THE occurrence of pain and stone at the site of intramuscular injection is relatively common and is considered a complication of this procedure. The most commonly reported adverse reaction is pain at the site of injection. This occurs because the skin and subcutaneous tissue are richly innervated and the pain receptors are stimulated by the needle as it penetrates and dissects the connective tissue. Muscle is less innervated, but solution infusion can be very painful, due to irritation due to the solution itself and pH. Skin pigmentation and hemorrhage occur due to extravasation of blood following injury of capillaries and vessels. The onset of nodule at the site may correspond to muscle contraction or abscess formation. The abscess is associated with increased temperature and local redness.
Usually local measures, such as the use of anti-inflammatory ointments, local heat or increased movement is sufficient to resolve the complications.
Other complications of intramuscular injections are quoted below:
- decreased limb sensitivity;
- abscess formation;
- infarction and local necrosis;
- atrophy of the skin and adipose tissue;
- muscle spasm;
- tissue fibrosis;
- bruise;
- lesion of the sciatic nerve.
The occurrence of complications depends on some factors, as:
- Type of medication introduced: may be irritant, diluted in oily solvent or slow absorption, high concentration;
- Volume injected incompatible with muscle structure: may increase local tension, vascular compression; local edema, along with the toxic effect, can cause muscle infarction, fibrosis, and necrosis;
- Wrong place of application regarding the quality of the injected medication: there are medications that require great muscle mass, since a surface allows a marked rate of absorption;
- Inappropriate use of technique;
- Inappropriate choice of needle and syringe: medication retained in adipose tissue is very slowly absorbed and nodulations may occur; in the emaciated patient, can reach innervations or bone structures. Contaminated syringe or needle may lead to septicemia;
- Inadequate choice of area to be introduced to the medication: the deltoid muscle (in the arm) is the last to be used due to the circumflex nerve and vessel branches in its left lower portion;
- Unawareness of anatomy and pharmacology by professionals, as well as lack of practice and skill;
- Multiple injections in one place: after repeated injections at the same site, bleeding, depressions, fibrosis and other complications may occur due to the concentration, pH, chemical nature of the drug and absorption kinetics.
If you experience complications following intramuscular injection, you should seek the health care service where you have been given more guidance.
