Reperfusion injury occurs in the lung by free radical mechanisms

Pyrrolidine dithiocarbamate reduces lung reperfusion injury

BACKGROUND

The inflammatory cascade has emerged as the primary mediator of reperfusion injury. Nuclear factor kappaB (NF-kappaB) is a rapid response transcription factor that activates genes responsible for the mediators of inflammation. Heat shock protein 70 (HSP70) has been shown to protect against lung injury. We hypothesized that the antioxidant pyrrolidine dithiocarbamate (PDTC), an inhibitor of NF-kappaB and upregulator of HSP70, would decrease lung injury after ischemia and reperfusion.

METHODS

Using our isolated, ventilated, blood-perfused rabbit lung model, all groups underwent lung harvest followed by 10-h storage (4 degrees C) and blood reperfusion for 30 min. Group I lungs (n = 5) served as controls. In group II lungs (n = 5), both lung and blood donors received PDTC (100 mg/kg) intravenously 30 min before harvest. NF-kappaB activity was evaluated with electrophoretic mobility shift assay, and Western blot was performed for HSP70.

RESULTS

Group II demonstrated superior pulmonary function. Although HSP70 expression was somewhat elevated in group II lungs, NF-kappaB binding activity was not different between the groups.

CONCLUSIONS

PDTC improves pulmonary function after ischemia and reperfusion in an isolated rabbit lung model. The improved function correlates with elevated HSP70 expression during initial reperfusion, independent of NF-kappaB activity.

A comparison of the new preservation solution Celsior to Euro-Collins and University of Wisconsin solutions in lung reperfusion injury

BACKGROUND

The lung is particularly susceptible to reperfusion injury, both experimentally and clinically after transplantation. The extracellular-type preservation solution Celsior, which has been predominantly studied in cardiac preservation, has components designed to prevent cell swelling, free radical injury, energy depletion, and calcium overload. Using an isolated blood-perfused rat lung model, we investigated whether Celsior would decrease preservation injury and improve lung function after cold ischemic storage and reperfusion compared to Euro-Collins (EC) and University of Wisconsin (UW) solutions.

METHODS

Lewis rat lungs were isolated, flushed with the respective cold preservation solution, and then stored at 4 degrees C for 6 or 12 hr. After ischemic storage, the lung block was suspended from a force transducer, ventilated with 100% O2, and reperfused for 90 min with fresh blood via a cannula in the pulmonary artery. Lung compliance, alveolar-arterial oxygen difference, and outflow oxygen tension were all measured. The capillary filtration coefficient (Kf), a sensitive measure of changes in microvascular permeability, was determined.

RESULTS

For 6 hr of cold storage, lungs stored in Celsior had lower Kf values than those stored in EC, indicating decreased microvascular permeability. No other significant differences were noted between Celsior and EC or UW. For 12 hr of cold storage, Celsior provided increased oxygenation, decreased alveolar-arterial O2 differences, increased compliance, and decreased Kf values as compared to both EC and UW.

CONCLUSIONS

Celsior provides better lung preservation than EC or UW as demonstrated by increased oxygenation, decreased capillary permeability, and improved lung compliance, particularly at 12-hr storage times. These results are highly relevant, inasmuch as EC and UW are the most common clinically used lung preservation solutions. Further studies of Celsior in experimental and clinical lung transplantation, as well as in other solid organs, are indicated.

Neutrophil modulation results in improved pulmonary function after 12 and 24 hours of preservation

Neutrophils are important mediators of reperfusion injury, and suppression of neutrophil function or numbers can reduce reperfusion injury and improve long-term organ preservation in transplantation. NPC 15669, a leumedin, is a novel compound that prevents recruitment of neutrophils at inflammatory foci by inhibiting CD11b/CD18 adhesion molecule expression. NPC 15669 was used to inhibit neutrophil adhesion during reperfusion of isolated rabbit lungs after 12 and 24 hours of cold storage. Lungs (New Zealand White male rabbits, 2 to 3 kg) were flushed with 4 degrees C Euro-Collins (EC) solution, harvested en bloc, stored under various study conditions, and reperfused for 3 hours with fresh whole blood at 37 degrees C in an isolated perfusion system at constant flow and an inspired oxygen fraction of 1. Four groups (n = 6 each) were studied. Group I underwent immediate whole blood reperfusion. Group II were stored for 12 hours in 4 degrees C EC solution before reperfusion. Group III were stored for 12 hours in 4 degrees C EC solution and reperfused with whole blood containing NPC 15669 (10 mg/kg whole body weight). Group IV were stored for 24 hours in 4 degrees C EC solution and reperfused with whole blood containing NPC 15669 (10 mg/kg). Pulmonary artery and peak airway pressures were significantly lower and compliance higher in groups III and IV lungs after 3 hours of reperfusion (p < 0.05) compared with group I. Group I and III lungs had significantly less edema than group II (p < 0.05). The arterial partial pressure of oxygen was similar in all stored groups (II to IV).(ABSTRACT TRUNCATED AT 250 WORDS)

[Anesthesia and intensive care for heart-lung transplantation]

Since Shumway carried out the first successful heart-lung transplant (HLT) in Stanford in 1981, HLT has become a new therapeutic means for patients with end-stage pulmonary disease or arterial hypertension. However, it is still rarely carried out because of a lack of donors and the complexity of the surgery and postoperative course. This review described the criteria for proper donor and recipient selection, as well as the anaesthetic and postoperative management of HLT patients at Marie Lannelongue Hospital. The lack of suitable organ grafts results, at least in part, from improper donor management. Pulmonary oedema by fluid overloading and excessive haemodilution should be carefully prevented. Low doses of catecholamines and vasopressin maintain circulatory stability and convenient organ function. The indications for HLT (primary pulmonary hypertension, Eisenmenger's complex, and end-stage bronchopulmonary disease) are all characterized by severe pulmonary hypertension, hypoxaemia and cardiac failure. Careful anaesthetic induction is required to avoid circulatory collapse. Cardiopulmonary bypass (CPB) should be started early, so that mediastinal dissection may be carried out in satisfactory haemodynamic conditions. After unclamping the aorta, circulatory support with fluid and catecholamine infusion is often required. High inspired oxygen fraction and end-expiratory positive pressure may be required because of reperfusion pulmonary oedema. Blood transfusion is often needed as there are major blood losses due to dissection of the posterior mediastinum during CPB. Postoperative catecholamine administration is prolonged over several days. Negative fluid balance is often necessary to reduce pulmonary oedema. Improvement in surgical technique, early extubation, and late prescription of steroids have reduced the incidence of tracheal complications. Acute renal failure often occurs as a result of prolonged CPB, hypovolaemia, drug nephrotoxicity and sepsis. Bacterial complications (pneumonia, mediastinitis) are the main causes of early death. After the 15th postoperative day, opportunistic infections and allograft rejection are the main complications. Since 1981, major advances in HLT recipient management resulted in improved survival rates (70-80% at 1 year, and 60-70% at 2 years for the best teams). Despite the complexity of management, and the longterm threat of obliterative bronchiolitis, HLT is, at present time, the only possibility for these young patients to recover a normal quality of life.

Oxygen free radical scavengers decrease reperfusion injury in lung transplantation

An in vivo canine model was used to assess the ability of an oxygen free radical scavenger to decrease reperfusion injury in lung transplantation. In 12 dogs, the left lungs were transplanted after they had been preserved for 24 hours at 4 degrees C after pulmonary artery flushing with modified Eurocollins solution. In 6 dogs, dimethylthiourea, a potent oxygen free radical scavenger, was added to the flush solution and was also given to the recipients just before reperfusion. In all animals, the contralateral pulmonary artery and bronchus were ligated and lung function was assessed for 12 hours or until death. Three dogs died prematurely in the control group, whereas only 1 dog died prematurely in the dimethylthiourea group. This resulted in a statistically significant difference in the average length of survival (p less than 0.05). Pulmonary artery and right atrial pressures were significantly lower in the dimethylthiourea group during the first 6 hours (p less than 0.05). Treatment with dimethylthiourea resulted in a significantly higher arterial oxygen tension at 4 hours, and intrapulmonary shunt tended to be lower. Thus, it would appear that dimethylthiourea has a protective effect on lungs preserved for 24 hours before transplantation in dogs.

Improved lung preservation using a dimethylthiourea flush

The purpose of this study was to evaluate the ability of dimethylthiourea (DMTU), a low molecular weight hydroxyl free radical scavenger, to improve preservation of the lung for transplantation. Following preservation, 15 isolated canine left lower lobes were reperfused for 90 min with autologous blood. Five group I lobes served as controls and were not subjected to ischemia prior to reperfusion. Five group II lobes were flushed and submerged in a cold Euro-Collins solution and stored for 4 hr at 4 degrees C prior to reperfusion. Group III lobes were flushed with a 20 mM DMTU-enhanced Euro-Collins solution, stored for 4 hr, and then reperfused. The isogravimetric method was utilized to determine the capillary permeability coefficient (Kfc) for the reperfused lobes. The Kfc values were 0.10 +/- 0.01, 0.17 +/- 0.01, and 0.10 +/- 0.008 ml/min/mm Hg/100 g lung for groups I, II, and III, respectively (P less than 0.01 II vs I, III). Extravascular lung water values in the reperfused lobe were 4.44 +/- 0.45, 6.57 +/- 0.38, and 5.23 +/- 0.22 ml/g blood free dry lung weight for groups I, II, and III (P less than .05, II vs. I, III). Lung lipid peroxidation, measured as thiobarbituric acid-reactive material, was higher in group II, 146 +/- 6 nmole/g, than in either group I, 90 +/- 5 nmole/g, or group III, 91 +/- 4 nmole/g (P less than 0.01). The results indicate that the addition of DMTU improves hypothermic lung preservation by reducing lipid peroxidation and edema formation upon reperfusion.

Reperfusion injury in the lung preserved for 24 hours

The left lower lobes of 28 canine lungs were isolated, preserved, and then reperfused for 150 minutes. Five groups of lobes were studied: group 1, control (n = 5); group 2, one hour of warm ischemia (n = 5); group 3, one hour of warm ischemia + oxygen free radical scavengers (n = 5); group 4, 24 hours of cold ischemia (n = 8); and group 5, 24 hours of cold ischemia + oxygen free radical scavengers (n = 5). Oxygen free radical scavengers consisted of superoxide dismutase and catalase (100 micrograms/mL) given at the moment of reflow. Extravascular lung water (grams per gram of blood-free dry lobe weight) after reperfusion was 2.75 +/- 0.19, 5.46 +/- 0.60, 4.08 +/- 0.37, 9.43 +/- 0.98, and 6.91 +/- 0.95 for groups 1 through 5, respectively (p less than 0.05, groups 2 through 5 versus group 1; p less than 0.05, group 2 versus group 3 and group 4 versus group 5). Lung tissue lipid peroxidation, measured as thiobarbituric acid reactive material, was 117 +/- 14, 314 +/- 19, and 163 +/- 25 nmol/g dry lobe weight for groups 1, 4, and 5, respectively (p less than 0.05, group 4 versus group 1 and group 4 versus group 5). The data suggest that oxygen free radical scavengers attenuate reperfusion injury after long-term hypothermic lung preservation.