Pulmonary preservation studies: effects on endothelial function and pulmonary adenine nucleotides

Terbutaline improves ischemia-reperfusion injury after left-sided orthotopic rat lung transplantation

Beta2-agonists have been shown to increase alveolar fluid reabsorption, and at least part of their effect depends on active sodium transport from the alveolus into the epithelial cell by the amiloride-sensitive epithelial sodium channel (ENaC). Few data exist on their effect in the injured lung. The authors therefore investigated the effect of intrabronchially administered terbutaline pretransplantation by measuring outcome 1 day after experimental donor lung transplantation with severe injury due to prolonged ischemia. Orthotopic single left-sided lung allotransplantation was performed in female rats (Wistar to Wistar) after a total ischemic time of 20 hours. Graft PaO2/FiO2 in 6 recipients treated with 10(-4) M terbutaline in 500 microL NaCl 0.9% was superior 24 hours after transplantation, with a PaO2 of 329 (111 [SD]) mm Hg versus 5 vehicle controls with 44 (15) mm Hg (P = .002). The beneficial effect of 10(-4) M terbutaline was abrogated by 10(-4) M of the sodium channel blocker amiloride to 71 (34) mm Hg in 3 recipients (P = .028 versus terbutaline 10(-4) M). Ten recipients receiving 10(-5) M terbutaline in 500 microL NaCl 0.9% showed inconsistent improvements of gas exchange, with a PaO2 of 158 (+/- 153) mm Hg (P = .058). Terbutaline at a high dose significantly improved the transplanted rat lung function at 24 hours after transplantation. Part of it may be via activating epithelial sodium transport, thus suggesting an important role of alveolar fluid transport in such a model of acute lung injury.

[Assessment of ischemia-reperfusion injury and early acute rejection in experimental lung transplantation after prolonged ischemia]

OBJECTIVE

To assess ischemia-reperfusion injury and early acute rejection of the lung subjected to ischemia for 10 hours.

MATERIAL AND METHODS

Fifteen of 30 Sprague-Dawley rats underwent transplantation of a left lung that had been subjected to ischemic times of 4 (n=5), 6 (n=5), or 10 hours (n=5). The cardiopulmonary block was removed from the donor, the left lung was dissected, and the transplant was carried out using the cuff technique. The cardiopulmonary block was extracted after 48 hours. We assessed postoperative progress, ischemia-reperfusion injury and acute rejection of the transplanted and contralateral lungs. Statistical probabilities were analyzed using the chi2 and Fisher exact tests.

RESULTS

Clinical course was not worse after an ischemic time of 10 hours (P=.711). No significant differences were observed in histological markers of ischemia-reperfusion injury and acute rejection or in clinical course in relation to the different ischemic times; nor was clinical course related to the presence or severity of lesions or rejection. Similarly, acute rejection was unrelated to ischemia-reperfusion injury (P>.05).

CONCLUSIONS

In this study, a prolonged ischemic time of 10 hours was not associated with ischemia-reperfusion injuries, with more severe acute rejection, or with a worse clinical course. Acute rejection was also unrelated to the presence or severity of ischemia-reperfusion injury.

Percutaneous autologous venous valve transplantation: Short-term feasibility study in an ovine model

BACKGROUND

Limited experience with bioprosthetic venous valve percutaneously inserted into femoral veins in 15 patients has been promising in short-term results only to show disappointing long-term results. Percutaneous autogenous venous valve (PAVV) transplantation was explored in an ovine model as a possible alternative treatment.

METHODS

PAVV consisted of a vein segment containing a valve that was attached to a stent template. The stent templates (n = 9) were designed and hand made in our research laboratory. They consist of two stainless steel square stents 13 or 15 mm in diameter to fit the ovine jugular veins (JV), which ranges from 10 to 15 mm in diameter. A valve-containing segment of JV was harvested and attached with sutures and barbs inside the stent template (n = 9). The valve devices were then manually folded and front loaded inside the 4 cm chamber of the 13F delivery sheath and delivered into the contralateral JV by femoral vein approach. Transplanted PAVVs were studied by immediate and 3 months venograms. Animals were euthanized at 3 months, and jugular veins harvested to perform angioscopic evaluations in vitro.

RESULTS

PAVV transplantation was successful in all nine animals. Good valve function with no reflux was observed on immediate and 3 months venograms in eight valves. The transplanted maximal JV diameter ranged from 10.2 mm to 15.4 mm (mean 13.1 +/- 1.5 mm). Venoscopic examination revealed intact, flexible, nonthickened valve leaflets in eight specimens. One PAVV exhibited normal function of one leaflet only; the other cusp was accidentally cut during the transplantation procedure. All transplanted autologous valves were free of thrombus and incorporated into the vein wall of the host vessel.

CONCLUSION

This study demonstrated that autogenous valve transplants remained patent and competent without long-term anticoagulation for up to 3 months. The percutaneous autogenous venous valve may provide in future minimally invasive treatment for patients with chronic deep venous insufficiency, but long-term studies need to be done to document its continued patency and function.

Ex-vivo perfusion and ventilation of rat lungs from non-heart-beating donors before transplant

BACKGROUND

We developed an ex-vivo circuit to evaluate human lungs retrieved from non-heart-beating donors. We assessed the effect of a similar circuit on the function of transplanted rat lungs retrieved from non-heart-beating donors.

METHODS

One hour after death, Sprague-Dawley rat heart-lung blocks were flushed with 20 mL of cold Perfadex, stored cold for 1 hour, then warmed to 37 degrees C in a circuit perfused with Earle's crystalloid solution with or without washed porcine erythrocytes (hematocrit 12% to 15%). At 37 degrees C, lungs were ventilated for 15 minutes with alveolar gas, perfusion-cooled to 20 degrees C, flushed again with cold Perfadex, and then stored cold for 2.5 hours. The left lung was transplanted using a modified cuff technique with flow probes on the main and left pulmonary arteries. After 1 hour of reperfusion, arterial blood gases from the left pulmonary vein and wet/dry weight ratio (W/D) of both donor lungs were determined. Lungs transplanted after retrieval from heart-beating or non-heart-beating donors served as controls (n = 6 per group).

RESULTS

Lungs gained weight in the circuit but W/D and PO2 were similar after transplantation for all groups. After transplantation, vascular resistance was higher and dynamic compliance was lower for lungs perfused in the circuit. Myeloperoxidase and conjugated diene levels were modestly elevated in lungs transplanted from non-heart-beating donors irrespective of perfusion in the circuit.

CONCLUSIONS

Rat lungs are suitable for transplant after ex-vivo perfusion and ventilation. This model closely mimics methods used to evaluate the function of lungs retrieved from human non-heart-beating donors and can economically evaluate ex-vivo therapies for lungs retrieved from non-heart-beating donors.

Endothelium-dependent relaxation of canine pulmonary artery after prolonged lung graft preservation in University of Wisconsin solution: role of L-arginine supplementation

BACKGROUND

The University of Wisconsin (UW) solution has been demonstrated to enhance pulmonary allograft preservation. Endothelial nitric oxide (NO) production has been shown to be significantly impaired after ischemia and reperfusion (I/R) injury. The present experiments aimed to determine the protective effects of pulmonary endothelium-dependent function by using supplemental NO in University of Wisconsin (UW) solution following prolonged lung graft preservation.

METHODS

Thirty-six healthy mongrel dogs underwent thoracotomy to expose the left lung. In addition to a group given UW solution (n = 4), 100 micromol/liter l-arginine, (n = 7), 100 micromol/liter N(G)-monomethyl-l-arginine (l-NMMA n = 7) and 1.0 micromol/liter 3-morpholinosydnonimine (SIN-1, n = 18 respectively, were added to UW solution, and infused from the aortic root and pulmonary artery to the pulmonary vein. The perfused lung was then allowed to inflate to its maximum volume for 24-hour oxygenated preservation in each supplemented condition of UW solution at 4 degrees C. In the SIN-1 group, the preservation period was further divided into 8 hours and 16 hours, respectively. Rings of the third-order pulmonary artery of the inflated lung were then suspended in organ chambers to measure isometric force.

RESULTS

Endothelium-dependent relaxation (EDR) to acetylcholine, adenosine diphosphate and sodium fluoride of the pulmonary rings in the l-arginine group was significantly preserved compared with UW-solution-only group. The l-NMMA group showed significant EDR impairment after 24-hour preservation compared with the UW solution group. Similar to the l-arginine group, the SIN-1 group showed significant EDR protection with 8-hour preservation, but not with 24-hour preservation. In contrast, EDR to calcium ionophore A23187 showed no EDR changes after 24-hour preservation in any of the supplemented groups.

CONCLUSIONS

Supplemental l-arginine in UW solution ameliorates impaired pulmonary EDR following prolonged lung preservation of up to 24 hours.