Resistance during an injection refers to the sensation of increased pressure or difficulty encountered when attempting to push down the syringe plunger. This feeling can range from a slight stiffness to a complete inability to depress the plunger. While some degree of resistance can be a normal part of the injection process, it can also signal an underlying issue that requires attention. Understanding this sensation is important for ensuring the safe and effective delivery of medication.
Common Causes of Resistance
Several factors can contribute to resistance experienced during an injection. A common cause involves the needle’s characteristics, such as its gauge. Smaller gauge needles, indicated by higher numbers like 27G or 30G, have a narrower internal diameter, which can increase the force required to inject fluid, especially if the fluid is thick. A bent or dull needle tip can also impede smooth penetration and cause resistance.
The properties of the fluid being injected play a significant role. Solutions with high viscosity naturally exhibit greater internal resistance to flow. Certain medications, such as some forms of testosterone or oil-based antipsychotics, are known for their high viscosity.
Tissue density at the injection site can also contribute to resistance. Injecting into dense muscle tissue, scar tissue, or an area where the muscle is tensed can create a firmer barrier. In some cases, hitting a blood vessel or bone can cause a sudden increase in resistance.
Problems with the syringe itself can also manifest as resistance. A sticking plunger, often caused by dried medication residue or inadequate lubrication within the syringe barrel, makes it difficult to push. A bent plunger can also create friction against the syringe barrel. Additionally, an air lock, where trapped air prevents the smooth flow of liquid, can contribute to the feeling of resistance.
Strategies to Minimize Resistance
Implementing specific strategies can help reduce or avoid resistance during injections. Selecting the appropriate needle is a primary step; a suitable needle gauge and length should be chosen based on the medication’s viscosity and the intended injection site. For instance, thicker, lower-gauge needles (e.g., 21G, 22G) are often recommended for viscous solutions to facilitate easier flow.
Proper injection technique also minimizes resistance. It helps to ensure there are no air bubbles in the syringe before injection. Depressing the plunger slowly and steadily allows the medication to disperse into the tissue more comfortably. Before insertion, allowing alcohol applied to the skin to fully dry can prevent a stinging sensation and create a cleaner injection path. For intramuscular injections, encouraging the muscle to relax can significantly decrease tissue resistance.
Rotating injection sites regularly prevents the buildup of scar tissue, which can increase resistance over time. If minor resistance is encountered during injection, a slight adjustment of the needle’s position, without fully withdrawing and re-inserting, might alleviate the issue. Applying gentle, continuous pressure can sometimes overcome slight resistance, allowing the medication to be delivered.
When Resistance Signals a Problem
While some resistance is normal, certain signs indicate that it might be a significant problem requiring immediate attention. Severe pain or a burning sensation during the injection, beyond typical discomfort, can be a warning sign. The rapid development of swelling or spreading redness at the injection site also suggests an issue.
Inability to inject the full dose of medication, even with reasonable pressure, signals a problem. Backflow of blood or injected fluid into the syringe can indicate the needle has entered a blood vessel. Later signs, such as fever, chills, or pus at the injection site, signal a potential infection.
If any of these concerning signs appear, it is advisable to stop the injection. If the needle becomes bent or the resistance is unmanageable, the needle and syringe should be safely discarded, and a new, sterile set should be prepared for a different injection site. Consulting a healthcare professional is important if concerns arise or if resistance is consistently encountered.