Parenteral administration of medicines may be hypodermic or subcutaneous (SC), intraarticular (into a joint), intradermal, intramuscular (IM), intravenous (IV — into a vein) intraperitoneal (into the abdominal cavity), epidural, or subconjunctival (beneath the eyelid). Precautions must be taken against the introduction of bacteria, dirt, etc. The hair should be clipped away at the site of injection, and the skin cleaned with spirit or an antiseptic. Needles and syringes should be sterilised before use, unless of the disposal type intended for once-only use and already sterilised and in a sealed wrapper.
Where the material to be injected is already fluid, this is generally guaranteed sterile by the manufacturers, and is put up in sealed vials. In cases where the drug has to be dissolved in water first, sterile water must be used. Manufacturers usually supply ampoules of sterile water with drugs that have to be dissolved; their instructions for use must be followed carefully. Neglect of these precautions is likely to be followed by the formation of an abscess at the point of injection or even by septicaemia.
For subcutaneous injections, a fold of the skin is picked up between the thumb and forefinger of the left hand, and the needle is inserted into the middle of this fold. The nozzle of the syringe, preloaded with the injection fluid, is slipped into the head of the needle and the piston is slowly but firmly pressed home so as to expel the contents into the loose tissues under the skin. Care should be taken that all air-bubbles are excluded from the barrel of the syringe, as it is unwise to introduce them.
A number of proprietary multi-injection devices are manufactured for herd inoculations.
Restless animals should always be secured so that they will not make a sudden plunge when the needle is introduced, and break the stem of the needle. Abscesses in hams are common in pigs, and doubtless result from anti-anaemia intramuscular injections made without due precautions as to cleanliness and to broken-off needles.
The sciatic nerve may be damaged as the result of an intramuscular injection into a pig’s ham, with paralysis of the limb possibly following. This site should be avoided, and it has been recommended that the injection be given into the muscles of the neck, just behind the ear, and not into fatty tissue.
Care must be taken not to make what should be a subcutaneous injection into the chest. This danger was illustrated when a farmer injected 500 lambs, using a multidose syringe intended for cattle, and with a 6 mm needle. Within a week 17 of the lambs had died; autopsy showed pyothorax and a pure growth of Actinomyces pyogenes. It has been demonstrated that it is possible to reach the pleural cavity with a cattle syringe, especially in thin lambs; many other ‘vaccine failures’ may have been due to inadvertent injections into the chest. Alternative sites, such as the side of the neck, would appear to offer a much reduced chance of complications.
With intravenous injections of certain preparations, severe tissue damage may follow if some of the drug enters the vein wall or surrounding tissue; the manufacturers’ instructions must be followed.
Inoculations should not be carried out in a dusty shed.
(See ANTHRAX; also AMPOULE; DETERGENT RESIDUE; ENEMA.)
Large-bore needles Use of these is not without risk, especially when liver biopsies are carried out by means of suction through a needle, inserted intraperitoneally and attached to a syringe.
Accidental self-inoculation may occur owing to the sudden violent movement of a large animal. People have been infected with BRUCELLOSIS in this way; and veterinary surgeons have died from IMMOBILON. Accidental self-injection with oil-based vaccines requires prompt hospital attention.