Insulin Administration: SYRINGE
Parts of a Syringe
A syringe consists of an outer barrel and an inner plunger or the piston. The barrel has a tip to which the needle is fixed. The piston should fit the barrel properly and should neither be too tight nor too loose.
The space which remains after the plunger is pushed completely into the barrel of the syringe is called "dead space". When this space is practically absent, it is said to be "zero dead space". A syringe is most accurate when it has "zero dead space".
Material of the Syringe
A syringe may either be made of glass (reusable) or of plastic (disposable). The glass insulin syringes have now become obsolete. The disposable insulin syringes available today have needles fixed to the syringe. Greater the gauge of the needle, the finer it is. Disposable plastic syringes have the following advantages over glass syringes:
- Cleaning or sterilization not required. (See guidelines)
- Virtually zero dead space.
- Possible to measure confidently even one unit of insulin.
- Safe.
- No injection abscess if simple rules of hygiene are followed.
- Convenient during travel.
- Cheap. No breakage; saves fuel. Considering the advantages, it is recommended strongly that all diabetics requiring insulin should use plastic insulin syringes only.
Marks on the Syringe
One should note the capacity of the insulin syringe, namely, 1 ml. If insulin is of the U40 variety that is, strength of 40 units per ml, and the capacity of the insulin syringe is 1 ml, it is obvious that one cannot draw more than 40 units insulin with such a syringe.
The strength of insulin and the type of syringe should match each other. U40 insulin should be injected with U40 syringe only.
Single Scale
The disposable insulin syringe commonly available in India at present is of 1 ml capacity. U40 scale is embossed red and U100 scale is embossed black on the syringe. One ml U40/U100 is divided into 40 units or 100 units respectively.
There are large divisions and smaller divisions. One large division is equal to 5,10,15... units and each small division corresponds to one unit. Numbers 5,10,15.... arc embossed on the barrel. If one has to measure 12 units insulin, one should take the piston (plunger) up to 2 small divisions beyond the 10 mark.
Guidelines for storage and sterlization of plastic insulin syringes
Disposable plastic insulin syringes should not be cleaned, washed or boiled before use. They are to be used as such. Cleaning the needle with alcohol/spirit is not recommended because it may remove the silicon coating of the needle that makes for less painful skin puncture. The needle should be recapped after each use. While recapping the needle, the syringe should be supported with one hand and the cap should be replaced with a straight motion of thumb and forefinger of the opposite hand. Guiding both the needle and the cap to meet in mid-air should be avoided because this frequently results in needle-stick injury.
A syringe being reused may be stored at room temperature. The potential benefits or risks, if any, of refrigerating the syringe in use are unknown.
Guidelines for reuse of "disposable" insulin syringes
Manufacturers of "disposable" plastic syringes recommend that they be used only once, because the sterility of a reused syringe cannot be guaranteed.
For most patients, however, it appears both safe and practical, for the syringe to be reused, if the patient so desires. This is because most insulin preparations contain additives that inhibit growth of bacteria commonly found on the skin. The syringe should be discarded when the needle becomes dull, has been bent or has come in contact with any surface other than the skin and rubber cork of insulin bulb or if the markings on the syringe become faint.
Syringe reuse may carry an increased risk of infection for some individuals. Patients with poor personal hygiene, acute concurrent illness, open wounds on the hands or decreased resistance to infection should not reuse a syringe.
Patients reusing the syringe should inspect periodically the skin around an injection site for unusual redness or signs of infection. Individuals should consult their physicians before initiating the practice of syringe reuse and whenever injection site infection is suspected.
Syringes must never be shared with another person because of the risk of acquiring a blood-borne viral infection like hepatitis B or acquired immune deficiency syndrome (AIDS).
Insulin Vial
Insulin is marketed in liquid form and measured in term of units. An insulin via! contains 10 ml insulin. The strength of the insulin that is, 40 units, 100 units or 80 units per ml, is stated on the vial and the carton and should be verified. When purchasing insulin, the patient should ensure the prescribed type, strength and species. Expiry date, stated on the vial and the carton should be verified. Insulin should not be used after its expiry date. The insulin vial should be inspected before use. Rapid acting, insulin glargine and short-acting insulin should be clear like water and other insulin types should be uniformly cloudy. If this is not so, the insulin vial should be discarded.