Effects of irradiation on the pulmonary vascular fluid and protein exchange.

Abstract

In anesthetized sheep, ventilated by positive pressure, pulmonary arterial and left atrial pressures, cardiac output, and lung lymph flow (Qlym) were measured and lymph-to-plasma protein concentration ratio (L/P) was determined. Four sheep were irradiated with 60Co on the bilateral lower lobes, avoiding irradiation on the heart and the caudal mediastinal lymph node. Qlym increased during and after irradiation, and reached a new steady state (160% increase), while pulmonary arterial or left atrial pressure did not change. In 4 control experiments, pulmonary hemodynamics, Qlym or L/P did not change. Therefore the increased fluid or protein flux after irradiation cannot be ascribed only to abnormal pulmonary hemodynamics. Endothelial damages seem to play a role in the increase of fluid filtration and protein permeability. -radiation effects; pulmonary vascular permeability; fluid filtration; protein exchange; lung lymph Post-radiation pneumonitis (Rubin and Casarett 1968) and post-radiation fibrosis (Liebow 1975) were well known as late complication of the irradiation therapy for lung diseases. Maisin (1970) observed that the ultrastructure of all types of lung cells changed 3 hr after 2,000 cads irradiation in mice, but acute reactions of the pulmonary microcirculation to irradiation have not been well known. This paper reports immediate reactions of the pulmonary hemodynamics and transvascular fluid and protein exchange to irradiation in anesthetized sheep. METHODSEight yielding sheep, weighing 38-58 kg, were incubated and anesthetized with 0.5-1.0 % halothane in 40% 02 and 60% N2 using a positive pressure ventilator (607E, Harvard Apparatus, Mass., USA), set at 15 breaths/ min to deliver a tidal volume of approximately 500 ml at a peak air way pressure of 15 cmH2O. After left thoracotomy, polyvinyl catheters were inserted into the pulmonary artery and the left atrium for measurement of pressures (PPA and PLA). A thermister catheter was inserted into the pulmonary artery via the jugular vein for the determination of thermodilution-cardiac output (Qc). The right thorax was opened and caudal portion of the caudal mediastinal lymph node (CMN) Received for publication, March 1, 1982. 309

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“…We believe this reflects the coarse-fractionated dose regime and the relatively small volume targeted in the present study. Indeed it has previously been shown that sheep will develop radiation pneumonitis typical of that seen in humans given sufficient dose and lung volume targeted 37 – 41 . Unilateral single fraction high dose irradiation (30 Gy) of the sheep thorax produced radiation pneumonitis typical of the syndrome in humans at 4 weeks after irradiation 41 , and whole lung single fraction irradiation (15 Gy) of sheep resulted in the development of progressive dyspnoea three weeks after exposure; however animals were killed at 4 weeks precluding longer term assessment 38 .…”