Part three of this four-part series looks at the advantages and disadvantages of parenteral administration Show Shepherd M (2011) Administration of drugs 3: parenteral. Nursing Times; 107: 36, early online publication.
Parenteral drug administration means any non-oral means of administration, but is generally interpreted as relating to injecting directly into the body, bypassing the skin and mucous membranes. The common parenteral routes are intramuscular (IM), subcutaneous (SC) and intravenous (IV). Box 1 outlines the advantages and disadvantages of parenteral routes.
Advantages
Disadvantages
Parenteral administration requires an appropriate injection technique. If performed incorrectly – for example using the wrong size needle or cannula – it can cause damage to nerves, muscle and vasculature and may adversely affect drug absorption. Intramuscular and subcutaneousIn general, IM and SC injection of drugs establishes a deposit or “depot” that will be released gradually into the systemic circulation. The drug’s formulation will influence the period over which it is released; for example, the formulation of antipsychotic agents such as flupentixol in oil allows them to be administered once a month or every three months. IntravenousThe IV route carries the greatest risk of any route of drug administration. By administering directly into the systemic circulation, either by direct injection or infusion, the drug is instantaneously distributed to its sites of action. This route of administration can be complex and confusing. It may require dose calculations, dilutions, information to be gathered on administration rates and compatibilities with other IV solutions, as well as the use of programmable infusion devices. The preparation of IV medicines requires the use of an aseptic technique, often in a ward environment that is unsuited to such work. To minimise the risk of errors, it is imperative that practitioners can demonstrate competence to practise safely, and have access to expert information and advice. Box 2 lists considerations for preparing IV drugs. Box 2. Considerations for IV administration
The National Patient Safety Agency (2007) has highlighted the risks associated with the preparation and administration of injectable medicines and proposed a set of competencies. These provide a useful basis for the creation of policy and training in this area.
Martin Shepherd is head of medicines management at Chesterfield Royal Hospital Foundation Trust National Patient Safety Agency (2007) Promoting Safer Use of Injectable Medicines. London: NPSA. Intradermal injections (ID) are injections administered into the dermis, just below the epidermis. The ID injection route has the longest absorption time of all parenteral routes. These types of injections are used for sensitivity tests, such as TB (see Figure 7.13), allergy, and local anesthesia tests. The advantage of these tests is that the body reaction is easy to visualize, and the degree of reaction can be assessed. The most common sites used are the inner surface of the forearm and the upper back, under the scapula. Choose an injection site that is free from lesions, rashes, moles, or scars, which may alter the visual inspection of the test results (Lynn, 2011). Equipment used for ID injections is a tuberculin syringe calibrated in tenths and hundredths of a millilitre, and a 1/4 to 1/2 in., 26 or 27 gauge needle. The dosage of an ID injection is usually under 0.5 ml. The angle of administration for an ID injection is 5 to 15 degrees. Once the ID injection is completed, a bleb (small blister) should appear under the skin. Checklist 56 outlines the steps to administer an intradermal injection.
Subcutaneous InjectionsSubcutaneous (SC) injections are administered into the adipose tissue layer just below the epidermis and dermis. This tissue has few blood vessels, so drugs administered by this route have a slow, sustained rate of absorption. Sites for SC injections include the outer aspect of the upper arm, the abdomen (from below the costal margin to the iliac crest) within one inch of the belly button, anterior aspects of the thighs, upper back, and upper ventral gluteal area (Lynn, 2011) (see Figure 7.14). Figure 7.14 SC injection sitesChoose a site that is free of skin lesions and bony prominences. Site rotation prevents the formation of lipohypertrophy or lipoatrophy in the skin. Physical exercise or application of hot or cold compresses influences the rate of drug absorption by altering local blood flow to the tissues. Any condition that impairs that blood flow to the subcutaneous tissue contradicts the use of subcutaneous injections. Examples of subcutaneous medications include insulin, opioids, heparin, epinephrine, and allergy medication (Perry et al., 2014). To administer an SC injection, a 25 to 30 gauge, 3/8 in. to 5/8 in. needle is used. Some subcutaneous injections come prefilled with the syringe attached. Always confirm that the right-size needle is appropriate for the patient before use. Subcutaneous injections are usually given at a 45- to 90-degree angle. The angle is based on the amount of subcutaneous tissue present. Generally, give shorter needles at a 90-degree angle and longer needles at a 45-degree angle (Lynn, 2011). SC injections do not need to be aspirated as the likelihood of injecting into a blood vessel is small. Usually, no more than 1 ml of medication is given subcutaneously, as larger amounts may cause discomfort to the patient and may not be absorbed appropriately (Lynn, 2011). There are varying opinions on whether to pinch the skin during administration. Pinching is advised for thinner patients in order to lift the adipose tissue up and away from the underlying muscle and tissue. If pinching is used, release the pinch when the needle is inserted to avoid injecting into compressed tissue. Note, too, that elevating or pinching the skin has been found to increase the risk of injury, as the needle may pierce the opposite side of the skin fold and enter the skin of the health care worker (Black, 2013). The abdomen is the best location for an SC injection if a patient has little peripheral SC tissue. If patient is obese, use a needle that is long enough to insert through the tissue at the base of the skin fold (Perry et al., 2014). Insulin SC InjectionsInsulin is considered a high-risk medication, and special care must be taken to ensure the correct amount of medication and type of insulin is administered at the correct time. As well, safety checks related to a patient receiving SC insulin should be carried out (Ellis & Parush, 2012). Table 7.5 lists specific guidelines for administering insulin (and see Figure 7.15).
Special considerations:
Heparin SC InjectionsHeparin is an anticoagulant used to reduce the risk of thrombosis formation by suppressing clot formation (Perry et al., 2014). Heparin is also considered a high-alert medication (ISMP, 2014). Table 7.6 provides specific guidelines to consider before and after administering heparin.
Checklist 57 provides the steps to complete a subcutaneous injection.
Video 7.3
Video 7.4 |