ObjectiveTo investigate the effects of esophageal cooling (EC) on lung injury and systemic inflammatory response after cardiopulmonary resuscitation in swine.MethodsThirty-two domestic male white pigs were randomly divided into sham group (S group, n=5), normothermia group (NT group, n=9), surface cooling group (SC group, n=9), and EC group (n=9). The animals in the S group only experienced the animal preparation. The animal model was established by 8 min of ventricular fibrillation and then 5 min of cardiopulmonary resuscitation in the other three groups. A normal temperature of (38.0±0.5)℃ was maintained by surface blanket throughout the experiment in the S and NT groups. At 5 min after resuscitation, therapeutic hypothermia was implemented via surface blanket or EC catheter to reach a target temperature of 33℃, and then maintained until 24 h post resuscitation, and followed by a rewarming rate of 1℃/h for 5 h in the SC and EC groups. At 1, 6, 12, 24 and 30 h after resuscitation, the values of extra-vascular lung water index (ELWI) and pulmonary vascular permeability index (PVPI) were measured, and meanwhile arterial blood samples were collected to measure the values of oxygenation index (OI) and venous blood samples were collected to measure the serum levels of tumor necrosis factor-α (TNF-α) and inerleukin-6 (IL-6). At 30 h after resuscitation, the animals were euthanized, and then the lung tissue contents of TNF-α, IL-6 and malondialdehyde, and the activities of superoxide dismutase (SOD) were detected.ResultsAfter resuscitation, the induction of hypothermia was significantly faster in the EC group than that in the SC group (2.8 vs. 1.5℃/h, P<0.05), and then its maintenance and rewarming were equally achieved in the two groups. The values of ELWI and PVPI significantly decreased and the values of OI significantly increased from 6 h after resuscitation in the EC group and from 12 h after resuscitation in the SC group compared with the NT group (all P<0.05). Additionally, the values of ELWI and PVPI were significantly lower and the values of OI were significantly higher from 12 h after resuscitation in the EC group than those in the SC group [ELWI: (13.4±3.1) vs. (16.8±2.7) mL/kg at 12 h, (12.4±3.0) vs. (16.0±3.6) mL/kg at 24 h, (11.1±2.4) vs. (13.9±1.9) mL/kg at 30 h; PVPI: 3.7±0.9 vs. 5.0±1.1 at 12 h, 3.4±0.8 vs. 4.6±1.0 at 24 h, 3.1±0.7 vs. 4.2±0.7 at 30 h; OI: (470±41) vs. (417±42) mm Hg (1 mm Hg=0.133 kPa) at 12 h, (462±39) vs. (407±36) mm Hg at 24 h, (438±60) vs. (380±33) mm Hg at 30 h; all P<0.05]. The serum levels of TNF-α and IL-6 significantly decreased from 6 h after resuscitation in the SC and EC groups compared with the NT group (all P<0.05). Additionally, the serum levels of IL-6 from 6 h after resuscitation and the serum levels of TNF-α from 12 h after resuscitation were significantly lower in the EC group than those in the SC group [IL-6: (299±23) vs. (329±30) pg/mL at 6 h, (336±35) vs. (375±30) pg/mL at 12 h, (297±29) vs. (339±36) pg/mL at 24 h, (255±20) vs. (297±33) pg/mL at 30 h; TNF-α: (519±46) vs. (572±49) pg/mL at 12 h, (477±77) vs. (570±64) pg/mL at 24 h, (436±49) vs. (509±51) pg/mL at 30 h; all P<0.05]. The contents of TNF-α, IL-6, and malondialdehyde significantly decreased and the activities of SOD significantly increased in the SC and EC groups compared with the NT group (all P<0.05). Additionally, lung inflammation and oxidative stress were further significantly alleviated in the EC group compared with the SC group [TNF-α: (557±155) vs. (782±154) pg/mg prot; IL-6: (616±134) vs. (868±143) pg/mg prot; malondialdehyde: (4.95±1.53) vs. (7.53±1.77) nmol/mg prot; SOD: (3.18±0.74) vs. (2.14±1.00) U/mg prot; all P<0.05].ConclusionTherapeutic hypothermia could be rapidly induced by EC after resuscitation, and further significantly alleviated post-resuscitation lung injury and systemic inflammatory response compared with conventional surface cooling.