The Research Of Observing The Influence Of The Specific Gravity Factor Of Lumbar Anesthetics On The Regulation Of Anesthesia Level Based On The Experimental System Of 3D Printed Transparent Human Spinal Canal Model

Background:Subarachnoid nerve block（abbreviated as spinal anesthesia）is one of the traditional anesthesia methods,and it is also the main method of clinical anesthesia at present.Its effectiveness and safety are the core concerns during the implementation of clinical anesthesia.The anesthesia plane,or block plane,refers to the boundary of the disappearance of skin sensation,which needs to reach the range required for surgery within a short period of time after the injection of the drug solution,but at the same time,it is necessary to avoid the impact on the patient caused by the excessively high plane.Therefore,anesthesia level control is the most important link in clinical anesthesia and teaching of spinal anesthesia.Currently,the influencing factors of anesthesia level regulation include several qualitative research conclusions:drug injection volume,drug injection speed,body position,specific gravity,etc.Some clinical trials have also conducted studies on the impact of drug specific gravity on patient anesthesia levels,but students are unable to help understand the production process of anesthesia levels through visual observation.In order to solve the practical and fundamental problems of insufficient anesthesia plane control data and teaching tools for spinal anesthesia liquid diffusion under direct vision,our research group has designed a 3D printing human transparent vertebral canal model experimental system,which includes two parts:a bionic human transparent vertebral canal model invented by our research group and an experimental operation platform.The system has the characteristics of better simulating the anatomical and physiological structure of the human vertebral canal cavity and the clinical procedures of spinal anesthesia,distinguishing its distribution and diffusion by the color of the drug solution,and facilitating visual observation of the regularity of drug diffusion kinetics under spinal anesthesia with the naked eye.We plan to conduct a study on the specific gravity factors of local anesthetic fluid on this experimental operating platform to explore the impact of the specific gravity factors of local anesthetic fluid on the factors that regulate the level of anesthesia during subarachnoid block.Objective:To observe the injection of different specific gravity spinal anesthetics into the transparent human spinal canal cavity by the 3D printing transparent human spinal canal model experimental system.The characteristic laws of the diffusion of local anethetics were studied using color resolution methods,providing research data on the regulation of spinal anesthesia nerve block plane for clinical teaching and practice.Method:1.Production of the 3D-printed transparent human spinal canal model experimental systemEstablish a three-dimensional database based on the standard human supine spine electronic computed tomography（CT）scan（CT）as the data model,and use a digital technology printer to 3D-print transparent spinal canal model.Development and application of model bracket system.Combined with the characteristics of this model,a special fixed bracket was developed,and the model was fixed in the supine position after the stent,which could simulate the free conversion of the flat supine position,flat lying position,head high foot low position,and head low foot high position during clinical anesthesia.Closed 3D printing of human transparent spinal canal lumen model,cerebrospinal fluid perfusion channel,and an open closing valve at the cervical vertebrae opening,cerebrospinal fluid discharge port at the lumbar sacral nerve root.At room temperature of 25°C,artificial cerebrospinal fluid was perfused into the lumen of the 3D printed human transparent spinal canal model,and the lumens of the spinal canal was still colorless and transparent.2 Experimental operationPreparation of each specific gravity chemical solution:（1）Preparation of hyperbaric chemical solution:Group H_1/2:the ratio of 0.75%bupivacaine to 10%glucose injection was 1:2Group H_1/3:The ratio of 0.75%bupivacaine to 10%glucose injection was 1:3（2）Preparation of isobaric chemical solution:Group I:0.75%bupivacaine stock solution was applied（3）Preparation of hypobaric liquid preparation:Group L_1/2:the ratio of 0.75%bupivacaine to sterilized water for injection was 1:2.Group L_1/3:the ratio of 0.75%bupivacaine to sterilized water for injection was 1:3.An equal amount of methylene blue is added to the same amount of various specific gravity liquids.The model was placed in the lateral decubitus position at the level of the ground,the L_2-3 cone gap was selected as the injection point,the end of the lumbar anesthesia puncture needle was connected to the electronic injection pump,and 2ml of the drug solution was pushed into the spinal cavity at a uniform speed of 10s（720m L/h）,and the diffusion of the drug solution after 5 min,10 min,15min,and 5 min after the supine position was recorded as L_1/2T_10s,L1/2T5min,L1/2T10min,L1/2T15min,L1/2T20mi,L1/3T10s,L1/3T5min,L1/3T10min,L1/3T15min,L1/3T20min;H1/2T10s,H1/2T5min,H1/2T10min,H1/2T15min,H1/2T20min;H_1/3T_10s,H_1/3T_5min,H_1/3T_10min,H_1/3T_15min,H_1/3T_20min.Repeat 5 times per set.All data is processed and analyzed using SPSS26.0 statistical software.The measurement data were expressed by mean±standard deviation（±s）,and the T-test was used for intra-group comparisons and the test for variance between groups,with P<0.05 as the difference statistically significant.Outcome:1.Local anesthetics with different specific gravity exhibit different diffusion patterns in the cerebrospinal fluid within the spinal canal.The hypobaric bupivacaine closely adheres to the upper sidewall in a semi shuttle shape,arcuate downward,and gradually diffuses to almost all lumens;the isobaric mixes in the center of cerebrospinal fluid;The hyperbaric bupivacaine spreads close to the lower lateral wall,with the arc upward during injection,and most of the solution spreads to the sacrococcygeal side in the lateral lying position.After turning to the supine position,it spreads close to the posterior and towards the cephalic side.2.At T_10s,a small amount of hypobaric and hyperbaric local anesthetics was found near the lower or upper nerve root,and then gradually diffused.There was almost no liquid in the lower or upper nerve root,but almost all of it was distributed on the opposite side.In the diffusion of hypobaric,isobaric,and hyperbaric bupivacaine,uneven diffusion of liquid medicine was observed.The color of the solution on both sides of the head and tail of the hypobaric,isobaric,and hyperbaric bupivacaine was lighter than the middle,while the color of the solution on the tail side was the darkest,and the closer it was to the head side,the lighter it was.3.Compared to equal weight solutions,the diffusion distance and diffusion range at the head side of hypobaric and hyperbaric solutions are larger.The diffusion range and cephalic diffusion distance of hypobaric solution at the same time are farther and faster than those of hyperbaric ones,but the amount of liquid in the hypobaric group near the ganglion segment where the liquid distributed is less.Conclusion:1.Using the 3D printing transparent human spinal canal model experimental platform,it is possible to simulate and visually observe the diffusion state and laws of local anesthetics in the vertebral canal,increasing the understanding of subarachnoid anesthesia.2.The distribution and diffusion laws of local anesthetics with different specific gravity are different:the hypobaric drugs are distributed and diffused in a semi shuttle shaped arc down against the upper sidewall;The hyperbaric anesthetic is distributed and diffused in a semi shuttle shaped arc upward and tightly against the lower sidewall;The isobaric drug diffuses uniformly in the spinal canal cavity.Hypobaric and hyperbaric medicine can form unilateral nerve block.3.Large diffusion range of hypobaric anesthetics,which can achieve high plane retardation;Due to its smaller diffusion range and higher drug concentration near the ganglia,the hyperbaric will be more sufficient for low plane block in lateral recumbent position;The diffusion range and cephalic diffusion distance of local anesthetic liquid with isobaric anesthetics are the shortest.Hypobaric anesthetics are lighter and faster than reconstituted cephalic diffusion,making it more difficult to control the anesthesia level compared to other groups..