Objective: To establish a temporary pulmonary hilum clamping model for thoracic damage control surgery, as well as to determine the safety time latitude of this manipulation.
Methods: Pigs were anaesthetised and instrumented with a thermodilution cardiac output catheter. The left pulmonary hilum was clamped with a urethral catheter after thoracotomy, maintained for three different time periods (n=6 for each group), 90min (C90), 120min (C120) and 150min (C150) and then unclamped. Haemodynamic data were recorded and the serum samples were collected for D-dimer detection and other haematological analysis. A 1-cm(3) pulmonary tissue of the left lower lobe was also obtained for histological study before clamping, at the end of clamping and at 0.5, 1, 1.5, 2 and 4h after unclamping.
Results: Postoperative survival rate in each group of the pigs was as follows: 100% (all six) of C90, 83.3% (five of six) of C120, and 33.3% (two of six) of C150. Blood pressure (BP) and heart rate (HR) increased after clamping and gradually declined after unclamping. The animals of C150 group suffered highest BP and HR, respiratory index, pulmonary dynamic compliance and cardiac output. Platelet count showed no significant changes between the C90 and C120 groups, whereas a decline was noticed in the C150 group. Pulmonary vascular resistance increased significantly after pulmonary hilum clamping; when unclamped, there were minor changes in animals of C90 and C120 groups while there was a persistent elevation in the C150 group. An elevated D-dimer was detected in the C150 group, whereas it was normal in the C90 and C120 groups. There was significantly serious inflammatory cell infiltration, perivascular oedema and haemorrhagic infiltration in the C150 group compared with the C90 and C120 groups.
Conclusions: We established a pulmonary hilum clamping animal model for investigating pulmonary damage. By studying the haemodynamic and lung function changes of three different unilateral pulmonary hilum clamping time, it was determined that 120min was the longest safety time for hilum clamping without lethal pulmonary injury in porcine models.