine female WI rats weighing 300-400 g were used. Discs 8 mm in diameter were cut out of dry IHA membranes made of IHA with a swelling rate (wet weight/dry weight) of either 2.47 (high-swelling IHA) or 1.94 (low-swelling IHA). They were placed in saline to swell and then washed with saline before subcutaneous implantation in four pockets in each rat. The high-swelling IHA started to degrade more rapidly than the low-swelling IHA. There was no evidence of degradation of the low-swelling IHA until day 7, but once it had started, the speed of degradation tended to be similar to that of the high-swelling IHA. The present results showed that, when IHA is implanted subcutaneously in rats, it is degraded over time in a phased process. The swelling rate required for the use of IHA as a postoperative adhesion barrier was also suggested.