I was "googling" looking at proper IM injection procedures and found an article which included a section on aspiration and how it isn't needed and there is no scientific basis for it. I've cut and paste that section below along with a link to the entire article.
1.7 Needle aspiration
Whether or not to teach students to perform needle aspiration when administering IM injections is a questions frequently
asked by nursing practice instructors. Needle aspiration is performed by pulling back on the plunger of the syringe after
inserting the needle into the client; if blood appears in the syringe, the nurse assumes the needle is in a blood vessel, and
withdraws the needle prior to injection. There is no scientific evidence to support the need for aspiration [37], and several
evidence-based reasons not to perform aspiration. First, the sites used for intramuscular injection are not in close proximity
large blood vessels [38], so the likelihood of inadvertently hitting a blood vessel is slight. Second, for needle aspiration to be
effective, it must be sustained for at least 5-10 seconds, which is far longer than the quick 1-2 second aspiration generally
performed by nurses and other health professionals. One study notes that only 3% of vaccinators aspirated for the
recommended 5-10 seconds [37]. Third, rapid injection without aspiration was less painful for the client, likely because
aspiration, when performed properly for 5-10 seconds, results in longer contact time between the needle and the tissue and
inevitable movement of the needle within the tissue during aspiration [38, 39]. Finally, “bleeding at the injection site is
common, and does not indicate incorrect injection technique” (p. S68) [39]. Therefore, needle aspiration should not be
performed because it is unnecessary and increases pain at the injection site.
- http://www.sciedu.ca/journal/index.php/jnep/article/viewFile/1888/1291
1.7 Needle aspiration
Whether or not to teach students to perform needle aspiration when administering IM injections is a questions frequently
asked by nursing practice instructors. Needle aspiration is performed by pulling back on the plunger of the syringe after
inserting the needle into the client; if blood appears in the syringe, the nurse assumes the needle is in a blood vessel, and
withdraws the needle prior to injection. There is no scientific evidence to support the need for aspiration [37], and several
evidence-based reasons not to perform aspiration. First, the sites used for intramuscular injection are not in close proximity
large blood vessels [38], so the likelihood of inadvertently hitting a blood vessel is slight. Second, for needle aspiration to be
effective, it must be sustained for at least 5-10 seconds, which is far longer than the quick 1-2 second aspiration generally
performed by nurses and other health professionals. One study notes that only 3% of vaccinators aspirated for the
recommended 5-10 seconds [37]. Third, rapid injection without aspiration was less painful for the client, likely because
aspiration, when performed properly for 5-10 seconds, results in longer contact time between the needle and the tissue and
inevitable movement of the needle within the tissue during aspiration [38, 39]. Finally, “bleeding at the injection site is
common, and does not indicate incorrect injection technique” (p. S68) [39]. Therefore, needle aspiration should not be
performed because it is unnecessary and increases pain at the injection site.
- http://www.sciedu.ca/journal/index.php/jnep/article/viewFile/1888/1291
