Study Of The Effect Of Spinal Anesthesia Injection Velocity On The Adjustment Of Anesthesia Level Based On 3D Printed Human Transparent Spinal Canal Lumen Model Experimental System

Background:Subarachnoid block anesthesia,referred to as spinal anesthesia,is a commonly used clinical anesthesia method,in which local anesthetic is injected into the subarachnoid space and acts on the spinal cord and nerve roots to produce anesthetic effects.It is widely used in abdominal,pelvic,perineal and lower limb surgeries because of its rapid onset,small amount of anesthetics,precise analgesic effect and good muscle relaxation effect.The precise control of the anesthetic level of spinal anesthesia is the key point and difficulty in clinical and teaching work.The level of anesthesia that can meet the needs of surgical operations requires adequate analgesia and muscle relaxation,but must also prevent the patient from suffering from respiratory and circulatory depression,nausea and vomiting due to too high a level;while too low a level of anesthesia cannot meet the needs of surgery.Clinical research data and anesthesia textbooks have concluded qualitatively that the level of lumbar anesthesia regulation is related to the injection speed.However,there is a lack of systematic data on the correlation between quantitative drug injection speed and anesthesia level.This group used 3D printing transparent human vertebral cavity model test system to observe isovolumetric and isopecific local anesthetic 0.75%bupivacaine hydrochloride pushed at different speeds by color discrimination method,and measured the anesthesia plane in each group during the induction time of anesthesia,and conducted a quantitative study on the correlation between anesthesia plane and injection speed to provide data basis for clinical anesthesia and teaching.Objective:By applying 3D printing transparent human spinal cavity lumbar anesthesia experimental system,we observed the effect of anesthesia level regulation by pushing isovolumetric and isotonic drugs（0.75%bupivacaine hydrochloride）in a lying position and at different speeds,and provided quantitative research data on the speed of spinal anesthesia injection and anesthesia level regulation for teaching and clinical work.Methods:1.Establishment of 3D printing transparent human spinal canal model experimental system（1）To establish a 3D three-dimensional database based on the data model of a standard human spine in a horizontal position with electronic computed tomography（CT）,and to 3D print a 3D transparent spinal canal model using a digital technology printer.（2）Model brace system development and application.Combined with the characteristics of this model to develop a special fixed bracket,the model is fixed in the supine position behind the bracket,which can simulate the flat supine position,flat lateral position,head high and foot low position,head low and foot high position during clinical anesthesia to switch freely.A white soft ruler is affixed to the left side of the 3D printed transparent spinal canal model to measure the diffusion distance of local anesthetic in the transparent canal lumen of the spinal canal.The3D-printed human transparent spinal canal lumen model was sealed,and the cerebrospinal fluid perfusion channel and open-close valve were established at the cervical spine opening,while the cerebrospinal fluid discharge port was established.At room temperature of 25℃,artificial cerebrospinal fluid was infused into the lumen of the 3D printed human transparent vertebral canal model,and the lumen of the vertebral canal still appeared colorless and transparent at this time.2.Experimental procedureThe model was set in horizontal lateral position,L2-3 was selected as the puncture point,the tip of the lumbar anesthesia needle was punctured into the vertebral canal lumen,the end of the needle was connected to a syringe attached to a syringe pump,five groups of injection rates were established:900 ml/h,720 ml/h,540 ml/h,360 ml/h,180 ml/h.Each group was injected with 2 ml of 0.75%specific gravity of bupivacaine hydrochloride solution with methylene blue added as a tracer.Bupivacaine hydrochloride solution,the experimental results were recorded by taking pictures with a cell phone,the diffusion distance of local anesthetic at the completion of injection was recorded as T _{injection phase},and after resting the model was transferred from lateral to supine position,the diffusion distance was recorded as T_60sat this time,and then rested for 5 min,10 min,15 min,and recorded as T_5min,T_10min,T_15min,respectively.each group of experiments were repeated five times and the results were recorded.Results:1.In the T injection phase,the injection velocity increased and the diffusion distance increased both on the cephalic and caudal sides.The comparison between groups was statistically significant（P<0.05）.drug distribution in the injection phase reached the level of T12 in group V1,between T12 and L1 in group V2,between T12 and L1 in group V3,between T12 and L1 in group V4,and between L1 and L2 in group V5.2.In the T15min phase,the injection speed is greater than 360ml/h（0.1ml/s）,the speed decreases,the local anesthetic diffusion distance decreases,the injection speed is 0.1ml/s,the T15min phase diffusion distance shows a transitive increase,the speed further decreases,the diffusion distance further increases,there is a statistically significant difference between the group comparisons.group V1 T15min phase drug can diffuse to T8 level,group V2 to the level between T8 and T9,group V3 to the level between T8 and T9,group V4 to the level between T7 and T8,and group V5 to the level between T7 and T8.Conclusion:1.The 3D printed transparent spinal canal model invented by this group has the advantage of visual observation of the appearance of the diffusion of local anesthetic in the canal lumen.It precisely simulates the physiological situation of human spinal canal according to the bionic principle,such as the shape,volume and curvature of the vertebral canal lumen and has the basic functions of clinical teaching and research,and has the advantages of high repeatability and convenient operation.2.The injection rate can have an effect on the diffusion of local anesthetic in the spinal canal lumen.Both the injection phase and the diffusion phase play a role.In the injection phase,the increase in velocity will confer greater kinetic energy to the local anesthetic,In the diffusion phase,the diffusion of local anesthetic in the form of turbulent flow depends on the original kinetic energy given to the injected phase when the difference in velocity is not significant;the diffusion of local anesthetic in the form of laminar flow has less resistance in the lumen and relies on the potential energy of liquid tension generated by the local concentration of the drug to diffuse distally.3.The drug can be pushed at 900 ml/h speed T15min phase drug can be diffused to T8 level,720 ml/h speed group T15min to the level between T8 and T9,540 ml/h speed group T15min to the level between T8 and T9,360 ml/h speed group T15min to the level between T7 and T8,180 ml/h speed group T15min to the level between level between T7 and T8.generated by the local concentration of the drug in the spinal canal.