Extended ex vivo preservation of the heart and lungs

The clinical potential of ex vivo lung perfusion

The number of patients listed for lung transplantation largely exceeds the number of available transplantable organs because of both a shortage of organ donors and a low utilization rate of donor lungs. Normothermic ex vivo lung perfusion (EVLP) is a method that maintains the organ in physiologically protective conditions outside the body during preservation, and shows great promise to increase utilization of donor lungs by allowing more accurate evaluation, as well as treatment and repair, of damaged donor lungs prior to transplantation. This article will cover the rationale, technical details and results of experimental and clinical studies with EVLP. The significant potential applications of EVLP in lung transplantation, lung regeneration and oncology are discussed.

Effects of a bradykinin B(2) receptor antagonist on ischemia-reperfusion injury in a canine lung transplantation model

BACKGROUND

This study investigated the effects of a bradykinin B(2) receptor antagonist, FR173657 (FR), on ischemia-reperfusion (I/R) injury in a canine lung transplantation model.

METHODS

Eighteen pairs of weight-matched dogs were randomly divided into 3 groups. Six pairs were assigned to the FR(D+R) group, in which FR (100 nmol/kg/h) was administered to the transplant donor continuously beginning 30 minutes before ischemia until the onset of ischemia, and FR was administered to the transplant recipient beginning 30 minutes before reperfusion and continuing for 2 hours after reperfusion. Another 6 pairs of dogs were assigned to the FR(R) group, in which FR was administered only to the recipient in the same manner as in the FR(D+R) group. The other pairs were assigned to the control group, in which vehicle alone was administered. Orthotopic left lung transplantation was performed after 12-hour cold storage in Euro-Collins solution. Fifteen minutes after reperfusion, the right pulmonary artery and the right stem bronchus were ligated. The animals were measured for 4 hours after reperfusion for left pulmonary vascular resistance (L-PVR), cardiac output (CO), arterial oxygen pressure (PaO(2)) and alveolar-arterial oxygen pressure difference (A-aD(O(2))). Lung specimens were harvested for measurement of the wet-to-dry lung weight ratio (WDR), histopathologic studies and polymorphonuclear neutrophil (PMN) count.

RESULTS

Compared with the control group, PaO(2), A-aDO(2), L-PVR and CO were all significantly (p < 0.05) improved and WDR significantly (p < 0.05) lower in both the FR(D+R) and FR(R) groups. Moreover, in the FR-treated groups, histologic tissue edema was mild, and PMN infiltration was significantly (p < 0.05) reduced.

CONCLUSIONS

The bradykinin B(2) receptor antagonist, FR173657, ameliorates I/R injury in lung grafts, indicating that protection of lung grafts can be achieved by the administration of FR solely to the transplant recipient.

Effects of a bradykinin B(2) receptor antagonist, FR173657, on pulmonary ischemia-reperfusion injury in dogs

BACKGROUND

This study investigated the effects of a bradykinin B(2) receptor antagonist, FR173657 (FR), on pulmonary ischemia-reperfusion (I/R) injury.

METHODS

Twenty-four mongrel dogs were divided into four groups (n = 6 each). In Groups I, II and III, FR doses of 33, 100 and 300 nmol/kg per hour, respectively, were administered continuously beginning 30 minutes before ischemia and continuing for 2 hours after reperfusion. In Group IV, vehicle alone was administered. Warm ischemia was induced for 3 hours by clamping the left pulmonary artery and veins. Simultaneously, the left stem bronchus was bisected and then anastomosed before reperfusion. Fifteen minutes after reperfusion, the right pulmonary artery and bronchus were ligated. Left pulmonary vascular resistance (L-PVR), cardiac output (CO), arterial oxygen pressure (PaO(2)) and the alveolar - arterial oxygen pressure difference (A-aDO2) were measured for 4 hours after reperfusion. Lung tissue was harvested for wet-to-dry weight ratio (WDR) measurements, histopathologic studies and polymorphonuclear neutrophil (PMN) counts. Serum thromboxane (TX) B(2), 6-keto-prostaglandin (PG) F(1alpha) and leukotriene (LT) B(4) levels were also measured.

RESULTS

PaO(2), A-aDO2, L-PVR and CO were significantly (p < 0.05) improved and WDR was significantly (p < 0.05) lower in Groups II and III than in Group IV. Histologic tissue edema was mild, and PMN infiltration was significantly (p < 0.05) reduced in Groups I, II and III compared with Group IV. TXB(2) levels were significantly (p < 0.05) lower in Group II than in Group IV, whereas 6-keto-PGF(1alpha) levels were not significantly different. LTB(4) levels were significantly (p < 0.05) lower in Groups II and III than in Group IV.

CONCLUSIONS

FR appears to have a protective effect on pulmonary I/R injury stemming from the inhibition of eicosanoid release.

The effect of a selective cyclooxygenase-2 inhibitor in extended liver resection with ischemia in dogs

BACKGROUND

Pringle's procedure is commonly used during liver surgery, and it sometimes causes liver failure. Metabolites of arachidonic acid, which are converted by cyclooxygenase (Cox), are involved in ischemia-reperfusion injury. This study evaluated the effects of FK 3311, which selectively inhibits Cox-2, on ischemia-reperfusion injury during liver resection in dogs.

MATERIALS AND METHODS

The animals were divided into four groups and subjected to 60 min of warm ischemia by partial inflow occlusion. The FK-treated groups (FK0.2: 0.2 mg/kg, FK1: 1 mg/kg, FK3: 3mg/kg) received FK3311, and the control group received vehicle. Following reperfusion, the nonischemic lobes were resected and remnant liver function was evaluated.

RESULTS

Tissue blood flow and serum glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, and lactate dehydrogenase were significantly better in the FK1 and FK3 groups, especially FK1, than in the control group. Thromboxane B(2) was significantly lower in the FK1 and FK3 groups than in the control group. The level of 6-keto-prostaglandin F(1alpha) was significantly lower in the FK3 group and relatively unchanged in the FK1 group. Histological damage was milder in the FK1 group. There were significantly fewer polymorphonuclear neutrophils in the FK1 group than in the control group.

CONCLUSIONS

FK3311 ameliorates the ischemia-reperfusion injury caused by Pringle's procedure during extensive liver resection. This agent may be clinically useful in extended liver surgery involving vascular isolation.

Effects of FK3311 on pulmonary ischemia-reperfusion injury in a canine model

BACKGROUND

This study investigated the effects of a selective COX-2 inhibitor, FK3311, on warm ischemia-reperfusion (I/R) injury in the canine lung.

MATERIALS AND METHODS

Sixteen adult mongrel dogs were used in this study. In the FK group (n = 8), FK (1 mg/kg) was administered intravenously 15 min before ischemia and 15 min before reperfusion. In the control group (n = 8), a vehicle was injected in the same manner. Warm ischemia was induced for 3 h by clamping the left pulmonary artery, veins, and bronchus. Five-minute clamping tests of the right pulmonary artery were performed before ischemia and 30 min after reperfusion. During the test, left pulmonary vascular resistance (L-PVR), cardiac output (CO), and arterial oxygen pressure (PaO(2)) were measured. The lung specimens were simultaneously harvested for wet-to-dry weight ratio (WDR) measurements, histopathological studies, and polymorphonuclear neutrophil (PMN) counts. Serum thromboxane (Tx) B(2) and 6-keto-prostaglandin (PG) F(1alpha) (stable metabolites of TxA(2) and PGI(2), respectively) were also measured 30 min after reperfusion.

RESULTS

L-PVR, CO, PaO(2), and WDR were significantly (P < 0.05) better in the FK group than in the control group. Histological tissue edema was mild, and PMN infiltration was significantly (P < 0.05) reduced in the FK group compared to the control group. The serum TxB(2) levels were significantly (P < 0.05) lower in the FK group than in the control group, while 6-keto-PGF(1alpha) levels were not significantly (P < 0.05) reduced. Two-day survival rate was significantly (P < 0.05) better in the FK group than in the control group.

CONCLUSIONS

FK has protective effects on pulmonary I/R injury stemming from marked inhibition of TxA(2).

Effects of perfluorocarbon emulsions on cultured human endothelial cells

Perfluorocarbons (PFCs) and their emulsions (PFCEs) were used in organ preservation before transplantation, but not in organ perfusion. Our purpose was to achieve organ perfusion with a PFCE at room temperature or at 37 degrees C, i. e. with oxygenation, to prevent damages related to reoxygenation after hypoxia. Therefore, we first investigated the effect of such emulsions on endothelial cells, the first cells to be in contact with the emulsion. A stem emulsion was prepared from perfluorooctyl bromide (90% w/v), emulsified with egg yolk phospholipids (2% w/v) and stabilized with a mixed fluorocarbon-hydrocarbon "molecular dowel" (1.4% w/v) (droplets of ca 0.2 micron in diameter). This emulsion was found to be stable when diluted with cell culture media or organ preservation fluids. Endothelial cells from human umbilical vein (HUVECs) were cultured in multiwell plates in M199 medium (with growth factors, 10% foetal calf serum and 5% human serum). Confluent cells were incubated overnight with 51Cr, washed and overlayed with M199 (control) or the above PFCE diluted 2x or 4x with M199 (test). After incubation, the cytotoxicity of the PFCEs was estimated by measuring 51Cr release and observing cell morphology by electron and light microscopy. The percentages of released 51Cr were identical to those of the control cells for the 2x, 3x or 4x diluted PFCEs at 4, 25 or 37 degrees C. After return to the M199 medium, the cells grew and multiplied normally. We conclude that the diluted PFCEs were devoid of cytotoxicity. The 2x diluted PFCE was however partially taken up by the cells: by microscopy, we observed intracellular PFC droplets and by density gradient analysis we found a slight increase in cellular density. The diluted PFCEs were compared to classical organ preservation solutions : HUVECs were incubated with UW (University of Wisconsin) or EC (EuroCollins) solutions at +4 and 37 degrees C (3, 17 or 24 h of incubation). The solutions were observed to be toxic to the cells under these conditions, with cell mortality after return to the M199 medium. This cytotoxicity may be attributed to the high K+ concentration of UW and EC, since similar assays performed on HUVECs with Hank's solution adjusted to 100 mM K+ showed a similar % of 51Cr release. UW and EC are therefore not acceptable as dilution media for PFCEs.

Perfluorocarbons: recent developments and implications for neurosurgery

Over the last 30 years, perfluorocarbons (PFCs) have been extensively investigated as oxygen carriers. Early studies indicated that these compounds could be used as blood substitutes or protective agents against ischemia. Adverse characteristics such as instability, short intravascular half-life, and uncertainties concerning possible toxicity precluded wide clinical application. However, advances in PFC technology have led to the development of improved second-generation oxygen carriers that incorporate well-tolerated emulsifiers (egg-yolk phospholipids). The authors review recent developments in this field and consider the potential role of PFCs in future neurosurgical practice. Diagnostic applications could include their use to assess cerebral blood flow, local oxygen tension, and brain metabolism or to achieve enhanced imaging and precise staging of inflammatory, neoplastic, or vascular disease processes by means of computerized tomography, ultrasonography, and magnetic resonance studies. Therapeutic applications could include cerebral protection, an adjunctive role in radiotherapy of malignant brain tumors, protection against air embolism, the preservation of organs for transplantation, and ventilatory support in head-injured patients with compromised lung function. In addition, PFCs have been used successfully as a tool in ophthalmic microsurgery and potentially they could fulfill a similar role in microneurosurgery.

Granulocyte sequestration and early failure in the autoperfused heart-lung preparation

We investigated the role of pulmonary granulocyte sequestration in the development of early failure of the autoperfused working heart-lung preparation. A significant decline in the total circulating leukocyte count in 21 preparations at 60 minutes of perfusion (5.0 to 1.4 x 10(3)/microL; 28% of baseline; p less than 0.001) was observed. Differential cell counts in 14 of these preparations revealed a predominant decrease in granulocyte count (8.7% of baseline) and a moderate decline in lymphocyte count (46% of baseline). In study I, indium 111-labeled autologous granulocytes were injected intravenously into 10 adult New Zealand White rabbits. In group I (n = 5), an autoperfused working heart-lung preparation was harvested and perfused for 60 minutes. In group II (controls, n = 5), the heart-lung block was harvested following 60 minutes of in situ perfusion. Organ blocks were imaged before and after saline flush. There was a significant decline in granulocyte counts at 60 minutes of perfusion in group I versus no change in group II (I, 2.3 +/- 0.4 to 0.3 +/- 0.1; p less than 0.01; II, 1.7 +/- 0.2 to 2.3 +/- 0.5; not significant; x 10(3)/microL +/- standard error of the mean). Postflush lung activity was significantly increased in group I versus group II (I, 3,751 +/- 566; II, 1,867 +/- 532; p less than 0.05; counts +/- standard error of the mean). In study II, 15 autoperfused preparations were divided into two groups. Group I (n = 10) preparations were controls. Group II (n = 5) animals were depleted of leukocytes by pretreating with nitrogen mustard. Group I (controls) produced a bimodal survival distribution (Ia, 8.2 +/- 1.0; Ib, 26.4 +/- 2.0; hours +/- standard error of the mean). Group II survival was significantly longer than that of group Ia and similar to that of group Ib (II, 25.3 +/- 2.2; p less than 0.01 versus group Ia, not significant versus group Ib; hours +/- standard error of the mean). Hemodynamic profiles for group II closely paralleled those of group Ib. In conclusion, pulmonary sequestration of granulocytes occurs early in the autoperfused working heart-lung preparation (within 60 minutes of autoperfusion), and preoperative leukocyte depletion prolongs survival of the autoperfused working heart-lung preparation by eliminating the subset group Ia (short survivors) seen in untreated preparations.