Oliver A.R. Binns

Reperfusion injury significantly impacts clinical outcome after pulmonary transplantation

BACKGROUND Reperfusion injury after pulmonary transplantation can contribute significantly to postoperative pulmonary dysfunction. We hypothesized that posttransplantation reperfusion injury would result in an increase in both in-hospital mortality and morbidity. We also hypothesized that the incidence of reperfusion injury would be dependent upon the cause of recipient lung disease and the interval of donor allograft ischemia. METHODS We performed a retrospective study of all lung transplant recipients at our institution from June 1990 until June 1998. One hundred patients received 120 organs during this time period. We compared two groups of patients in this study: those experiencing a significant reperfusion injury (22%) and those who did not (78%). RESULTS In-hospital mortality was significantly greater in patients experiencing reperfusion injury (40.9% versus 11.7%, p < 0.02). Posttransplantation reperfusion injury also resulted in prolonged ventilation (393.5 versus 56.8 hours, p < 0.001) and an increased length of stay in both the intensive care unit (22.2 versus 10.5 days, p < 0.01) and in the hospital (48.8 versus 25.6 days, p < 0.03). The incidence of reperfusion injury could not be attributed to length of donor organ ischemia (221.5 versus 252.9 minutes, p < 0.20). The clinical impact of reperfusion injury was significantly greater in patients undergoing transplantation for preexisting pulmonary hypertension (6/14) than those with chronic obstructive pulmonary disease or emphysema alone (6/54) (42.9% versus 11.1%, p < 0.012). CONCLUSIONS Clinically significant pulmonary reperfusion injury increased in-hospital mortality and morbidity resulting in prolonged ventilation, length of stay in the intensive care unit, and cost of hospitalization. The incidence of reperfusion injury was not dependent upon the duration of donor organ ischemia but increased with the presence of preoperative pulmonary hypertension. These findings suggest that recipient pathophysiology and donor allograft quality may play important roles in determining the incidence of reperfusion injury.

Pulmonary function after non—heart-beating lung donation in a survival model

BACKGROUND Lung procurement from recently deceased cadavers has been suggested to enlarge the limited donor pool. We hypothesized that lungs harvested from non-heart-beating donors (NHBD) would function as well as those harvested from heart-beating donors. METHODS Sixteen adult swine underwent left lung allotransplantation. Controls received lungs procured from heart-beating donors, NHBD pigs received lungs immediately harvested from donors after death from asphyxiation, and NHBD-15 and NHBD-30 pigs received lungs harvested after 15 and 30 minutes after asphyxiation. RESULTS After 1 week of survival, mean dynamic airway compliance (mL/cm H2O +/- standard error of the mean) was 16.3 +/- 0.7 in controls, and 17.3 +/- 1.0, 16.4 +/- 6.0, and 7.3 +/- 1.6 in the NHBD, NHBD-15, and NHBD-30 groups, respectively (p = 0.02, NHBD-30 versus others combined). No significant differences were noted in the pulmonary venous partial pressure of oxygen or pulmonary vascular hemodynamics compared with controls. CONCLUSIONS The decrease in airway compliance noted in the NHBD-30 group may reflect an exacerbation of reperfusion injury caused by 30 minutes of warm ischemia during organ retrieval. We conclude that posttransplantation lung function using an NHBD with up to 15 minutes of warm ischemia is equivalent to lung function after heart-beating harvest.

Intravenous Phenylephrine Preconditioning of Cardiac Grafts From Non–Heart-Beating Donors

BACKGROUND Hypoxia and warm ischemia produce severe injury to cardiac grafts harvested from non-heartbeating donors. To potentially improve recovery of such grafts, we studied the effects of intravenous phenylephrine preconditioning. METHODS Thirty-seven blood-perfused rabbit hearts were studied. Three groups of non-heart-beating donors underwent intravenous treatment with phenylephrine at 12.5 (n = 8), 25 (n = 7), or 50 microg/kg (n = 7) before initiation of apnea. Non-heart-beating controls (n = 8) received saline vehicle. Hypoxic cardiac arrest occurred after 6 to 12 minutes of apnea, followed by 20 minutes of warm in vivo ischemia. A 45-minute period of ex vivo reperfusion ensued. Nonischemic controls (n = 7) were perfused without antecedent hypoxia or ischemia. RESULTS Phenylephrine 25 microg/kg significantly delayed the onset of hypoxic cardiac arrest compared with saline controls (9.6 +/- 0.5 versus 7.7 +/- 0.4 minutes; p = 0.00001), yet improved recovery of left ventricular developed pressure compared with saline controls (57.1 +/- 5.3 versus 41.0 +/- 3.4 mm Hg; p = 0.04). Phenylephrine 25 microg/kg also yielded a trend toward less myocardial edema than saline vehicle (p = 0.09). CONCLUSIONS Functional recovery of nonbeating cardiac grafts is improved by preconditioning. We provide evidence that the myocardium can be preconditioned with phenylephrine against hypoxic cardiac arrest.

Non-heart-beating donors: A model of thoracic allograft injury

4ACKGROUND. Non-heart-beating donors (NHBDs) have been proposed for the critical shortage of donors for cardiac and pulmonary transplantation. We determined the effects of prearrest hypoxia and postarrest warm ischemia on cardiac and pulmonary allografts procured from NHBDs undergoing hypoxic arrest. METHODS. Rabbit hearts and lungs were procured from separate donors and placed on isolated blood perfusion circuits. Controls were excised and perfused without ischemia. Heart from NHBDs underwent either prearrest hypoxic perfusion alone or consecutive periods of prearrest hypoxic perfusion and 20 minutes of postarrest warm ischemia. A third group of hearts underwent 30 minutes of warm, global ischemia alone. Two groups of pulmonary allografts were studied using similar hypoxic perfusion/20-minute ischemia and 30-minute ischemia donors. RESULTS. Prearrest hypoxic perfusion clearly causes significant dysfunction of cardiac allografts from NHBDs compared with nonischemic controls. Prearrest hypoxic perfusion combined with postarrest ischemia results in an additive degree of dysfunction more severe than a similar period of warm ischemia alone. Both groups of experimental lungs displayed function similar to that of nonischemic controls in terms of pulmonary hemodynamics, airway resistance, and oxygenation potential. CONCLUSIONS. We conclude that prearrest hypoxic perfusion significantly contributes to the dysfunction of NHBD cardiac allografts. Pulmonary allografts may be more amenable to procurement of NHBDs.

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.

Intratracheal Surfactant Administration Preserves Airway Compliance During Lung Reperfusion

BACKGROUND Decreased airway compliance after lung transplantation has been observed with severe ischemia-reperfusion injury. Further, it has been shown that the surfactant system is impaired after lung preservation and reperfusion. We hypothesized that surfactant replacement after allograft storage could preserve airway compliance during reperfusion. METHODS Rabbit lungs were harvested after flush with 50 mL/kg of cold saline solution. Immediate control lungs were studied with an isolated ventilation/perfusion apparatus using venous rabbit blood recirculated at 40 mL/min, room-air ventilation at 20 breaths/min, and constant airway pressure (n = 8). Twenty-four-hour control lungs were preserved at 4 degrees C for 24 hours and then similarly studied (n = 7). Surfactant lungs underwent similar harvest and preservation for 24 hours, but received 1.5 mL/kg of intratracheal surfactant 5 minutes before reperfusion (n = 10). Airway pressure and flow were recorded continuously during 30 minutes of reperfusion. Tidal volume and airway compliance were calculated at 30 minutes. RESULTS Tidal volume was 33.67 +/- 0.57, 15.75 +/- 5.72, and 29.83 +/- 1.07 mL in the immediate control, 24-hour control, and surfactant groups, respectively (p = 0.004, surfactant versus 24-hour control). Airway compliance was 1.94 +/- 0.27, 0.70 +/- 0.09, and 1.46 +/- 0.10 mL/mm Hg in the immediate control, 24-hour control, and surfactant groups, respectively (p = 0.002, surfactant versus 24-hour control). CONCLUSIONS We conclude that surfactant administration before reperfusion after 24 hours of cold storage preserves tidal volume and airway compliance in the isolated ventilated/perfused rabbit model of lung reperfusion injury.

Both blood and crystalloid-based extracellular solutions are superior to intracellular solutions for lung preservation☆☆☆★★★♢♢♢

OBJECTIVE Lung transplantation remains limited by donor organ ischemic time, inadequate graft preservation, and reperfusion injury. We evaluated lung preservation with use of an extracellular solution, with or without the addition of blood, as compared with preservation with the intracellular Euro-Collins solution. METHODS With use of an isolated, whole blood perfused/ventilated rabbit lung model, we studied three groups of animals. Lungs were flushed with Euro-Collins, low-potassium dextran, or 20% blood-low-potassium dextran solution. Lungs were harvested en bloc, stored inflated at 4 degrees C for 18 hours, and then reperfused at 60 ml/min with whole blood. Continuous measurements of pulmonary artery pressure, pulmonary vascular resistance, and dynamic airway compliance were obtained. Fresh, nonrecirculated venous blood was used to determine the single-pass pulmonary venous-arterial oxygen gradient. RESULTS Lungs preserved with Euro-Collins solution demonstrated elevated pulmonary artery pressure and pulmonary vascular resistance when compared with those preserved with low-potassium dextran and 20% blood-low-potassium dextran solutions (pulmonary artery pressure: 40.8 +/- 2.2 mm Hg vs 28.9 +/- 2.4 mm Hg and 28.3 +/- 1.5 mm Hg, respectively, p < 0.001; pulmonary vascular resistance: 46.0 +/- 3.1 x 10(3) dynes x sec x cm(-5) vs 29.0 +/- 4.2 x 10(3) dynes x sec x cm(-5) and 28.8 +/- 2.3 x 10(3) dynes x sec x cm(-5), respectively, p < 0.001). Euro-Collins solution-preserved lungs demonstrated a significant drop in compliance when compared with those preserved with low-potassium dextran and 20% blood-low-potassium dextran (-21.9% +/- 4.7% vs 1.8% +/- 3.3% and 1.4% +/- 6.2%, respectively; p = 0.002). Oxygenation was improved with low-potassium dextran and 20% blood-low-potassium dextran solutions as compared with that with Euro-Collins solution (296.3 +/- 54.6 mm Hg and 290.2 +/- 66.4 mm Hg, respectively, vs 37.2 +/- 4.6 mm Hg; p = 0.001). CONCLUSIONS Extracellular solutions provided superior preservation of pulmonary function in this rabbit lung model of ischemia-reperfusion. However, the addition of blood does not confer any demonstrable advantage over low-potassium dextran solution alone with use of an 18-hour period of cold ischemia.

Thromboxane receptor blockade improves oxygenation in an experimental model of acute lung injury

BACKGROUND Adult respiratory distress syndrome remains a major cause of morbidity and mortality. We investigated the role of thromboxane receptor antagonism in an experimental model of acute lung injury that mimics adult respiratory distress syndrome. METHODS Three groups of rabbit heart-lung preparations were studied for 30 minutes in an ex vivo blood perfusion/ventilation system. Saline control (SC) lungs received saline solution during the first 20 minutes of study. Injury control (IC) lungs received an oleic acid-ethanol solution during the first 20 minutes. Thromboxane receptor blockade (TRB) lungs received the same injury as IC lungs, but a thromboxane receptor antagonist (SQ30741) was added to the blood perfusate just prior to study. Blood gases were obtained at 10-minute intervals, and tidal volume, pulmonary artery pressure, and lung weight were continuously recorded. Oxygenation was assessed by measuring the percent change in oxygen tension over the 30-minute study period. Tissue samples were collected from all lungs for histologic evaluation. RESULTS Significant differences were found between SC and IC lungs as well as TRB and IC lungs when comparing pulmonary artery pressure (SC = 33.1 +/- 2.2 mm Hg, TRB = 35.4 +/- 2.1 mm Hg, IC = 60.4 +/- 11.1 mm Hg; p < 0.02) and percent change in oxygenation (SC = -20.6% +/- 10.3%, TRB = -24.2% +/- 9.5%, IC = -57.1% +/- 6.2%; p < 0.03). None of the other variables demonstrated significant differences. CONCLUSIONS Thromboxane receptor blockade prevents the pulmonary hypertension and the decline in oxygenation seen in an experimental model of acute lung injury that mimics adult respiratory distress syndrome.

Neutrophil endopeptidase inhibitor improves pulmonary function during reperfusion after eighteen-hour preservation

BACKGROUND Reperfusion injury remains a significant problem after lung transplantation and is thought to be in part mediated by neutrophils. Ulinastatin inhibits release of elastase and cathepsin G from neutrophil granules. We hypothesized that inhibition of these neutrophi endopeptidases (proteases) would attenuate pulmonary reperfusion injury. METHODS With an isolated, whole blood-perfused, ventilated rabbit lung model, we studied the effects of ulinastatin. All lungs were flushed with cold Euro-Collins solution, harvested en bloc, stored inflated at 4 degrees C for 18 hours, and reperfused with whole blood. The 18-hour control lungs (n = 8) were stored and reperfused. Low-dose (n = 8) and high-dose (n = 7) groups were treated with total doses of ulinastatin of 25,000 and 50,000 units, respectively, during flush and reperfusion. An additional control group of lungs (n = 8) was harvested, flushed, and immediately reperfused. RESULTS The pulmonary artery pressure was significantly lower in the high-dose group than in the 18-hour control group (36.7 +/- 1.8 vs 44.8 +/- 2.9 mm Hg, p = 0.034). The percentage decrease in dynamic airway compliance was significantly less in the high-dose group than in the 18-hour control group (-13.8% +/- 4.4% vs -25.1% +/- 3.7%, p = 0.032). Both low-dose and high-dose ulinastatin treatments did not result in a significant improvement in oxygenation with respect to the 18-hour control group (72.2 +/- 25.8 vs 32.5 +/- 4.9 mm Hg, p = 0.21). CONCLUSIONS Ulinastatin diminishes reperfusion injury after 18 hours of hypothermic pulmonary ischemia, with resultant improvements in pulmonary artery pressure and airway compliance. Improvement in pulmonary function after preservation and reperfusion with a neutrophil endopeptidase inhibitor confirms the role of endopeptidases in reperfusion injury and suggests an intervention to reduce their detrimental effects on early graft function.

Mature pulmonary lobar transplants grow in an immature environment

OBJECTIVE Mature lobar transplantation will increase the pediatric donor organ pool, but it remains unknown whether such grafts will grow in a developing recipient and provide adequate long-term support. We hypothesized that a mature pulmonary lobar allograft implanted in an immature recipient would grow. METHODS We investigated our hypothesis in a porcine orthotopic left lung transplant model using animals matched by the major histocompatibility complex to minimize the effects of chronic rejection. Twenty-three immature animals (< 12 weeks of age and < 10 kg total body weight) received either sham left thoracotomy (SH control, n = 4), left upper lobectomy to study compensatory growth (UL control, n = 4), age-matched immature whole left lung transplants (IWL TXP, n = 6), mature (donor > 1 yr in age and > 40 kg in total body weight) left lower lobe transplants (MLL TXP, n = 5), or mature left upper lobe transplants (MUL TXP, n = 4). Twelve weeks after implantation, functional residual capacity of the left lung was measured and arterial blood gas samples were obtained after the native right lung had been excluded. The graft was excised and weighed, and samples for microscopy and wet/dry ratios were collected. RESULTS Initial and final graft weights were as follows: IWL TXP group (34.6 +/- 1.5 and 107.8 +/- 5.9 gm, p < 0.0001), MLL TXP group (72.4 +/- 6.8 and 111.4 +/- 8.7, p < 0.001), and MUL TXP group (32.8 +/- 1.3 and 92.8 +/- 7.1 gm, respectively, p < 0.004). No significant differences between groups were demonstrated when functional residual capacity, wet/dry ratios, or oxygenation were compared. Immunohistochemical staining for the nuclear antigen Ki-67 demonstrated dividing pneumocytes. CONCLUSIONS We conclude that a mature lobar graft implanted into an immature recipient grows by pneumocyte division in this model. Mature lobar transplants can be expected to grow and provide adequate long-term function in developing recipients.