Survival and graft function in a large animal lung transplant model after 30 h preservation and substitution of the nitric oxide pathway.

OBJECTIVE: Substitution of the nitric oxide- (NO-) pathway improves early graft function following lung transplantation. We previously demonstrated that 8-Br-cGMP (second messenger of NO) to the flush solution and tetrahydrobiopterin (BH4, coenzyme of NO synthase) given as additive during reperfusion improve post-transplant graft function. In the present study, the combined treatment with 8-Br-cGMP and BH4 was evaluated. METHODS: Unilateral left lung transplantation was performed in weight matched outbred pigs (24-31 kg). In group I, grafts were preserved for 30 h (n=5). 8-Br-cGMP (1mg/kg) was added to the flush solution (Perfadex, 1.5l, 1 degrees C) and BH4 (10mg/kg/h) was given to the recipient for 5h after reperfusion. In group II, lungs were transplanted after a preservation time of 30 h (n=3) and prostaglandin E(1) (250 g) was given into the pulmonary artery (PA) prior to flush. In all recipients 1h after reperfusion the contralateral right PA and bronchus were ligated to assess graft function only. Survival time after reperfusion, extravascular lung water index (EVLWI), hemodynamic variables, and gas exchange (PaO(2)) were assessed during a 12h observation period. RESULTS: All recipients in group I survived the 12h assessment, whereas none of the group II animals survived more than 4h after reperfusion with a rapid increase of EVLWI up to 24.8+/-6.7 ml/kg. In contrast, in group I EVLWI reached up to 8.9+/-1.5 ml/kg and returned to nearly normal levels at 12h (6.1+/-0.8 ml/kg). In two animals of group I the gas exchange deteriorated slightly. The other three animals showed normal arterial oxygenation over the entire observation time. CONCLUSION: Our data indicate that the combined substitution of the NO pathway during preservation and reperfusion reduces ischemia/reperfusion injury substantially and that this treatment even allows lung transplantation after 30 h preservation in this model.

8-Br-cyclic GMP given during reperfusion improves post-transplant lung edema and free radical injury.

UNLABELLED: Substitution of the NO-pathway reduces ischemia/reperfusion injury following lung transplantation. 8-Br-cGMP is a membrane permeable analogue of cGMP, the second messenger of NO. In this study the effect of continuous administration of 8-Br-cGMP on early graft function was evaluated. METHODS: Unilateral left lung transplantation was performed in 10 weight-matched pigs (23-30 kg). Donor lungs were flushed with 1.51 cold (1 degree C) LPD solution and preserved for 20 hours. In Group I (n = 5), 8-Br-cGMP (0.2 mg/kg/h) was given continuously over the entire observation time starting 15 min before reperfusion. Group II served as control, no 8-Br-cGMP was administered. In both groups, 250 microg PGE1 was injected into the pulmonary artery (PA) before flush. One hour after reperfusion the recipients contralateral right PA and bronchus were ligated to assess isolated graft function only. Extravascular lung water index (EVLWI), pulmonary vascular resistance, mean PA pressure, mean systemic arterial pressure and gas exchange were assessed during a 5-hour observation period. Lipid peroxidation as indicator for free radical mediated injury and neutrophil migration to the allograft were measured at the end of the assessment. RESULTS: EVLWI was significantly reduced in animals treated with 8-Br-cGMP (overall difference P = 0.024) with a peak 2 hours after reperfusion (Group I, 8.2+/-0.3 mg/ml vs Group II, 10.1+/-0.6 mg/ml; P = 0.039). Also in Group I the free radical mediated tissue injury was significantly lower when compared to Group II (Group I, 61.8+/-12.3 pmol/g vs Group II, 120.7+/-7.2 pmol/g; P = 0.006). A tendency towards a reduced neutrophil migration after 8-Br-cGMP infusion was shown; however, the changes in comparison to the control animals were not statistically significant (Group I, 1.0+/-0.2 deltaOD/mg/min vs Group II, 1.7+/-0.3 deltaOD/mg/min; P = 0.13). Pulmonary- and systemic hemodynamics, and allograft gas exchange did not differ between groups. CONCLUSIONS: The results indicate that substitution of the NO pathway by administration of the second messenger cGMP at the time of reperfusion improves post-transplant lung allograft function.

8-Br-cGMP is superior to prostaglandin E1 for lung preservation.

BACKGROUND: Substitution of the nitric oxide (NO) pathway reduces ischemia/reperfusion injury after lung transplantation. 8-Br-cGMP is a membrane-permeable analogue of cGMP, the second messenger of NO. In this study, we evaluated the effect of administration of 8-Br-cGMP in the flush solution on early graft function. METHODS: Unilateral left lung transplantation was performed in 10 weight-matched pairs of outbred pigs (24 to 31 kg). Donor lungs were flushed with 1.5 L cold (1 degree C) low potassium dextrane (LPD) solution and preserved for 20 hours. In group I (n = 5), 8-Br-cGMP (1 mg/kg) was added to the flush solution. In group II (n = 5), 8 microg/kg prostaglandin E1 (PGE1) was injected into the pulmonary artery (PA) before flush. One hour after reperfusion, the recipients' contralateral right PA and bronchus were ligated to assess graft function only. cGMP levels in the PA and pulmonary vein were measured. Extravascular lung water index (EVLWI), pulmonary vascular resistance, mean PA pressure, and gas exchange (PaO2) were assessed during a 5-hour observation period. Lipid peroxidation (thiobarbituric acid-reactive substance) and neutrophil migration to the allograft (myeloperoxidase activity) were measured at the end of the assessment. RESULTS: In group I, a significant reduction of EVLWI (group I, 6.7 +/- 1.0 mL/kg vs group II, 10.1 +/- 0.6 ml/kg after 2 hours of reperfusion; p = 0.022), TBARS (group I, 65.6 +/- 10.0 pmol/g vs group II, 120.8 +/- 7.2 pmol/g, p = 0.0039), and MPO activity (group I, 0.8 +/- 0.1 change in optical density, (deltaOD)/mg/min vs group II, 1.7 +/- 0.3 deltaOD/mg/min, p = 0.036) was noted in comparison with group II. PaO2 levels tended to be higher in cGMP-treated animals, but the changes were not significant. Hemodynamic parameters did not differ between groups. CONCLUSIONS: In this large animal model of lung allograft ischemia/reperfusion injury, 8-Br-cGMP as additive to the flush solution improves posttransplant lung edema, lipid peroxidation, and neutrophil migration to the allograft. This effect is not attributable to improved flush by vasodilation, as we compared 8-Br-cGMP with PGE1 given before flush in control animals.