American Surgical Association
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Arteriovenous Carbon Dioxide Removal Improves Survival In An Ovine Model of Severe Smoke and Burn Injury
Joseph B Zwischenberger, Manuel E Cevallos*, Kelley M Campbell*, Susan E Keeney, Daniel L Traber, Helen E Rudloff*, Kimberly H Palkowetz*, Xiaoqin Zhou*, Frank C Schmalstieg*
University of Texas Medical Branch, Galveston, TX

OBJECTIVE(S): Arteriovenous CO2 removal with low tidal volume ventilation (AVCO2R) was compared to high frequency percussive ventilation (HFPV) and low tidal volume (6 ml/kg) (LTV) ventilation for pathophysiology and survival in a sheep model of lethal ARDS.
METHODS: Ewes (40-45 kg) were subjected to 48 breaths of cotton smoke and a 40% body surface area 3rd degree burn. The animals were then randomized after reaching criteria for ARDS (P/F < 200) to either LTV (n=9), AVCO2R (n=7), or HFPV (n=10) treatment, then sacrificed at 96 h post-injury. Laser scanning confocal microscopy was used to quantitatively assess nuclear condensation in neutrophils as median fluorescent intensity (MFI) (measure of apoptosis) of Hoescht-stained nuclei. Myeloperoxidase (MPO) in lung tissue was measured spectrophotometrically.
RESULTS: Survival to 96 h post-injury was significantly improved for AVCO2R than LTV (RR=4.64+/-3.76, p<0.05), but comparison with HFPV showed p=0.12 (RR=2.68 +/- 1.69). MPO in lung tissue was 7.2 +/- 3.7 (LTV), 5.7 +/-3.1(HFPV), and 2.3 +/- 1.6 (AVCO2R) U/g (p<0.05). Lung tissue neutrophils were significantly more apoptotic and decreased in number for AVCO2R (90 MFI) than HFPV (70 MFI) or LTV (65 MFI) (p<0.001) at 96h post-injury.
CONCLUSIONS: Survival was significantly better for AVCO2R than LTV. Neutrophils in the AVCO2R treated animals were more apoptotic, decreased in number, and may have been more efficiently removed by resident macrophages producing less inflammation in the lung. Reduced deposition of MPO in lung tissue for AVCO2R-treated animals is consistent with this conclusion.

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