Where should an intramuscular (IM) injection be given? Nurses learn there are four possible sites: the arm (deltoid); thigh (vastus lateralis); upper outer posterior buttock (gluteus maximus), also referred to as the dorsogluteal site; and the lateral hip (gluteus medius), also called the ventrogluteal site. Choosing which site to use has been, for the most part, a matter of personal preference (the nurse's or the patient's), tradition, or convenience. But two recent surveys, both authored by nurses, provide a more scientific rationale for IM site selection (AACN Clin.Iss.Crit.Care 5[2]: 207-214, May 1994; Applied Nurs.Res. 8[1]: 23-33, Feb. 1995).

These comprehensive surveys of research reports and case study literature about IM injections revealed that administering medication intramuscularly can produce a variety of serious adverse effects, including skin and tissue trauma, muscle fibrosis and contracture, nerve palsies and paralysis, and infectious processes such as abscesses or gangrene. The authors identified some techniques nurses can use to reduce the risk of these reactions, one of which is choosing the best injection site.

Both surveys cited an impressive body of literature demonstrating that some complications of IM injection are linked specifically to the injection site. Of the four possible sites for IM injection, the authors found only one-the ventrogluteal-that had not been associated with any adverse effects whatsoever. While that may be due at least in part to the fact that nurses seldom use the ventrogluteal site, the authors believe that some anatomical features may make it superior to others. These include the lack of major nerves or blood vessels in the area, an ample and well-developed muscle mass, and the ease of identifying landmarks for the site. (To establish the location, you place the heel of your right hand over the patient's left greater trochanter, or vice versa, and position your index finger on or toward the anterior superior iliac spine, then stretch your middle finger away from your index finger. The center of the triangle formed by your fingers and the iliac crest is your injection site.)

Another advantage of the ventrogluteal site is that injections into this area are less likely to be inadvertently deposited into subcutaneous (SC), rather than muscle, tissue. Unintended SC injection is related to difficulty with assessing the thickness of the SC fat pad. Besides altering drug absorption and response, this practice can cause injury to SC tissue.

The dorsogluteal fat pad is of inconsistent thickness (1 to 9 cm), whereas the ventrogluteal is more uniform among individuals (3.75 cm or less). Muscle underlying this thickness at the ventrogluteal site is easily penetrated with the usual 11/2-inch needle used for IM injections. The authors of both surveys cited an experiment in which nurses and student nurses who were attempting to administer IM injections in the dorsogluteal site actually penetrated into muscle tissue in less than 5% of the females and less than 15% of the males in the study.

Despite these reports' finding that the advantages of the ventrogluteal site have been recognized for almost 45 years, it remains the most infrequently used. Yet the evidence for its superiority over other sites is compelling, and both author groups of these surveys recommend that it be considered the site of choice for IM injections. We're long overdue for putting this research into practice.

Ann Jacobson, RN, PhD