Bruising at injection sites may be related to nicking superficial vessels, and is usually not due to poor injection technique. However, the problem may be worsened in patients taking anticoagulants, corticosteroids, or nonsteroidal antiinflammatory drugs, and in the elderly.
Painful injections may be related to the use of alcohol at the site—if the site is dirty, patients should wash it with soap and water prior to injection but otherwise no skin preparation is recommended. Injection of cold insulin, or syringes that have been reused too many times so the needle is dulled, can also cause pain. So can a technically correct injection in patients who are nervous or hypersensitive to pain. Use of an ice cube on the site for a few minutes prior to injection often helps. When the problem is extreme, applying Emla cream 30 minutes before the injection can be beneficial. Also, switching to the thinnest available needle (31 gauge for insulin pens and 30 gauge for syringes) should be tried.
An important cause of painful injections is when they are i.m. Insulin is designed to be given s.q., which is generally painless. Kinetic properties of the different insulins are determined by how they exist in the subcutaneous space (crystals, hexamers, dimers, monomers). Only monomers and dimers can be absorbed into the blood; lyspro and aspart exist as monomers, accounting for their rapid action; Regular as dimers and hexamers, causing its multihour effect; and intermediate and long-acting insulins as crystals, so the effect is much longer. If patients inadvertently inject i.m.—that is, do not pinch the skin enough, causing them to go through the subcutaneous space—absorption into the blood is faster than usual, resulting in a quick effect and occasionally frank hypoglycemia. Intramuscular injections hurt. A useful way to identify i.m. injections is to differentiate pain on inserting the needle into the skin—any of the previous causes, including pain hypersensitivity—from pain when the plunger is pushed in—i.m. injection. To avoid this problem, injections are generally given at a 90° angle, but children or thin adults may need a 45° angle, especially in areas with little subcutaneous fat. The practice of pinching a small fold of skin should be reinforced.
Allergic reactions are rare and usually localized. Rubber and latex allergies related to latex in syringes or rubber stoppers on vials can be mistaken for an insulin allergy. Latex-free syringes are available (Terumo Corporation). Preservatives or other chemicals in the buffer, such as zinc or protamine, can cause allergic reactions, but this is rare. Since human insulin has come to the market, serious insulin allergies are quite rare.
Lipoalrophy is a sinking or pitting of the subcutaneous tissue around an injection site that is believed to be an allergic response to a specific insulin species
sites, and to discuss alternative sites and proper site rotation. Lipohypertrophy usually resolves if the site is not used for several months. It is essential that providers inspect injection sites routinely. Also, patients will often state that they use their abdomen, but on inspection and more careful discussion, it is discovered that only a small area is used, which is hypertrophied. Individuals on multiple daily injections who use only one or two sites (especially arms and legs) are at the highest risk. Patients should be taught to rotate among individual sites.
Was this article helpful?