| Hypodermic needle | |
|---|---|
 Differentbevels on hypodermic needles | |
| Classification | Medical device |
| Industry | Healthcare |
| Application | Injection |
| Inventor | Francis Rynd |
| Invented | 1844 (182 years ago) (1844) |
Ahypodermic needle (fromGreek ὑπο- (hypo- = under), and δέρμα (derma = skin)) is a very thin, hollow tube with one sharp tip. As one of the most important intravenous inventions in the field ofdrug administration, it is one of a category of medical tools which enter the skin, calledsharps.[1] It is commonly used with asyringe, a hand-operated device with a plunger, toinject substances into the body (e.g.,saline solution, solutions containing various drugs or liquid medicines) or extract fluids from the body (e.g., blood). Large-bore hypodermic intervention is especially useful in catastrophic blood loss or treatingshock. It was invented byFrancis Rynd in 1844.
A hypodermic needle is used for rapid delivery of liquids, or when the injected substance cannot be ingested, either because it would not beabsorbed (as withinsulin), or because it would harm theliver. It is also useful to deliver certain medications that cannot be delivered orally due to vomiting. There are many possibleroutes for an injection, withintramuscular (into amuscle) andintravenous (into avein) being the most common. A hypodermic syringe has the ability to retain liquid and blood in it up to years after the last use and a great deal of caution should be taken to use a new syringe every time.
The hypodermic needle also serves an important role in research environments where sterile conditions are required. The hypodermic needle significantly reduces contamination duringinoculation of a sterilesubstrate. The hypodermic needle reduces contamination for two reasons: First, its surface is extremely smooth, which prevents airbornepathogens from becoming trapped between irregularities on the needle's surface, which would subsequently be transferred into the media (e.g.agar) as contaminants; second, the needle's surface is extremely sharp, which significantly reduces the diameter of the hole remaining after puncturing the membrane and consequently prevents microbes larger than this hole from contaminating the substrate.[2][3][4][5]
The ancientGreeks andRomans knew injection as a method of medicinal delivery from observations of snakebites and poisoned weapons.[6] There are also references to "anointing" and "inunction" in theOld Testament as well as the works ofHomer, but injection as a legitimate medical tool was not truly explored until the 17th century.[7]
Christopher Wren performed the earliest confirmed experiments with crude hypodermic needles, performing intravenous injection into dogs in 1656.[7] These experiments consisted of using animalbladders (as the syringe) andgoosequills (as the needle) to administer drugs such asopium intravenously to dogs. Wren and others' main interest was to learn if medicines traditionally administered orally would be effective intravenously. In the 1660s,Johann Daniel Major ofKiel andJohann Sigismund Elsholtz ofBerlin were the first to experiment with injections in humans.[6][8]
The 19th century saw the development of medicines that were effective in small doses, such as opiates and strychnine. This spurred a renewed interest in direct, controlled application of medicine. "Some controversy surrounds the question of priority in hypodermic medication."[9] Irish physicianFrancis Rynd is generally credited with the first successful injection in 1844, in theMeath Hospital inDublin,Ireland.[10][11]
Alexander Wood's main contribution was the all-glass syringe in 1851, which allowed the user to estimate dosage based on the levels of liquid observed through the glass.[12] Wood used hypodermic needles and syringes primarily for the application of localized, subcutaneous injection (localized anesthesia) and therefore was not as interested in precise dosages.[8]
Simultaneous to Wood's work in Edinburgh,Charles Pravaz of Lyon also experimented with sub-dermal injections in sheep using a syringe of his own design. Pravaz designed a hypodermic needle measuring 3 cm (1.18 in) long and 5 mm (0.2 in) in diameter; it was made entirely of silver.[citation needed]
Charles Hunter, a London surgeon, is credited with the coining of the term "hypodermic" to describe subcutaneous injection in 1858. The name originates from two Greek words:hypo, "under", andderma, "skin". Furthermore, Hunter is credited with acknowledging the systemic effects of injection after noticing that a patient's pain was alleviated regardless of the injection's proximity to the pained area.[7][8] Hunter and Wood were involved in a lengthy dispute over not only the origin of the modern hypodermic needle, but also because of their disagreement as to the medicine's effect once administered.[13]
Dr. Francis Rynd used the first "Hollow Needle" as a hypodermic syringe on Ms. Margaret Cox in Ireland on June 3rd, 1844. Dr. Wood can be largely credited with the popularization and acceptance of injection as a medical technique, as well as the widespread use and acceptance of the hypodermic needle. The basic technology of the hypodermic needle has stayed largely unchanged since the 19th century, but as the years progressed and medical and chemical knowledge improved, small refinements have been made to increase safety and efficacy, with needles being designed and tailored for very particular uses. Hypodermic needles remain essential to large volume administration or exchange in settings oftrauma ordialysis. The trend of needle specification for use began in the 1920s, particularly for the administration of insulin todiabetics.[14]
The onset of World War II spurred the early development of partially disposable syringes for the administration ofmorphine andpenicillin on the battlefield. Development of thefully disposable hypodermic needle was spurred on in the 1950s for several reasons. TheKorean War created blood shortages and in response disposable, sterile syringes were developed for collecting blood. The widespreadimmunization against polio during the period required the development of a fully disposable syringe system.[14]
The 1950s also saw the rise and recognition of cross-contamination from used needles. This led to the development of the first fully disposable plastic syringe by New Zealand pharmacist Colin Murdoch in 1956.[15] This period also marked a shift in interest from needle specifications to general sterility and safety.[14]
The 1980s saw therise of the HIV epidemic and with it renewed concern over the safety of cross-contamination from used needles. New safety controls were designed on disposable needles to ensure the safety of medical workers in particular. These controls were implemented on the needles themselves, such as retractable needles, but also in the handling of used needles, particularly in the use ofhard-surface disposal receptacles found in every medical office today.[14]
By 2008, all-plastic needles were in production and in limited use. One version was made ofVectra (plastic)aromaticliquid crystal polymer tapered from 1.2 mm at the hub to 0.72 mm at the tip (equivalent to 22 gauge metal needle), with an ID/OD ratio of 70%.[16]
Hypodermic needles are normally made from astainless-steel orNiobium tube[17] through a process known astube drawing where the tube is drawn through progressively smallerdies to make the needle. The end of the needle isbevelled to create a sharp pointed tip, letting the needle easily penetrate the skin.[18]
The main system for measuring the diameter of a hypodermic needle is theBirmingham gauge (also known as the Stubs Iron Wire Gauge); theFrench gauge is used mainly for catheters. Various needle lengths are available for any given gauge. Needles in common medical use range from 7 gauge (the largest) to 34 (the smallest). 21-gauge needles are most commonly used for drawing blood for testing purposes, and 16- or 17-gauge needles are most commonly used for blood donation, as the larger luminal cross-sectional area results in lower fluid shear, reducing harm to red blood cells while also allowing more blood to be collected in a shorter time.[19]
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 or twist-on fitting. These are sometimes referred to as "Luer Lock" connections, referring to the trademarkLuer-Lok. The male and female luer lock and hub—produced by pharmaceutical equipment manufacturers—are two of the most critical parts of disposable hypodermic needles.[20]
Hypodermic needles are usually used by medical professionals (dentists,phlebotomists,physicians,pharmacists,nurses,paramedics), but they are sometimes used by patients themselves. This is most common withtype one diabetics, who may require severalinsulin injections a day.[21] It also occurs with patients who haveasthma or other severeallergies. Such patients may need to takedesensitization injections or they may need to carry injectable medicines to use for first aid in case of a severe allergic reaction. In the latter case, such patients often carry a syringe loaded withepinephrine (e.g.EpiPen),[22]diphenhydramine (e.g.Benadryl), ordexamethasone. Rapid injection of one of these drugs may stop a severe allergic reaction.
Multiple sclerosis patients may also treat themselves by injection; several MS therapies, including variousinterferon preparations, are designed to be self-administered by subcutaneous or intramuscular injection.[23]
Hypodermic needles are also used forerotic piercing.[24]
It is estimated that anywhere from nearly 3.5 to 10% of the world's population may have aphobia of needles (trypanophobia),[25] and it is much more common in children, ages 5–17. Topical anesthetics can be used to desensitize the area where the injection will take place to reduce pain and discomfort.[26] For children, various techniques may be effective at reducing distress or pain related to needles.[27] Techniques include: distraction,hypnosis, combinedcognitive behavioral therapy, and breathing techniques.[27]
-solution.jpg)
