Lung preservation: the importance of endothelial and alveolar type II cell integrity

Influence of oxygen in inflation gas during lung ischemia on ischemia-reperfusion injury

OBJECTIVES

Previous studies have reported that hyperinflation during lung ischemia improves pulmonary function after reperfusion. However, it has not been clarified whether hyperinflation itself or oxygen in inflation gas causes good pulmonary function. The aim of this study is to evaluate the effect of oxygen in pulmonary inflation gas during lung ischemia on ischemia-reperfusion injury.

METHODS

Twenty-one mongrel dogs were randomly divided into three groups: the lung during a 90-minute period of warm ischemia was inflated to 30 cm H2O with 100% oxygen in group A and 100% nitrogen in group B; it was not inflated in group C. Pulmonary function and hemodynamics were measured before ischemia and 1, 2, and 3 hours after reperfusion. Total protein and phosphorus of phospholipid in bronchoalveolar lavage fluid were measured 210 minutes after reperfusion. Adenine nucleotide levels in lung tissue were estimated 210 minutes after reperfusion.

RESULTS

No significant differences in pulmonary function and hemodynamics were noted between group A and group B, but these two groups had significantly better pulmonary function and hemodynamics than group C. No significant differences were detected in the concentrations of total protein and phosphorus of phospholipids in bronchoalveolar lavage fluid and in adenine nucleotide levels of lung tissue after reperfusion among the three groups.

CONCLUSIONS

The results indicate that pulmonary inflation during warm ischemia improves pulmonary function and hemodynamics after reperfusion in this model. The effect is caused by inflation itself and is not due to oxygen as a metabolic substrate during warm ischemia.

Exogenous surfactant treatment before and after sixteen hours of ischemia in experimental lung transplantation

OBJECTIVE

A syngeneic, acute, double lung transplant model in the rat was used to determine the impact of exogenous surfactant treatment on graft function after prolonged cold storage.

METHODS

The donor grafts were flush perfused, preserved for 16 hours, and then reperfused for 120 minutes. Untreated lungs served as controls (group I). In group II the recipient received a 200 mg/kg dose of surfactant (CuroSurf) before reperfusion. In groups III and IV, surfactant was administered before perfusion and harvesting (III, 20 mg/kg; IV, 200 mg/kg). Serial measurements of graft pulmonary vascular resistance, alveolar-arterial oxygen difference, and compliance were obtained. Final graft assessment included weight gain and histologic study.

RESULTS

Repeated-measures analysis of variance showed significant improvement of graft performance in respect to compliance, alveolar-arterial oxygen difference, and pulmonary vascular resistance in donor surfactant treatment group IV (200 mg/kg) in comparison with recipient treatment (group II) and untreated controls (group I). Reducing the donor surfactant supplementation from 200 mg/kg to 20 mg/kg (group III) improved oxygenation and lung compliance as compared with untreated controls. Grafts in groups I and II had significantly more weight gain after 2 hours of reperfusion. Recipient treatment resulted in significantly more pulmonary hemorrhage in histologic sections.

CONCLUSION

Donor treatment with exogenous surfactant is advantageous for preservation of graft function after extended ischemia. Positive effects may be seen with as little as 20 mg/kg of exogenous surfactant given before donor organ perfusion.

Low-dose sodium nitroprusside reduces pulmonary reperfusion injury

BACKGROUND

Reperfusion injury is a significant cause of early allograft dysfunction after lung transplantation. We hypothesized that direct pulmonary arterial infusion of an intravascular nitric oxide donor, sodium nitroprusside (SNP), would ameliorate pulmonary reperfusion injury more effectively than inhaled nitric oxide without causing profound systemic hypotension.

METHODS

Using an isolated, ventilated, whole-blood-perfused rabbit lung model, we studied the effects of both inhaled and intravascular nitric oxide during lung reperfusion. Group I (control) lungs (New Zealand White rabbits, 3 to 3.5 kg) were harvested en bloc, flushed with Euro-Collins solution, and then stored inflated for 18 hours at 4 degrees C. Lungs were then reperfused with whole blood and ventilated with 60% oxygen for 30 minutes. Groups II, III, and IV received pulmonary arterial infusions of SNP at 0.2, 1.0, and 5.0 micrograms.kg-1.min-1, respectively, whereas group V was ventilated with 60% oxygen and nitric oxide at 80 ppm during reperfusion.

RESULTS

Pulmonary arterial infusions of SNP even at 0.2 microgram.kg-1.min-1 (group II) showed significant improvements in pulmonary artery pressure (31.35 +/- 0.8 versus 40.37 +/- 3.3 mm Hg; p < 0.05) and pulmonary vascular resistance (38,946 +/- 1,269 versus 52,727 +/- 3,421 dynes.s/cm-5; p < 0.05) when compared with control (group I) lungs after 30 minutes of reperfusion. Infusions of SNP at 1.0 microgram.kg-1.min-1 (group III) showed additional significant improvements in dynamic airway compliance (1.98 +/- 0.10 versus 1.46 +/- 0.02 mL/mm Hg; p < 0.05), venous-arterial oxygenation gradient (116.00 +/- 24.4 versus 34.43 +/- 2.5 mm Hg; p < 0.05), and wet-to-dry ratio (6.9 +/- 0.9 versus 9.1 +/- 2.2; p < 0.05) when compared with control (group I) lungs. Lungs that received inhaled nitric oxide at 80 ppm (group V) were significantly more compliant (1.82 +/- 0.13 versus 1.46 +/- 0.02 mL/mm Hg; p < 0.05) than control (group I) lungs.

CONCLUSIONS

Pulmonary arterial infusion of low-dose SNP during lung reperfusion significantly improves pulmonary hemodynamics, oxygenation, compliance, and edema formation. These effects were achieved at doses of SNP that did not cause profound systemic hypotension. Direct intravascular infusion of SNP via pulmonary arterial catheters could potentially abate reperfusion injury immediately after allograft implantation.

Inhaled nitric oxide and pentoxifylline in rat lung transplantation from non-heart-beating donors. The Paris-Sud University Lung Transplantation Group

BACKGROUND

In non-heart-beating donor lung transplantation, postmortem warm ischemia poses a special challenge. Inhaled nitric oxide and pentoxifylline have been shown to attenuate ischemia-reperfusion injury after lung transplantation. We hypothesized that concomitant administration of inhaled nitric oxide and pentoxifylline would result in a synergistic effect on ischemia-reperfusion lung injury.

METHODS

Lungs were harvested from non-heart-beating donors after 30 minutes of in situ warm ischemia, flushed, and stored for 2 hours at 4 degrees C before left lung transplantation in rats. Inhaled nitric oxide (30 ppm) was added during cadaver ventilation and reperfusion; pentoxifylline was given intravenously throughout reperfusion. The following groups were studied (n = 8 each): control, pentoxifylline, nitric oxide, and nitric oxide+pentoxifylline. Hemodynamic indices and arterial blood gases were obtained after ligation of the right pulmonary artery. Lung myeloperoxidase and wet/dry ratio were measured after death.

RESULTS

All rats that did not receive nitric oxide died within 10 minutes after ligation. Inhaled nitric oxide significantly decreased pulmonary vascular resistance and improved recipient survival. Nitric oxide + pentoxifylline improved pulmonary vascular resistance, arterial oxygen tension, and survival even further and reduced lung myeloperoxidase as compared with the group that received nitric oxide only. Preservation solution flush time was significantly decreased in both groups receiving nitric oxide, suggesting that inhaled nitric oxide used during cadaver ventilation allows for a more even distribution of the preservation solution.

CONCLUSIONS

We conclude that treatment with inhaled nitric oxide + pentoxifylline results in a synergistic protection from ischemia-reperfusion injury after non-heart-beating donor lung transplantation. This is likely the result of a dual action on the graft vasculature and neutrophil sequestration.

Mitigation of injury in canine lung grafts by exogenous surfactant therapy

BACKGROUND

Exogenous surfactant therapy of lung donors improves the preservation of normal canine grafts. The current study was designed to determine whether exogenous surfactant can mitigate the damage in lung grafts induced by mechanical ventilation before procurement.

METHODS AND RESULTS

Five donor dogs were subjected to 8 hours of mechanical ventilation (tidal volume 45 ml/kg). This produced a significant decrease in oxygen tension (p = 0.007) and significant increases in bronchoscopic lavage fluid neutrophil count (p = 0.05), protein concentration (p = 0.002), and the ratio of poorly functioning small surfactant aggregates to superiorly functioning large aggregates (p = 0.02). Five other animals given instilled bovine lipid extract surfactant and undergoing mechanical ventilation in the same manner demonstrated no significant change in oxygen tension values, lavage fluid protein concentration, or the ratio of small to large aggregates. All 10 lung grafts were then stored for 17 hours at 4 degrees C. Left lungs were transplanted and reperfused for 6 hours. After 6 hours of reperfusion the ratio of oxygen tension to inspired oxygen fraction was 307 +/- 63 mm Hg in lung grafts administered surfactant versus 73 +/- 14 mm Hg in untreated grafts (p = 0.007). Furthermore, peak inspired pressure was significantly (p < 0.05) lower in treated animals from 90 to 360 minutes of reperfusion. Analysis of lavage fluid of transplanted grafts after reperfusion revealed small to large aggregate ratios of 0.17 +/- 0.04 and 0.77 +/- 0.17 in treated versus untreated grafts, respectively (p = 0.009).

CONCLUSIONS

Instillation of surfactant before mechanical ventilation reduced protein leak, maintained a low surfactant small to large aggregate ratio, and prevented a decrease of oxygen tension in donor animals. After transplantation, surfactant-treated grafts had superior oxygen tension values and a higher proportion of superiorly functioning surfactant aggregate forms in the air space than untreated grafts. Exogenous surfactant therapy can protect lung grafts from ventilation-induced injury and may offer a promising means to expand the donor pool.

Pulmonary retransplantation: does the indication for operation influence postoperative lung function?

OBJECTIVE

An international series of pulmonary retransplantation was updated to determine the factors associated with pulmonary function, bronchiolitis obliterans syndrome stage, and survival after operation.

METHODS

One hundred sixty patients underwent retransplantation in 35 centers from 1985 to 1995. Logistic regression methods were used to determine variables associated with 3-month and 2-year survival after retransplantation. Values of forced expiratory volume in 1 second were contrasted between groups by unpaired, two-tailed t tests.

RESULTS

The median follow-up in surviving recipients was 780 days. Actuarial survival was 45% +/- 4%, 41% +/- 4%, and 33% +/- 4% at 1, 2, and 3 years, respectively. On multivariable analysis, the only predictor of 3-month survival was preoperative ambulatory status (p = 0.005), whereas center experience with at least five pulmonary retransplantations was the sole predictor of 2-year survival (p = 0.04). The prevalence of stage 3 (severe) bronchiolitis obliterans syndrome was 12% at 1 year, 15% at 2 years, and 33% at 3 years after retransplantation. Retransplant recipients with stage 3 bronchiolitis obliterans syndrome at 1 year had a significantly worse actuarial survival than those with stages 0 to 2 (p < 0.01). By 3 years after retransplantation, the forced expiratory volume in 1 second was significantly lower in patients who underwent reoperation because of obliterative bronchiolitis than in patients who underwent retransplantation because of acute graft failure or an airway complication (p = 0.02). Only 31% of patients who underwent retransplantation because of obliterative bronchiolitis were free of bronchiolitis obliterans syndrome at 3 years versus 83% of patients who underwent retransplantation because of other indications (p = 0.02).

CONCLUSIONS

Preoperative ambulatory status predicts early survival and center volume predicts intermediate-term outcome after retransplantation. Improved management strategies are necessary to prevent the development of progressive graft dysfunction after retransplantation for obliterative bronchiolitis.