Injection Techniques



Intradermal route





The intradermal route provides a local, rather than systemic, effect and is used primarily for diagnostic purposes such as allergy or tuberculin testing, or for local anaesthetics.

To give an ID injection a 25-gauge needle is inserted at a 10-15° angle, bevel up, just under the epidermis, and up to 0.5ml is injected until a wheal appears on the skin surface (Fig. 1). If it is being used for allergen testing, the area should be labelled indicating the antigen so that an allergic response can be monitored after a specified time lapse.

The sites suitable for intradermal testing are similar to those for subcutaneous
injections (Fig. 2) but also include the inner forearm and shoulder blades (Springhouse Corporation 1993).




When testing for allergies, it is essential to ensure that an anaphylactic shock kit is easily accessible in case the patient develops a hypersensitive reaction
(Campbell 1995).


Subcutaneous route





The subcutaneous route is used for a slow, sustained absorbtion of medication, up to 1-2ml being injected into the subcutaneous tissue.

Figure 2 shows suitable locations for SC injections. Traditionally, SC injections have been given at a 45° angle into a raised skin fold (Thow and Home 1990).
However, with the introduction of shorter insulin needles (5, 6 or 8mm), the recommendation for insulin injections is now an angle of 90° (Burden 1994). The skin should be pinched up to lift the adipose tissue away from the underlying muscle, especially in thin patients (Fig. 3).

Insulin that is injected into muscle is absorbed more rapidly and can lead to glucose instability and potential hypoglycaemia. Hypoglycaemic episodes may also occur if the anatomical location of the injection is
changed, as insulin is absorbed at varying rates from different anatomical sites (Peragallo-Dittko 1997).
Therefore insulin injections should be systematically rotated within an anatomical site – for example, using the upper arms or abdomen for several months, before there is a planned move elsewhere in the body
(Burden 1994).

It is no longer necessary to aspirate after needle insertion before injecting subcutaneously.

It has also been noted that aspiration before administration of heparin increases the risk of haematoma formation (Springhouse Corporation 1993).


Intramuscular route


Intramuscular injections deliver medication into well perfused muscle, providing rapid systemic action and absorbing relatively large doses; from 1ml in the deltoid site to 5ml elsewhere in adults (these values should be halved for children). The choice of site should take into consideration the patient’s general physical status and age, and the amount of drug to be given. The proposed site for injection should be inspected for signs of inflammation, swelling, and infection, and any skin lesions should be avoided. Similarly, two to four hours after the injection, the site should be checked to ensure there has been no adverse reaction.

If injections are repeated frequently, the sites should be documented to ensure an even rotation. This reduces patient discomfort from overuse
of any one area and lessens the likelihood of the development of complications, such as muscle atrophy or sterile abscesses resulting from poor absorbtion(Springhouse Corporation 1993).


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