The pattern of early lung parenchymal and air space injury following acute blood loss.
Acute lung injury is a frequent clinical occurrence following blood loss and trauma. The nature of this injury remains poorly understood.


OBJECTIVE
To examine the relative parenchymal and intra-alveolar distribution of inflammation in a rat model of hemorrhage and resuscitation.


METHODS
Rats were anesthetized and subjected to hemorrhage followed by resuscitation with shed blood and saline. Myeloperoxidase activity of lung homogenates and cytology of bronchoalveolar lavage fluid were used to measure total lung and intra-alveolar neutrophil invasion. Extravasation of i.v.-administered [125I]-albumin was used to determine total lung and alveolar permeability. Permeability results were analyzed using their base-10 logarithmic transformations.


RESULTS
86 animals were studied. Whole-lung myeloperoxidase activity was increased (control = 0.34 +/- 0.16 units, injured = 0.84 +/- 0.43 units, p < 0.01), while there was no difference in intra-alveolar leukocyte counts (injured = 1.85 +/- 1.30 x 10(5)/mL, control = 2.44 +/- 1.75 x 10(5)/mL, p = 0.40), suggesting that the cellular component of the injury was more severe in the intravascular and interstitial spaces. There was a strong trend toward increased permeability in the interstitial compartment, and a significant increase in permeability in the intra-alveolar compartment (whole-lung permeability: control = -0.27 +/- 0.19 units, injured = 0.10 +/- 0.55 units, p = 0.06; alveolar permeability: control = -2.00 +/- 0.47 units, injured = -1.32 +/- 0.49 units, p < 0.01), suggesting that the loss of integrity to macromolecules was not limited to the interstitium.


CONCLUSIONS
Hemorrhage and resuscitation resulted in an acute lung injury characterized by extravasation of intravascular protein into both the interstitium and the intra-alveolar space. Neutrophil invasion of the lung was demonstrable only in the interstitial compartment.
Emergency Medicine Research Laboratories and the Section of Emergency Medicine, the University of Michigan, Ann Arbor 48109-0303, USA. jyounger@umich.edu
J G
JG
Younger
A S
AS
Taqi
P F
PF
Jost
G O
GO
Till
K J
KJ
Johnson
S A
SA
Stern
R B
RB
Hirschl
D000818:Animals; D015824:Blood-Air Barrier; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology; D007249:Inflammation; D007958:Leukocyte Count; D008171:Lung Diseases / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009504:Neutrophils; D011446:Prospective Studies; D051381:Rats; D017207:Rats, Sprague-Dawley; D012151:Resuscitation; D012771:Shock, Hemorrhagic / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy