Establishment Of Rabbit Auricular Skin Flap Model Of Hyaluronic Acid Induced Artery Embolism And Evaluation Of Intravascular Thrombolytic Effect Of Hyaluronidase

Objectives1. Study vessel course and distribution in the cervical and auricular area of rabbit in order to provide anatomical knowledge for establishing rabbit auricular skin flap model and selective trans-external carotid artery thrombolysis.2. Create rabbitislanded auricular skin flap.3. Create rabbit islanded auricular skin flap model of hyaluronic acid(HA) induced artery embolism; Study the effect of dose of HA embolus on the flap reperfusion area; Observe vascular pathological changes.4. Study the role of intravascular hyaluronidase (HAase) in treating skin flap ischemia caused by HA induced artery embolism. Compare the different effect of intravenous thrombolysis and selective intra-arterial thrombolysis with HAaseMethods1. Create rabbit craniocervical vascular cast in eight rabbits and study the vascular anatomy.2. Create islanded auricular skin flap based on posterior auricular artery and medial branch of posterior auricular vein in five rabbits. Study the skin flap perfusion and survival by fluorescein angiography(FA) at five time points,4 hour,24 hour,3 day,5 day and 7 day.3. Inject 10 μl,20 μl,40 μl of HA, respectively, to posterior auricular artery in eighteen rabbits after islanded skin flaps were created. FA was taken at five time points:4 hour,24 hour,3 day,5 day and 7day. Compare the difference of area percentage of flap perfusion between different embolus dose groups at the same time point. Observe the vascular pathological changes at 24 hour and on 7 day.4. Create auricular skin flap model of 20 μl HA artery emblism in twenty rabbits which were divided into four groups. IVT-NaCI group:intravenous thrombolysis with saline; IVT-HAase group:intravenous thrombolysis with HAase; IAT-NaCI group:intra-arterial thrombolysis with saline; IAT-HAase group:intra-arterial thrombolysis with HAase. The 20 μl HA embolism group in the third section was taken as control group. Area percentage of flap perfusion was compared between different groups on 7 day.Results1. Occipital artery, superficial temporal artery, maxillary artery, facial artery and lingual artery were five major braches of rabbit external carotid artery. Although the arising location of those arteries varied, the course of those arteries were constant. The blood supply of rabbit auricular skin derived from multiple vessel sources. The posterior auricular artery was the major source artery, accompanied by the medial branch of posterior auricular vein.2. The rabbit islanded auricular skin flap based on posterior auricular artery and medial branch of posterior auricular vein was successfully created with 100% perfusion.3. FA examination was not applicable for the 4 hour group because the fluorescence was mottled. All the 10μl group revealed significantly higher area percentage of flap perfusion than 20μl group, and 20μl group significantly higher than 40μl group(P<0.05), except that no significant difference was found between the 10μl group and the 20μl group at the time point 24 hour. Infiltration of eosinophils was identified in the HA blocked arteries and veins. Inflammation of artery was predominant at time point 24 hour, however inflammation of vein became predominant at time point 7 day. Recanalization was noticed in the proximal posterior auricular artery which was blocked by HA at time point 7 day.4. The mean area percentage of flap perfusion was 76.54±6.92、74.08±9.14、 76.94±6.68、76.95±8.72 and 95.47±3.38 in the control group, IVT-NaCI group, IVT-HAase group, IAT-HAase group at time point 7 day, respectively. The area percentage of flap perfusion of IAT-HAases group was significantly higher than the other four groups(P<0.05). No significant difference was found between the other four groups.Conclusions1. The anatomy study of rabbit craniocervical region showed that selective intra-arterial thrombolysis of branches of superficial temporal artery by trans-external carotid artery cannulation was feasible. Creation of rabbit islanded auricular skin flap based on posterior auricular artery and the medial branch of posterior auricular vein was feasible.2. The rabbit islanded auricular skin flap was successfully created with perfect perfusion.3. The rabbit islanded auricular skin flap model of HA induced artery embolism was successfully created. Flap reperfusion occurred after HA embolism. The larger dose of embolus, the less reperfusion area, the larger skin flap ischemic area. Spontaneous recanalization of the artery blocked by HA could occur. Inflammation of both arteries and veins could be caused by HA embolism.4. The selective intra-arterial thrombolysis with HAase can reduce HA artery embolism induced ischemia and skin flap necrotic area effectively. However, the role of intravenous use of HAase as thrombolytic agent need further investigation.