Many believe that the syringe (from the Greek “sirinx”, or “cane”, “conduit”) is a banal product due to its common use.In reality, modern syringes are the result of continuous technological improvement, which has occurred over almost two centuries of history,for the creation of increasingly effective devices both for injections and for withdrawals.
The invention of disposable syringes: origin and history
Already in the 1600s some doctors experimented with forms of intravenous injection and transfusion, but it was only in the mid-1800s that two scientists,the Frenchman Charles Gabriel Pravaz and the Scotsman Alexander Wood developed a needle thin enough to pierce the skin.
Thus the syringe was born, understood as the object we know today.
For Wood this device was used to inject morphine into patients suffering from chronic neuralgia,while Pravaz used it to inoculate a solution of iron chloride to study coagulation.
The first syringes were metal,while Pravaz's syringe was made of glass and the advancement of the piston was regulated by a screw system: by rotating the butterfly it was possible to dose the quantity of liquid to be injected while the piston was made up of leather discs.
It was washed and reused on multiple patients, with a serious risk of contamination.In the early years of the twentieth century, precisely to allow safer sterilization, the syringe became completely made of glass.
In reality, not even this solution was able to guarantee an appropriate level of sterilization and so in the 1950s the first models of plastic disposable syringe were introduced,polypropylene and polyethylene, which solved this problem.However, the use of these syringes was slow to spread in Europe at least until the end of the 1970s.
Subsequent technological improvements have allowed increasingly diversified uses.
Different needles for different types of injection
The syringe needles are available in different sizes and are intendedto perform a variety of functions.
The choice of size of syringe needles depends on the drug being used and, sometimes, also on the size of the patient himself.
The needle diameters determine the gauge size.The type of injection needed will determine the caliber but also the length of the needle used.
In healthcare facilities safety syringes are also used, which have a mechanism that covers the needle once the injection has been given,to reduce the risk of the operator or patient coming into contact with an infected needle.
There are mainly five types of injections,for each of which the characteristics of the needle change:
- Intramuscular: drugs injected into certain muscle sites
- Subcutaneous: drugs injected into the subcutaneous fat between the skin and muscle
- Intravenous: drugs injected directly into the veins
- Intradermal: drugsinjected into the dermal layer of the skin;can be injected into the volar area of the forearm, the dorsal area of the arm and forearm, the scapular area and the upper chest
- Intraosseous: solutions injected into the bone in the absence of venous access,locations vary depending on the age of the individual.
The injection carried out through the intramuscular syringe is, by definition, inoculated into the depth of the muscle. Vaccines, for example, are commonly injections given with an intramuscular syringe.Drugs injected intramuscularly act faster than those taken orally: the injection is performed inside a muscle tissue rich in blood vessels which facilitates the circulation of the drug in the blood. These types of injections usually require longer and slightly thicker needles.The common size of a needle for an intramuscular injection would be 20 or 22 gauge gauge, in 5-10 ml syringes with 6-8 cm long needles.
Injections via a subcutaneous syringe are typically carried out for the administration of drugs into the first layer of fat which is located just under the skin.This type of syringe is suitable for all those substances whose absorption must be very slow. Insulin injections are a classic example of subcutaneous injections. The needles used for subcutaneous injections are thinner and shorter.For a subcutaneous injection, 25 or 30 gauge needles, 1.5 cm to 2 cm long, are used.
Other needles used to administer medications are those connected to an intravenous line that leads to a bag of fluids.This technique consists in the direct introduction of a substance into the venous blood circulation via a needle, of short length, inserted into one of the easily accessible veins: usually the anterior ones of the elbow crease and forearm.
The intradermal injection,that is, the one that does not go beyond the first layer of skin, is carried out to verify tolerance to certain allergens as well as to induce intradermal reactions useful in the diagnosis of diseases such as tuberculosis and brucellosis.Syringes of maximum 1 ml are used for very slow release drugs, with short needles up to 1.5 cm.
Finally, the intraosseous injection consists of positioning a strong needle through the cortical bone and into the medullary cavity to urgently infuse fluids and blood products into critically ill patients.For this type of injections,very resistant and large caliber needles are used.
The different types of syringe needles
In the medical world there are different types of syringe needles depending on the functions they are called upon to perform.
Cannula needles
The needle cannula is a device that is usedfor the cannulation of a vein for intravenous administration of drugs. It is composed of a small plastic tube called a cannula (equipped with a protective cap), inside which the needle is inserted which serves to pierce the epidermis and facilitate positioning of the needle in the vein.The needle is removed once the cannula is completely inserted and positioned, which can then be used for the passage of liquids or drugs.It is completed by two clamps used to secure it to the patient's skin, in order to avoid accidental movements of the cannula which could cause damage or cause it to slip off.
The flow regulator, also called inflow regulator,it is a long tube that allows the passage of the solution from the bottle to the patient's vein and is composed of a drip chamber, clamp and actual flow regulator,to control the rate of the liquid to be administered.
Butterfly needles
The butterfly needle is a short device, equipped with small plastic wings that facilitate the introduction of the same into a peripheral vein. It is available in multiple sizes.They are commonly used for collections defined as "vacuum-packed" with the aid of a further device, the shirt.
The needles are individually packaged to allow the choice of the right needle for the patient. Some needles are already attached to standard-sized syringes.All are disposable. A needle is made up of three parts: the mouth, which fits over the tip of the syringe, the shank that connects to the mouth, and the bevel or slanted tip, which is the tip of the needle.The needles vary in length from 0.9 to 4 cm.
The healthcare worker chooses the length of the needle based on the patient's size and weight and the type of tissue.
Hypodermic needles
The hypodermic needles are sterile devices,used for injection of pharmacological substances at the hypodermic level or for drainage of fluids from the body.
Hypodermic needles consist of a sharp stainless steel cannula, which allows painless penetration into the skin and its underlying layers.A barrel is generally welded to the cannula.They are thin and pointed needles, the cannula of which is generally covered with a plastic needle cover to prevent accidental punctures.
Insulin needles
The insulin needles allow the administration of this particular drug in diabetic patients.Precise rules have recently been established which list the minimum safety requirements, characteristics, length and sterility conditions to be respected when choosing these medical devices.
The syringes used for insulin administration are small,equipped with a graduated scale in International Units of insulin, and generally have the characters written in larger size, to meet the specific needs of diabetic patients.
Furthermore, alongside the classic traditional syringe,diabetic patients have access to a special "pen" loaded with pre-filled cartridges to be able to carry out multiple injections by replacing only the needle.
Mesotherapy needles and Acupuncture needles
Mesotherapy needles and Acupuncture needles are increasingly in demand on the market and are similar to each other in shape andin size, even if they have different ways of use.
The mesotherapy needles are generally very short and thin, varying in length between 3 and 6 mm, ideal for a series of “microinjections” of drug into the dermis.This technique is often used to eliminate fluid stagnation in the skin and subcutaneous tissues.
The acupuncture needles on the other hand are not used for injecting drugs.Acupuncture is a traditional Chinese medical technique that involves the insertion and manipulation of needles into a part of the body to relieve pain or provide therapy.
They therefore act on well-defined energy points of the body.Disposable sterile needles are used, made of steel with a copper handle, with a diameter of approximately 0.30 mm and a variable length, between eight millimeters and seven centimeters, based on their purpose and on which part of the body they are to be used.
