Intensive Care Medicine (ICM) Practice Exam

During administration of an I.M. injection into the lower extremity, the patient is complaining about sharp pain. What might be the most probable cause of it?

1. Injection was too fast

2. You hit a bone

3. You hit a nerve

4. You applied medication onto the fascia

The correct answer is: You hit a nerve

When administering an intramuscular injection into the lower extremity, sharp pain experienced by the patient can often be attributed to nerve involvement. The lower extremity is home to several important nerves, such as the sciatic nerve, femoral nerve, and others. If the needle inadvertently penetrates or irritates a nerve during the injection process, the patient is likely to report sharp or shooting pain immediately. This occurs because nerves are sensitive structures and can produce significant discomfort when disturbed. The other possibilities, while they may also lead to discomfort, are less likely to result in the acute, sharp pain characteristic of nerve involvement. For instance, injecting too quickly typically causes discomfort but usually not a sharp, localized pain. Hitting a bone might cause some discomfort but is usually accompanied by a sensation of resistance rather than a sharp pain. Additionally, applying medication onto the fascia typically wouldn't elicit sharp pain unless it caused significant irritation, which is less common. In summary, the sharp pain during the intramuscular injection is most indicative of nerve impact, making it the most probable cause in this scenario.