Chapter 15: Medicines optimization: ensuring quality and safety
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Intramuscular injections
Definition
Evidence‐based approaches
Site and volume of injection
Selecting the site requires correct identification of the muscle groups by using landmarks to identify the relevant anatomical features (Hunter [136]). Choice will be influenced by the patient's physical condition and age. Intramuscular injections should be given into the densest part of the muscle (Pope [288]). Active patients will probably have greater muscle mass than older or emaciated patients (Hunter [136]).
The choice of muscle bed depends on the volume of medication to be injected; however, it appears that it is the medicine rather than just the volume that affects how a patient tolerates an injection. Malkin ([182]) uses Botox injections as an example where a volume of 1–3 mL can be injected into facial muscle groups, supporting the view that tolerance of the drug is more important than the volume.
Current research evidence suggests that there are five sites that can be used for the administration of intramuscular injections (Rodger and King [303], Tortora and Derrickson [353]). There is debate over which site to use. The two recommended are the vastus lateralis site and the ventrogluteal site, but most nurses tend to use the dorsogluteal site as it is more familiar (Greenway [108]).
Ventrogluteal site
The ventrogluteal site (Figure 15.29a) is relatively free of major nerves and blood vessels, and the muscle is large and well defined, making it easy to locate (Greenway [108]). It is located by placing the palm of the hand on the patient's opposite greater trochanter (right hand on left hip). The index finger is then extended to the anterior superior iliac spine to make a V. Injection in the centre of the V will ensure the injection is given into the gluteus medius muscle (Hunter [136]). This is the site of choice for intramuscular injections (Cocoman and Murray [41]) and is used for antibiotics, antiemetics, deep intramuscular and Z‐track injections in oil, narcotics and sedatives. Up to 2.5 mL can be safely injected into the ventrogluteal site (Rodger and King [303]).
Figure 15.29 Intramuscular injection sites. Source: Adapted from Rodger and King ([303]) with permission of John Wiley & Sons.
Deltoid site
The deltoid site (Figure 15.29b) has the advantage of being easily accessible whether the patient is standing, sitting or lying down. It is found by visualizing a triangle where the horizontal line is located 2.5–5.0 cm below the acromial process and the mid‐point of the lateral aspect of the arm, in line with the axilla, to form the apex (Hunter [136]). The injection is then given 2.5 cm down from the acromial process, avoiding the radial and brachial nerves. Owing to the small area of this site, the number and volume of injections that can be given into it are limited. Only small‐volume, non‐irritating medications, such as vaccines, antiemetics and narcotics, should be administered into this muscle. Rodger and King ([303]) state that the maximum volume that should be administered at this site is 1 mL.
Dorsogluteal site
The dorsogluteal site (Figure 15.29c), or upper outer quadrant, is the traditional site of choice and is used for deep intramuscular and Z‐track injections. It is located by using imaginary lines to divide the buttocks into four quarters. However, this site carries the danger of the needle hitting the sciatic nerve and the superior gluteal arteries (Small [336]). The gluteus muscle has the lowest drug absorption rate and this can result in a build‐up in the tissues, increasing the risk of overdose (Malkin [182]). The muscle mass is also likely to have atrophied in elderly, non‐ambulant and emaciated patients. Finally, it appears that there is a risk that the medication will not reach the muscle due to the amount of subcutaneous tissue in this area (Greenway [108]) and so it is not recommended for routine immunizations due to the poor absorption and risk of nerve injury (Public Health England [291], WHO [370]). In adults, up to 4 mL can be safely injected into this site (Rodger and King [303]).
Rectus femoris site
The rectus femoris site (Figure 15.29d) is a well‐defined muscle found by measuring a hand's breadth from the greater trochanter and the knee joint, which identifies the middle third of the quadriceps muscle (Hunter [136]). It is used for antiemetics, narcotics, sedatives, injections in oil, deep intramuscular injections and Z‐track injections. It is rarely used by nurses, but is easily accessed for self‐administration of injections or for infants (Workman [376]). At this site, 1–5 mL can be injected (1–3 mL in children).
Vastus lateralis site
The vastus lateralis site (Figure 15.29d) is used for deep intramuscular and Z‐track injections. One of the advantages of this site is its ease of access and, more importantly, there are no major blood vessels or significant nerve structures associated with this site. It is the best option in obese patients (Nisbet [255]). Up to 5 mL can be safely injected (Rodger and King [303]).
Rate of administration
It is recommended that the plunger is depressed at a rate of 10 seconds per millilitre.
Technique
The syringe should be held like a pen so it can be inserted with a dart‐like motion. The nurse should assess whether aspiration is appropriate; if there is a risk that the medication, dose, administration rate, complications of injections associated with the patient's condition, or accidental administration via the intravenous route would be harmful to the patient, then aspiration should be undertaken (Thomas et al. [348]). If aspiration is indicated, this should be over 5–10 seconds to ensure effectiveness and to reduce the risk of patient harm (Mraz et al. [223]).
The Z‐track method reduces the leakage of medication through the subcutaneous tissue, decreases the chance of skin lesions forming at the injection site and may hurt less. It involves pulling the skin of the injection site downwards or laterally, which moves the cutaneous and subcutaneous tissues by approximately 2–3 cm, and inserting the needle at a 90° angle to the skin (Antipuesto [10], Take 5 [345]). The injection is given and the needle withdrawn, releasing the retracted skin at the same time. This manoeuvre seals off the puncture track.
Pre‐procedural considerations
Equipment
The most commonly used size of needle for intramuscular injections is 21 G (23 G may also be used in a thin patient) but it does depend on the viscosity of the medication. The more important aspect of the needle is the length. The correct choice of needle length will result in fewer adverse events and reduce complications relating to abscess, pain and bruising (Malkin [182]). Needles should be long enough to penetrate the muscle and still allow a quarter of the needle to remain external to the skin (Workman [376]). Lenz ([173]) states that when choosing the correct needle length for intramuscular injections, it is important to assess the muscle mass of the injection site, the amount of subcutaneous fat and the weight of the patient. Without such an assessment, most injections intended for gluteal muscle are deposited in the gluteal fat.
For the deltoid and vastus lateralis muscles, to determine the most suitable size of needle to use, the muscle should be grasped between the thumb and forefinger to determine the depth of the muscle mass or the amount of subcutaneous fat at the injection site. For the gluteal muscles, the layer of fat and skin above the muscle should be gently lifted with the thumb and forefinger for the same reasons as before.
The patient's weight indicates the length of needle to use:
- children: 16 mm needle
- 31.5–90.0 kg: 25 mm needle
- above 90 kg: 38 mm needle.
Women have more subcutaneous tissue than men so a longer needle will be needed (Pope [288]).
Procedure guideline 15.20
