Everything about Hypodermic Needle totally explained
» For the theory on mass media effects, see Hypodermic needle model.
"Hypodermic" redirects here. For the song by The Offspring, see Ignition (album).
A
hypodermic needle is a hollow needle commonly used with a
syringe to
inject substances into the body. They may also be used to take liquid samples from the body, for example taking blood from a vein in
venipuncture.
A hypodermic needle is used for instant delivery of a drug, or when the injected substance can't be ingested, either because it wouldn't be absorbed (as with
insulin), or because it would harm the
liver (as with
testosterone). There are many possible
routes for an injection.
Single use hypodermics
Virtually all current hypodermic needles and their associated
syringes are designed for single use because they're hard to decontaminate and need sharpening after repeat use. Re-using or sharing needles can transmit many
blood-borne diseases, including
HIV and
hepatitis C. Needles are normally used only once and disposed of in a
sharps container. This is has been true for decades in the industrialized West, but in developing countries, such as in most of
Africa, needles are often reused — and sharpened and sterilized between uses. This means that such needles become a common route of infection, for
AIDS and other diseases. The first non-African AIDS patient — and the first whose name is known — was
Grethe Rask, a
Danish surgeon in a rural hospital in
Zaire in 1976. In this hospital, throwaway needles and gloves were a fantasy: needles and gloves were reused until obviously unusable. Although she was skilled in sterile procedure, she was often spashed with blood and other body fluids and may have accidentally suffered a needle-stick injury. Her story is told in Chapter 1 of
And the Band Played On, by
Randy Shilts.
Single-use syringes, which have automatic mechanisms to prevent reuse, have been developed to stop the spread of disease in medical settings, examples of which include medical-personnel exposure and
immunizations (External Link
) . One type is a pre-filled plastic blister with a hypodermic needle attached via a one-way
valve.
(External Link)
Manufacture
Hypodermic needles are normally made from a stainless-steel tube drawn through progressively smaller dies to make the needle. The end is bevelled to create a sharp pointed tip. This lets the needle easily penetrate the skin. When a hypodermic needle is inserted, the bevel should be facing upwards.
Needle gauge
The diameter of the needle is indicated by the needle
gauge. Various needle lengths are available for any given gauge. There are a number of systems for gauging needles, including the
Stubs Needle Gauge, and the
French Catheter Scale. Needles in common medical use range from 7 gauge (the largest) to 33 (the smallest) on the Stubs scale. Twenty-one-gauge needles are most commonly used for drawing blood for testing purposes, and sixteen- or seventeen-gauge needles are most commonly used for blood donation, as they're large enough to allow red blood cells to pass through the needle without rupturing (this also allows more blood to be collected in a shorter amount of time). Smaller-gauge needles will rupture the red blood cells, and if this occurs, the blood is useless for the patient that's receiving it. Although reusable needles remain useful for some scientific applications, disposable needles are far more common in medicine. Disposable needles are embedded in a plastic or aluminium hub that attaches to the syringe barrel by means of a press-fit (
Luer-Slip™) or twist-on (Luer-Lok™) fitting.
Non-specialist use
Hypodermic needles are usually used by medical professionals — physicians, nurses, paramedics — but they're sometimes used by patients themselves. This is most common with type one
diabetics, who may require several
insulin injections a day. It also occurs with patients who have
asthma or other severe
allergies. Such patients may need to take
desensitization injections; or they may need to carry injectable medicines to use for first aid in case of a severe allergic reaction. Such patients often carry a syringe loaded with
epinephrine; some also carry syringes loaded with
Benadryl and
Decadron. The rapid injection of these drugs may stop a severe allergic reaction, prevent
anaphylactic shock, and make an
emergency room trip unnecessary, although it may be disconcerting to spectators. Hypodermic needles are also used illicitly in
recreational intravenous drug use, for this reason it's illegal in many jurisdictions to possess used or unused needles without an approved medical reason.
Industrial use
Disposable plastic syringes equipped with unbeveled blunt-tip Luer-Lok™ or Luer-Slip™ needles are often used in industry to apply precise amounts of lubricants, adhesives, and various other liquids and pastes.
Phobia
It is estimated that about 10% of the adult population may have a
phobia of needles (
Trypanophobia), and it's much more common in children. There is some basis for this phobia, because not all medical personnel have the necessary skill with hypodermic needles. This is particularly with
intravenous uses, where incorrect insertion may easily damage the vein. It isn't unusual for a nurse or doctor to take several tries to start an IV; a dozen tries isn't unknown. Typically, a large hospital has one "deadeye" — usually, a
pediatric anesthesiologist — who can put needles in tiny or contracted veins, but this person isn't always available.
Further Information
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