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Related theory

Subcutaneous tissue is not richly supplied with blood vessels and so medication is absorbed more slowly than when given intramuscularly. The rate of absorption is influenced by factors that affect blood flow to tissues such as physical exercise or local application of hot or cold compresses (Perry 2007). Other conditions can prevent or delay absorption due to an impaired blood flow so in these conditions subcutaeous injections are contraindicated, for example circulatory shock, occlusive vascular disease (Perry 2007).

Evidence-based approaches

Injection sites

Sites recommended are the abdomen in the umbilical region, the lateral or posterior aspect of the lower part of the upper arm, the thighs (under the greater trochanter rather than mid-thigh) and the buttocks (Downie et al. 2003) (Figure 13.22). It has been found that the amount of subcutaneous tissue varies more than was previously thought; this is particularly significant for administration of insulin as inadvertent intramuscular administration can result in rapid absorption and hypoglycaemic episodes (King 2003). Rotation of sites can decrease the likelihood of irritation and ensure improved absorption. If using the abdominal area then try to inject each subsequent injection 2.5 cm from the previous one (Chernecky et al. 2002). Injection sites should be free of infection, skin lesions, scars, birthmarks, bony prominences and large underlying muscles or nerves (Perry 2007).

Figure 13.22 Sites recommended for subcutaneous injection.

Reproduced from Elkin et al. (2007).

The skin should be gently pinched into a fold to elevate the subcutaneous tissue which lifts the adipose tissue away from the underlying muscle (Workman 1999). The practice of aspirating to ensure a blood vessel has not been pierced is no longer recommended as it has been shown that this is unlikely to occur (Peragallo-Dittko 1997, Perry 2007). The maximum volume tolerable using this route for injection is 2 mL and drugs should be highly soluble to prevent irritation (Downie et al. 2003).

Preprocedural considerations

Equipment

Injections are usually given using a 25 G needle. To ensure medication reaches the subcutaneous tissue, the rule is: if you can grasp 2 inches of tissue, insert the needle at a 90° angle and for 1 inch, insert needle at a 45° angle (Chernecky et al. 2002, Perry 2007). With the introduction of shorter needles (13 mm), it is recommended that insulin injections be given at an angle of 90° (King 2003). The length of the needle should be selected by pinching the skin tissue and selecting a needle one-half the width of the skinfold (Chernecky et al. 2002). Shorter needles should also be used at a 45° angle in children and underweight adults.

Specific patient preparations

It has been stated that it is not necessary to use an alcohol swab to clean the skin prior to administration of injections providing the skin is socially clean. If unsure or in immunocompromised patients, the skin should be prepared using an antiseptic swab (Dann 1969, Downie et al. 2003).

Procedure guideline 13.18 Medication: subcutaneous injection

Essential equipment

Alcohol swab

Needle

Syringe containing prepared medication

Sharps bin

Non-sterile gloves

Preprocedure

Action Rationale

1 Explain and discuss the procedure with the patient. To ensure that the patient understands the procedure and gives their valid consent (Griffith and Jordan 2003, E; NMC 2008b, C; NMC 2008c, C).

2 Consult the patient’s prescription chart and ascertain the following:

Drug

Dose

Date and time of administration

Route and method of administration

Diluent as appropriate

Validity of prescription

Signature of doctor.

To ensure that the patient is given the correct drug in the prescribed dose using the appropriate diluent and by the correct route (NMC 2008a, C; NPSA 2007d, C).

3 Wash hands. To prevent contamination of medication and equipment (DH 2007, C).

Procedure

4 Close the curtains or door and assist the patient into the required position. To ensure patient’s privacy and dignity. E

To allow