Application of Intravenous Indwelling Needle in Undergraduate’s Pharmacology Teaching Experiment

Yifei CHEN, Jun LU, Jingchen WEI, Linglin CHEN, Liang LU, Zhikai DAI*, Yongwen LI*

1. Pharmacy Department, Guilin Medical University, Guilin 541199, China; 2. Guangxi Colleges and Universities Key Laboratory of Pharmacology, Guilin 541199, China

Abstract In this study, an intravenous indwelling needle was placed in the central artery of rabbit ear for collecting blood. The results show that this method greatly improves the success rate of blood sampling and well controls the experimental time. The students’ unanimous feedback was that the method is simple and easy to operate, which is of great help to the stability of the experimental results.

Key words Intravenous indwelling needle, Pharmacology, Teaching experiment

1 Introduction

Blood is a common test sample in pharmacology teaching experiments. For experiments that require a relatively large amount of blood, such as half-life determination experiment, the ear veins of rabbits are commonly used for blood collection. However, in daily experimental teaching, it is found that the success rate of current blood sampling with disposable syringes is low, and it usually takes a long time, greatly influencing the final experimental results. Intravenous indwelling needle is a commonly used clinical infusion tool. It is easy to puncture, and the puncture technique is easy to master. Intravenous indwelling needle protects patients’ blood vessel, relieving their pain and letting them feel comfortable.

Intravenous indwelling needle is composed of a stainless steel needle core, a soft outer catheter and a plastic needle seat. During puncture, the outer catheter and needle core are pierced into the blood vessel together. When the catheter is fed into the blood vessel, the needle core is withdrawn, and only the soft outer catheter is left in the blood vessel for infusion, which will cause less damage to the blood vessel and is suitable for continuous operation. The half-life determination of sodium salicylate is a routine experiment in undergraduate’s pharmacology teaching experiment of Guilin Medical University. Students are required to take blood 3 times during the experiment, but most of them fail to collect enough blood in the 3rd and even 2nd time. In this context, intravenous indwelling needle is introduced to ensure the smooth progress of blood collection.

2 Materials

The materials used mainly included disposable intravenous indwelling needles of 18G Y type or 20G Y type (Jiangxi Fenglin Instrument Co., Ltd.), 1 mL disposable syringes, rabbit boxes, gloves and heparin solution (1 000 U/mL).

3 Methods

3.1CatheterplacementFirst, suitable blood vessel is selected. The currently used method is to take flood from the veins of the ears of rabbits. However, due to the thin venous wall and low blood pressure, intravenous indwelling needle is easy to cause the blood vessels to close. Therefore, the artery in the center of the rabbit ear is a better choice for catheter placement.

After the suitable blood vessel is selected, experiment is arranged in groups of 3 students. Each rabbit is put in a rabbit box first. Student A is responsible for fixing the rabbit’s head; student B is responsible for removing the coat from the blood collection site, and student C is responsible for preparing heparin solution and hemostatic cotton balls. After preparation, student B fills the entire intravenous indwelling needle with heparin solution (Fig.1). After fixing the ear of the rabbit with the left hand, he/she holds the intravenous indwelling needle in the right hand and pierces the skin toward the proximal end at an angle of less than 30° at the end of the central artery and pierces the blood vessel. After seeing the blood return, the angle is lowered, and the needle is inserted 1-2 mm further. The rabbit’s ears are firmly held. After student C helps slowly withdraw the steel needle from the catheter, student B continues to slowly feed the outer catheter into the blood vessel of the rabbit’s ear to approximately 2/3 the length of the catheter. The catheter is left in the blood vessel. Finally, the catheter and extension tube are fixed on the back of the rabbit’s ear with rape for use.

3.2BloodcollectionStudent B holds the Y-shaped part in the left hand, and inserts the syringe from the positive pressure interface in the right hand. The heparin filled in the catheter is drawn and discarded, and then 1 mL of blood is drawn. After the blood collection, student C quickly injects about 0.3 mL of heparin from the positive pressure interface. This blood collection method can control the amount of blood collected each time, and the blood collection time is short. What’s more, blood collection can be repeated without piercing the needle repeatedly.

Fig.1 Disposable intravenous indwelling needle (18G Y type)

4 Discussion

With the advancement of the infusion concept of "zero steel needle tolerance", intravenous indwelling needles have been widely used clinically for their protecting blood vessels, reducing the pain caused by repeated puncture to the patients, and ensuring the safeness and effectiveness of drug treatment[1-2]. Rabbits are timid and easily startled by nature. The blood vessels are prone to spasmodic contraction after multiple blood collections with traditional disposable syringes, bringing difficulties to blood collection, prolonging the experiment time, and leading to poor experimental results. In addition, undergraduate students have uneven proficiency in blood collection technique, and in experiments that require multiple blood samplings, the blade cutting method is inevitably used for blood collection, increasing the possibility of blood sample contamination. The disposable intravenous indwelling needle blood collection method used in this article is simple to operate, and students’ acceptance is high. After the central artery is fixed, blood can be taken multiple times quickly and easily, avoiding vasospasmodic contraction caused by multiple administrations and interference of intravenous drugs on blood samples to the greatest extent. It is of great help to ensure the smooth progress of the experiment and make the experimental results more stable and reliable. Finally, the points that need to be paid attention to in the experimental operation are summarized. (i) When placing the catheter, the distal end of the central artery is chosen as much as possible to insert the needle. This ensures that if the first puncture fails, there is still a chance for another puncture. (ii) When the catheter is inserted into the blood vessel, about 1/3 of it is left outside the blood vessel. The left part can’t be too long or too short. If it is too long, the catheter is easy to fall out; and if it is too short, there is no room to insert further if congestion occurs. (iii) After the blood collection is completed, the entire line of the intravenous indwelling needle must be filled with heparin solution again to avoid the pipeline from being blocked caused by blood clotting. (iv) When collecting blood, fast suction is forbidden to avoid deformation of the catheter wall and spastic contraction.