Trends in lung pH and PO2 after circulatory arrest: implications for non-heart-beating donors and cell culture models of lung ischemia-reperfusion injury.
BACKGROUND
A better understanding of lung tissue environment after circulatory arrest would allow more accurate cell culture models to study ischemia-reperfusion lung injury and facilitate retrieval of lungs from non-heart-beating donors.


METHODS
To establish the time course of changes in pH and PO2 in lung tissue after circulatory arrest, 12 Sprague-Dawley rats were sacrificed. After sternotomy, pH and PO2 microelectrodes were inserted into the lungs and sealed by application of Focal Seal. Rats were maintained at normothermia (37 degrees C). Two groups of rats (n = 6 atelectatic, n = 6 room air-inflated) were followed for 4 hours after arrest, when lung tissue adenine nucleotide levels were measured by chromatography and cell death was quantified by trypan blue exclusion. Human umbilical vein endothelial cells underwent simulated ischemia and 6 hours of cold storage by replacement of culture medium with cold Perfadex. Interleukin (IL)-6 and IL-8 were measured in medium 21 hours later by enzyme-linked immunosorbent assay (ELISA).


RESULTS
In both groups of rats, lung [H+] increased linearly with time. In atelectatic lungs, PO2 fell precipitously, but in inflated lungs, PO2 decreased linearly for 60 to 75 minutes post-mortem and then became stable. After 4 hours at 37 degrees C, most parenchymal lung cells were dead in both groups. IL-6 and IL-8 levels increased significantly in medium of cultured endothelial cells subjected to cold storage without hypoxia.


CONCLUSIONS
In room-air-inflated lungs maintained at 37 degrees C, oxygen consumption continues for at least 1 hour after circulatory arrest. Warm atelectasis is poorly tolerated. Hypothermic storage can induce elaboration of cytokines by endothelial cells in the absence of hypoxia.
Koukoulis
Giovanna
G
Department of Cardiothoracic Surgery, San Matteo Hospital, University of Pavia, Pavia, Italy.
Caldwell
Ray
R
Inokawa
Hidetoshi
H
Button
Brian
B
Sevala
Mayura
M
Lyles
Johnnie D
JD
Takashima
Seiki
S
Blackwell
John
J
Randell
Scott H
SH
Egan
Thomas M
TM
D000818:Animals; D018929:Cell Culture Techniques; D015687:Cell Hypoxia; D002470:Cell Survival; D002851:Chromatography, High Pressure Liquid; D050792:Circulatory Arrest, Deep Hypothermia Induced; D016207:Cytokines / Q000096:biosynthesis; D042783:Endothelial Cells; D006323:Heart Arrest; D006863:Hydrogen-Ion Concentration; D015850:Interleukin-6 / Q000032:analysis; D016209:Interleukin-8 / Q000032:analysis; D008168:Lung / Q000737:chemistry / Q000378:metabolism*; D016040:Lung Transplantation; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D001261:Pulmonary Atelectasis; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000503:physiopathology*; D014470:Umbilical Cord / Q000098:blood supply
D016207:Cytokines; D015850:Interleukin-6; D016209:Interleukin-8; D010100:Oxygen