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J Thorac Cardiovasc Surg 2006;132:304-311
© 2006 The American Association for Thoracic Surgery
General Thoracic Surgery |
a Department of Thoracic Surgery, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
b Department of Clinical Pharmacology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
c Department of Nuclear Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
d Department of Radiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
e Department of Anesthesiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
f Department of Oncology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
g Department of Cardiothoracic Surgery, University Hospital of Vienna, Austria
Received for publication October 12, 2005; accepted for publication December 30, 2005. * Address for reprints: Hans-Beat Ris, MD, Department of Thoracic Surgery University Hospital of Lausanne CH 1011 Lausanne, Switzerland. (Email: Hans-Beat.Ris{at}chuv.hospvd.ch).
| Abstract |
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METHODS: White pigs underwent single-pass lung perfusion with doxorubicin (320 µg/mL), labeled 99mTc-microspheres, and Indian ink. Visual assessment of the ink distribution and perfusion scintigraphy of the perfused lung was performed. 99mTc activity and doxorubicin levels were measured by gamma counting and high-performance liquid chromatography on 15 tissue samples from each perfused lung at predetermined localizations.
RESULTS: Overall doxorubicin uptake in the perfused lung was significantly higher (P = .001) and the plasma concentration was significantly lower (P < .0001) after all isolated lung perfusion techniques, compared with intravenous administration, without differences between them. Pulmonary artery infusion (blood flow occlusion) showed an equally high doxorubicin uptake in the perfused lung but a higher systemic leakage than surgical isolated lung perfusion (P < .0001). The geometric coefficients of variation of the doxorubicin lung tissue levels were 175%, 279%, 226%, and 151% for antegrade, retrograde, combined antegrade and retrograde isolated lung perfusion, and pulmonary artery infusion by endovascular inflow occlusion (blood flow occlusion), respectively, compared with 51% for intravenous administration (P = .09). 99mTc activity measurements of the samples paralleled the doxorubicin level measurements, indicating a trend to a more heterogeneous spatial regional blood flow and drug distribution after isolated lung perfusion and blood flow occlusion compared with intravenous administration.
CONCLUSIONS: Cytostatic lung perfusion results in a high overall doxorubicin uptake, which is, however, heterogeneously distributed within the perfused lung.
| Introduction |
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The current study was designed to compare different cytostatic ILP techniques with respect to the spatial distribution of 99mTc-labeled microspheres and doxorubicin levels within the perfused lung in a porcine model. Antegrade ILP (a-ILP) (perfusion through the pulmonary artery), retrograde ILP (r-ILP) (perfusion through the pulmonary veins), combined antegrade and retrograde ILP (c-ILP), and cytostatic pulmonary artery infusion with inflow occlusion of the pulmonary artery by a percutaneously placed balloon catheter were compared with IV administration in this respect.
| Methods |
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Animals and Housing
White pigs with a body weight of 25 kg were used. All animals received humane care and were treated in accordance with the Animal Welfare Act, the National Institute of Health "Guidelines for the Care and Use of Laboratory Animals," and the guidelines of the Local Ethical Committee of the University of Lausanne.
Isolated Lung Perfusion
Induction of anesthesia was performed by intramuscular administration of ketamine (10 mg/kg body weight) followed by IV pentothal (10 mg/kg). After tracheal intubation, anesthesia was maintained with 0.50% ± 0.05% halothane and 70% nitrous oxide during ventilation. Continuous IV infusion of fentanyl 5 µg · kg · h and pancuronium 0.5 mg · kg · h was performed. The lungs were ventilated with a volume-controlled ventilator with positive end-expiratory pressure of 3 to 4 cm H2O throughout and therefore during lung perfusion. The tidal volume was 10 mL/kg, and ventilation frequency was adjusted to maintain PACO
2 between 4.5 and 5.5 kPa. All animals were placed on a heating pad while body temperature was maintained at 38°C. The ventilated gas and IV fluids were at room temperature.
A standard median sternothoracotomy extending to the right neck and into the left chest was performed. The right carotid artery and jugular vein were dissected out, and an arterial and central venous 6F catheter were inserted for arterial blood pressure monitoring, fluid perfusion, drug administration, and collection of blood samples. The hilar structures of the left lung were dissected, and the left pulmonary artery and superior and inferior pulmonary veins were individually dissected, encircled, and proximally clamped after IV administration of heparin (2 mg/kg). A custom-made silicon cannula was introduced into the pulmonary artery after arteriotomy. The inferior and superior pulmonary veins were separately cannulated with 2 identical cannulae that were joined with a Y-connector during infusion.
11
Single-pass, gravity-driven perfusion was performed. The bag containing the perfusion solution was positioned 50 cm above the level of the animal's heart, and the bag and the inflow cannula were connected using a light-shielded standard perfusion tube. Both lungs were ventilated during perfusion. a-ILP consisted of administration of the perfusate (500 mL) through the pulmonary artery over 20 minutes and collection of the effluent through the 2 venous cannulae. r-ILP consisted of the administration of the perfusate through the pulmonary veins (250 mL each) over 20 minutes and collection of the effluent by the arterial cannula. c-ILP consisted of the administration of 250 mL of the perfusate through the pulmonary artery over 10 minutes and 250 mL through the pulmonary veins over 10 minutes. The animals were sacrificed at the end of the perfusion, and the perfused and nonperfused lungs were harvested for visual inspection and assessment of 99mTc activity and doxorubicin tissue concentration measurements, respectively.
Cytostatic Lung Perfusion by Endovascular Blood Flow Occlusion Technique
Anesthesia, ventilation, dissection, and catheterization of the carotid artery and jugular vein (without sternotomy) were performed as previously described. A right-sided groin dissection was performed, and a Swan-Ganz catheter was introduced into the femoral vein. The tip of the catheter was placed at the level of the proximal left pulmonary artery under fluoroscopic control. The balloon of the Swan-Ganz catheter was inflated, which led to occlusion of the proximal left pulmonary artery, and on-table pulmonary angiography was performed to confirm the correct position of the catheter. Five-hundred milliliters of the perfusate was administered as a single-pass gravity-driven perfusion over 20 minutes
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through the catheter distal to the inflated balloon. After completion of the perfusion, on-table pulmonary angiography was repeated to confirm the correct position of the catheter. The catheter was removed, and the femoral vein was ligated. The animals were sacrificed, and the lungs were harvested for visual inspection, assessment of 99mTc activity, and doxorubicin tissue concentration measurements.
Intravenous Administration of the Perfusate (Controls)
Induction of anesthesia, dissection, and cannulation of the carotid artery and jugular vein was performed as previously described. Oxygen (2-4 L/min) was supplied by a use of a mask during spontaneous respiration. Five-hundred milliliters of the perfusate were administered through the catheter placed in the jugular vein by gravity. The animals were sacrificed, and the perfused and contralateral lungs were harvested.
Assessment of the Spatial Perfusion Pattern by Ink Staining and Perfusion Scintigraphy
After sacrifice of the animal, the whole perfused and contralateral nonperfused lungs were harvested. The pattern of ink distribution of the entire perfused lung was assessed by visual inspection and photo documentation of the visceral, mediastinal, and diaphragmatic pleura of the perfused lung. The perfused lung was cut in half through the hilum and displayed as an "open book." Perfusion scintigraphy of both lungs was then performed with a
-camera. Fifteen lung tissue samples were harvested in each perfused lung at predetermined locations according to a mapping as shown in Figure 1.
99mTc activity was assessed in a quantitative manner in each sample by gamma-counting followed by storing them at 80 °C for doxorubicin concentration measurements.
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Evaluation of Doxorubicin Distribution in the Lung Tissue: Data Presentation and Statistics
Because the tissue concentrations of doxorubicin are distributed according to a log-normal distribution, the calculations and statistics have been done after transformation of the data in their natural logarithm (ln). The doxorubicin mean tissue concentration in the perfused lung was calculated for each pig separately and for each treatment group and expressed as geometric means:
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The homogeneity of doxorubicin distribution was evaluated by calculating the variance of the doxorubicin tissue levels in each perfused lung separately (s2
lung
), and by calculating the intra-lung variance for each treatment group (s2
intra-lung
). s2
intra-lung
represents the mean variance of the doxorubicin levels of each lung separately (s2
lung
) for a treatment group. The overall variance (s2
tot
) of a treatment group can be described as follows:
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Then, as for the mean concentrations, the variances were obtained from the ln-transformed data and back-calculated, applying the exponential function, to get the geometric coefficients of variation (CV,%). CVlung
(%) is the geometric coefficient of variation for each lung separately, and CVintra-lung
(%) is the intra-lung geometric coefficient of variation for a treatment group:
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, these corresponding standard deviation.
, the corresponding percent deviation
CV% = (pd 1) 100
For statistical analysis, a 1-way completely randomized design analysis of variance was performed with the software Statistix version 8.0 for Windows (Analytical Software, Tallahassee, Fla). Statistical analysis was run with the ln-transformed data of (1) Clung and (2) s2 lung to determine the treatment effect on the (1) doxorubicin lung levels (Ctreat ) and (2) homogeneity of doxorubicin distribution (CV intra-lung ). If the criteria for a statistical difference were met, the Tukey's all-pairwise comparison test was performed to find out which groups differ from the others.
| Results |
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100 times) after ILP than after IV and BFO administration (P < .0001) without differences between the ILP techniques applied. There was no significant difference in plasma doxorubicin concentrations between IV administration and BFO perfusion.
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| Comment |
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combined with interferon-
.
6
Our experimental study was designed to study the spatial pattern of pulmonary blood flow and drug distribution according to the mode of perfusion technique applied in comparison with IV drug administration. The IV administration was performed during spontaneous breathing because it should reflect as closely as possible the clinical context of IV application of a cytostatic agent.
Most of the experimental work on ILP has been performed on a tumor-bearing rodent model allowing the assessment of a diversity of antineoplastic agents.
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However, the size of the lung in this model does not easily allow the assessment of the spatial pattern of blood flow and drug distribution during ILP, which requires the harvesting of various tissue samples at different localizations of the perfused lung. A tumor-free porcine model was therefore used in this respect, which has been used for ILP.
8,11,12
A similar technique as described by Glenny and colleagues
15,16
has been applied for the assessment of regional blood flow and doxorubicin distribution for different techniques of cytostatic lung perfusion.
Retrograde ILP has the theoretic potential to perfuse the parts of the lung supplied by both the pulmonary and bronchial artery. This might result in a more homogeneous drug delivery to all structures of the perfused lung. r-ILP has been assessed for paclitaxel-based ILP in sheep combined with hyperthermia and has been demonstrated to be feasible and associated with a substantial pharmacokinetic advantage compared with IV administration.
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In addition, results emerging from retrograde flushing of the donor lungs with the preservation solution during the procurement of the graft for lung transplantation suggest that there is improved flow to the airways compared with antegrade flushing.
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Combined ILP allows the delivery of the perfusate to the pulmonary arteries and veins and has been used during lung transplantation.
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Cytostatic lung perfusion with pulmonary artery infusion and inflow occlusion by a percutaneously placed balloon catheter (BFO)
8,12,19,20
has 2 theoretic advantages. First it could alleviate any changes in perfusion pattern caused by the surgery itself. Second it allows repeated regional chemotherapy delivery without operation. Cisplatin-based BFO has been compared with ILP in a porcine model with lower lung and higher systemic drug levels and a more heterogeneous drug distribution compared with ILP.
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In a previous experimental study, we compared doxorubicin-based ILP with BFO in a porcine model.
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Overall drug uptake was similar after both techniques, but BFO resulted in higher doxorubicin plasma concentrations than ILP. However, disappointing results were obtained in clinical trials using the BFO technique.
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This experimental study revealed that all methods of ILP showed an excellent separation of the systemic and pulmonary circulations, and increased drug uptake of the perfused lungs compared with IV administration. Although r-ILP or c-ILP may theoretically result in an increased leakage because of retrograde flushing of the bronchial arteries, the plasma doxorubicin concentrations after r-ILP and c-ILP were not different from a-ILP in this model. r-ILP or c-ILP did not show an increased overall drug uptake compared with a-ILP, but the bronchial circulation represents only 5% of the pulmonary circulation. BFO resulted in a similar overall doxorubicin uptake in the perfused lung but revealed a significantly higher systemic leakage as observed after ILP. However, the small number of animals per group and the wide variation of mean drug lung tissue levels for each animal (CVlung) and each treatment group (CVintra-lung) render identification of any significant difference between methods of cytostatic perfusion difficult.
We found a significant correlation between 99mTc activity and doxorubicin level for each lung specimen in all treatment groups, indicating that doxorubicin distribution correlates with regional blood flow during ILP. However, all methods of cytostatic perfusions (including BFO) resulted in a marked spatial heterogeneity of regional 99mTc activity and doxorubicin levels in the perfused lung tissues, which was neither anatomic (lobar or segmental) nor explained by a hydrostatic gradient. These differences were apparent both macroscopically and microscopically. In contrast, IV administration resulted in a less heterogeneous (but not homogeneous) 99mTc activity and doxorubicin distribution within lung tissue but also in significantly lower drug tissue levels compared with ILP and BFO.
Spatial heterogeneity of regional blood flow during ILP may be related to anesthetic and ventilatory management, the presence of ventilation-perfusion mismatch and hypothermia caused by thoracotomy and manipulation of the lung, and acute changes of oxygen tension.
15,21,22
Despite the avoidance of sternotomy and manipulation of the lung during BFO, the spatial regional blood flow and drug distribution in the perfused lung was as heterogeneous as after ILP. We speculate that the heterogeneous spatial blood flow and doxorubicin distribution in the perfused lung after BFO may be related to (1) a hypoxia-induced regional redistribution of blood flow (caused by a temporary occlusion of the pulmonary artery), (2) an acute vascular reactivity of the pulmonary blood vessels exposed to the concentrated perfusion solution leading to localized vasoconstriction and to a consecutive redistribution of pulmonary blood flow, and (3) a difference in anesthetic and ventilatory management compared with IV administration (absence of myorelaxant, endotracheal intubation, and controlled ventilation in the IV group).
A wide inter-animal variation was not only observed for the overall doxorubicin uptake in the perfused lungs but also with respect to the regional 99mTc activity and doxorubicin levels in the perfused lung tissues, for all experimental groups assessed. IV administration also resulted in a marked inter-animal variability of regional blood flow and drug distribution with a geometric coefficient of variation for drug tissue levels of 51% for that treatment group. Previous experiments have studied the pattern of regional pulmonary blood flow distribution on ventilated dogs and demonstrated a marked spatial heterogeneity of regional perfusion over time that varied between animals.
15
However, a heterogeneous spatial pattern of pulmonary blood flow distribution was also found under physiologic conditions in standing awake dogs, which was stable over days suggesting inhomogeneous pulmonary blood flow distribution not only in anesthetized animals but also under physiologic conditions in awake standing animals at rest.
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| Conclusion |
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| Footnotes |
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Financial support was provided by a grant from the Swiss National Science Foundation and Foundation Naef.
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