[Study on injury of vascular intima with hemostatic clamp and optimization of protective strategy]

Objective: To explore the intimal injury of two kinds of hemostatic clips under different clamping forces, and to optimize and verify the calculation formula of minimum occlusion force (MOF), so as to provide theoretical basis for selecting appropriate hemostatic clips to reduce vascular injury. Methods: A total of 96 male SD rats with body weight ranging from 280 to 300 g (Animal Experimental Center of Shanxi Medical University) were randomly assigned to metal hemostatic clip group (n=48) and disposable hemostatic clip group (n=48) by random number table method. Each group was further divided into four subgroups with clamping forces of 0.3, 0.6, 0.9 and 1.2 N for abdominal aortic injury experiments. The damage to the vascular intima was observed under a scanning electron microscope. A vascular closure model was established for mathematical analysis to derive the theoretical calculation formula of the arterial blood management factor (MOF). According to blood pressure (BP), blood vessel diameter (D) and hemostatic clamp width (W), the average values of theoretical and actual MOF data were analyzed by paired t test to verify the accuracy of the formula. From January 2021 to December 2022, six patients (with 12 branch arteries) who presented with oral and maxillofacial malignancies at the Department of Oral and Maxillofacial Surgery, Shanxi Medical University School and Hospital of Stomatology, were included to validate the accuracy of the MOF formula. Results: Under electron microscopy, when the clamping force was 0.3 N, the one-time hemostatic clip caused very little damage to the vascular intima (grade 1 injury), with only a few folds being flattened. When the clamping force was 0.6 N, both types of hemostatic clips caused partial peeling of the intima surface (grade 2-3 injury). However, when the clamping force was adjusted to 0.9 and 1.2 N, the damage caused by both types of hemostatic clips was more severe (grade 3-4 injury), with large areas of intima peeling or even disappearance. In some specimens of the metal hemostatic clip group, the damage even reached the muscular layer. Vascular closure model analysis showed that MOF=2×(1/2×π×D×W×BP), the mean diameter of abdominal aorta of 24 SD rats was (1.41±0.07) mm, the blood pressure was (83.29±11.56) mmHg (1 mmHg=0.133 kPa). The theoretical MOF value was (0.096±0.015) N, the actual clamping force (ACF) was (0.095±0.012) N, there was no statistical significance between the two groups (t=-0.35, P=0.725). In clinical application, the MOF calculation formula was used to select the appropriate hemostatic clip for 12 arteries, successfully blocking the blood flow, verifying the accuracy of the formula. Conclusions: Hemostatic clips can cause damage to the inner membrane of blood vessels, and the greater the clamping force, the more severe the damage. Disposable hemostatic clips have certain advantages in avoiding excessive damage to the inner membrane of blood vessels. The theoretical MOF calculation formula has a certain degree of reliability and can be used as a reference to select the appropriate hemostatic clip with low damage.