Induced hypothermia as a new approach to lung rest for the acutely injured lung.
OBJECTIVE
To investigate whether low-frequency ventilation during hypothermia could attenuate lung injury associated with endotoxin and mechanical ventilation.


METHODS
: Experimental animal study.


METHODS
University-affiliated animal laboratory.


METHODS
Forty-eight Sprague-Dawley rats.


METHODS
: Lipopolysaccharide was administered to rats intratracheally to induce acute lung injury. After 1 hr of this treatment, animals were assigned to normothermia-only (NO, rectal temperature 37 degrees C, ventilatory frequency 90/min), normothermia-lung rest (NR, 37 degrees C, 45/min), hypothermia-only (HO, 27 degrees C, 90/min), or hypothermia-lung rest (HR, 27 degrees C, 45/min). After 1 hr of injurious ventilation, the lungs of the rats were removed for bronchoalveolar lavage and histologic examination.


RESULTS
Compared with the normothermia groups (NO, NR), the neutrophil counts (per milliliter) (NO, 7708 +/- 5704; NR, 10,479 +/- 11,152; HO, 1638 +/- 955; HR, 805 +/- 591) and interleukin-1beta levels (pg/mL) (1180 +/- 439, 1081 +/- 652, 620 +/- 426, 420 +/- 182, respectively) in the bronchoalveolar lavage fluid, the wet-to-dry lung weight ratios (6.0 +/- 0.4, 5.7 +/- 0.4, 5.6 +/- 0.2, 5.2 +/- 0.2, respectively), and histologic acute lung injury scores (8.3 +/- 2.7, 10.4 +/- 3.1, 3.5 +/- 2.1, 3.1 +/- 2.2, respectively) of the hypothermia groups (HO, HR) were lower (all p < .001). Compared with the HO group, the neutrophil counts and protein content (HO, 1367 +/- 490 mug/mL vs. HR, 831 +/- 369 mug/mL) in the bronchoalveolar lavage fluid, the serum lactate dehydrogenase levels (units/mL) (9.1 +/- 3.6 vs. 5.3 +/- 1.5), and the wet-to-dry lung weight ratios of the HR group were lower (all p < .05).


CONCLUSIONS
Reduction of ventilatory frequency in conjunction with hypothermia attenuated many variables of acute lung injury in rats. Use of hypothermia could be exploited as a new approach to lung rest for the ventilatory management of the acutely injured lung.
Hong
Sang-Bum
SB
Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
Koh
Younsuck
Y
Lee
In-Chul
IC
Kim
Mi Joung
MJ
Kim
Woo Sung
WS
Kim
Dong-Soon
DS
Kim
Won Dong
WD
Lim
Chae-Man
CM
D000208:Acute Disease; D000818:Animals; D018893:Bronchoalveolar Lavage; D002245:Carbon Dioxide / Q000378:metabolism; D006979:Hyperthermia, Induced; D007375:Interleukin-1 / Q000032:analysis; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D007958:Leukocyte Count; D008168:Lung / Q000473:pathology / Q000502:physiology*; D008171:Lung Diseases / Q000209:etiology / Q000473:pathology / Q000628:therapy*; D008297:Male; D009504:Neutrophils / Q000166:cytology; D009929:Organ Size; D011506:Proteins / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012121:Respiration, Artificial / Q000379:methods; D012146:Rest
D007375:Interleukin-1; D011506:Proteins; D002245:Carbon Dioxide; D007770:L-Lactate Dehydrogenase